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Colak H, Sendesen E, Turkyilmaz MD. Subcortical auditory system in tinnitus with normal hearing: insights from electrophysiological perspective. Eur Arch Otorhinolaryngol 2024:10.1007/s00405-024-08583-3. [PMID: 38555317 DOI: 10.1007/s00405-024-08583-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 02/26/2024] [Indexed: 04/02/2024]
Abstract
PURPOSE The mechanism of tinnitus remains poorly understood; however, studies have underscored the significance of the subcortical auditory system in tinnitus perception. In this study, our aim was to investigate the subcortical auditory system using electrophysiological measurements in individuals with tinnitus and normal hearing. Additionally, we aimed to assess speech-in-noise (SiN) perception to determine whether individuals with tinnitus exhibit SiN deficits despite having normal-hearing thresholds. METHODS A total 42 normal-hearing participants, including 22 individuals with chronic subjective tinnitus and 20 normal individuals, participated in the study. We recorded auditory brainstem response (ABR) and speech-evoked frequency following response (sFFR) from the participants. SiN perception was also assessed using the Matrix test. RESULTS Our results revealed a significant prolongation of the O peak, which encodes sound offset in sFFR, for the tinnitus group (p < 0.01). The greater non-stimulus-evoked activity was also found in individuals with tinnitus (p < 0.01). In ABR, the tinnitus group showed reduced wave I amplitude and prolonged absolute wave I, III, and V latencies (p ≤ 0.02). Our findings suggested that individuals with tinnitus had poorer SiN perception compared to normal participants (p < 0.05). CONCLUSION The deficit in encoding sound offset may indicate an impaired inhibitory mechanism in tinnitus. The greater non-stimulus-evoked activity observed in the tinnitus group suggests increased neural noise at the subcortical level. Additionally, individuals with tinnitus may experience speech-in-noise deficits despite having a normal audiogram. Taken together, these findings suggest that the lack of inhibition and increased neural noise may be associated with tinnitus perception.
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Affiliation(s)
- Hasan Colak
- Biosciences Institute, Newcastle University, Newcastle Upon Tyne, UK.
| | - Eser Sendesen
- Department of Audiology, Hacettepe University, Ankara, Turkey
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Marchetta P, Dapper K, Hess M, Calis D, Singer W, Wertz J, Fink S, Hage SR, Alam M, Schwabe K, Lukowski R, Bourien J, Puel JL, Jacob MH, Munk MHJ, Land R, Rüttiger L, Knipper M. Dysfunction of specific auditory fibers impacts cortical oscillations, driving an autism phenotype despite near-normal hearing. FASEB J 2024; 38:e23411. [PMID: 38243766 DOI: 10.1096/fj.202301995r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/04/2023] [Accepted: 12/22/2023] [Indexed: 01/21/2024]
Abstract
Autism spectrum disorder is discussed in the context of altered neural oscillations and imbalanced cortical excitation-inhibition of cortical origin. We studied here whether developmental changes in peripheral auditory processing, while preserving basic hearing function, lead to altered cortical oscillations. Local field potentials (LFPs) were recorded from auditory, visual, and prefrontal cortices and the hippocampus of BdnfPax2 KO mice. These mice develop an autism-like behavioral phenotype through deletion of BDNF in Pax2+ interneuron precursors, affecting lower brainstem functions, but not frontal brain regions directly. Evoked LFP responses to behaviorally relevant auditory stimuli were weaker in the auditory cortex of BdnfPax2 KOs, connected to maturation deficits of high-spontaneous rate auditory nerve fibers. This was correlated with enhanced spontaneous and induced LFP power, excitation-inhibition imbalance, and dendritic spine immaturity, mirroring autistic phenotypes. Thus, impairments in peripheral high-spontaneous rate fibers alter spike synchrony and subsequently cortical processing relevant for normal communication and behavior.
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Affiliation(s)
- Philine Marchetta
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Konrad Dapper
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Morgan Hess
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Dila Calis
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Wibke Singer
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Jakob Wertz
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Stefan Fink
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Steffen R Hage
- Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - Mesbah Alam
- Experimental Neurosurgery, Department of Neurosurgery, Hannover Medical School, Hannover, Germany
| | - Kerstin Schwabe
- Experimental Neurosurgery, Department of Neurosurgery, Hannover Medical School, Hannover, Germany
| | - Robert Lukowski
- Institute of Pharmacy, Pharmacology, Toxicology and Clinical Pharmacy, University of Tübingen, Tübingen, Germany
| | - Jerome Bourien
- Institute for Neurosciences Montpellier, Institut National de la Santé et de la Recherche Médical, University of Montpellier, Montpellier, France
| | - Jean-Luc Puel
- Institute for Neurosciences Montpellier, Institut National de la Santé et de la Recherche Médical, University of Montpellier, Montpellier, France
| | - Michele H Jacob
- Department of Neuroscience, Tufts University School of Medicine, Sackler School of Biomedical Sciences, Boston, Massachusetts, USA
| | - Matthias H J Munk
- Department of Psychiatry & Psychotherapy, University of Tübingen, Tübingen, Germany
- Department of Biology, Technical University Darmstadt, Darmstadt, Germany
| | - Rüdiger Land
- Department of Experimental Otology, Institute of Audioneurotechnology, Hannover Medical School, Hannover, Germany
| | - Lukas Rüttiger
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Marlies Knipper
- Molecular Physiology of Hearing, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
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Radulovic T, Rajaram E, Ebbers L, Pagella S, Winklhofer M, Kopp-Scheinpflug C, Nothwang HG, Milenkovic I, Hartmann AM. Serine 937 phosphorylation enhances KCC2 activity and strengthens synaptic inhibition. Sci Rep 2023; 13:21660. [PMID: 38066086 PMCID: PMC10709408 DOI: 10.1038/s41598-023-48884-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/30/2023] [Indexed: 12/18/2023] Open
Abstract
The potassium chloride cotransporter KCC2 is crucial for Cl- extrusion from mature neurons and thus key to hyperpolarizing inhibition. Auditory brainstem circuits contain well-understood inhibitory projections and provide a potent model to study the regulation of synaptic inhibition. Two peculiarities of the auditory brainstem are (i) posttranslational activation of KCC2 during development and (ii) extremely negative reversal potentials in specific circuits. To investigate the role of the potent phospho-site serine 937 therein, we generated a KCC2 Thr934Ala/Ser937Asp double mutation, in which Ser937 is replaced by aspartate mimicking the phosphorylated state, and the neighbouring Thr934 arrested in the dephosphorylated state. This double mutant showed a twofold increased transport activity in HEK293 cells, raising the hypothesis that auditory brainstem neurons show lower [Cl-]i. and increased glycinergic inhibition. This was tested in a mouse model carrying the same KCC2 Thr934Ala/Ser937Asp mutation by the use of the CRISPR/Cas9 technology. Homozygous KCC2 Thr934Ala/Ser937Asp mice showed an earlier developmental onset of hyperpolarisation in the auditory brainstem. Mature neurons displayed stronger glycinergic inhibition due to hyperpolarized ECl-. These data demonstrate that phospho-regulation of KCC2 Ser937 is a potent way to interfere with the excitation-inhibition balance in neural circuits.
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Affiliation(s)
- Tamara Radulovic
- Division of Physiology School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Research Center Neurosensory Science, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Ezhilarasan Rajaram
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-University Munich, 82152, Planegg-Martinsried, Germany
| | - Lena Ebbers
- Division of Neurogenetics, School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Sara Pagella
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-University Munich, 82152, Planegg-Martinsried, Germany
| | - Michael Winklhofer
- Research Center Neurosensory Science, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Institute for Biology and Environmental Sciences IBU, Carl Von Ossietzky University of Oldenburg, 26111, Oldenburg, Germany
| | - Conny Kopp-Scheinpflug
- Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-University Munich, 82152, Planegg-Martinsried, Germany
| | - Hans Gerd Nothwang
- Division of Neurogenetics, School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Research Center Neurosensory Science, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Center of Excellence Hearing4all, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Ivan Milenkovic
- Division of Physiology School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Research Center Neurosensory Science, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Anna-Maria Hartmann
- Division of Neurogenetics, School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
- Research Center Neurosensory Science, Carl Von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
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Lee J, Clause A, Kandler K. Structural and Functional Development of Inhibitory Connections from the Medial Nucleus of the Trapezoid Body to the Superior Paraolivary Nucleus. J Neurosci 2023; 43:7766-7779. [PMID: 37734946 PMCID: PMC10648534 DOI: 10.1523/jneurosci.0920-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 08/21/2023] [Accepted: 09/13/2023] [Indexed: 09/23/2023] Open
Abstract
The medial nucleus of the trapezoid body (MNTB) in the auditory brainstem is the principal source of synaptic inhibition to several functionally distinct auditory nuclei. Prominent projections of individual MNTB neurons comprise the major binaural nuclei that are involved in the early processing stages of sound localization as well as the superior paraolivary nucleus (SPON), which contains monaural neurons that extract rapid changes in sound intensity to detect sound gaps and rhythmic oscillations that commonly occur in animal calls and human speech. While the processes that guide the development and refinement of MNTB axon collaterals to the binaural nuclei have become increasingly understood, little is known about the development of MNTB collaterals to the monaural SPON. In this study, we investigated the development of MNTB-SPON connections in mice of both sexes from shortly after birth to three weeks of age, which encompasses the time before and after hearing onset. Individual axon reconstructions and electrophysiological analysis of MNTB-SPON connectivity demonstrate a dramatic increase in the number of MNTB axonal boutons in the SPON before hearing onset. However, this proliferation was not accompanied by changes in the strength of MNTB-SPON connections or by changes in the structural or functional topographic precision. However, following hearing onset, the spread of single-axon boutons along the tonotopic axis increased, indicating an unexpected decrease in the tonotopic precision of the MNTB-SPON pathway. These results provide new insight into the development and organization of inhibition to SPON neurons and the regulation of developmental plasticity in diverging inhibitory pathways.SIGNIFICANCE STATEMENT The superior paraolivary nucleus (SPON) is a prominent auditory brainstem nucleus involved in the early detection of sound gaps and rhythmic oscillations. The ability of SPON neurons to fire at the offset of sound depends on strong and precise synaptic inhibition provided by glycinergic neurons in the medial nucleus of the trapezoid body (MNTB). Here, we investigated the anatomic and physiological maturation of MNTB-LSO connectivity in mice before and after the onset of hearing. We observed a period of bouton proliferation without accompanying changes in topographic precision before hearing onset. This was followed by bouton elimination and an unexpected decrease in the tonotopic precision after hearing onset. These results provide new insight into the development of inhibition to the SPON.
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Affiliation(s)
- Jongwon Lee
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Amanda Clause
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Karl Kandler
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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Goh RZ, Phillips IB, Firestone C. The perception of silence. Proc Natl Acad Sci U S A 2023; 120:e2301463120. [PMID: 37428927 PMCID: PMC10629541 DOI: 10.1073/pnas.2301463120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 05/10/2023] [Indexed: 07/12/2023] Open
Abstract
Auditory perception is traditionally conceived as the perception of sounds-a friend's voice, a clap of thunder, a minor chord. However, daily life also seems to present us with experiences characterized by the absence of sound-a moment of silence, a gap between thunderclaps, the hush after a musical performance. In these cases, do we positively hear silence? Or do we just fail to hear, and merely judge or infer that it is silent? This longstanding question remains controversial in both the philosophy and science of perception, with prominent theories holding that sounds are the only objects of auditory experience and thus that our encounter with silence is cognitive, not perceptual. However, this debate has largely remained theoretical, without a key empirical test. Here, we introduce an empirical approach to this theoretical dispute, presenting experimental evidence that silence can be genuinely perceived (not just cognitively inferred). We ask whether silences can "substitute" for sounds in event-based auditory illusions-empirical signatures of auditory event representation in which auditory events distort perceived duration. Seven experiments introduce three "silence illusions"-the one-silence-is-more illusion, silence-based warping, and the oddball-silence illusion-each adapted from a prominent perceptual illusion previously thought to arise only from sounds. Subjects were immersed in ambient noise interrupted by silences structurally identical to the sounds in the original illusions. In all cases, silences elicited temporal distortions perfectly analogous to the illusions produced by sounds. Our results suggest that silence is truly heard, not merely inferred, introducing a general approach for studying the perception of absence.
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Affiliation(s)
- Rui Zhe Goh
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD21218
- Department of Philosophy, Johns Hopkins University, Baltimore, MD21218
| | - Ian B. Phillips
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD21218
- Department of Philosophy, Johns Hopkins University, Baltimore, MD21218
| | - Chaz Firestone
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD21218
- Department of Philosophy, Johns Hopkins University, Baltimore, MD21218
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6
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Pressey JC, de Saint-Rome M, Raveendran VA, Woodin MA. Chloride transporters controlling neuronal excitability. Physiol Rev 2023; 103:1095-1135. [PMID: 36302178 DOI: 10.1152/physrev.00025.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Synaptic inhibition plays a crucial role in regulating neuronal excitability, which is the foundation of nervous system function. This inhibition is largely mediated by the neurotransmitters GABA and glycine that activate Cl--permeable ion channels, which means that the strength of inhibition depends on the Cl- gradient across the membrane. In neurons, the Cl- gradient is primarily mediated by two secondarily active cation-chloride cotransporters (CCCs), NKCC1 and KCC2. CCC-mediated regulation of the neuronal Cl- gradient is critical for healthy brain function, as dysregulation of CCCs has emerged as a key mechanism underlying neurological disorders including epilepsy, neuropathic pain, and autism spectrum disorder. This review begins with an overview of neuronal chloride transporters before explaining the dependent relationship between these CCCs, Cl- regulation, and inhibitory synaptic transmission. We then discuss the evidence for how CCCs can be regulated, including by activity and their protein interactions, which underlie inhibitory synaptic plasticity. For readers who may be interested in conducting experiments on CCCs and neuronal excitability, we have included a section on techniques for estimating and recording intracellular Cl-, including their advantages and limitations. Although the focus of this review is on neurons, we also examine how Cl- is regulated in glial cells, which in turn regulate neuronal excitability through the tight relationship between this nonneuronal cell type and synapses. Finally, we discuss the relatively extensive and growing literature on how CCC-mediated neuronal excitability contributes to neurological disorders.
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Affiliation(s)
- Jessica C Pressey
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Miranda de Saint-Rome
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Vineeth A Raveendran
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Morse K, Vander Werff KR. Onset-offset cortical auditory evoked potential amplitude differences indicate auditory cortical hyperactivity and reduced inhibition in people with tinnitus. Clin Neurophysiol 2023; 149:223-233. [PMID: 36963993 DOI: 10.1016/j.clinph.2023.02.164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 12/26/2022] [Accepted: 02/05/2023] [Indexed: 02/25/2023]
Abstract
OBJECTIVE The current study investigates evidence of hypothesized reduced central inhibition and/or increased excitation in individuals with tinnitus by evaluating cortical auditory onset versus offset responses. METHODS Cortical auditory evoked potentials (CAEPs) were recorded to the onset and offset of 3-second white noise stimuli in tinnitus and control groups matched in pairs by age, hearing, and sex (n = 26 total). Independent t-tests and 2-way mixed model ANOVA were used to evaluate onset-offset differences in amplitude, area, and latency of CAEP components by group. The predictive influence of tinnitus presence and associated participant characteristics on CAEP outcomes was assessed by multiple regression proportional reduction in error. RESULTS The tinnitus group had significantly larger onset minus offset P2 amplitudes (ΔP2 amplitudes) than control group participants. No other component variables differed significantly. ΔP2 amplitude was best predicted by tinnitus status and not significantly influenced by other variables such as hearing loss or age. CONCLUSIONS Hypothesized reduced central inhibition and/or increased excitation in tinnitus participants was partially supported by a group difference in ΔP2 amplitude. SIGNIFICANCE This was the first study to evaluate CAEP onset minus offset differences to investigate changes in central excitation/inhibition in individuals with tinnitus versus controls in matched groups.
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Affiliation(s)
- Kenneth Morse
- West Virginia University, Division of Communication Sciences and Disorders, USA.
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Sibille J, Kremkow J, Koch U. Absence of the Fragile X messenger ribonucleoprotein alters response patterns to sounds in the auditory midbrain. Front Neurosci 2022; 16:987939. [PMID: 36188480 PMCID: PMC9523263 DOI: 10.3389/fnins.2022.987939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/26/2022] [Indexed: 11/13/2022] Open
Abstract
Among the different autism spectrum disorders, Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. Sensory and especially auditory hypersensitivity is a key symptom in patients, which is well mimicked in the Fmr1 -/- mouse model. However, the physiological mechanisms underlying FXS’s acoustic hypersensitivity in particular remain poorly understood. Here, we categorized spike response patterns to pure tones of different frequencies and intensities from neurons in the inferior colliculus (IC), a central integrator in the ascending auditory pathway. Based on this categorization we analyzed differences in response patterns between IC neurons of wild-type (WT) and Fmr1 -/- mice. Our results report broadening of frequency tuning, an increased firing in response to monaural as well as binaural stimuli, an altered balance of excitation-inhibition, and reduced response latencies, all expected features of acoustic hypersensitivity. Furthermore, we noticed that all neuronal response types in Fmr1 -/- mice displayed enhanced offset-rebound activity outside their excitatory frequency response area. These results provide evidence that the loss of Fmr1 not only increases spike responses in IC neurons similar to auditory brainstem neurons, but also changes response patterns such as offset spiking. One can speculate this to be an underlying aspect of the receptive language problems associated with Fragile X syndrome.
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Affiliation(s)
- Jérémie Sibille
- Institute for Biology, Freie Universität Berlin, Berlin, Germany
- Neuroscience Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
- *Correspondence: Jérémie Sibille, ,
| | - Jens Kremkow
- Neuroscience Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
| | - Ursula Koch
- Institute for Biology, Freie Universität Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
- Ursula Koch,
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Hartmann AM, Nothwang HG. NKCC1 and KCC2: Structural insights into phospho-regulation. Front Mol Neurosci 2022; 15:964488. [PMID: 35935337 PMCID: PMC9355526 DOI: 10.3389/fnmol.2022.964488] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Inhibitory neurotransmission plays a fundamental role in the central nervous system, with about 30–50% of synaptic connections being inhibitory. The action of both inhibitory neurotransmitter, gamma-aminobutyric-acid (GABA) and glycine, mainly relies on the intracellular Cl– concentration in neurons. This is set by the interplay of the cation chloride cotransporters NKCC1 (Na+, K+, Cl– cotransporter), a main Cl– uptake transporter, and KCC2 (K+, Cl– cotransporter), the principle Cl– extruder in neurons. Accordingly, their dysfunction is associated with severe neurological, psychiatric, and neurodegenerative disorders. This has triggered great interest in understanding their regulation, with a strong focus on phosphorylation. Recent structural data by cryogenic electron microscopy provide the unique possibility to gain insight into the action of these phosphorylations. Interestingly, in KCC2, six out of ten (60%) known regulatory phospho-sites reside within a region of 134 amino acid residues (12% of the total residues) between helices α8 and α9 that lacks fixed or ordered three-dimensional structures. It thus represents a so-called intrinsically disordered region. Two further phospho-sites, Tyr903 and Thr906, are also located in a disordered region between the ß8 strand and the α8 helix. We make the case that especially the disordered region between helices α8 and α9 acts as a platform to integrate different signaling pathways and simultaneously constitute a flexible, highly dynamic linker that can survey a wide variety of distinct conformations. As each conformation can have distinct binding affinities and specificity properties, this enables regulation of [Cl–]i and thus the ionic driving force in a history-dependent way. This region might thus act as a molecular processor underlying the well described phenomenon of ionic plasticity that has been ascribed to inhibitory neurotransmission. Finally, it might explain the stunning long-range effects of mutations on phospho-sites in KCC2.
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Affiliation(s)
- Anna-Maria Hartmann
- Division of Neurogenetics, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- *Correspondence: Anna-Maria Hartmann,
| | - Hans Gerd Nothwang
- Division of Neurogenetics, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Center of Excellence Hearing4all, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
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Pätz C, Console-Meyer L, Felmy F. Structural arrangement of auditory brainstem nuclei in the bats Phyllostomus discolor and Carollia perspicillata. J Comp Neurol 2022; 530:2762-2781. [PMID: 35703441 DOI: 10.1002/cne.25355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 04/24/2022] [Accepted: 05/14/2022] [Indexed: 11/10/2022]
Abstract
The structure of the mammalian auditory brainstem is evolutionarily highly plastic, and distinct nuclei arrange in a species-dependent manner. Such anatomical variability is present in the superior olivary complex (SOC) and the nuclei of the lateral lemniscus (LL). Due to the structure-function relationship in the auditory brainstem, the identification of individual nuclei supports the understanding of sound processing. Here, we comparatively describe the nucleus arrangement and the expression of functional markers in the auditory brainstem of the two bat species Phyllostomus discolor and Carollia perspicillata. Using immunofluorescent labeling, we describe the arrangement and identity of the SOC and LL nuclei based on the expression of synaptic markers (vesicular glutamate transporter 1 and glycine transporter 2), calcium-binding proteins, as well as the voltage-gated ion channel subunits Kv1.1 and HCN1. The distribution of excitatory and inhibitory synaptic labeling appears similar between both species and matches with that of other mammals. The detection of calcium-binding proteins indicates species-dependent differences and deviations from other mammals. Kv1.1 and HCN1 show largely the same expression pattern in both species, which diverges from other mammals, indicating functional adaptations in the cellular physiology of bat neurons.
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Affiliation(s)
- Christina Pätz
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Laura Console-Meyer
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Felix Felmy
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
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11
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Solyga M, Barkat TR. Emergence and function of cortical offset responses in sound termination detection. eLife 2021; 10:e72240. [PMID: 34910627 PMCID: PMC8673837 DOI: 10.7554/elife.72240] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 11/28/2021] [Indexed: 11/20/2022] Open
Abstract
Offset responses in auditory processing appear after a sound terminates. They arise in neuronal circuits within the peripheral auditory system, but their role in the central auditory system remains unknown. Here, we ask what the behavioral relevance of cortical offset responses is and what circuit mechanisms drive them. At the perceptual level, our results reveal that experimentally minimizing auditory cortical offset responses decreases the mouse performance to detect sound termination, assigning a behavioral role to offset responses. By combining in vivo electrophysiology in the auditory cortex and thalamus of awake mice, we also demonstrate that cortical offset responses are not only inherited from the periphery but also amplified and generated de novo. Finally, we show that offset responses code more than silence, including relevant changes in sound trajectories. Together, our results reveal the importance of cortical offset responses in encoding sound termination and detecting changes within temporally discontinuous sounds crucial for speech and vocalization.
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12
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Beebe NL, Zhang C, Burger RM, Schofield BR. Multiple Sources of Cholinergic Input to the Superior Olivary Complex. Front Neural Circuits 2021; 15:715369. [PMID: 34335196 PMCID: PMC8319744 DOI: 10.3389/fncir.2021.715369] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 06/24/2021] [Indexed: 11/23/2022] Open
Abstract
The superior olivary complex (SOC) is a major computation center in the brainstem auditory system. Despite previous reports of high expression levels of cholinergic receptors in the SOC, few studies have addressed the functional role of acetylcholine in the region. The source of the cholinergic innervation is unknown for all but one of the nuclei of the SOC, limiting our understanding of cholinergic modulation. The medial nucleus of the trapezoid body, a key inhibitory link in monaural and binaural circuits, receives cholinergic input from other SOC nuclei and also from the pontomesencephalic tegmentum. Here, we investigate whether these same regions are sources of cholinergic input to other SOC nuclei. We also investigate whether individual cholinergic cells can send collateral projections bilaterally (i.e., into both SOCs), as has been shown at other levels of the subcortical auditory system. We injected retrograde tract tracers into the SOC in gerbils, then identified retrogradely-labeled cells that were also immunolabeled for choline acetyltransferase, a marker for cholinergic cells. We found that both the SOC and the pontomesencephalic tegmentum (PMT) send cholinergic projections into the SOC, and these projections appear to innervate all major SOC nuclei. We also observed a small cholinergic projection into the SOC from the lateral paragigantocellular nucleus of the reticular formation. These various sources likely serve different functions; e.g., the PMT has been associated with things such as arousal and sensory gating whereas the SOC may provide feedback more closely tuned to specific auditory stimuli. Further, individual cholinergic neurons in each of these regions can send branching projections into both SOCs. Such projections present an opportunity for cholinergic modulation to be coordinated across the auditory brainstem.
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Affiliation(s)
- Nichole L Beebe
- Department of Anatomy and Neurobiology, Hearing Research Focus Group, Northeast Ohio Medical University, Rootstown, OH, United States.,Brain Health Research Institute, Kent State University, Kent, OH, United States
| | - Chao Zhang
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - R Michael Burger
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - Brett R Schofield
- Department of Anatomy and Neurobiology, Hearing Research Focus Group, Northeast Ohio Medical University, Rootstown, OH, United States.,Brain Health Research Institute, Kent State University, Kent, OH, United States
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13
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Li H, Wang J, Liu G, Xu J, Huang W, Song C, Wang D, Tao HW, Zhang LI, Liang F. Phasic Off responses of auditory cortex underlie perception of sound duration. Cell Rep 2021; 35:109003. [PMID: 33882311 PMCID: PMC8154544 DOI: 10.1016/j.celrep.2021.109003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 02/25/2021] [Accepted: 03/23/2021] [Indexed: 11/30/2022] Open
Abstract
It has been proposed that sound information is separately streamed into onset and offset pathways for parallel processing. However, how offset responses contribute to auditory perception remains unclear. Here, loose-patch and whole-cell recordings in awake mouse primary auditory cortex (A1) reveal that a subset of pyramidal neurons exhibit a transient "Off" response, with its onset tightly time-locked to the sound termination and its frequency tuning similar to that of the transient "On" response. Both responses are characterized by excitation briefly followed by inhibition, with the latter mediated by parvalbumin (PV) inhibitory neurons. Optogenetically manipulating sound-evoked A1 responses at different temporal phases or artificially creating phantom sounds in A1 further reveals that the A1 phasic On and Off responses are critical for perceptual discrimination of sound duration. Our results suggest that perception of sound duration is dependent on precisely encoding its onset and offset timings by phasic On and Off responses.
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Affiliation(s)
- Haifu Li
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Jian Wang
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Guilong Liu
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Jinfeng Xu
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Weilong Huang
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Changbao Song
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Dijia Wang
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China
| | - Huizhong W Tao
- Center for Neural Circuits & Sensory Processing Disorders, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA; Department of Physiology & Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Li I Zhang
- Center for Neural Circuits & Sensory Processing Disorders, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA; Department of Physiology & Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - Feixue Liang
- School of Biomedical Engineering, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Mental Health of the Ministry of Education, Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou 510515, China; Department of Anesthesiology, Zhujiang Hospital of Southern Medical University, Guangzhou 510220, China.
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14
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Eckert P, Marchetta P, Manthey MK, Walter MH, Jovanovic S, Savitska D, Singer W, Jacob MH, Rüttiger L, Schimmang T, Milenkovic I, Pilz PKD, Knipper M. Deletion of BDNF in Pax2 Lineage-Derived Interneuron Precursors in the Hindbrain Hampers the Proportion of Excitation/Inhibition, Learning, and Behavior. Front Mol Neurosci 2021; 14:642679. [PMID: 33841098 PMCID: PMC8033028 DOI: 10.3389/fnmol.2021.642679] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/26/2021] [Indexed: 12/16/2022] Open
Abstract
Numerous studies indicate that deficits in the proper integration or migration of specific GABAergic precursor cells from the subpallium to the cortex can lead to severe cognitive dysfunctions and neurodevelopmental pathogenesis linked to intellectual disabilities. A different set of GABAergic precursors cells that express Pax2 migrate to hindbrain regions, targeting, for example auditory or somatosensory brainstem regions. We demonstrate that the absence of BDNF in Pax2-lineage descendants of BdnfPax2KOs causes severe cognitive disabilities. In BdnfPax2KOs, a normal number of parvalbumin-positive interneurons (PV-INs) was found in the auditory cortex (AC) and hippocampal regions, which went hand in hand with reduced PV-labeling in neuropil domains and elevated activity-regulated cytoskeleton-associated protein (Arc/Arg3.1; here: Arc) levels in pyramidal neurons in these same regions. This immaturity in the inhibitory/excitatory balance of the AC and hippocampus was accompanied by elevated LTP, reduced (sound-induced) LTP/LTD adjustment, impaired learning, elevated anxiety, and deficits in social behavior, overall representing an autistic-like phenotype. Reduced tonic inhibitory strength and elevated spontaneous firing rates in dorsal cochlear nucleus (DCN) brainstem neurons in otherwise nearly normal hearing BdnfPax2KOs suggests that diminished fine-grained auditory-specific brainstem activity has hampered activity-driven integration of inhibitory networks of the AC in functional (hippocampal) circuits. This leads to an inability to scale hippocampal post-synapses during LTP/LTD plasticity. BDNF in Pax2-lineage descendants in lower brain regions should thus be considered as a novel candidate for contributing to the development of brain disorders, including autism.
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Affiliation(s)
- Philipp Eckert
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Philine Marchetta
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Marie K Manthey
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany.,Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, United States
| | - Michael H Walter
- Department for Animal Physiology, Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Sasa Jovanovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Daria Savitska
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Wibke Singer
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Michele H Jacob
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, United States
| | - Lukas Rüttiger
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Thomas Schimmang
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
| | - Ivan Milenkovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Peter K D Pilz
- Department for Animal Physiology, Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Marlies Knipper
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
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15
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Bondanelli G, Deneux T, Bathellier B, Ostojic S. Network dynamics underlying OFF responses in the auditory cortex. eLife 2021; 10:e53151. [PMID: 33759763 PMCID: PMC8057817 DOI: 10.7554/elife.53151] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/19/2021] [Indexed: 11/13/2022] Open
Abstract
Across sensory systems, complex spatio-temporal patterns of neural activity arise following the onset (ON) and offset (OFF) of stimuli. While ON responses have been widely studied, the mechanisms generating OFF responses in cortical areas have so far not been fully elucidated. We examine here the hypothesis that OFF responses are single-cell signatures of recurrent interactions at the network level. To test this hypothesis, we performed population analyses of two-photon calcium recordings in the auditory cortex of awake mice listening to auditory stimuli, and compared them to linear single-cell and network models. While the single-cell model explained some prominent features of the data, it could not capture the structure across stimuli and trials. In contrast, the network model accounted for the low-dimensional organization of population responses and their global structure across stimuli, where distinct stimuli activated mostly orthogonal dimensions in the neural state-space.
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Affiliation(s)
- Giulio Bondanelli
- Laboratoire de Neurosciences Cognitives et Computationelles, Département d’études cognitives, ENS, PSL University, INSERMParisFrance
- Neural Computation Laboratory, Center for Human Technologies, Istituto Italiano di Tecnologia (IIT)GenoaItaly
| | - Thomas Deneux
- Départment de Neurosciences Intégratives et Computationelles (ICN), Institut des Neurosciences Paris-Saclay (NeuroPSI), UMR 9197 CNRS, Université Paris SudGif-sur-YvetteFrance
| | - Brice Bathellier
- Départment de Neurosciences Intégratives et Computationelles (ICN), Institut des Neurosciences Paris-Saclay (NeuroPSI), UMR 9197 CNRS, Université Paris SudGif-sur-YvetteFrance
- Institut Pasteur, INSERM, Institut de l’AuditionParisFrance
| | - Srdjan Ostojic
- Laboratoire de Neurosciences Cognitives et Computationelles, Département d’études cognitives, ENS, PSL University, INSERMParisFrance
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16
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Kopp-Scheinpflug C, Forsythe ID. Nitric Oxide Signaling in the Auditory Pathway. Front Neural Circuits 2021; 15:759342. [PMID: 34712124 PMCID: PMC8546346 DOI: 10.3389/fncir.2021.759342] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 09/23/2021] [Indexed: 01/12/2023] Open
Abstract
Nitric oxide (NO) is of fundamental importance in regulating immune, cardiovascular, reproductive, neuromuscular, and nervous system function. It is rapidly synthesized and cannot be confined, it is highly reactive, so its lifetime is measured in seconds. These distinctive properties (contrasting with classical neurotransmitters and neuromodulators) give rise to the concept of NO as a "volume transmitter," where it is generated from an active source, diffuses to interact with proteins and receptors within a sphere of influence or volume, but limited in distance and time by its short half-life. In the auditory system, the neuronal NO-synthetizing enzyme, nNOS, is highly expressed and tightly coupled to postsynaptic calcium influx at excitatory synapses. This provides a powerful activity-dependent control of postsynaptic intrinsic excitability via cGMP generation, protein kinase G activation and modulation of voltage-gated conductances. NO may also regulate vesicle mobility via retrograde signaling. This Mini Review focuses on the auditory system, but highlights general mechanisms by which NO mediates neuronal intrinsic plasticity and synaptic transmission. The dependence of NO generation on synaptic and sound-evoked activity has important local modulatory actions and NO serves as a "volume transmitter" in the auditory brainstem. It also has potentially destructive consequences during intense activity or on spill-over from other NO sources during pathological conditions, when aberrant signaling may interfere with the precisely timed and tonotopically organized auditory system.
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Affiliation(s)
- Conny Kopp-Scheinpflug
- Neurobiology Laboratory, Division of Neurobiology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
| | - Ian D Forsythe
- Auditory Neurophysiology Laboratory, Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom
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17
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Endogenous Cholinergic Signaling Modulates Sound-Evoked Responses of the Medial Nucleus of the Trapezoid Body. J Neurosci 2020; 41:674-688. [PMID: 33268542 DOI: 10.1523/jneurosci.1633-20.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 10/29/2020] [Accepted: 11/21/2020] [Indexed: 11/21/2022] Open
Abstract
The medial nucleus of trapezoid body (MNTB) is a major source of inhibition in auditory brainstem circuitry. The MNTB projects well-timed inhibitory output to principal sound-localization nuclei in the superior olive (SOC) as well as other computationally important centers. Acoustic information is conveyed to MNTB neurons through a single calyx of Held excitatory synapse arising from the cochlear nucleus. The encoding efficacy of this large synapse depends on its activity rate, which is primarily determined by sound intensity and stimulus frequency. However, MNTB activity rate is additionally influenced by inhibition and possibly neuromodulatory inputs, albeit their functional role is unclear. Happe and Morley (2004) discovered prominent expression of α7 nAChRs in rat SOC, suggesting possible engagement of ACh-mediated modulation of neural activity in the MNTB. However, the existence and nature of this putative modulation have never been physiologically demonstrated. We probed nicotinic cholinergic influences on acoustic responses of MNTB neurons from adult gerbils (Meriones unguiculatus) of either sex. We recorded tone-evoked MNTB single-neuron activity in vivo using extracellular single-unit recording. Piggyback multibarrel electrodes enabled pharmacological manipulation of nAChRs by reversibly applying antagonists to two receptor types, α7 and α4β2. We observed that tone-evoked responses are dependent on ACh modulation by both nAChR subtypes. Spontaneous activity was not affected by antagonist application. Functionally, we demonstrate that ACh contributes to sustaining high discharge rates and enhances signal encoding efficacy. Additionally, we report anatomic evidence revealing novel cholinergic projections to MNTB arising from pontine and superior olivary nuclei.SIGNIFICANCE STATEMENT This study is the first to physiologically probe how acetylcholine, a pervasive neuromodulator in the brain, influences the encoding of acoustic information by the medial nucleus of trapezoid body, the most prominent source of inhibition in brainstem sound-localization circuitry. We demonstrate that this cholinergic input enhances neural discrimination of tones from noise stimuli, which may contribute to processing important acoustic signals, such as speech. Additionally, we describe novel anatomic projections providing cholinergic input to the MNTB. Together, these findings shed new light on the contribution of neuromodulation to fundamental computational processes in auditory brainstem circuitry and to a more holistic understanding of modulatory influences in sensory processing.
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18
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Abstract
Being able to pick out particular sounds, such as speech, against a background of other sounds represents one of the key tasks performed by the auditory system. Understanding how this happens is important because speech recognition in noise is particularly challenging for older listeners and for people with hearing impairments. Central to this ability is the capacity of neurons to adapt to the statistics of sounds reaching the ears, which helps to generate noise-tolerant representations of sounds in the brain. In more complex auditory scenes, such as a cocktail party — where the background noise comprises other voices, sound features associated with each source have to be grouped together and segregated from those belonging to other sources. This depends on precise temporal coding and modulation of cortical response properties when attending to a particular speaker in a multi-talker environment. Furthermore, the neural processing underlying auditory scene analysis is shaped by experience over multiple timescales.
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19
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Fischl MJ, Weisz CJC. In Vitro Wedge Slice Preparation for Mimicking In Vivo Neuronal Circuit Connectivity. J Vis Exp 2020. [PMID: 32894269 DOI: 10.3791/61664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In vitro slice electrophysiology techniques measure single-cell activity with precise electrical and temporal resolution. Brain slices must be relatively thin to properly visualize and access neurons for patch-clamping or imaging, and in vitro examination of brain circuitry is limited to only what is physically present in the acute slice. To maintain the benefits of in vitro slice experimentation while preserving a larger portion of presynaptic nuclei, we developed a novel slice preparation. This "wedge slice" was designed for patch-clamp electrophysiology recordings to characterize the diverse monaural, sound-driven inputs to medial olivocochlear (MOC) neurons in the brainstem. These neurons receive their primary afferent excitatory and inhibitory inputs from neurons activated by stimuli in the contralateral ear and corresponding cochlear nucleus (CN). An asymmetrical brain slice was designed which is thickest in the rostro-caudal domain at the lateral edge of one hemisphere and then thins towards the lateral edge of the opposite hemisphere. This slice contains, on the thick side, the auditory nerve root conveying information about auditory stimuli to the brain, the intrinsic CN circuitry, and both the disynaptic excitatory and trisynaptic inhibitory afferent pathways that converge on contralateral MOC neurons. Recording is performed from MOC neurons on the thin side of the slice, where they are visualized using DIC optics for typical patch-clamp experiments. Direct stimulation of the auditory nerve is performed as it enters the auditory brainstem, allowing for intrinsic CN circuit activity and synaptic plasticity to occur at synapses upstream of MOC neurons. With this technique, one can mimic in vivo circuit activation as closely as possible within the slice. This wedge slice preparation is applicable to other brain circuits where circuit analyses would benefit from preservation of upstream connectivity and long-range inputs, in combination with the technical advantages of in vitro slice physiology.
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Affiliation(s)
- Matthew J Fischl
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH;
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20
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Rajaram E, Pagella S, Grothe B, Kopp-Scheinpflug C. Physiological and anatomical development of glycinergic inhibition in the mouse superior paraolivary nucleus following hearing onset. J Neurophysiol 2020; 124:471-483. [PMID: 32667247 DOI: 10.1152/jn.00053.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Neural circuits require balanced synaptic excitation and inhibition to ensure accurate neural computation. Our knowledge about the development and maturation of inhibitory synaptic inputs is less well developed than that concerning excitation. Here we describe the maturation of an inhibitory circuit within the mammalian auditory brainstem where counterintuitively, inhibition drives action potential firing of principal neurons. With the use of combined anatomical tracing and electrophysiological recordings from mice, neurons of the superior paraolivary nucleus (SPN) are shown to receive converging glycinergic input from at least four neurons of the medial nucleus of the trapezoid body (MNTB). These four axons formed 30.71 ± 2.72 (means ± SE) synaptic boutons onto each SPN neuronal soma, generating a total inhibitory conductance of 80 nS. Such strong inhibition drives the underlying postinhibitory rebound firing mechanism, which is a hallmark of SPN physiology. In contrast to inhibitory projections to the medial and lateral superior olives, the inhibitory projection to the SPN does not exhibit experience-dependent synaptic refinement following the onset of hearing. These findings emphasize that the development and function of neural circuits cannot be inferred from one synaptic target to another, even if both originate from the same neuron.NEW & NOTEWORTHY Neuronal activity regulates development and maturation of neural circuits. This activity can include spontaneous burst firing or firing elicited by sensory input during early development. For example, auditory brainstem circuits involved in sound localization require acoustically evoked activity to form properly. Here we show, that an inhibitory circuit, involved in processing sound offsets, gaps, and rhythmically modulated vocal communication signals, matures before the onset of acoustically evoked activity.
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Affiliation(s)
- Ezhilarasan Rajaram
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University, Munich, Germany
| | - Sara Pagella
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University, Munich, Germany
| | - Benedikt Grothe
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany
| | - Conny Kopp-Scheinpflug
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany
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21
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Liu J, Whiteway MR, Sheikhattar A, Butts DA, Babadi B, Kanold PO. Parallel Processing of Sound Dynamics across Mouse Auditory Cortex via Spatially Patterned Thalamic Inputs and Distinct Areal Intracortical Circuits. Cell Rep 2020; 27:872-885.e7. [PMID: 30995483 DOI: 10.1016/j.celrep.2019.03.069] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 10/24/2018] [Accepted: 03/18/2019] [Indexed: 12/17/2022] Open
Abstract
Natural sounds have rich spectrotemporal dynamics. Spectral information is spatially represented in the auditory cortex (ACX) via large-scale maps. However, the representation of temporal information, e.g., sound offset, is unclear. We perform multiscale imaging of neuronal and thalamic activity evoked by sound onset and offset in awake mouse ACX. ACX areas differed in onset responses (On-Rs) and offset responses (Off-Rs). Most excitatory L2/3 neurons show either On-Rs or Off-Rs, and ACX areas are characterized by differing fractions of On and Off-R neurons. Somatostatin and parvalbumin interneurons show distinct temporal dynamics, potentially amplifying Off-Rs. Functional network analysis shows that ACX areas contain distinct parallel onset and offset networks. Thalamic (MGB) terminals show either On-Rs or Off-Rs, indicating a thalamic origin of On and Off-R pathways. Thus, ACX areas spatially represent temporal features, and this representation is created by spatial convergence and co-activation of distinct MGB inputs and is refined by specific intracortical connectivity.
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Affiliation(s)
- Ji Liu
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Matthew R Whiteway
- Applied Mathematics and Statistics and Scientific Computation Program, University of Maryland, College Park, MD 20742, USA
| | - Alireza Sheikhattar
- Department of Electrical & Computer Engineering, University of Maryland, College Park, MD 20742, USA
| | - Daniel A Butts
- Department of Biology, University of Maryland, College Park, MD 20742, USA; Applied Mathematics and Statistics and Scientific Computation Program, University of Maryland, College Park, MD 20742, USA; Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA
| | - Behtash Babadi
- Department of Electrical & Computer Engineering, University of Maryland, College Park, MD 20742, USA
| | - Patrick O Kanold
- Department of Biology, University of Maryland, College Park, MD 20742, USA; Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA.
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22
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Weible AP, Yavorska I, Wehr M. A Cortico-Collicular Amplification Mechanism for Gap Detection. Cereb Cortex 2020; 30:3590-3607. [PMID: 32055848 DOI: 10.1093/cercor/bhz328] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Auditory cortex (AC) is necessary for the detection of brief gaps in ongoing sounds, but not for the detection of longer gaps or other stimuli such as tones or noise. It remains unclear why this is so, and what is special about brief gaps in particular. Here, we used both optogenetic suppression and conventional lesions to show that the cortical dependence of brief gap detection hinges specifically on gap termination. We then identified a cortico-collicular gap detection circuit that amplifies cortical gap termination responses before projecting to inferior colliculus (IC) to impact behavior. We found that gaps evoked off-responses and on-responses in cortical neurons, which temporally overlapped for brief gaps, but not long gaps. This overlap specifically enhanced cortical responses to brief gaps, whereas IC neurons preferred longer gaps. Optogenetic suppression of AC reduced collicular responses specifically to brief gaps, indicating that under normal conditions, the enhanced cortical representation of brief gaps amplifies collicular gap responses. Together these mechanisms explain how and why AC contributes to the behavioral detection of brief gaps, which are critical cues for speech perception, perceptual grouping, and auditory scene analysis.
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Affiliation(s)
- Aldis P Weible
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Iryna Yavorska
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Michael Wehr
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
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23
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Chien VSC, Maess B, Knösche TR. A generic deviance detection principle for cortical On/Off responses, omission response, and mismatch negativity. BIOLOGICAL CYBERNETICS 2019; 113:475-494. [PMID: 31428855 PMCID: PMC6848254 DOI: 10.1007/s00422-019-00804-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 08/07/2019] [Indexed: 05/04/2023]
Abstract
Neural responses to sudden changes can be observed in many parts of the sensory pathways at different organizational levels. For example, deviants that violate regularity at various levels of abstraction can be observed as simple On/Off responses of individual neurons or as cumulative responses of neural populations. The cortical deviance-related responses supporting different functionalities (e.g., gap detection, chunking, etc.) seem unlikely to arise from different function-specific neural circuits, given the relatively uniform and self-similar wiring patterns across cortical areas and spatial scales. Additionally, reciprocal wiring patterns (with heterogeneous combinations of excitatory and inhibitory connections) in the cortex naturally speak in favor of a generic deviance detection principle. Based on this concept, we propose a network model consisting of reciprocally coupled neural masses as a blueprint of a universal change detector. Simulation examples reproduce properties of cortical deviance-related responses including the On/Off responses, the omitted-stimulus response (OSR), and the mismatch negativity (MMN). We propose that the emergence of change detectors relies on the involvement of disinhibition. An analysis of network connection settings further suggests a supportive effect of synaptic adaptation and a destructive effect of N-methyl-D-aspartate receptor (NMDA-r) antagonists on change detection. We conclude that the nature of cortical reciprocal wiring gives rise to a whole range of local change detectors supporting the notion of a generic deviance detection principle. Several testable predictions are provided based on the network model. Notably, we predict that the NMDA-r antagonists would generally dampen the cortical Off response, the cortical OSR, and the MMN.
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Affiliation(s)
- Vincent S. C. Chien
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, Leipzig, Germany
| | - Burkhard Maess
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, Leipzig, Germany
| | - Thomas R. Knösche
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, Leipzig, Germany
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Yin TC, Smith PH, Joris PX. Neural Mechanisms of Binaural Processing in the Auditory Brainstem. Compr Physiol 2019; 9:1503-1575. [DOI: 10.1002/cphy.c180036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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25
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Alternative classifications of neurons based on physiological properties and synaptic responses, a computational study. Sci Rep 2019; 9:13096. [PMID: 31511545 PMCID: PMC6739481 DOI: 10.1038/s41598-019-49197-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 08/16/2019] [Indexed: 01/25/2023] Open
Abstract
One of the central goals of today's neuroscience is to achieve the conceivably most accurate classification of neuron types in the mammalian brain. As part of this research effort, electrophysiologists commonly utilize current clamp techniques to gain a detailed characterization of the neurons' physiological properties. While this approach has been useful, it is not well understood whether neurons that share physiological properties of a particular phenotype would also operate consistently under the action of natural synaptic inputs. We approached this problem by simulating a biophysically diverse population of model neurons based on 3 generic phenotypes. We exposed the model neurons to two types of stimulation to investigate their voltage responses under conventional current step protocols and under simulated synaptic bombardment. We extracted standard physiological parameters from the voltage responses elicited by current step stimulation and spike arrival times descriptive of the model's firing behavior under synaptic inputs. The biophysical phenotypes could be reliably identified using classification based on the 'static' physiological properties, but not the interspike interval-based parameters. However, the model neurons associated with the biophysically different phenotypes retained cell type specific features in the fine structure of their spike responses that allowed their accurate classification.
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Slow NMDA-Mediated Excitation Accelerates Offset-Response Latencies Generated via a Post-Inhibitory Rebound Mechanism. eNeuro 2019; 6:ENEURO.0106-19.2019. [PMID: 31152098 PMCID: PMC6584069 DOI: 10.1523/eneuro.0106-19.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/17/2019] [Accepted: 05/02/2019] [Indexed: 01/03/2023] Open
Abstract
In neural circuits, action potentials (spikes) are conventionally caused by excitatory inputs whereas inhibitory inputs reduce or modulate neuronal excitability. We previously showed that neurons in the superior paraolivary nucleus (SPN) require solely synaptic inhibition to generate their hallmark offset response, a burst of spikes at the end of a sound stimulus, via a post-inhibitory rebound mechanism. In addition SPN neurons receive excitatory inputs, but their functional significance is not yet known. Here we used mice of both sexes to demonstrate that in SPN neurons, the classical roles for excitation and inhibition are switched, with inhibitory inputs driving spike firing and excitatory inputs modulating this response. Hodgkin–Huxley modeling suggests that a slow, NMDA receptor (NMDAR)-mediated excitation would accelerate the offset response. We find corroborating evidence from in vitro and in vivo recordings that lack of excitation prolonged offset-response latencies and rendered them more variable to changing sound intensity levels. Our results reveal an unsuspected function for slow excitation in improving the timing of post-inhibitory rebound firing even when the firing itself does not depend on excitation. This shows the auditory system employs highly specialized mechanisms to encode timing-sensitive features of sound offsets which are crucial for sound-duration encoding and have profound biological importance for encoding the temporal structure of speech.
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Fu Z, Xu N, Zhang G, Zhou D, Liu L, Tang J, Jen PHS, Chen Q. Evoked potential study of the inferior collicular response to constant frequency-frequency modulation (CF-FM) sounds in FM and CF-FM bats. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:239-252. [DOI: 10.1007/s00359-019-01326-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 02/26/2019] [Accepted: 02/28/2019] [Indexed: 12/20/2022]
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Garand D, Mahadevan V, Woodin MA. Ionotropic and metabotropic kainate receptor signalling regulates Cl - homeostasis and GABAergic inhibition. J Physiol 2019; 597:1677-1690. [PMID: 30570751 PMCID: PMC6418771 DOI: 10.1113/jp276901] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 12/19/2018] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS Potassium-chloride co-transporter 2 (KCC2) plays a critical role in regulating chloride homeostasis, which is essential for hyperpolarizing inhibition in the mature nervous system. KCC2 interacts with many proteins involved in excitatory neurotransmission, including the GluK2 subunit of the kainate receptor (KAR). We show that activation of KARs hyperpolarizes the reversal potential for GABA (EGABA ) via both ionotropic and metabotropic signalling mechanisms. KCC2 is required for the metabotropic KAR-mediated regulation of EGABA , although ionotropic KAR signalling can hyperpolarize EGABA independent of KCC2 transporter function. The KAR-mediated hyperpolarization of EGABA is absent in the GluK1/2-/- mouse and is independent of zinc release from mossy fibre terminals. The ability of KARs to regulate KCC2 function may have implications in diseases with disrupted excitation: inhibition balance, such as epilepsy, neuropathic pain, autism spectrum disorders and Down's syndrome. ABSTRACT Potassium-chloride co-transporter 2 (KCC2) plays a critical role in the regulation of chloride (Cl- ) homeostasis within mature neurons. KCC2 is a secondarily active transporter that extrudes Cl- from the neuron, which maintains a low intracellular Cl- concentration [Cl- ]. This results in a hyperpolarized reversal potential of GABA (EGABA ), which is required for fast synaptic inhibition in the mature central nervous system. KCC2 also plays a structural role in dendritic spines and at excitatory synapses, and interacts with 'excitatory' proteins, including the GluK2 subunit of kainate receptors (KARs). KARs are glutamate receptors that display both ionotropic and metabotropic signalling. We show that activating KARs in the hippocampus hyperpolarizes EGABA , thus strengthening inhibition. This hyperpolarization occurs via both ionotropic and metabotropic KAR signalling in the CA3 region, whereas it is absent in the GluK1/2-/- mouse, and is independent of zinc release from mossy fibre terminals. The metabotropic signalling mechanism is dependent on KCC2, although the ionotropic signalling mechanism produces a hyperpolarization of EGABA even in the absence of KCC2 transporter function. These results demonstrate a novel functional interaction between a glutamate receptor and KCC2, a transporter critical for maintaining inhibition, suggesting that the KAR:KCC2 complex may play an important role in excitatory:inhibitory balance in the hippocampus. Additionally, the ability of KARs to regulate chloride homeostasis independently of KCC2 suggests that KAR signalling can regulate inhibition via multiple mechanisms. Activation of kainate-type glutamate receptors could serve as an important mechanism for increasing the strength of inhibition during periods of strong glutamatergic activity.
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MESH Headings
- Animals
- CA1 Region, Hippocampal/cytology
- CA1 Region, Hippocampal/metabolism
- CA1 Region, Hippocampal/physiology
- CA3 Region, Hippocampal/cytology
- CA3 Region, Hippocampal/metabolism
- CA3 Region, Hippocampal/physiology
- Cells, Cultured
- Chlorides/metabolism
- Female
- Homeostasis
- Inhibitory Postsynaptic Potentials
- Male
- Mice
- Mice, Inbred C57BL
- Mossy Fibers, Hippocampal/metabolism
- Mossy Fibers, Hippocampal/physiology
- Pyramidal Cells/metabolism
- Pyramidal Cells/physiology
- Receptors, GABA/metabolism
- Receptors, Kainic Acid/metabolism
- Symporters/metabolism
- K Cl- Cotransporters
- GluK2 Kainate Receptor
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Affiliation(s)
- Danielle Garand
- Department of Cell and Systems BiologyUniversity of TorontoTorontoONCanada
| | - Vivek Mahadevan
- Department of Cell and Systems BiologyUniversity of TorontoTorontoONCanada
| | - Melanie A. Woodin
- Department of Cell and Systems BiologyUniversity of TorontoTorontoONCanada
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Joris PX, Trussell LO. The Calyx of Held: A Hypothesis on the Need for Reliable Timing in an Intensity-Difference Encoder. Neuron 2018; 100:534-549. [PMID: 30408442 PMCID: PMC6263157 DOI: 10.1016/j.neuron.2018.10.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 08/16/2018] [Accepted: 10/15/2018] [Indexed: 12/18/2022]
Abstract
The calyx of Held is the preeminent model for the study of synaptic function in the mammalian CNS. Despite much work on the synapse and associated circuit, its role in hearing remains enigmatic. We propose that the calyx is one of the key adaptations that enables an animal to lateralize transient sounds. The calyx is part of a binaural circuit that is biased toward high sound frequencies and is sensitive to intensity differences between the ears. This circuit also shows marked sensitivity to interaural time differences, but only for brief sound transients ("clicks"). In a natural environment, such transients are rare except as adventitious sounds generated by other animals moving at close range. We argue that the calyx, and associated temporal specializations, evolved to enable spatial localization of sound transients, through a neural code congruent with the circuit's sensitivity to interaural intensity differences, thereby conferring a key benefit to survival.
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Affiliation(s)
- Philip X Joris
- Laboratory of Auditory Neurophysiology, Department of Neurosciences, University of Leuven, Leuven B-3000, Belgium.
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
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30
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Kopp-Scheinpflug C, Sinclair JL, Linden JF. When Sound Stops: Offset Responses in the Auditory System. Trends Neurosci 2018; 41:712-728. [DOI: 10.1016/j.tins.2018.08.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 07/30/2018] [Accepted: 08/10/2018] [Indexed: 11/17/2022]
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31
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Cordshagen A, Busch W, Winklhofer M, Nothwang HG, Hartmann AM. Phosphoregulation of the intracellular termini of K +-Cl - cotransporter 2 (KCC2) enables flexible control of its activity. J Biol Chem 2018; 293:16984-16993. [PMID: 30201606 DOI: 10.1074/jbc.ra118.004349] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/01/2018] [Indexed: 12/22/2022] Open
Abstract
The pivotal role of K+-Cl- cotransporter 2 (KCC2) in inhibitory neurotransmission and severe human diseases fosters interest in understanding posttranslational regulatory mechanisms such as (de)phosphorylation. Here, the regulatory role of the five bona fide phosphosites Ser31, Thr34, Ser932, Thr999, and Thr1008 was investigated by the use of alanine and aspartate mutants. Tl+-based flux analyses in HEK-293 cells demonstrated increased transport activity for S932D (mimicking phosphorylation) and T1008A (mimicking dephosphorylation), albeit to a different extent. Increased activity was due to changes in intrinsic activity, as it was not caused by increased cell-surface abundance. Substitutions of Ser31, Thr34, or Thr999 had no effect. Additionally, we show that the indirect actions of the known KCC2 activators staurosporine and N-ethylmaleimide (NEM) involved multiple phosphosites. S31D, T34A, S932A/D, T999A, or T1008A/D abrogated staurosporine mediated stimulation, and S31A, T34D, or S932D abolished NEM-mediated stimulation. This demonstrates for the first time differential effects of staurosporine and NEM on KCC2. In addition, the staurosporine-mediated effects involved both KCC2 phosphorylation and dephosphorylation with Ser932 and Thr1008 being bona fide target sites. In summary, our data reveal a complex phosphoregulation of KCC2 that provides the transporter with a toolbox for graded activity and integration of different signaling pathways.
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Affiliation(s)
- Antje Cordshagen
- From the Neurogenetics group, Center of Excellence Hearing4all, School of Medicine and Health Sciences
| | - Wiebke Busch
- From the Neurogenetics group, Center of Excellence Hearing4all, School of Medicine and Health Sciences
| | - Michael Winklhofer
- Institute for Biology and Environmental Sciences IBU, and.,Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Hans Gerd Nothwang
- From the Neurogenetics group, Center of Excellence Hearing4all, School of Medicine and Health Sciences.,Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Anna-Maria Hartmann
- From the Neurogenetics group, Center of Excellence Hearing4all, School of Medicine and Health Sciences, .,Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
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32
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Gjoni E, Aguet C, Sahlender DA, Knott G, Schneggenburger R. Ultrastructural basis of strong unitary inhibition in a binaural neuron. J Physiol 2018; 596:4969-4982. [PMID: 30054922 DOI: 10.1113/jp276015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 07/18/2018] [Indexed: 12/15/2022] Open
Abstract
KEY POINTS Neurons of the lateral superior olive (LSO) in the brainstem receive powerful glycinergic inhibition that originates from the contralateral ear, and that plays an important role in sound localization. We investigated the ultrastructural basis for strong inhibition of LSO neurons using serial block face scanning electron microscopy. The soma and the proximal dendrite of an LSO neuron are surrounded by a high density of inhibitory axons, whereas excitatory axons are much sparser. A given inhibitory axon establishes contacts via several large axonal thickenings, called varicosities, which typically elaborate several active zones (range 1-11). The number of active zones across inhibitory axon segments is variable. These data thus provide an ultrastructural correlate for the strong and multiquantal, but overall variable, unitary IPSC amplitude observed for inhibitory inputs to LSO neuron. ABSTRACT Binaural neurons in the lateral superior olive (LSO) integrate sound information arriving from each ear, and powerful glycinergic inhibition of these neurons plays an important role in this process. In the present study, we investigated the ultrastructural basis for strong inhibitory inputs onto LSO neurons using serial block face scanning electron microscopy. We reconstructed axon segments that make contact with the partially reconstructed soma and proximal dendrite of a mouse LSO neuron at postnatal day 18. Using functional measurements and the Sr2+ method, we find a constant quantal size but a variable quantal content between 'weak' and 'strong' unitary IPSCs. A 3-D reconstruction of a LSO neuron and its somatic synaptic afferents reveals how a large number of inhibitory axons intermingle in a complex fashion on the soma and proximal dendrite of an LSO neuron; a smaller number of excitatory axons was also observed. A given inhibitory axon typically contacts an LSO neuron via several large varicosities (average diameter 3.7 μm), which contain several active zones (range 1-11). The number of active zones across individual axon segments was highly variable. These data suggest that the variable unitary IPSC amplitude is caused by a variable number of active zones between inhibitory axons that innervate a given LSO neuron. The results of the present study show that relatively large multi-active zone varicosities, which can be repeated many times in a given presynaptic axon, provide the ultrastructural basis for the strong multiquantal inhibition received by LSO neurons.
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Affiliation(s)
- Enida Gjoni
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Clémentine Aguet
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Master's Program Life Science and Technology, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Daniela A Sahlender
- Bioelectron Microscopy Core Facility, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Graham Knott
- Bioelectron Microscopy Core Facility, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ralf Schneggenburger
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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Gjoni E, Zenke F, Bouhours B, Schneggenburger R. Specific synaptic input strengths determine the computational properties of excitation-inhibition integration in a sound localization circuit. J Physiol 2018; 596:4945-4967. [PMID: 30051910 DOI: 10.1113/jp276012] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 07/18/2018] [Indexed: 02/03/2023] Open
Abstract
KEY POINTS During the computation of sound localization, neurons of the lateral superior olive (LSO) integrate synaptic excitation arising from the ipsilateral ear with inhibition from the contralateral ear. We characterized the functional connectivity of the inhibitory and excitatory inputs onto LSO neurons in terms of unitary synaptic strength and convergence. Unitary IPSCs can generate large conductances, although their strength varies over a 10-fold range in a given recording. By contrast, excitatory inputs are relatively weak. The conductance associated with IPSPs needs to be at least 2-fold stronger than the excitatory one to guarantee effective inhibition of action potential (AP) firing. Computational modelling showed that strong unitary inhibition ensures an appropriate slope and midpoint of the tuning curve of LSO neurons. Conversely, weak but numerous excitatory inputs filter out spontaneous AP firing from upstream auditory neurons. ABSTRACT The lateral superior olive (LSO) is a binaural nucleus in the auditory brainstem in which excitation from the ipsilateral ear is integrated with inhibition from the contralateral ear. It is unknown whether the strength of the unitary inhibitory and excitatory inputs is adapted to allow for optimal tuning curves of LSO neuron action potential (AP) firing. Using electrical and optogenetic stimulation of afferent synapses, we found that the strength of unitary inhibitory inputs to a given LSO neuron can vary over a ∼10-fold range, follows a roughly log-normal distribution, and, on average, causes a large conductance (9 nS). Conversely, unitary excitatory inputs, stimulated optogenetically under the bushy-cell specific promoter Math5, were numerous, and each caused a small conductance change (0.7 nS). Approximately five to seven bushy cell inputs had to be active simultaneously to bring an LSO neuron to fire. In double stimulation experiments, the effective inhibition window caused by IPSPs was short (1-3 ms) and its length depended on the inhibitory conductance; an ∼2-fold stronger inhibition than excitation was needed to suppress AP firing. Computational modelling suggests that few, but strong, unitary IPSPs create a tuning curve of LSO neuron firing with an appropriate slope and midpoint. Furthermore, weak but numerous excitatory inputs reduce the spontaneous AP firing that LSO neurons would otherwise inherit from their upstream auditory neurons. Thus, the specific connectivity and strength of unitary excitatory and inhibitory inputs to LSO neurons is optimized for the computations performed by these binaural neurons.
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Affiliation(s)
- Enida Gjoni
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Friedemann Zenke
- Laboratory of Computational Neuroscience, Brain Mind Institute, School of Life Science and School of Computer and Communication Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Centre for Neural Circuits and Behaviour, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Brice Bouhours
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ralf Schneggenburger
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Science, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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Gómez-Álvarez M, Gourévitch B, Felix RA, Nyberg T, Hernández-Montiel HL, Magnusson AK. Temporal information in tones, broadband noise, and natural vocalizations is conveyed by differential spiking responses in the superior paraolivary nucleus. Eur J Neurosci 2018; 48:2030-2049. [PMID: 30019495 DOI: 10.1111/ejn.14073] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/12/2018] [Accepted: 06/26/2018] [Indexed: 12/31/2022]
Abstract
Communication sounds across all mammals consist of multiple frequencies repeated in sequence. The onset and offset of vocalizations are potentially important cues for recognizing distinct units, such as phonemes and syllables, which are needed to perceive meaningful communication. The superior paraolivary nucleus (SPON) in the auditory brainstem has been implicated in the processing of rhythmic sounds. Here, we compared how best frequency tones (BFTs), broadband noise (BBN), and natural mouse calls elicit onset and offset spiking in the mouse SPON. The results demonstrate that onset spiking typically occurs in response to BBN, but not BFT stimulation, while spiking at the sound offset occurs for both stimulus types. This effect of stimulus bandwidth on spiking is consistent with two of the established inputs to the SPON from the octopus cells (onset spiking) and medial nucleus of the trapezoid body (offset spiking). Natural mouse calls elicit two main spiking peaks. The first spiking peak, which is weak or absent with BFT stimulation, occurs most consistently during the call envelope, while the second spiking peak occurs at the call offset. This suggests that the combined spiking activity in the SPON elicited by vocalizations reflects the entire envelope, that is, the coarse amplitude waveform. Since the output from the SPON is purely inhibitory, it is speculated that, at the level of the inferior colliculus, the broadly tuned first peak may improve the signal-to-noise ratio of the subsequent, more call frequency-specific peak. Thus, the SPON may provide a dual inhibition mechanism for tracking phonetic boundaries in social-vocal communication.
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Affiliation(s)
- Marcelo Gómez-Álvarez
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Boris Gourévitch
- Unité de Génétique et Physiologie de l'Audition, INSERM, Institut Pasteur, Sorbonne Université Paris, Paris, France.,CNRS, Paris, France
| | | | - Tobias Nyberg
- Division of Neuronic Engineering, Department of Biomedical Engineering and Health Systems, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Hebert L Hernández-Montiel
- Laboratorio de Neurobiología y Bioingeniería Celular, Clínica del Sistema Nervioso, Universidad Autónoma de Querétaro, Santiago de Querétaro, México
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
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35
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Yin XL, Jie HQ, Liang M, Gong LN, Liu HW, Pan HL, Xing YZ, Shi HB, Li CY, Wang LY, Yin SK. Accelerated Development of the First-Order Central Auditory Neurons With Spontaneous Activity. Front Mol Neurosci 2018; 11:183. [PMID: 29904342 PMCID: PMC5990604 DOI: 10.3389/fnmol.2018.00183] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 05/11/2018] [Indexed: 11/24/2022] Open
Abstract
In developing sensory systems, elaborate morphological connectivity between peripheral cells and first-order central neurons emerges via genetic programming before the onset of sensory activities. However, how the first-order central neurons acquire the capacity to interface with peripheral cells remains elusive. By making patch-clamp recordings from mouse brainstem slices, we found that a subset of neurons in the cochlear nuclei, the first central station to receive peripheral acoustic impulses, exhibits spontaneous firings (SFs) as early as at birth, and the fraction of such neurons increases during the prehearing period. SFs are reduced but not eliminated by a cocktail of blockers for excitatory and inhibitory synaptic inputs, implicating the involvement of intrinsic pacemaker channels. Furthermore, we demonstrate that these intrinsic firings (IFs) are largely driven by hyperpolarization- and cyclic nucleotide-gated channel (HCN) mediated currents (Ih), as evidenced by their attenuation in the presence of HCN blockers or in neurons from HCN1 knockout mice. Interestingly, genetic deletion of HCN1 cannot be fully compensated by other pacemaker conductances and precludes age-dependent up regulation in the fraction of spontaneous active neurons and their firing rate. Surprisingly, neurons with SFs show accelerated development in excitability, spike waveform and firing pattern as well as synaptic pruning towards mature phenotypes compared to those without SFs. Our results imply that SFs of the first-order central neurons may reciprocally promote their wiring and firing with peripheral inputs, potentially enabling the correlated activity and crosstalk between the developing brain and external environment.
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Affiliation(s)
- Xin-Lu Yin
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Hui-Qun Jie
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Min Liang
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Li-Na Gong
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Han-Wei Liu
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Hao-Lai Pan
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Ya-Zhi Xing
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Hai-Bo Shi
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Chun-Yan Li
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Lu-Yang Wang
- Programs in Neurosciences & Mental Health, Department of Physiology, Sick Kids Research Institute, Toronto, ON, Canada
| | - Shan-Kai Yin
- Department of Otorhinolaryngology, The Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
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36
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Beiderbeck B, Myoga MH, Müller NIC, Callan AR, Friauf E, Grothe B, Pecka M. Precisely timed inhibition facilitates action potential firing for spatial coding in the auditory brainstem. Nat Commun 2018; 9:1771. [PMID: 29720589 PMCID: PMC5932051 DOI: 10.1038/s41467-018-04210-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 04/10/2018] [Indexed: 01/06/2023] Open
Abstract
The integration of excitatory and inhibitory synaptic inputs is fundamental to neuronal processing. In the mammalian auditory brainstem, neurons compare excitatory and inhibitory inputs from the ipsilateral and contralateral ear, respectively, for sound localization. However, the temporal precision and functional roles of inhibition in this integration process are unclear. Here, we demonstrate by in vivo recordings from the lateral superior olive (LSO) that inhibition controls spiking with microsecond precision throughout high frequency click trains. Depending on the relative timing of excitation and inhibition, neuronal spike probability is either suppressed or-unexpectedly-facilitated. In vitro conductance-clamp LSO recordings establish that a reduction in the voltage threshold for spike initiation due to a prior hyperpolarization results in post-inhibitory facilitation of otherwise sub-threshold synaptic events. Thus, microsecond-precise differences in the arrival of inhibition relative to excitation can facilitate spiking in the LSO, thereby promoting spatial sensitivity during the processing of faint sounds.
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Affiliation(s)
- Barbara Beiderbeck
- Department Biology II, Division of Neurobiology, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany
| | - Michael H Myoga
- Department Biology II, Division of Neurobiology, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany.,Max Planck Institute of Neurobiology, Am Klopferspitz 18, Martinsried, 82152, Germany
| | - Nicolas I C Müller
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Kaiserslautern, D-67653, Germany
| | - Alexander R Callan
- Department Biology II, Division of Neurobiology, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany
| | - Eckhard Friauf
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Kaiserslautern, D-67653, Germany
| | - Benedikt Grothe
- Department Biology II, Division of Neurobiology, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany. .,Max Planck Institute of Neurobiology, Am Klopferspitz 18, Martinsried, 82152, Germany.
| | - Michael Pecka
- Department Biology II, Division of Neurobiology, Ludwig-Maximilians-Universitaet Munich, Planegg-Martinsried, D-82152, Germany.
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37
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Tonotopic Variation of the T-Type Ca 2+ Current in Avian Auditory Coincidence Detector Neurons. J Neurosci 2017; 38:335-346. [PMID: 29167400 DOI: 10.1523/jneurosci.2237-17.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 11/13/2017] [Accepted: 11/14/2017] [Indexed: 12/29/2022] Open
Abstract
Neurons in avian nucleus laminaris (NL) are binaural coincidence detectors for sound localization and are characterized by striking structural variations in dendrites and axon initial segment (AIS) according to their acoustic tuning [characteristic frequency (CF)]. T-type Ca2+ (CaT) channels regulate synaptic integration and firing behavior at these neuronal structures. However, whether or how CaT channels contribute to the signal processing in NL neurons is not known. In this study, we addressed this issue with whole-cell recording and two-photon Ca2+ imaging in brain slices of posthatch chicks of both sexes. We found that the CaT current was prominent in low-CF neurons, whereas it was almost absent in higher-CF neurons. In addition, a large Ca2+ transient occurred at the dendrites and the AIS of low-CF neurons, indicating a localization of CaT channels at these structures in the neurons. Because low-CF neurons have long dendrites, dendritic CaT channels may compensate for the attenuation of EPSPs at dendrites. Furthermore, the short distance of AIS from the soma may accelerate activation of axonal CaT current in the neurons and help EPSPs reach spike threshold. Indeed, the CaT current was activated by EPSPs and augmented the synaptic response and spike generation of the neurons. Notably, the CaT current was inactivated during repetitive inputs, and these augmenting effects predominated at the initial phase of synaptic activity. These results suggested that dendritic and axonal CaT channels increase the sensitivity to sound at its onset, which may expand the dynamic range for binaural computation in low-CF NL neurons.SIGNIFICANCE STATEMENT Neurons in nucleus laminaris are binaural coincidence detectors for sound localization. We report that T-type Ca2+ (CaT) current was prominent at dendrites and the axonal trigger zone in neurons tuned to low-frequency sound. Because these neurons have long dendrites and a closer trigger zone compared with those tuned to higher-frequency sound, the CaT current augmented EPSPs at dendrites and accelerated spike triggers in the neurons, implying a strategic arrangement of the current within the nucleus. This effect was limited to the onset of repetitive inputs due to progressive inactivation of CaT current. The results suggested that the CaT current increases the sensitivity to sound at its onset, which may expand the dynamic range for binaural computation of low-frequency sound.
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38
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Ebbers L, Weber M, Nothwang HG. Activity-dependent formation of a vesicular inhibitory amino acid transporter gradient in the superior olivary complex of NMRI mice. BMC Neurosci 2017; 18:75. [PMID: 29073893 PMCID: PMC5659004 DOI: 10.1186/s12868-017-0393-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 10/13/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In the mammalian superior olivary complex (SOC), synaptic inhibition contributes to the processing of binaural sound cues important for sound localization. Previous analyses demonstrated a tonotopic gradient for postsynaptic proteins mediating inhibitory neurotransmission in the lateral superior olive (LSO), a major nucleus of the SOC. To probe, whether a presynaptic molecular gradient exists as well, we investigated immunoreactivity against the vesicular inhibitory amino acid transporter (VIAAT) in the mouse auditory brainstem. RESULTS Immunoreactivity against VIAAT revealed a gradient in the LSO and the superior paraolivary nucleus (SPN) of NMRI mice, with high expression in the lateral, low frequency processing limb and low expression in the medial, high frequency processing limb of both nuclei. This orientation is opposite to the previously reported gradient of glycine receptors in the LSO. Other nuclei of the SOC showed a uniform distribution of VIAAT-immunoreactivity. No gradient was observed for the glycine transporter GlyT2 and the neuronal protein NeuN. Formation of the VIAAT gradient was developmentally regulated and occurred around hearing-onset between postnatal days 8 and 16. Congenital deaf Claudin14 -/- mice bred on an NMRI background showed a uniform VIAAT-immunoreactivity in the LSO, whereas cochlear ablation in NMRI mice after hearing-onset did not affect the gradient. Additional analysis of C57Bl6/J, 129/SvJ and CBA/J mice revealed a strain-specific formation of the gradient. CONCLUSIONS Our results identify an activity-regulated gradient of VIAAT in the SOC of NRMI mice. Its absence in other mouse strains adds a novel layer of strain-specific features in the auditory system, i.e. tonotopic organization of molecular gradients. This calls for caution when comparing data from different mouse strains frequently used in studies involving transgenic animals. The presence of strain-specific differences offers the possibility of genetic mapping to identify molecular factors involved in activity-dependent developmental processes in the auditory system. This would provide an important step forward concerning improved auditory rehabilitation in cases of congenital deafness.
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Affiliation(s)
- Lena Ebbers
- Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Maren Weber
- Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Hans Gerd Nothwang
- Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
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39
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Oertel D, Cao XJ, Ison JR, Allen PD. Cellular Computations Underlying Detection of Gaps in Sounds and Lateralizing Sound Sources. Trends Neurosci 2017; 40:613-624. [PMID: 28867348 DOI: 10.1016/j.tins.2017.08.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/02/2017] [Accepted: 08/07/2017] [Indexed: 11/29/2022]
Abstract
In mammals, acoustic information arises in the cochlea and is transmitted to the ventral cochlear nuclei (VCN). Three groups of VCN neurons extract different features from the firing of auditory nerve fibers and convey that information along separate pathways through the brainstem. Two of these pathways process temporal information: octopus cells detect coincident firing among auditory nerve fibers and transmit signals along monaural pathways, and bushy cells sharpen the encoding of fine structure and feed binaural pathways. The ability of these cells to signal with temporal precision depends on a low-voltage-activated K+ conductance (gKL) and a hyperpolarization-activated conductance (gh). This 'tale of two conductances' traces gap detection and sound lateralization to their cellular and biophysical origins.
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Affiliation(s)
- Donata Oertel
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705 USA.
| | - Xiao-Jie Cao
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705 USA
| | - James R Ison
- Department of Brain and Cognitive Sciences, Meliora Hall, University of Rochester, Rochester, NY 14627, USA; Department of Neuroscience, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Paul D Allen
- Department of Otolaryngology, University of Rochester Medical Center, Rochester, NY 14642, USA
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40
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Felix Ii RA, Gourévitch B, Gómez-Álvarez M, Leijon SCM, Saldaña E, Magnusson AK. Octopus Cells in the Posteroventral Cochlear Nucleus Provide the Main Excitatory Input to the Superior Paraolivary Nucleus. Front Neural Circuits 2017; 11:37. [PMID: 28620283 PMCID: PMC5449481 DOI: 10.3389/fncir.2017.00037] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 05/19/2017] [Indexed: 12/26/2022] Open
Abstract
Auditory streaming enables perception and interpretation of complex acoustic environments that contain competing sound sources. At early stages of central processing, sounds are segregated into separate streams representing attributes that later merge into acoustic objects. Streaming of temporal cues is critical for perceiving vocal communication, such as human speech, but our understanding of circuits that underlie this process is lacking, particularly at subcortical levels. The superior paraolivary nucleus (SPON), a prominent group of inhibitory neurons in the mammalian brainstem, has been implicated in processing temporal information needed for the segmentation of ongoing complex sounds into discrete events. The SPON requires temporally precise and robust excitatory input(s) to convey information about the steep rise in sound amplitude that marks the onset of voiced sound elements. Unfortunately, the sources of excitation to the SPON and the impact of these inputs on the behavior of SPON neurons have yet to be resolved. Using anatomical tract tracing and immunohistochemistry, we identified octopus cells in the contralateral cochlear nucleus (CN) as the primary source of excitatory input to the SPON. Cluster analysis of miniature excitatory events also indicated that the majority of SPON neurons receive one type of excitatory input. Precise octopus cell-driven onset spiking coupled with transient offset spiking make SPON responses well-suited to signal transitions in sound energy contained in vocalizations. Targets of octopus cell projections, including the SPON, are strongly implicated in the processing of temporal sound features, which suggests a common pathway that conveys information critical for perception of complex natural sounds.
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Affiliation(s)
- Richard A Felix Ii
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
| | - Boris Gourévitch
- Institut Pasteur, Unité de Génétique et Physiologie de l'AuditionParis, France.,Institut National de la Santé et de la Recherche Médicale, UMRS 1120Paris, France.,Université Pierre et Marie CurieParis, France
| | - Marcelo Gómez-Álvarez
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden.,Neuroscience Institute of Castilla y León (INCyL), Universidad de SalamancaSalamanca, Spain.,Institute of Biomedical Research of Salamanca (IBSAL)Salamanca, Spain
| | - Sara C M Leijon
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
| | - Enrique Saldaña
- Neuroscience Institute of Castilla y León (INCyL), Universidad de SalamancaSalamanca, Spain.,Institute of Biomedical Research of Salamanca (IBSAL)Salamanca, Spain
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
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41
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Modeling Responses in the Superior Paraolivary Nucleus: Implications for Forward Masking in the Inferior Colliculus. J Assoc Res Otolaryngol 2017; 18:441-456. [PMID: 28097439 DOI: 10.1007/s10162-016-0612-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 12/20/2016] [Indexed: 12/19/2022] Open
Abstract
A phenomenological model of the responses of neurons in the superior paraolivary nucleus (SPON) of the rodent is presented in this study. Pure tones at the characteristic frequency (CF) and broadband noise stimuli evoke offset-type responses in these neurons. SPON neurons also phase-lock to the envelope of sinusoidally amplitude-modulated (SAM) stimuli for a range of modulation frequencies. Model SPON neuron received inhibitory input that was relayed by the ipsilateral medial nucleus of the trapezoid body from the contralateral model ventral cochlear nucleus neuron. The SPON model response was simulated by detecting the slope of its inhibitory postsynaptic potential. Responses of the proposed model to pure tones at CF and broadband noise were offset-type independent of the duration of the input stimulus. SPON model responses were also synchronized to the envelope of SAM stimuli with precise timing for a range of modulation frequencies. Modulation transfer functions (MTFs) obtained from the model response to SAM stimuli resemble the physiological MTFs. The output of the proposed SPON model provides an input for models of physiological responses at higher levels of the ascending auditory pathway and can also be utilized to infer possible mechanisms underlying gap detection and duration encoding as well as forward masking at the level of the auditory midbrain.
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42
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Deleting the HCN1 Subunit of Hyperpolarization-Activated Ion Channels in Mice Impairs Acoustic Startle Reflexes, Gap Detection, and Spatial Localization. J Assoc Res Otolaryngol 2017; 18:427-440. [PMID: 28050647 DOI: 10.1007/s10162-016-0610-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 12/14/2016] [Indexed: 10/20/2022] Open
Abstract
It has been proposed that the high temporal and spatial acuities of human listeners and animals tested in the hearing laboratory depend in part on the short time constants of auditory neurons that are able to preserve or sharpen the information conveyed in the timing of firing of auditory nerve fibers. We tested this hypothesis in a series of in vivo experiments, based on previous in vitro experiments showing that neuronal time constants are raised in brainstem slices when HCN1 channels are blocked or in slices obtained from Hcn1 -/- null mutant mice. We compared Hcn1 -/- and Hcn1 +/+ mice on auditory brainstem responses (ABRs) and behavioral measures. Those measures included temporal integration for acoustic startle responses (ASRs), ASR depression by noise offset, and ASR inhibition by gaps in noise and by shifts of a noise source along the azimuth as measures of temporal and spatial acuity. Hcn1 -/- mice had less sensitive ABR thresholds at 32 and 48 kHz. Their wavelet P1b was delayed, and wave 2 was absent in the 16 kHz/90 SPL waveform, indicating that groups of neurons early in the auditory pathways were delayed and fired asynchronously. Baseline ASR levels were lower in Hcn1 -/- mice, temporal integration was delayed, time constants for ASR depression by noise offset were higher, and their sensitivity to brief gaps and spatial acuity was diminished. HCN1 channels are also present in vestibular, cutaneous, digestive, and cardiac neurons that variously may contribute to the deficits in spatial acuity and possibly in ASR levels.
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43
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Raimondo JV, Richards BA, Woodin MA. Neuronal chloride and excitability - the big impact of small changes. Curr Opin Neurobiol 2016; 43:35-42. [PMID: 27992777 DOI: 10.1016/j.conb.2016.11.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/19/2016] [Accepted: 11/09/2016] [Indexed: 12/18/2022]
Abstract
Synaptic inhibition is a critical regulator of neuronal excitability, and in the mature brain the majority of synaptic inhibition is mediated by Cl--permeable GABAA receptors. Unlike other physiologically relevant ions, Cl- is dynamically regulated, and alterations in the Cl- gradient can have significant impact on neuronal excitability. Due to changes in the neuronal Cl- concentration, GABAergic transmission can bidirectionally regulate the induction of excitatory synaptic plasticity and gate the closing of the critical period for monocular deprivation in visual cortex. GABAergic circuitry can also provide a powerful restraining mechanism for the spread of excitation, however Cl- extrusion mechanisms can become overwhelmed and GABA can paradoxically contribute to pathological excitation such as the propagation of seizure activity.
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Affiliation(s)
- Joseph V Raimondo
- Division of Physiology, Department of Human Biology and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Anzio Road Observatory, 7925 Cape Town, South Africa
| | - Blake A Richards
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada; Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
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44
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Leijon SC, Peyda S, Magnusson AK. Temporal processing capacity in auditory-deprived superior paraolivary neurons is rescued by sequential plasticity during early development. Neuroscience 2016; 337:315-330. [DOI: 10.1016/j.neuroscience.2016.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 09/01/2016] [Accepted: 09/09/2016] [Indexed: 01/04/2023]
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45
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Curry RJ, Lu Y. Synaptic Inhibition in Avian Interaural Level Difference Sound Localizing Neurons. eNeuro 2016; 3:ENEURO.0309-16.2016. [PMID: 28032116 PMCID: PMC5168645 DOI: 10.1523/eneuro.0309-16.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/18/2016] [Accepted: 12/02/2016] [Indexed: 02/07/2023] Open
Abstract
Synaptic inhibition plays a fundamental role in the neural computation of the interaural level difference (ILD), an important cue for the localization of high-frequency sound. Here, we studied the inhibitory synaptic currents in the chicken posterior portion of the dorsal nucleus of the lateral lemniscus (LLDp), the first binaural level difference encoder of the avian auditory pathway. Using whole-cell recordings in brain slices, we provide the first evidence confirming a monosynaptic inhibition driven by direct electrical and chemical stimulation of the contralateral LLDp, establishing the reciprocal inhibitory connection between the two LLDps, a long-standing assumption in the field. This inhibition was largely mediated by GABAA receptors; however, functional glycine receptors were also identified. The reversal potential for the Cl- channels measured with gramicidin-perforated patch recordings was hyperpolarizing (-88 mV), corresponding to a low intracellular Cl- concentration (5.2 mm). Pharmacological manipulations of KCC2 (outwardly Cl- transporter) activity demonstrate that LLDp neurons can maintain a low intracellular Cl- concentration under a high Cl- load, allowing for the maintenance of hyperpolarizing inhibition. We further demonstrate that hyperpolarizing inhibition was more effective at regulating cellular excitability than depolarizing inhibition in LLDp neurons.
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Affiliation(s)
- Rebecca J. Curry
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University, Rootstown, Ohio 44272
- School of Biomedical Sciences, Kent State University, Kent, Ohio 44240
| | - Yong Lu
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University, Rootstown, Ohio 44272
- School of Biomedical Sciences, Kent State University, Kent, Ohio 44240
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46
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Fischl MJ, Burger RM, Schmidt-Pauly M, Alexandrova O, Sinclair JL, Grothe B, Forsythe ID, Kopp-Scheinpflug C. Physiology and anatomy of neurons in the medial superior olive of the mouse. J Neurophysiol 2016; 116:2676-2688. [PMID: 27655966 PMCID: PMC5133312 DOI: 10.1152/jn.00523.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/19/2016] [Indexed: 12/16/2022] Open
Abstract
In mammals with good low-frequency hearing, the medial superior olive (MSO) computes sound location by comparing differences in the arrival time of a sound at each ear, called interaural time disparities (ITDs). Low-frequency sounds are not reflected by the head, and therefore level differences and spectral cues are minimal or absent, leaving ITDs as the only cue for sound localization. Although mammals with high-frequency hearing and small heads (e.g., bats, mice) barely experience ITDs, the MSO is still present in these animals. Yet, aside from studies in specialized bats, in which the MSO appears to serve functions other than ITD processing, it has not been studied in small mammals that do not hear low frequencies. Here we describe neurons in the mouse brain stem that share prominent anatomical, morphological, and physiological properties with the MSO in species known to use ITDs for sound localization. However, these neurons also deviate in some important aspects from the typical MSO, including a less refined arrangement of cell bodies, dendrites, and synaptic inputs. In vitro, the vast majority of neurons exhibited a single, onset action potential in response to suprathreshold depolarization. This spiking pattern is typical of MSO neurons in other species and is generated from a complement of Kv1, Kv3, and IH currents. In vivo, mouse MSO neurons show bilateral excitatory and inhibitory tuning as well as an improvement in temporal acuity of spiking during bilateral acoustic stimulation. The combination of classical MSO features like those observed in gerbils with more unique features similar to those observed in bats and opossums make the mouse MSO an interesting model for exploiting genetic tools to test hypotheses about the molecular mechanisms and evolution of ITD processing.
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Affiliation(s)
- Matthew J Fischl
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany
| | - R Michael Burger
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania; and
| | - Myriam Schmidt-Pauly
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany
| | - Olga Alexandrova
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany
| | - James L Sinclair
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany
| | - Benedikt Grothe
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany
| | - Ian D Forsythe
- Department of Neuroscience, Psychology, and Behaviour, University of Leicester, Leicester, United Kingdom
| | - Conny Kopp-Scheinpflug
- Division of Neurobiology, Department of Biology II, Ludwig Maximilian University Munich, Planegg-Martinsried, Germany;
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47
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Hartwich H, Rosengauer E, Rüttiger L, Wilms V, Waterholter SK, Nothwang HG. Functional Role of γ-Crystallin N in the Auditory Hindbrain. PLoS One 2016; 11:e0161140. [PMID: 27517863 PMCID: PMC4982622 DOI: 10.1371/journal.pone.0161140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 07/30/2016] [Indexed: 12/20/2022] Open
Abstract
γ-crystallins are major components of the vertebrate lens but show expression in other tissues as well. Their extralenticular functions remain so far unclear. Here, we explored such roles in the rodent superior olivary complex in which previous analysis demonstrated developmentally regulated expression of Crygd, Cryge and Crygn. Immunohistochemistry with novel antibodies against Crygd/e and Crygn indicate that expression of Crygd/e was moderate and varied between the perinatal superior olivary complex of mice, rats, and gerbils. Crygn-immunoreactivity was more robust and consistently highest in the medial nucleus of the trapezoid body, but also present in other nuclei of the superior olivary complex. To analyze the function of Crygn in the auditory hindbrain, we used a Crygn allele with a floxed exon 2. Upon pairing with Egr2::Cre mice, exon 2, encoding the first two greek key motifs of Crygn, was deleted in the developing auditory hindbrain. Anatomical analysis of these mice revealed a 20% volume reduction in the medial nucleus of the trapezoid body and a 7% reduction in the lateral superior olive at postnatal day 25. This was due to cell loss between postnatal days 4 and 25, whereas cell size was unaffected. Auditory brainstem responses showed normal threshold but a significant increase in the amplitude of wave IV. Crygn is hence required for postmigratory survival and proper function of auditory hindbrain neurons. These results ascertain for the first time an essential extralenticular role for γ-crystallins in vivo.
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Affiliation(s)
- Heiner Hartwich
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Elena Rosengauer
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Lukas Rüttiger
- University of Tübingen, Department of Otolaryngology, Hearing Research Centre Tübingen (THRC), Molecular Physiology of Hearing, Elfriede Aulhorn Str. 5, 72076, Tübingen, Germany
| | - Viviane Wilms
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Sarah-Kristin Waterholter
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Hans Gerd Nothwang
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
- * E-mail:
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48
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Felix RA, Magnusson AK. Development of excitatory synaptic transmission to the superior paraolivary and lateral superior olivary nuclei optimizes differential decoding strategies. Neuroscience 2016; 334:1-12. [PMID: 27476438 DOI: 10.1016/j.neuroscience.2016.07.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 07/08/2016] [Accepted: 07/23/2016] [Indexed: 11/17/2022]
Abstract
The superior paraolivary nucleus (SPON) is a prominent structure in the mammalian auditory brainstem with a proposed role in encoding transient broadband sounds such as vocalized utterances. Currently, the source of excitatory pathways that project to the SPON and how these inputs contribute to SPON function are poorly understood. To shed light on the nature of these inputs, we measured evoked excitatory postsynaptic currents (EPSCs) in the SPON originating from the intermediate acoustic stria and compared them with the properties of EPSCs in the lateral superior olive (LSO) originating from the ventral acoustic stria during auditory development from postnatal day 5 to 22 in mice. Before hearing onset, EPSCs in the SPON and LSO are very similar in size and kinetics. After the onset of hearing, SPON excitation is refined to extremely few (2:1) fibers, with each strengthened by an increase in release probability, yielding fast and strong EPSCs. LSO excitation is recruited from more fibers (5:1), resulting in strong EPSCs with a comparatively broader stimulus-response range after hearing onset. Evoked SPON excitation is comparatively weaker than evoked LSO excitation, likely due to a larger fraction of postsynaptic GluR2-containing Ca2+-impermeable AMPA receptors after hearing onset. Taken together, SPON excitation develops synaptic properties that are suited for transmitting single events with high temporal reliability and the strong, dynamic LSO excitation is compatible with high rate-level sensitivity. Thus, the excitatory input pathways to the SPON and LSO mature to support different decoding strategies of respective coarse temporal and sound intensity information at the brainstem level.
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Affiliation(s)
- Richard A Felix
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.
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Augustin V, Bold C, Wadle SL, Langer J, Jabs R, Philippot C, Weingarten DJ, Rose CR, Steinhäuser C, Stephan J. Functional anisotropic panglial networks in the lateral superior olive. Glia 2016; 64:1892-911. [PMID: 27458984 DOI: 10.1002/glia.23031] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 06/24/2016] [Accepted: 06/30/2016] [Indexed: 12/12/2022]
Abstract
Astrocytes form large gap junctional networks that contribute to ion and neurotransmitter homeostasis. Astrocytes concentrate in the lateral superior olive (LSO), a prominent auditory brainstem center. Compared to the LSO, astrocyte density is lower in the region dorsal to the LSO (dLSO) and in the internuclear space between the LSO, the superior paraolivary nucleus (SPN). We questioned whether astrocyte networks exhibit certain properties that reflect the precise neuronal arrangement. Employing whole-cell patch-clamp and concomitant injection of a gap junction-permeable tracer, we analyzed size and orientation of astrocyte networks in LSO, dLSO, and SPN-LSO in acute brainstem slices of mice at postnatal days 10-20. The majority of LSO networks exhibited an oval topography oriented orthogonally to the tonotopic axis, whereas dLSO networks showed no preferred orientation. This correlated with the overall astrocyte morphology in both regions, i.e. LSO astrocyte processes were oriented mainly orthogonally to the tonotopic axis. To assess the spread of small ions within LSO networks, we analyzed the diffusion of Na(+) signals between cells using Na(+) imaging. We found that Na(+) not only diffused between SR101(+) astrocytes, but also from astrocytes into SR101(-) cells. Using PLP-GFP mice for tracing, we could show that LSO networks contained astrocytes and oligodendrocytes. Together, our results demonstrate that LSO astrocytes and LSO oligodendrocytes form functional anisotropic panglial networks that are oriented predominantly orthogonally to the tonotopic axis. Thus, our results point toward an anisotropic ion and metabolite diffusion and a limited glial crosstalk between neighboring isofrequency bands in the LSO. GLIA 2016;64:1892-1911.
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Affiliation(s)
- Vanessa Augustin
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Erwin Schroedinger-Strasse 13, Kaiserslautern, Germany
| | - Charlotte Bold
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Erwin Schroedinger-Strasse 13, Kaiserslautern, Germany
| | - Simon L Wadle
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Erwin Schroedinger-Strasse 13, Kaiserslautern, Germany
| | - Julia Langer
- Institute of Neurobiology, Universitaetsstasse 1, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Ronald Jabs
- Medical Faculty, Institute of Cellular Neurosciences, University of Bonn, Sigmund-Freud-Strasse 25, Bonn, Germany
| | - Camille Philippot
- Medical Faculty, Institute of Cellular Neurosciences, University of Bonn, Sigmund-Freud-Strasse 25, Bonn, Germany
| | - Dennis J Weingarten
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Erwin Schroedinger-Strasse 13, Kaiserslautern, Germany
| | - Christine R Rose
- Institute of Neurobiology, Universitaetsstasse 1, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Christian Steinhäuser
- Medical Faculty, Institute of Cellular Neurosciences, University of Bonn, Sigmund-Freud-Strasse 25, Bonn, Germany
| | - Jonathan Stephan
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Erwin Schroedinger-Strasse 13, Kaiserslautern, Germany.
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Abstract
UNLABELLED High temporal acuity of auditory processing underlies perception of speech and other rapidly varying sounds. A common measure of auditory temporal acuity in humans is the threshold for detection of brief gaps in noise. Gap-detection deficits, observed in developmental disorders, are considered evidence for "sluggish" auditory processing. Here we show, in a mouse model of gap-detection deficits, that auditory brain sensitivity to brief gaps in noise can be impaired even without a general loss of central auditory temporal acuity. Extracellular recordings in three different subdivisions of the auditory thalamus in anesthetized mice revealed a stimulus-specific, subdivision-specific deficit in thalamic sensitivity to brief gaps in noise in experimental animals relative to controls. Neural responses to brief gaps in noise were reduced, but responses to other rapidly changing stimuli unaffected, in lemniscal and nonlemniscal (but not polysensory) subdivisions of the medial geniculate body. Through experiments and modeling, we demonstrate that the observed deficits in thalamic sensitivity to brief gaps in noise arise from reduced neural population activity following noise offsets, but not onsets. These results reveal dissociable sound-onset-sensitive and sound-offset-sensitive channels underlying auditory temporal processing, and suggest that gap-detection deficits can arise from specific impairment of the sound-offset-sensitive channel. SIGNIFICANCE STATEMENT The experimental and modeling results reported here suggest a new hypothesis regarding the mechanisms of temporal processing in the auditory system. Using a mouse model of auditory temporal processing deficits, we demonstrate the existence of specific abnormalities in auditory thalamic activity following sound offsets, but not sound onsets. These results reveal dissociable sound-onset-sensitive and sound-offset-sensitive mechanisms underlying auditory processing of temporally varying sounds. Furthermore, the findings suggest that auditory temporal processing deficits, such as impairments in gap-in-noise detection, could arise from reduced brain sensitivity to sound offsets alone.
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