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Senesi M, Lewis V, Adlard PA, Finkelstein DI, Kim JH, Collins SJ. Tailored behavioural tests reveal early and progressive cognitive deficits in M1000 prion disease. Neurobiol Dis 2023; 180:106075. [PMID: 36914075 DOI: 10.1016/j.nbd.2023.106075] [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: 01/02/2023] [Revised: 03/03/2023] [Accepted: 03/07/2023] [Indexed: 03/13/2023] Open
Abstract
Prion diseases are pathogenically linked to the normal cellular prion protein (PrPC) misfolding into abnormal conformers (PrPSc), with PrPSc accumulation underpinning both transmission and neurotoxicity. Despite achieving this canonical understanding, however fundamental questions remain incompletely resolved, including the level of pathophysiological overlap between neurotoxic and transmitting species of PrPSc and the temporal profiles of their propagation. To further investigate the likely time of occurrence of significant levels of neurotoxic species during prion disease development, the well characterised in vivo M1000 murine model was employed. Following intracerebral inoculation, detailed serial cognitive and ethological testing at specified time points suggested subtle transition to early symptomatic disease from ∼50% of the overall disease course. In addition to observing a chronological order for impaired behaviours, different behavioural tests also showed distinctive profiles of evolving cognitive impairments with the Barnes maze demonstrating a relatively simple linear worsening of spatial learning and memory over an extended period while in contrast a conditioned fear memory paradigm previously untested in murine prion disease demonstrated more complex alterations during disease progression. These observations support the likely production of neurotoxic PrPSc from at least just prior to the mid-point of murine M1000 prion disease and illustrate the likely need to tailor the types of behavioural testing across the time course of disease progression for optimal detection of cognitive deficits.
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Affiliation(s)
- Matteo Senesi
- Department of Medicine, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Victoria Lewis
- Department of Medicine, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Paul A Adlard
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - David I Finkelstein
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Jee Hyun Kim
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia; The Institute for Mental and Physical Health and Clinical Translation, Deakin University, Geelong, Australia
| | - Steven J Collins
- Department of Medicine, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia.
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2
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Burchell A, Mansour Y, Kulesza R. Leveling up: a long-range olivary projection to the medial geniculate without collaterals to the central nucleus of the inferior colliculus in rats. Exp Brain Res 2022; 240:3217-3235. [PMID: 36271940 DOI: 10.1007/s00221-022-06489-2] [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: 05/27/2022] [Accepted: 10/17/2022] [Indexed: 11/04/2022]
Abstract
The medial nucleus of the trapezoid body (MNTB) is one of the monaural cell groups situated within the superior olivary complex (SOC), a constellation of brainstem nuclei with numerous roles in hearing. Principal MNTB neurons are glycinergic and express the calcium-binding protein, calbindin (CB). The MNTB receives its main glutamatergic, excitatory input from the contralateral cochlear nucleus via the calyx of Held and converts this into glycinergic inhibition directed toward nuclei in the SOC and the ventral and intermediate nuclei of the lateral lemniscus (VNLL and INLL). Through this inhibition, the MNTB plays essential roles in localization of sound sources and encoding spectral and temporal features of sound. In rats, very few MNTB neurons project to the inferior colliculus. However, our recent study of SOC projections to the auditory thalamus revealed a substantial number of retrogradely labeled MNTB neurons. This observation led us to examine whether the rat MNTB provides a long-range projection to the medial geniculate body (MGB). We examined this possible projection using retrograde and anterograde tract tracing and immunohistochemistry for CB and the glycine receptor. Our results demonstrate a significant projection to the MGB from the ipsilateral MNTB that does not involve a collateral projection to the inferior colliculus.
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Affiliation(s)
- Alyson Burchell
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16509, USA
| | - Yusra Mansour
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16509, USA.,Department of Otolaryngology, Henry Ford Macomb Hospital, Clinton Township, MI, USA
| | - Randy Kulesza
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16509, USA.
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3
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Wallace MN, Shackleton TM, Thompson Z, Palmer AR. Juxtacellular Labeling of Stellate, Disk and Basket Neurons in the Central Nucleus of the Guinea Pig Inferior Colliculus. Front Neural Circuits 2021; 15:721015. [PMID: 34790099 PMCID: PMC8592287 DOI: 10.3389/fncir.2021.721015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 07/06/2021] [Indexed: 12/20/2022] Open
Abstract
We reconstructed the intrinsic axons of 32 neurons in the guinea pig inferior colliculus (IC) following juxtacellular labeling. Biocytin was injected into cells in vivo, after first analyzing physiological response properties. Based on axonal morphology there were two classes of neuron: (1) laminar cells (14/32, 44%) with an intrinsic axon and flattened dendrites confined to a single fibrodendritic lamina and (2) translaminar cells (18/32, 56%) with axons that terminated in two or more laminae in the central nucleus (ICc) or the surrounding cortex. There was also one small, low-frequency cell with bushy-like dendrites that was very sensitive to interaural timing differences. The translaminar cells were subdivided into three groups of cells with: (a) stellate dendrites that crossed at least two laminae (8/32, 25%); (b) flattened dendrites confined to one lamina and that had mainly en passant axonal swellings (7/32, 22%) and (c) short, flattened dendrites and axons with distinctive clusters of large terminal boutons in the ICc (3/32, 9%). These terminal clusters were similar to those of cortical basket cells. The 14 laminar cells all had sustained responses apart from one offset response. Almost half the non-basket type translaminar cells (7/15) had onset responses while the others had sustained responses. The basket cells were the only ones to have short-latency (7–9 ms), chopper responses and this distinctive temporal response should allow them to be studied in more detail in future. This is the first description of basket cells in the auditory brainstem, but more work is required to confirm their neurotransmitter and precise post-synaptic targets.
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Affiliation(s)
- Mark N Wallace
- Hearing Sciences, Mental Health and Clinical Neurosciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Trevor M Shackleton
- Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Zoe Thompson
- Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Alan R Palmer
- Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, Nottingham, United Kingdom
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4
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Zimdahl JW, Thomas H, Bolland SJ, Leggett K, Barry KM, Rodger J, Mulders WHAM. Excitatory Repetitive Transcranial Magnetic Stimulation Over Prefrontal Cortex in a Guinea Pig Model Ameliorates Tinnitus. Front Neurosci 2021; 15:693935. [PMID: 34366777 PMCID: PMC8339289 DOI: 10.3389/fnins.2021.693935] [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: 04/12/2021] [Accepted: 07/01/2021] [Indexed: 11/13/2022] Open
Abstract
Tinnitus, a phantom auditory perception that can seriously affect quality of life, is generally triggered by cochlear trauma and associated with aberrant activity throughout the auditory pathways, often referred to as hyperactivity. Studies suggest that non-auditory structures, such as prefrontal cortex (PFC), may be involved in tinnitus generation, by affecting sensory gating in auditory thalamus, allowing hyperactivity to reach the cortex and lead to perception. Indeed, human studies have shown that repetitive transcranial magnetic stimulation (rTMS) of PFC can alleviate tinnitus. The current study investigated whether this therapeutic effect is achieved through inhibition of thalamic hyperactivity, comparing effects of two common clinical rTMS protocols with sham treatment, in a guinea pig tinnitus model. Animals underwent acoustic trauma and once tinnitus developed were treated with either intermittent theta burst stimulation (iTBS), 20 Hz rTMS, or sham rTMS (10 days, 10 min/day; weekdays only). Tinnitus was reassessed and extracellular recordings of spontaneous tonic and burst firing rates in auditory thalamus made. To verify effects in PFC, densities of neurons positive for calcium-binding proteins, calbindin and parvalbumin, were investigated using immunohistochemistry. Both rTMS protocols significantly reduced tinnitus compared to sham. However, spontaneous tonic firing decreased following 20 Hz stimulation and increased following iTBS in auditory thalamus. Burst rate was significantly different between 20 Hz and iTBS stimulation, and burst duration was increased only after 20 Hz treatment. Density of calbindin, but not parvalbumin positive neurons, was significantly increased in the most dorsal region of PFC indicating that rTMS directly affected PFC. Our results support the involvement of PFC in tinnitus modulation, and the therapeutic benefit of rTMS on PFC in treating tinnitus, but indicate this is not achieved solely by suppression of thalamic hyperactivity.
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Affiliation(s)
- Jack W Zimdahl
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Harrison Thomas
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Samuel J Bolland
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.,Perron Institute for Neurological and Translational Research, Crawley, WA, Australia
| | - Kerry Leggett
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Kristin M Barry
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Jennifer Rodger
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.,Perron Institute for Neurological and Translational Research, Crawley, WA, Australia
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5
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Mansour Y, Ahmed SN, Kulesza R. Abnormal morphology and subcortical projections to the medial geniculate in an animal model of autism. Exp Brain Res 2020; 239:381-400. [PMID: 33200290 DOI: 10.1007/s00221-020-05982-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 11/04/2020] [Indexed: 12/21/2022]
Abstract
Auditory dysfunction, including hypersensitivity and tinnitus, is a common symptom of autism spectrum disorder (ASD). Prenatal exposure to the antiseizure medication valproic acid (VPA) significantly increases the risk of ASD in humans and similar exposure is utilized as an animal model of ASD in rodents. Animals exposed to VPA in utero have abnormal activity in their auditory cortex in response to sounds, fewer neurons, abnormal neuronal morphology, reduced expression of calcium-binding proteins, and reduced ascending projections to the central nucleus of the inferior colliculus. Unfortunately, these previous studies of central auditory circuits neglect the medial geniculate (MG), which serves as an important auditory relay from the midbrain to the auditory cortex. Here, we examine the structure and connectivity of the medial geniculate (MG) in rats prenatally exposed to VPA. Our results indicate that VPA exposure results in significantly smaller and fewer neurons in the ventral and medial nuclei of the MG. Furthermore, injections of the retrograde tract tracer fluorogold (FG) in the MG result in significantly fewer FG+ neurons in the inferior colliculus, superior olivary complex, and ventral cochlear nucleus. Together, we interpret these findings to indicate that VPA exposure results in hypoplasia throughout the auditory circuits and that VPA has a differential impact on some long-range axonal projections from brainstem centers to the thalamus. Together, our findings support the widespread impact of VPA on neurons and sensory circuits in the developing brain.
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Affiliation(s)
- Yusra Mansour
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16504, USA
| | - Syed Naved Ahmed
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16504, USA
| | - Randy Kulesza
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, 1858 West Grandview Blvd, Erie, PA, 16504, USA.
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6
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Wu C, Shore SE. Inhibitory interneurons in a brainstem circuit adjust their inhibitory motifs to process multimodal input. J Physiol 2020; 599:631-645. [PMID: 33103245 DOI: 10.1113/jp280741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/22/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Inhibitory-interneuron networks, consisting of multiple forms of circuit motifs including reciprocal (inhibitory interneurons inhibiting other interneurons) and feedforward (inhibitory interneurons inhibiting principal neurons) connections, are crucial in processing sensory information. The present study applies a statistical method to in vivo multichannel spike trains of dorsal cochlear nucleus neurons to disentangle reciprocal and feedforward-inhibitory motifs. After inducing input-specific plasticity, reciprocal and feedforward inhibition are found to be differentially regulated, and the combined effect synergistically modulates circuit output. The findings highlight the interplay among different circuit motifs as a key element in neural computation. ABSTRACT Inhibitory interneurons play an essential role in neural computations by utilizing a combination of reciprocal (interneurons inhibiting each other) and feedforward (interneuron inhibiting the principal neuron) inhibition to process information. To disentangle the interplay between the two inhibitory-circuit motifs and understand their effects on the circuit output, in vivo recordings were made from the guinea pig dorsal cochlear nucleus, a cerebellar-like brainstem circuit. Spikes from inhibitory interneurons (cartwheel cell) and principal output neurons (fusiform cell) were compared before and after manipulating their common multimodal input. Using a statistical model based on the Cox method of modulated renewal process of spike train influence, reciprocal- and feedforward-inhibition motifs were quantified. In response to altered multimodal input, reciprocal inhibition was strengthened while feedforward inhibition was weakened, and the two motifs combined to modulate fusiform cell output and acoustic-driven responses. These findings reveal the cartwheel cell's role in auditory and multimodal processing, as well as illustrated the balance between different inhibitory-circuit motifs as a key element in neural computation.
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Affiliation(s)
- Calvin Wu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, USA
| | - Susan E Shore
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, USA.,Biomedical Engineering, University of Michigan, Ann Arbor, Michigan.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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7
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Shore SE, Wu C. Mechanisms of Noise-Induced Tinnitus: Insights from Cellular Studies. Neuron 2019; 103:8-20. [PMID: 31271756 DOI: 10.1016/j.neuron.2019.05.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/25/2019] [Accepted: 05/03/2019] [Indexed: 01/21/2023]
Abstract
Tinnitus, sound perception in the absence of physical stimuli, occurs in 15% of the population and is the top-reported disability for soldiers after combat. Noise overexposure is a major factor associated with tinnitus but does not always lead to tinnitus. Furthermore, people with normal audiograms can get tinnitus. In animal models, equivalent cochlear damage occurs in animals with and without behavioral evidence of tinnitus. But cochlear-nerve-recipient neurons in the brainstem demonstrate distinct, synchronized spontaneous firing patterns only in animals that develop tinnitus, driving activity in central brain regions and ultimately giving rise to phantom perception. Examining tinnitus-specific changes in single-cell populations enables us to begin to distinguish neural changes due to tinnitus from those that are due to hearing loss.
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Affiliation(s)
- Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Calvin Wu
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109, USA
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8
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Quraishe S, Newman T, Anderson L. Auditory temporal acuity improves with age in the male mouse auditory thalamus: A role for perineuronal nets? J Neurosci Res 2019; 98:1780-1799. [PMID: 31562661 DOI: 10.1002/jnr.24537] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 09/13/2019] [Accepted: 09/15/2019] [Indexed: 11/09/2022]
Abstract
The ability to perceive and interpret environmental sound accurately is conserved across many species and is fundamental for understanding communication via vocalizations. Auditory acuity and temporally controlled neuronal firing underpin this ability. Deterioration in neuronal firing precision likely contributes to poorer hearing performance, yet the role of neural processing by key nuclei in the central auditory pathways is not fully understood. Here, we record from the auditory thalamus (medial geniculate body [MGB]) of young and middle-aged, normally hearing male CBA/Ca mice. We report changes in temporal processing of auditory stimuli, with neurons recorded from ventral and medial MGB subdivisions of older animals more likely to synchronize to rapid temporally varying stimuli. MGB subdivisions also showed increased probability of neuronal firing and shorter response latencies to clicks in older animals. Histological investigation of neuronal extracellular specializations, perineuronal nets (PNNs) and axonal coats, in the MGB identified greater organization of PNNs around MGB neurons and the presence of axonal coats within older animals. This supports the observation that neural responses recorded from ventral and medial MGB of older mice were more likely to synchronize to temporally varying stimuli presented at faster repetition rates than those recorded from young adult animals. These changes are observed in animals with normal hearing thresholds, confirming that neural processing differs between the MGB subdivisions and such processing is associated with age-related changes to PNNs. Understanding these age-related changes and how they occur have important implications for the design of effective therapeutic interventions to improve speech intelligibility into later life.
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Affiliation(s)
- Shmma Quraishe
- School of Biological Sciences, B85, University of Southampton, Southampton, UK
| | - Tracey Newman
- Clinical and Experimental Sciences, B85, University of Southampton, Southampton, UK
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9
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Saldeitis K, Richter K, Fischer KD, Ohl FW, Mateos JM, Budinger E. Ultrastructure of giant thalamic terminals in the auditory cortex. Eur J Neurosci 2019; 50:3445-3453. [PMID: 31286598 DOI: 10.1111/ejn.14509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 06/24/2019] [Accepted: 06/27/2019] [Indexed: 11/28/2022]
Abstract
The auditory system comprises some very large axonal terminals like the endbulb and calyx of Held and "giant" corticothalamic synapses. Previously, we described a hitherto unknown population of giant thalamocortical boutons arising from the medial division of the medial geniculate body (MGm) in the Mongolian gerbil, which terminate over a wide cortical range but in a columnar manner particularly in the extragranular layers of the auditory cortex. As a first step towards an understanding of their potential functional role, we here describe their ultrastructure combining anterograde tract-tracing with biocytin and electron microscopy. Quantitative ultrastructural analyses revealed that biocytin-labelled MGm boutons reach much larger sizes than other, non-labelled boutons. Also, mitochondria occupy more space within labelled boutons whereas synapses are of similar size. Labelled boutons are very heterogeneous in size but homogeneous with respect to their ultrastructural characteristics, with asymmetric synapses containing clear, round vesicles and targeting dendritic spines. Functionally, the ultrastructure of the MGm terminals indicates that they form excitatory contacts, which may transmit their information in a rapid, powerful and high-fidelity manner onto strategically advantageous compartments of their cortical target cells.
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Affiliation(s)
- Katja Saldeitis
- Department Systems Physiology of Learning, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Cognitive Hearing in Primates Group, Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany
| | - Karin Richter
- Institute of Biochemistry and Cell Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Klaus-Dieter Fischer
- Institute of Biochemistry and Cell Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Frank W Ohl
- Department Systems Physiology of Learning, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - José M Mateos
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Eike Budinger
- Department Systems Physiology of Learning, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
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10
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Mellott JG, Beebe NL, Schofield BR. Bilateral projections to the thalamus from individual neurons in the inferior colliculus. J Comp Neurol 2018; 527:1118-1126. [PMID: 30536721 DOI: 10.1002/cne.24600] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 10/25/2018] [Accepted: 11/11/2018] [Indexed: 12/28/2022]
Abstract
The medial geniculate body (MG) receives a large input from the ipsilateral inferior colliculus (IC) and a smaller but substantial input from the contralateral IC. Both crossed and uncrossed inputs comprise a large percentage of glutamatergic cells and a smaller percentage of GABAergic cells. We used double labeling with fluorescent retrograde tracers to identify individual IC cells that project bilaterally to the MGs in adult guinea pigs. We also used immunohistochemistry for glutamic acid decarboxylase to distinguish GABAergic from glutamatergic cells that project bilaterally to the MG. We found cells in the IC that contained both retrograde tracers, indicating that they project bilaterally. Across cases, the bilaterally projecting cells constituted up to 37% of the cells that project to the ipsilateral MG and up to 73% of the cells that project to the contralateral MG. GABAergic cells averaged 20% of the bilaterally-projecting population. We conclude that a population of IC cells sends branching axonal projections to innervate the MG bilaterally. Most of the neurons in this population are glutamatergic, with a minority that are GABAergic. A mixed projection, with glutamatergic cells outnumbering GABAergic cells, originates from each of the major IC subdivisions (central nucleus, dorsal cortex, and lateral cortex). The bilaterally projecting cells are likely to serve functions different from the larger unilateral projections, perhaps synchronizing activity on the two sides of the auditory brain.
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Affiliation(s)
- Jeffrey G Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
| | - Nichole L Beebe
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
| | - Brett R Schofield
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
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11
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Zhu M, Li H, Gyanwali B, He G, Qi C, Yang X, Li Z, Yao Z, Wang Z, Tang A. Auditory brainstem responses after electrolytic lesions in bilateral subdivisions of the medial geniculate body of tree shrews. Neurol Sci 2017; 38:1617-1628. [PMID: 28616778 DOI: 10.1007/s10072-017-3013-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 05/26/2017] [Indexed: 11/27/2022]
Abstract
This study aimed to establish a tree shrew model of bilateral electrolytic lesions in the medial geniculate body (MGB) to determine the advantages of using a tree shrew model and to assess the pattern of sound processing in tree shrews after bilateral electrolytic damage in different parts of the MGB. The auditory brainstem responses (ABRs) of a normal control group (n = 30) and an electrical damage group (n = 30) were tested at 0 h, 24 h, 48 h, 72 h, 7 days, 15 days, and 30 days after surgery. (1) The bilateral ablations group exhibited a significant increase in the ABR threshold of the electrolytic damage group between pre- and post-operation. (2) There were significant increases in the I-VI latencies at 0 h after MGBd and MGBm lesions and at 24 h after MGBv lesion. (3) The amplitudes of wave VI were significantly decreased at 24 h and 48 h after MGBd lesion, at 72 h and 7 days after MGBm lesion, and at 24 h, 48 h, 72 h, and 7 days after MGBv lesion. (1) The electrolytic damage group suffered hearing loss that did not recover and appeared to be difficult to fully repair after bilateral ablation. (2) The latencies and amplitudes of responses in the MGB following bilateral electrolytic lesion were restored to pre-operation levels after 15-30 days, suggesting that a portion of the central nuclei lesion was reversible. (3) The tree shrew auditory animal model has many advantages compared to other animal models, such as greater complexity of brain structure and auditory nuclei fiber connections, which make the results of this experiment more useful for clinical diagnoses compared with studies using rats and guinea pigs.
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Affiliation(s)
- Meichan Zhu
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Heng Li
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Bibek Gyanwali
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Guangyao He
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Chenglin Qi
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Xuemin Yang
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Zhenhua Li
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Zhenxing Yao
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Zhi Wang
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China
| | - Anzhou Tang
- Department of Otorhinolaryngology and Head and Neck Surgery, First Affiliated Hospital of Guangxi Medical University, No.6 Shuangyong Road, Nanning, Guangxi, 530021, China.
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12
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Rueckriegel SM, Homola GA, Hummel M, Willner N, Ernestus RI, Matthies C. Probabilistic Fiber-Tracking Reveals Degeneration of the Contralateral Auditory Pathway in Patients with Vestibular Schwannoma. AJNR Am J Neuroradiol 2016; 37:1610-6. [PMID: 27256855 DOI: 10.3174/ajnr.a4833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 03/06/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Vestibular schwannomas cause progressive hearing loss by direct damage to the vestibulocochlear nerve. The cerebral mechanisms of degeneration or plasticity are not well-understood. Therefore, the goal of our study was to show the feasibility of probabilistic fiber-tracking of the auditory pathway in patients with vestibular schwannomas and to compare the ipsi- and contralateral volume and integrity, to test differences between the hemispheres. MATERIALS AND METHODS Fifteen patients with vestibular schwannomas were investigated before surgery. Diffusion-weighted imaging (25 directions) was performed on a 3T MR imaging system. Probabilistic tractography was performed for 3 partial sections of the auditory pathway. Volume and fractional anisotropy were determined and compared ipsilaterally and contralaterally. The laterality ratio was correlated with the level of hearing loss. RESULTS Anatomically reasonable tracts were depicted in all patients for the acoustic radiation. Volume was significantly decreased on the hemisphere contralateral to the tumor side for the acoustic radiation and diencephalic section, while fractional anisotropy did not differ significantly. Tracking did not yield meaningful tracts in 3 patients for the thalamocortical section and in 5 patients for the diencephalic section. No statistically significant correlations between the laterality quotient and classification of hearing loss were found. CONCLUSIONS For the first time, this study showed that different sections of the auditory pathway between the inferior colliculus and the auditory cortex can be visualized by using probabilistic tractography. A significant volume decrease of the auditory pathway on the contralateral hemisphere was observed and may be explained by transsynaptic degeneration of the crossing auditory pathway.
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Affiliation(s)
- S M Rueckriegel
- From the Departments of Neurosurgery (S.M.R., M.H., N.W., R.-I.E., C.M.)
| | - G A Homola
- Neuroradiology (G.A.H.), Würzburg University Hospital, Würzburg, Germany
| | - M Hummel
- From the Departments of Neurosurgery (S.M.R., M.H., N.W., R.-I.E., C.M.)
| | - N Willner
- From the Departments of Neurosurgery (S.M.R., M.H., N.W., R.-I.E., C.M.)
| | - R-I Ernestus
- From the Departments of Neurosurgery (S.M.R., M.H., N.W., R.-I.E., C.M.)
| | - C Matthies
- From the Departments of Neurosurgery (S.M.R., M.H., N.W., R.-I.E., C.M.)
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13
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Ceravolo L, Frühholz S, Grandjean D. Modulation of Auditory Spatial Attention by Angry Prosody: An fMRI Auditory Dot-Probe Study. Front Neurosci 2016; 10:216. [PMID: 27242420 PMCID: PMC4864064 DOI: 10.3389/fnins.2016.00216] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 04/29/2016] [Indexed: 11/16/2022] Open
Abstract
Emotional stimuli have been shown to modulate attentional orienting through signals sent by subcortical brain regions that modulate visual perception at early stages of processing. Fewer studies, however, have investigated a similar effect of emotional stimuli on attentional orienting in the auditory domain together with an investigation of brain regions underlying such attentional modulation, which is the general aim of the present study. Therefore, we used an original auditory dot-probe paradigm involving simultaneously presented neutral and angry non-speech vocal utterances lateralized to either the left or the right auditory space, immediately followed by a short and lateralized single sine wave tone presented in the same (valid trial) or in the opposite space as the preceding angry voice (invalid trial). Behavioral results showed an expected facilitation effect for target detection during valid trials while functional data showed greater activation in the middle and posterior superior temporal sulci (STS) and in the medial frontal cortex for valid vs. invalid trials. The use of reaction time facilitation [absolute value of the Z-score of valid-(invalid+neutral)] as a group covariate extended enhanced activity in the amygdalae, auditory thalamus, and visual cortex. Taken together, our results suggest the involvement of a large and distributed network of regions among which the STS, thalamus, and amygdala are crucial for the decoding of angry prosody, as well as for orienting and maintaining attention within an auditory space that was previously primed by a vocal emotional event.
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Affiliation(s)
- Leonardo Ceravolo
- Neuroscience of Emotion and Affective Dynamics Lab, Department of Psychology, University of GenevaGeneva, Switzerland; Department of Psychology, Swiss Center for Affective Sciences, University of GenevaGeneva, Switzerland
| | - Sascha Frühholz
- Neuroscience of Emotion and Affective Dynamics Lab, Department of Psychology, University of GenevaGeneva, Switzerland; Department of Psychology, Swiss Center for Affective Sciences, University of GenevaGeneva, Switzerland; Department of Psychology, University of ZurichZurich, Switzerland
| | - Didier Grandjean
- Neuroscience of Emotion and Affective Dynamics Lab, Department of Psychology, University of GenevaGeneva, Switzerland; Department of Psychology, Swiss Center for Affective Sciences, University of GenevaGeneva, Switzerland
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14
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Abstract
Tinnitus is a phantom auditory sensation that reduces quality of life for millions of people worldwide, and for which there is no medical cure. Most cases of tinnitus are associated with hearing loss caused by ageing or noise exposure. Exposure to loud recreational sound is common among the young, and this group are at increasing risk of developing tinnitus. Head or neck injuries can also trigger the development of tinnitus, as altered somatosensory input can affect auditory pathways and lead to tinnitus or modulate its intensity. Emotional and attentional state could be involved in the development and maintenance of tinnitus via top-down mechanisms. Thus, military personnel in combat are particularly at risk owing to combined risk factors (hearing loss, somatosensory system disturbances and emotional stress). Animal model studies have identified tinnitus-associated neural changes that commence at the cochlear nucleus and extend to the auditory cortex and other brain regions. Maladaptive neural plasticity seems to underlie these changes: it results in increased spontaneous firing rates and synchrony among neurons in central auditory structures, possibly generating the phantom percept. This Review highlights the links between animal and human studies, and discusses several therapeutic approaches that have been developed to target the neuroplastic changes underlying tinnitus.
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15
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Pannese A, Grandjean D, Frühholz S. Subcortical processing in auditory communication. Hear Res 2015; 328:67-77. [DOI: 10.1016/j.heares.2015.07.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/23/2015] [Accepted: 07/01/2015] [Indexed: 12/21/2022]
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16
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Wu C, Stefanescu RA, Martel DT, Shore SE. Listening to another sense: somatosensory integration in the auditory system. Cell Tissue Res 2015; 361:233-50. [PMID: 25526698 PMCID: PMC4475675 DOI: 10.1007/s00441-014-2074-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 11/18/2014] [Indexed: 12/19/2022]
Abstract
Conventionally, sensory systems are viewed as separate entities, each with its own physiological process serving a different purpose. However, many functions require integrative inputs from multiple sensory systems and sensory intersection and convergence occur throughout the central nervous system. The neural processes for hearing perception undergo significant modulation by the two other major sensory systems, vision and somatosensation. This synthesis occurs at every level of the ascending auditory pathway: the cochlear nucleus, inferior colliculus, medial geniculate body and the auditory cortex. In this review, we explore the process of multisensory integration from (1) anatomical (inputs and connections), (2) physiological (cellular responses), (3) functional and (4) pathological aspects. We focus on the convergence between auditory and somatosensory inputs in each ascending auditory station. This review highlights the intricacy of sensory processing and offers a multisensory perspective regarding the understanding of sensory disorders.
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Affiliation(s)
- Calvin Wu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, 48109, USA
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17
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Wu C, Stefanescu RA, Martel DT, Shore SE. Tinnitus: Maladaptive auditory-somatosensory plasticity. Hear Res 2015; 334:20-9. [PMID: 26074307 DOI: 10.1016/j.heares.2015.06.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 05/25/2015] [Accepted: 06/02/2015] [Indexed: 01/05/2023]
Abstract
Tinnitus, the phantom perception of sound, is physiologically characterized by an increase in spontaneous neural activity in the central auditory system. However, as tinnitus is often associated with hearing impairment, it is unclear how a decrease of afferent drive can result in central hyperactivity. In this review, we first assess methods for tinnitus induction and objective measures of the tinnitus percept in animal models. From animal studies, we discuss evidence that tinnitus originates in the cochlear nucleus (CN), and hypothesize mechanisms whereby hyperactivity may develop in the CN after peripheral auditory nerve damage. We elaborate how this process is likely mediated by plasticity of auditory-somatosensory integration in the CN: the circuitry in normal circumstances maintains a balance of auditory and somatosensory activities, and loss of auditory inputs alters the balance of auditory somatosensory integration in a stimulus timing dependent manner, which propels the circuit towards hyperactivity. Understanding the mechanisms underlying tinnitus generation is essential for its prevention and treatment. This article is part of a Special Issue entitled <Tinnitus>.
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Affiliation(s)
- Calvin Wu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA
| | - Roxana A Stefanescu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA
| | - David T Martel
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA
| | - Susan E Shore
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA.
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18
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Malmierca MS, Anderson LA, Antunes FM. The cortical modulation of stimulus-specific adaptation in the auditory midbrain and thalamus: a potential neuronal correlate for predictive coding. Front Syst Neurosci 2015; 9:19. [PMID: 25805974 PMCID: PMC4353371 DOI: 10.3389/fnsys.2015.00019] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/03/2015] [Indexed: 02/02/2023] Open
Abstract
To follow an ever-changing auditory scene, the auditory brain is continuously creating a representation of the past to form expectations about the future. Unexpected events will produce an error in the predictions that should “trigger” the network’s response. Indeed, neurons in the auditory midbrain, thalamus and cortex, respond to rarely occurring sounds while adapting to frequently repeated ones, i.e., they exhibit stimulus specific adaptation (SSA). SSA cannot be explained solely by intrinsic membrane properties, but likely involves the participation of the network. Thus, SSA is envisaged as a high order form of adaptation that requires the influence of cortical areas. However, present research supports the hypothesis that SSA, at least in its simplest form (i.e., to frequency deviants), can be transmitted in a bottom-up manner through the auditory pathway. Here, we briefly review the underlying neuroanatomy of the corticofugal projections before discussing state of the art studies which demonstrate that SSA present in the medial geniculate body (MGB) and inferior colliculus (IC) is not inherited from the cortex but can be modulated by the cortex via the corticofugal pathways. By modulating the gain of neurons in the thalamus and midbrain, the auditory cortex (AC) would refine SSA subcortically, preventing irrelevant information from reaching the cortex.
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Affiliation(s)
- Manuel S Malmierca
- Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCyL), University of Salamanca Salamanca, Spain ; Faculty of Medicine, Department of Cell Biology and Pathology, University of Salamanca Salamanca, Spain
| | - Lucy A Anderson
- Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCyL), University of Salamanca Salamanca, Spain
| | - Flora M Antunes
- Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCyL), University of Salamanca Salamanca, Spain
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19
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Truong DT, Rendall AR, Rosen GD, Fitch RH. Morphometric changes in subcortical structures of the central auditory pathway in mice with bilateral nodular heterotopia. Behav Brain Res 2014; 282:61-9. [PMID: 25549859 DOI: 10.1016/j.bbr.2014.12.046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 12/17/2014] [Accepted: 12/21/2014] [Indexed: 02/09/2023]
Abstract
Malformations of cortical development (MCD) have been observed in human reading and language impaired populations. Injury-induced MCD in rodent models of reading disability show morphological changes in the auditory thalamic nucleus (medial geniculate nucleus; MGN) and auditory processing impairments, thus suggesting a link between MCD, MGN, and auditory processing behavior. Previous neuroanatomical examination of a BXD29 recombinant inbred strain (BXD29-Tlr4(lps-2J)/J) revealed MCD consisting of bilateral subcortical nodular heterotopia with partial callosal agenesis. Subsequent behavioral characterization showed a severe impairment in auditory processing-a deficient behavioral phenotype seen across both male and female BXD29-Tlr4(lps-2J)/J mice. In the present study we expanded upon the neuroanatomical findings in the BXD29-Tlr4(lps-2J)/J mutant mouse by investigating whether subcortical changes in cellular morphology are present in neural structures critical to central auditory processing (MGN, and the ventral and dorsal subdivisions of the cochlear nucleus; VCN and DCN, respectively). Stereological assessment of brain tissue of male and female BXD29-Tlr4(lps-2J)/J mice previously tested on an auditory processing battery revealed overall smaller neurons in the MGN of BXD29-Tlr4(lps-2J)/J mutant mice in comparison to BXD29/Ty coisogenic controls, regardless of sex. Interestingly, examination of the VCN and DCN revealed sexually dimorphic changes in neuronal size, with a distribution shift toward larger neurons in female BXD29-Tlr4(lps-2J)/J brains. These effects were not seen in males. Together, the combined data set supports and further expands the observed co-occurrence of MCD, auditory processing impairments, and changes in subcortical anatomy of the central auditory pathway. The current stereological findings also highlight sex differences in neuroanatomical presentation in the presence of a common auditory behavioral phenotype.
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Affiliation(s)
- Dongnhu T Truong
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA
| | - Amanda R Rendall
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA
| | - Glenn D Rosen
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
| | - R Holly Fitch
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA.
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20
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Nakamoto KT, Shackleton TM, Magezi DA, Palmer AR. A function for binaural integration in auditory grouping and segregation in the inferior colliculus. J Neurophysiol 2014; 113:1819-30. [PMID: 25540219 DOI: 10.1152/jn.00472.2014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Responses of neurons to binaural, harmonic complex stimuli in urethane-anesthetized guinea pig inferior colliculus (IC) are reported. To assess the binaural integration of harmonicity cues for sound segregation and grouping, responses were measured to harmonic complexes with different fundamental frequencies presented to each ear. Simultaneously gated harmonic stimuli with fundamental frequencies of 125 Hz and 145 Hz were presented to the left and right ears, respectively, and recordings made from 96 neurons with characteristic frequencies >2 kHz in the central nucleus of the IC. Of these units, 70 responded continuously throughout the stimulus and were excited by the stimulus at the contralateral ear. The stimulus at the ipsilateral ear excited (EE: 14%; 10/70), inhibited (EI: 33%; 23/70), or had no significant effect (EO: 53%; 37/70), defined by the effect on firing rate. The neurons phase locked to the temporal envelope at each ear to varying degrees depending on signal level. Many of the cells (predominantly EO) were dominated by the response to the contralateral stimulus. Another group (predominantly EI) synchronized to the contralateral stimulus and were suppressed by the ipsilateral stimulus in a phasic manner. A third group synchronized to the stimuli at both ears (predominantly EE). Finally, a group only responded when the waveform peaks from each ear coincided. We conclude that these groups of neurons represent different "streams" of information but exhibit modifications of the response rather than encoding a feature of the stimulus, like pitch.
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Affiliation(s)
- Kyle T Nakamoto
- Medical Research Council Institute of Hearing Research, University Park, Nottingham, United Kingdom; Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio; and
| | - Trevor M Shackleton
- Medical Research Council Institute of Hearing Research, University Park, Nottingham, United Kingdom
| | - David A Magezi
- Laboratory for Cognitive and Neurological Sciences, Neurology Unit, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland
| | - Alan R Palmer
- Medical Research Council Institute of Hearing Research, University Park, Nottingham, United Kingdom
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21
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Mellott JG, Foster NL, Ohl AP, Schofield BR. Excitatory and inhibitory projections in parallel pathways from the inferior colliculus to the auditory thalamus. Front Neuroanat 2014; 8:124. [PMID: 25414646 PMCID: PMC4220731 DOI: 10.3389/fnana.2014.00124] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 10/17/2014] [Indexed: 01/06/2023] Open
Abstract
Individual subdivisions of the medial geniculate body (MG) receive a majority of their ascending inputs from 1 or 2 subdivisions of the inferior colliculus (IC). This establishes parallel pathways that provide a model for understanding auditory projections from the IC through the MG and on to auditory cortex. A striking discovery about the tectothalamic circuit was identification of a substantial GABAergic component. Whether GABAergic projections match the parallel pathway organization has not been examined. We asked whether the parallel pathway concept is reflected in guinea pig tectothalamic pathways and to what degree GABAergic cells contribute to each pathway. We deposited retrograde tracers into individual MG subdivisions (ventral, MGv; medial, MGm; dorsal, MGd; suprageniculate, MGsg) to label tectothalamic cells and used immunochemistry to identify GABAergic cells. The MGv receives most of its IC input (~75%) from the IC central nucleus (ICc); MGd and MGsg receive most of their input (~70%) from IC dorsal cortex (ICd); and MGm receives substantial input from both ICc (~40%) and IC lateral cortex (~40%). Each MG subdivision receives additional input (up to 32%) from non-dominant IC subdivisions, suggesting cross-talk between the pathways. The proportion of GABAergic cells in each pathway depended on the MG subdivision. GABAergic cells formed ~20% of IC inputs to MGv or MGm, ~11% of inputs to MGd, and 4% of inputs to MGsg. Thus, non-GABAergic (i.e., glutamatergic) cells are most numerous in each pathway with GABAergic cells contributing to different extents. Despite smaller numbers of GABAergic cells, their distributions across IC subdivisions mimicked the parallel pathways. Projections outside the dominant pathways suggest opportunities for excitatory and inhibitory crosstalk. The results demonstrate parallel tectothalamic pathways in guinea pigs and suggest numerous opportunities for excitatory and inhibitory interactions within and between pathways.
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Affiliation(s)
- Jeffrey G Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Nichole L Foster
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
| | - Andrew P Ohl
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Brett R Schofield
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
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Mellott JG, Bickford ME, Schofield BR. Descending projections from auditory cortex to excitatory and inhibitory cells in the nucleus of the brachium of the inferior colliculus. Front Syst Neurosci 2014; 8:188. [PMID: 25339870 PMCID: PMC4186273 DOI: 10.3389/fnsys.2014.00188] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 09/16/2014] [Indexed: 01/13/2023] Open
Abstract
Descending projections from the auditory cortex (AC) terminate in subcortical auditory centers from the medial geniculate nucleus (MG) to the cochlear nucleus, allowing the AC to modulate the processing of acoustic information at many levels of the auditory system. The nucleus of the brachium of the inferior colliculus (NBIC) is a large midbrain auditory nucleus that is a target of these descending cortical projections. The NBIC is a source of several auditory projections, including an ascending projection to the MG. This ascending projection appears to originate from both excitatory and inhibitory NBIC cells, but whether the cortical projections contact either of these cell groups is unknown. In this study, we first combined retrograde tracing and immunochemistry for glutamic acid decarboxylase (GAD, a marker of GABAergic cells) to identify GABAergic and non-GABAergic NBIC projections to the MG. Our first result is that GAD-immunopositive cells constitute ~17% of the NBIC to MG projection. We then used anterograde labeling and electron microscopy to examine the AC projection to the NBIC. Our second result is that cortical boutons in the NBIC form synapses with round vesicles and asymmetric synapses, consistent with excitatory effects. Finally, we combined fluorescent anterograde labeling of corticofugal axons with immunochemistry and retrograde labeling of NBIC cells that project to the MG. These final results suggest first that AC axons contact both GAD-negative and GAD-positive NBIC cells and, second, that some of cortically-contacted cells project to the MG. Overall, the results imply that corticofugal projections can modulate both excitatory and inhibitory ascending projections from the NBIC to the auditory thalamus.
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Affiliation(s)
- Jeffrey G Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH USA
| | - Martha E Bickford
- Department of Anatomical Sciences and Neurobiology, University of Louisville Louisville, KY USA
| | - Brett R Schofield
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH USA
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23
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Schofield BR, Mellott JG, Motts SD. Subcollicular projections to the auditory thalamus and collateral projections to the inferior colliculus. Front Neuroanat 2014; 8:70. [PMID: 25100950 PMCID: PMC4103406 DOI: 10.3389/fnana.2014.00070] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 06/27/2014] [Indexed: 01/03/2023] Open
Abstract
Experiments in several species have identified direct projections to the medial geniculate nucleus (MG) from cells in subcollicular auditory nuclei. Moreover, many cochlear nucleus cells that project to the MG send collateral projections to the inferior colliculus (IC) (Schofield et al., 2014). We conducted three experiments to characterize projections to the MG from the superior olivary and the lateral lemniscal regions in guinea pigs. For experiment 1, we made large injections of retrograde tracer into the MG. Labeled cells were most numerous in the superior paraolivary nucleus, ventral nucleus of the trapezoid body, lateral superior olivary nucleus, ventral nucleus of the lateral lemniscus, ventrolateral tegmental nucleus, paralemniscal region and sagulum. Additional sources include other periolivary nuclei and the medial superior olivary nucleus. The projections are bilateral with an ipsilateral dominance (66%). For experiment 2, we injected tracer into individual MG subdivisions. The results show that the subcollicular projections terminate primarily in the medial MG, with the dorsal MG a secondary target. The variety of projecting nuclei suggest a range of functions, including monaural and binaural aspects of hearing. These direct projections could provide the thalamus with some of the earliest (i.e., fastest) information regarding acoustic stimuli. For experiment 3, we made large injections of different retrograde tracers into one MG and the homolateral IC to identify cells that project to both targets. Such cells were numerous and distributed across many of the nuclei listed above, mostly ipsilateral to the injections. The prominence of the collateral projections suggests that the same information is delivered to both the IC and the MG, or perhaps that a common signal is being delivered as a preparatory indicator or temporal reference point. The results are discussed from functional and evolutionary perspectives.
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Affiliation(s)
- Brett R Schofield
- Auditory Neuroscience Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Jeffrey G Mellott
- Auditory Neuroscience Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Susan D Motts
- Department of Physical Therapy, Arkansas State University Jonesboro, AR, USA
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Imaizumi K, Lee CC. Frequency transformation in the auditory lemniscal thalamocortical system. Front Neural Circuits 2014; 8:75. [PMID: 25071456 PMCID: PMC4086294 DOI: 10.3389/fncir.2014.00075] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 06/16/2014] [Indexed: 12/02/2022] Open
Abstract
The auditory lemniscal thalamocortical (TC) pathway conveys information from the ventral division of the medial geniculate body to the primary auditory cortex (A1). Although their general topographic organization has been well characterized, functional transformations at the lemniscal TC synapse still remain incompletely codified, largely due to the need for integration of functional anatomical results with the variability observed with various animal models and experimental techniques. In this review, we discuss these issues with classical approaches, such as in vivo extracellular recordings and tracer injections to physiologically identified areas in A1, and then compare these studies with modern approaches, such as in vivo two-photon calcium imaging, in vivo whole-cell recordings, optogenetic methods, and in vitro methods using slice preparations. A surprising finding from a comparison of classical and modern approaches is the similar degree of convergence from thalamic neurons to single A1 neurons and clusters of A1 neurons, although, thalamic convergence to single A1 neurons is more restricted from areas within putative thalamic frequency lamina. These comparisons suggest that frequency convergence from thalamic input to A1 is functionally limited. Finally, we consider synaptic organization of TC projections and future directions for research.
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Affiliation(s)
- Kazuo Imaizumi
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine Baton Rouge, LA, USA
| | - Charles C Lee
- Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine Baton Rouge, LA, USA
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25
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Mellott JG, Foster NL, Nakamoto KT, Motts SD, Schofield BR. Distribution of GABAergic cells in the inferior colliculus that project to the thalamus. Front Neuroanat 2014; 8:17. [PMID: 24744703 PMCID: PMC3978371 DOI: 10.3389/fnana.2014.00017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/12/2014] [Indexed: 12/21/2022] Open
Abstract
A GABAergic component has been identified in the projection from the inferior colliculus (IC) to the medial geniculate body (MG) in cats and rats. We sought to determine if this GABAergic pathway exists in guinea pig, a species widely used in auditory research. The guinea pig IC contains GABAergic cells, but their relative abundance in the IC and their relative contributions to tectothalamic projections are unknown. We identified GABAergic cells with immunochemistry for glutamic acid decarboxylase (GAD) and determined that ~21% of IC neurons are GABAergic. We then combined retrograde tracing with GAD immunohistochemistry to identify the GABAergic tectothalamic projection. Large injections of Fast Blue, red fluorescent beads or FluoroGold were deposited to include all subdivisions of the MG. The results demonstrate a GABAergic pathway from each IC subdivision to the ipsilateral MG. GABAergic cells constitute ~22% of this ipsilateral pathway. In addition, each subdivision of the IC had a GABAergic projection to the contralateral MG. Measured by number of tectothalamic cells, the contralateral projection is about 10% of the size of the ipsilateral projection. GABAergic cells constitute about 20% of the contralateral projection. In summary, the results demonstrate a tectothalamic projection in guinea pigs that originates in part from GABAergic cells that project ipsilaterally or contralaterally to the MG. The results show similarities to both rats and cats, and carry implications for the role of GABAergic tectothalamic projections vis-à-vis the presence (in cats) or near absence (in rats and guinea pigs) of GABAergic interneurons in the MG.
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Affiliation(s)
- Jeffrey G Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Nichole L Foster
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
| | - Kyle T Nakamoto
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Susan D Motts
- Department of Physical Therapy, Arkansas State University Jonesboro, AR, USA
| | - Brett R Schofield
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
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Takemoto M, Hasegawa K, Nishimura M, Song WJ. The insular auditory field receives input from the lemniscal subdivision of the auditory thalamus in mice. J Comp Neurol 2014; 522:1373-89. [DOI: 10.1002/cne.23491] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 09/30/2013] [Accepted: 10/07/2013] [Indexed: 12/19/2022]
Affiliation(s)
- Makoto Takemoto
- Department of Sensory and Cognitive Physiology; Graduate School of Medical Sciences; Kumamoto University; umamoto 860-8556 Japan
| | - Kayoko Hasegawa
- Department of Sensory and Cognitive Physiology; Graduate School of Medical Sciences; Kumamoto University; umamoto 860-8556 Japan
| | - Masataka Nishimura
- Department of Sensory and Cognitive Physiology; Graduate School of Medical Sciences; Kumamoto University; umamoto 860-8556 Japan
| | - Wen-Jie Song
- Department of Sensory and Cognitive Physiology; Graduate School of Medical Sciences; Kumamoto University; umamoto 860-8556 Japan
- Program for Leading Graduate Schools; Health Life Science: Interdisciplinary and Globally Oriented (HIGO) Program, Kumamoto University; Kumamoto 860-8556 Japan
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Schofield BR, Motts SD, Mellott JG, Foster NL. Projections from the dorsal and ventral cochlear nuclei to the medial geniculate body. Front Neuroanat 2014; 8:10. [PMID: 24634646 PMCID: PMC3942891 DOI: 10.3389/fnana.2014.00010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 02/18/2014] [Indexed: 11/13/2022] Open
Abstract
Direct projections from the cochlear nucleus (CN) to the medial geniculate body (MG) mediate a high-speed transfer of acoustic information to the auditory thalamus. Anderson etal. (2006) used anterograde tracers to label the projection from the dorsal CN (DCN) to the MG in guinea pigs. We examined this pathway with retrograde tracers. The results confirm a pathway from the DCN, originating primarily from the deep layers. Labeled cells included a few giant cells and a larger number of small cells of unknown type. Many more labeled cells were present in the ventral CN (VCN). These cells, identifiable as multipolar (stellate) or small cells, were found throughout much of the VCN. Most of the labeled cells were located contralateral to the injection site. The CN to MG pathway bypasses the inferior colliculus (IC), where most ascending auditory information is processed. Anderson etal. (2006) hypothesized that CN-MG axons are collaterals of axons that reach the IC. We tested this hypothesis by injecting different fluorescent tracers into the MG and IC and examining the CN for double-labeled cells. After injections on the same side of the brain, double-labeled cells were found in the contralateral VCN and DCN. Most double-labeled cells were in the VCN, where they accounted for up to 37% of the cells labeled by the MG injection. We conclude that projections from the CN to the MG originate from the VCN and, less so, from the DCN. A significant proportion of the cells send a collateral projection to the IC. Presumably, the collateral projections send the same information to both the MG and the IC. The results suggest that T-stellate cells of the VCN are a major source of direct projections to the auditory thalamus.
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Affiliation(s)
- Brett R Schofield
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
| | - Susan D Motts
- Department of Physical Therapy, Arkansas State University Jonesboro, AR, USA
| | - Jeffrey G Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA
| | - Nichole L Foster
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
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28
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Duque D, Malmierca MS, Caspary DM. Modulation of stimulus-specific adaptation by GABA(A) receptor activation or blockade in the medial geniculate body of the anaesthetized rat. J Physiol 2013; 592:729-43. [PMID: 24099802 DOI: 10.1113/jphysiol.2013.261941] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Stimulus-specific adaptation (SSA), which describes adaptation to repeated sounds concurrent with the maintenance of responsiveness to uncommon ones, may be an important neuronal mechanism for the detection of and attendance to rare stimuli or for the detection of deviance. It is well known that GABAergic neurotransmission regulates several different response properties in central auditory system neurons and that GABA is the major inhibitory neurotransmitter acting in the medial geniculate body (MGB). The mechanisms underlying SSA are still poorly understood; therefore, the primary aim of the present study was to examine what role, if any, MGB GABAergic circuits play in the generation and/or modulation of SSA. Microiontophoretic activation of GABA(A) receptors (GABA(A)Rs) with GABA or with the selective GABA(A)R agonist gaboxadol significantly increased SSA (computed with the common SSA index, CSI) by decreasing responses to common stimuli while having a lesser effect on responses to novel stimuli. In contrast, GABA(A)R blockade using gabazine resulted in a significant decrease in SSA. In all cases, decreases in the CSI during gabazine application were accompanied by an increase in firing rate to the stimulus paradigm. The present findings, in conjunction with those of previous studies, suggest that GABA(A)-mediated inhibition does not generate the SSA response, but can regulate the level of SSA sensitivity in a gain control manner. The existence of successive hierarchical levels of processing through the auditory system suggests that the GABAergic circuits act to enhance mechanisms to reduce redundant information.
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Affiliation(s)
- Daniel Duque
- Department of Pharmacology, Southern Illinois University School of Medicine, 801 North Rutledge, Springfield, IL 62702, USA.
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29
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Bartlett EL. The organization and physiology of the auditory thalamus and its role in processing acoustic features important for speech perception. BRAIN AND LANGUAGE 2013; 126:29-48. [PMID: 23725661 PMCID: PMC3707394 DOI: 10.1016/j.bandl.2013.03.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 02/28/2013] [Accepted: 03/19/2013] [Indexed: 05/17/2023]
Abstract
The auditory thalamus, or medial geniculate body (MGB), is the primary sensory input to auditory cortex. Therefore, it plays a critical role in the complex auditory processing necessary for robust speech perception. This review will describe the functional organization of the thalamus as it relates to processing acoustic features important for speech perception, focusing on thalamic nuclei that relate to auditory representations of language sounds. The MGB can be divided into three main subdivisions, the ventral, dorsal, and medial subdivisions, each with different connectivity, auditory response properties, neuronal properties, and synaptic properties. Together, the MGB subdivisions actively and dynamically shape complex auditory processing and form ongoing communication loops with auditory cortex and subcortical structures.
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van den Brink RL, Cohen MX, van der Burg E, Talsma D, Vissers ME, Slagter HA. Subcortical, modality-specific pathways contribute to multisensory processing in humans. ACTA ACUST UNITED AC 2013; 24:2169-77. [PMID: 23529004 DOI: 10.1093/cercor/bht069] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Oftentimes, we perceive our environment by integrating information across multiple senses. Recent studies suggest that such integration occurs at much earlier processing stages than once thought possible, including in thalamic nuclei and putatively unisensory cortical brain regions. Here, we used diffusion tensor imaging (DTI) and an audiovisual integration task to test the hypothesis that anatomical connections between sensory-related subcortical structures and sensory cortical areas govern multisensory processing in humans. Twenty-five subjects (mean age 22 years, 22 females) participated in the study. In line with our hypothesis, we show that estimated strength of white-matter connections between the first relay station in the auditory processing stream (the cochlear nucleus), the auditory thalamus, and primary auditory cortex predicted one's ability to combine auditory and visual information in a visual search task. This finding supports a growing body of work that indicates that subcortical sensory pathways do not only feed forward unisensory information to the cortex, and suggests that anatomical brain connectivity contributes to multisensory processing ability in humans.
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Affiliation(s)
| | - M X Cohen
- Department of Psychology and Cognitive Science Center Amsterdam, University of Amsterdam, Amsterdam, 1081XA, The Netherlands
| | - E van der Burg
- School of Psychology, University of Sydney, Sydney, NSW 2006, Australia
| | - D Talsma
- Department of Experimental Psychology, Ghent University, Ghent, B-9000, Belgium
| | - M E Vissers
- Department of Psychology and Cognitive Science Center Amsterdam, University of Amsterdam, Amsterdam, 1081XA, The Netherlands
| | - H A Slagter
- Department of Psychology and Cognitive Science Center Amsterdam, University of Amsterdam, Amsterdam, 1081XA, The Netherlands
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31
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Rabang CF, Bartlett EL. A computational model of cellular mechanisms of temporal coding in the medial geniculate body (MGB). PLoS One 2011; 6:e29375. [PMID: 22195049 PMCID: PMC3241713 DOI: 10.1371/journal.pone.0029375] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 11/28/2011] [Indexed: 12/04/2022] Open
Abstract
Acoustic stimuli are often represented in the early auditory pathway as patterns of neural activity synchronized to time-varying features. This phase-locking predominates until the level of the medial geniculate body (MGB), where previous studies have identified two main, largely segregated response types: Stimulus-synchronized responses faithfully preserve the temporal coding from its afferent inputs, and Non-synchronized responses, which are not phase locked to the inputs, represent changes in temporal modulation by a rate code. The cellular mechanisms underlying this transformation from phase-locked to rate code are not well understood. We use a computational model of a MGB thalamocortical neuron to test the hypothesis that these response classes arise from inferior colliculus (IC) excitatory afferents with divergent properties similar to those observed in brain slice studies. Large-conductance inputs exhibiting synaptic depression preserved input synchrony as short as 12.5 ms interclick intervals, while maintaining low firing rates and low-pass filtering responses. By contrast, small-conductance inputs with Mixed plasticity (depression of AMPA-receptor component and facilitation of NMDA-receptor component) desynchronized afferent inputs, generated a click-rate dependent increase in firing rate, and high-pass filtered the inputs. Synaptic inputs with facilitation often permitted band-pass synchrony along with band-pass rate tuning. These responses could be tuned by changes in membrane potential, strength of the NMDA component, and characteristics of synaptic plasticity. These results demonstrate how the same synchronized input spike trains from the inferior colliculus can be transformed into different representations of temporal modulation by divergent synaptic properties.
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Affiliation(s)
- Cal F. Rabang
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Edward L. Bartlett
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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32
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Anderson LA, Linden JF. Physiological differences between histologically defined subdivisions in the mouse auditory thalamus. Hear Res 2011; 274:48-60. [PMID: 21185928 PMCID: PMC3078334 DOI: 10.1016/j.heares.2010.12.016] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 12/09/2010] [Accepted: 12/20/2010] [Indexed: 12/03/2022]
Abstract
The auditory thalamic area includes the medial geniculate body (MGB) and the lateral part of the posterior thalamic nucleus (Pol). The MGB can be subdivided into a ventral subdivision, forming part of the lemniscal (primary) auditory pathway, and medial and dorsal subdivisions, traditionally considered (alongside the Pol) part of the non-lemniscal (secondary) pathway. However, physiological studies of the auditory thalamus have suggested that the Pol may be more appropriately characterised as part of the lemniscal pathway, while the medial MGB may be part of a third (polysensory) pathway, with characteristics of lemniscal and non-lemniscal areas. We document physiological properties of neurons in histologically identified areas of the MGB and Pol in the anaesthetised mouse, and present evidence in favour of a distinctive role for medial MGB in central auditory processing. In particular, medial MGB contains a greater proportion of neurons with short first-spike latencies and high response probabilities than either the ventral or dorsal MGB, despite having low spontaneous rates. Therefore, medial MGB neurons appear to fire more reliably in response to auditory input than neurons in even the lemniscal, ventral subdivision. Additionally, responses in the Pol are more similar to those in the ventral MGB than the dorsal MGB.
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Affiliation(s)
| | - Jennifer F. Linden
- Ear Institute, University College London, London WC1X 8EE, UK
- Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK
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Krützfeldt NOE, Logerot P, Kubke MF, Wild JM. Connections of the auditory brainstem in a songbird, Taeniopygia guttata. I. Projections of nucleus angularis and nucleus laminaris to the auditory torus. J Comp Neurol 2010; 518:2109-34. [PMID: 20394061 DOI: 10.1002/cne.22334] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Auditory information is important for social and reproductive behaviors in birds generally, but is crucial for oscine species (songbirds), in particular because in these species auditory feedback ensures the learning and accurate maintenance of song. While there is considerable information on the auditory projections through the forebrain of songbirds, there is no information available for projections through the brainstem. At the latter levels the prevalent model of auditory processing in birds derives from an auditory specialist, the barn owl, which uses time and intensity parameters to compute the location of sounds in space, but whether the auditory brainstem of songbirds is similarly functionally organized is unknown. To examine the songbird auditory brainstem we charted the projections of the cochlear nuclei angularis (NA) and magnocellularis (NM) and the third-order nucleus laminaris (NL) in zebra finches using standard tract-tracing techniques. As in other avian species, the projections of NM were found to be confined to NL, and NL and NA provided the ascending projections. Here we report on differential projections of NA and NL to the torus semicircularis, known in birds as nucleus mesencephalicus lateralis, pars dorsalis (MLd), and in mammals as the central nucleus of the inferior colliculus (ICc). Unlike the case in nonsongbirds, the projections of NA and NL to MLd in the zebra finch showed substantial overlap, in agreement with the projections of the cochlear nuclei to the ICc in mammals. This organization could suggest that the "what" of auditory stimuli is as important as "where."
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Affiliation(s)
- Nils O E Krützfeldt
- Department of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, PB 92019 Auckland, New Zealand
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34
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Kusmierek P, Rauschecker JP. Functional specialization of medial auditory belt cortex in the alert rhesus monkey. J Neurophysiol 2009; 102:1606-22. [PMID: 19571201 DOI: 10.1152/jn.00167.2009] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Responses of neural units in two areas of the medial auditory belt (middle medial area [MM] and rostral medial area [RM]) were tested with tones, noise bursts, monkey calls (MC), and environmental sounds (ES) in microelectrode recordings from two alert rhesus monkeys. For comparison, recordings were also performed from two core areas (primary auditory area [A1] and rostral area [R]) of the auditory cortex. All four fields showed cochleotopic organization, with best (center) frequency [BF(c)] gradients running in opposite directions in A1 and MM than in R and RM. The medial belt was characterized by a stronger preference for band-pass noise than for pure tones found medially to the core areas. Response latencies were shorter for the two more posterior (middle) areas MM and A1 than for the two rostral areas R and RM, reaching values as low as 6 ms for high BF(c) in MM and A1, and strongly depended on BF(c). The medial belt areas exhibited a higher selectivity to all stimuli, in particular to noise bursts, than the core areas. An increased selectivity to tones and noise bursts was also found in the anterior fields; the opposite was true for highly temporally modulated ES. Analysis of the structure of neural responses revealed that neurons were driven by low-level acoustic features in all fields. Thus medial belt areas RM and MM have to be considered early stages of auditory cortical processing. The anteroposterior difference in temporal processing indices suggests that R and RM may belong to a different hierarchical level or a different computational network than A1 and MM.
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Affiliation(s)
- Pawel Kusmierek
- Department of Physiology and Biophysics, Georgetown University, NRB WP23, 3970 Reservoir Rd. NW, Washington, DC, USA.
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35
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Abstract
Neurons in the primary auditory cortex respond less strongly to a commonly occurring "standard" tone than to the same tone when it is rare or "deviant." This phenomenon, called "stimulus-specific adaptation" (SSA), has been proposed as a possible single-neuron correlate of the mismatch negativity, a cortical evoked potential associated with stimulus novelty. Previous studies in cat did not observe SSA in single neurons in the auditory thalamus. However, these reports did not differentiate between the auditory thalamic subdivisions and did not examine the effects of changing the stimulus presentation rate. To explore the possibility of thalamic SSA more completely, we recorded extracellularly from 30 single units and 22 multiunit clusters in the ventral, medial, and dorsal subdivisions of the mouse medial geniculate body (MGB), while presenting the anesthetized animals with sequences of standard and deviant tones at interstimulus intervals of 400, 500 and 800 ms. We found SSA in the auditory thalamus at all three stimulus presentation rates, primarily in the medial subdivision but to a lesser degree also in the ventral MGB. Thalamic SSA was evident from the earliest onset of tone-evoked activity, although the latencies of responses to standard and deviant tones were not significantly different. Together with related findings of SSA in neurons of the "belt" regions of the inferior colliculus, these results demonstrate that SSA is present at subcortical levels, primarily in but not restricted to the nonlemniscal auditory pathway.
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36
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Abstract
Of the three major subdivisions of the auditory thalamus, the medial subdivision is the only one that receives a direct projection from the dorsal cochlear nucleus. Those cells in the medial auditory thalamus that receive the projection from the dorsal cochlear nucleus continue to the auditory cortex. A combination of anterograde and retrograde anatomical tracer injections made in the dorsal cochlear nucleus and the auditory cortex respectively, revealed terminal boutons which were directly apposed onto the dendrites and cell bodies of neurons in the medial auditory thalamus. The presence of a monosynaptic pathway, which transfers information from the first relay in the auditory system to the last, suggests that this pathway may rapidly convey very basic information to the auditory cortex.
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37
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Izquierdo M, Gutiérrez-Conde P, Merchán M, Malmierca M. Non-plastic reorganization of frequency coding in the inferior colliculus of the rat following noise-induced hearing loss. Neuroscience 2008; 154:355-69. [DOI: 10.1016/j.neuroscience.2008.01.057] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2007] [Revised: 01/28/2008] [Accepted: 01/29/2008] [Indexed: 11/25/2022]
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38
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Distribution and phenotypes of unipolar brush cells in relation to the granule cell system of the rat cochlear nucleus. Neuroscience 2008; 154:29-50. [PMID: 18343594 DOI: 10.1016/j.neuroscience.2008.01.035] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 01/16/2008] [Indexed: 11/21/2022]
Abstract
In most mammals the cochlear nuclear complex (CN) contains a distributed system of granule cells (GCS), whose parallel fiber axons innervate the dorsal cochlear nucleus (DCN). Like their counterpart in cerebellum, CN granules are innervated by mossy fibers of various origins. The GCS is complemented by unipolar brush (UBCs) and Golgi cells, and by stellate and cartwheel cells of the DCN. This cerebellum-like microcircuit modulates the activity of the DCN's main projection neurons, the pyramidal, giant and tuberculoventral neurons, and is thought to improve auditory performance by integrating acoustic and proprioceptive information. In this paper, we focus on the rat UBCs, a chemically heterogeneous neuronal population, using antibodies to calretinin, metabotropic glutamate receptor 1alpha (mGluR1alpha), epidermal growth factor substrate 8 (Eps8) and the transcription factor T-box gene Tbr2 (Tbr2). Eps8 and Tbr2 labeled most of the CN's UBCs, if not the entire population, while calretinin and mGluR1alpha distinguished two largely separate subsets with overlapping distributions. By double labeling with antibodies to Tbr2 and the alpha6 GABA receptor A (GABAA) subunit, we found that UBCs populate all regions of the GCS and occur at remarkably high densities in the DCN and subpeduncular corner, but rarely in the lamina. Although GCS subregions likely share the same microcircuitry, their dissimilar UBC densities suggest they may be functionally distinct. UBCs and granules are also present in regions previously not included in the GCS, namely the rostrodorsal magnocellular portions of ventral cochlear nucleus, vestibular nerve root, trapezoid body, spinal tract and sensory and principal nuclei of the trigeminal nerve, and cerebellar peduncles. The UBC's dendritic brush receives AMPA- and NMDA-mediated input from an individual mossy fiber, favoring singularity of input, and its axon most likely forms several mossy fiber-like endings that target numerous granule cells and other UBCs, as in the cerebellum. The UBCs therefore, may amplify afferent signals temporally and spatially, synchronizing pools of target neurons.
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Loftus WC, Malmierca MS, Bishop DC, Oliver DL. The cytoarchitecture of the inferior colliculus revisited: a common organization of the lateral cortex in rat and cat. Neuroscience 2008; 154:196-205. [PMID: 18313229 DOI: 10.1016/j.neuroscience.2008.01.019] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 12/27/2007] [Accepted: 01/02/2008] [Indexed: 11/19/2022]
Abstract
The inferior colliculus (IC) is the major component of the auditory midbrain and contains three major subdivisions: a central nucleus, a dorsal cortex, and a lateral cortex (LC). Discrepancies in the nomenclature and parcellation of the LC in the rat and cat seem to imply different, species-specific functions for this region. To establish a comparable parcellation of the LC for both rat and cat, we investigated its histochemistry and inputs. In both species, the deep lateral cortex is marked by a transition between the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) rich superficial cortex and a cytochrome oxidase (CO) rich central nucleus. In both species, focal injections of anterograde tracers in the cochlear nucleus at sites of known best frequency produced bands of labeled inputs in two different subdivisions of the IC. A medial band of axons terminated in the central nucleus, while shorter bands were located laterally and oriented nearly perpendicularly to the medial bands. In the rat, these lateral bands were located in the third, deepest layer of the lateral (external) cortex. In the cat, the bands were located in a region that was previously ascribed to the central nucleus, but now considered to belong to the third, deepest layer of the LC, the ventrolateral nucleus. In both species, the LC inputs had a tonotopic organization. In view of this parallel organization, we propose a common parcellation of the IC for rat and cat with a new nomenclature. The deep layer of the LC, previously referred to as layer 3 in the rat, is designated as the 'ventrolateral nucleus' of the LC, making it clear that this region is thought to be homologous with the ventrolateral nucleus in the cat. The similar organization of the LC implies that this subdivision of the IC has similar functions in cats and rats.
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Affiliation(s)
- W C Loftus
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3401, USA
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40
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Xu M, Liu CH, Xiong Y, He J. Corticofugal modulation of the auditory thalamic reticular nucleus of the guinea pig. J Physiol 2007; 585:15-28. [PMID: 17855753 PMCID: PMC2375454 DOI: 10.1113/jphysiol.2007.142240] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Neuronal responses to auditory stimuli and electrical stimulation were examined in 104 neurones in the auditory sector of thalamic reticular nucleus (TRN) and nine medial geniculate (MGB) neurones from anaesthetized guinea pigs. TRN neurones showed rhythmic spontaneous activities. TRN neurones changed firing pattern over time, from tonic to burst in a time interval of several seconds to tens of seconds. One-third of the TRN neurones (25/76) responded to the acoustic stimulus in a slow oscillation mode, either producing a spike burst at one time and responded with nothing another time, or producing a spike burst at one time and a single spike at the other. Thirty-two of 40 neurones received a corticofugal modulation effect. Nineteen of 32 neurones responded directly to electrical stimulation of the cortex with an oscillation of the same rhythm (7-14 Hz) as its auditory-evoked oscillation. Six neurones changed their firing pattern from burst to tonic when the auditory cortex was activated. As the TRN applied inhibition to the MGB, the oscillatory nature of inhibition would affect the fidelity of MGB relays. Thus, it was unlikely that the MGB was in relay mode when the TRN was in a slow oscillation mode. These results hint at a possible mechanism for the modulation of states of vigilance through the corticofugal pathway via the TRN.
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Affiliation(s)
- Min Xu
- Institute of Neuroscience, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Yueyang Road, Shanghai, China
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41
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Wallace MN, Anderson LA, Palmer AR. Phase-locked responses to pure tones in the auditory thalamus. J Neurophysiol 2007; 98:1941-52. [PMID: 17699690 DOI: 10.1152/jn.00697.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Accurate temporal coding of low-frequency tones by spikes that are locked to a particular phase of the sine wave (phase-locking), occurs among certain groups of neurons at various processing levels in the brain. Phase-locked responses have previously been studied in the inferior colliculus and neocortex of the guinea pig and we now describe the responses in the auditory thalamus. Recordings were made from 241 single units, 32 (13%) of which showed phase-locked responses. Units with phase-locked responses were mainly (82%) located in the ventral division of the medial geniculate body (MGB), and also the medial division (18%), but were not found in the dorsal or shell divisions. The upper limiting frequency of phase-locking varied greatly between units (60-1,100 Hz) and between anatomical divisions. The upper limit in the ventral division was 520 Hz and in the medial was 1,100 Hz. The range of steady-state delays calculated from phase plots also varied: ventral division, 8.6-14 ms (mean 11.1 ms; SD 1.56); medial division, 7.5-11 ms (mean 9.3 ms; SD 1.5). Taken together, these measurements are consistent with the medial division receiving a phase-locked input directly from the brain stem, without an obligatory relay in the inferior colliculus. Cells in both the ventral and medial divisions of the MGB showed a response that phase-locked to the fundamental frequency of a guinea pig purr and may be involved in analyzing communication calls.
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Affiliation(s)
- Mark N Wallace
- Medical Research Council, Institute of Hearing Research, University Park, Nottingham, UK.
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42
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Palmer AR, Hall DA, Sumner C, Barrett DJK, Jones S, Nakamoto K, Moore DR. Some investigations into non-passive listening. Hear Res 2007; 229:148-57. [PMID: 17275232 DOI: 10.1016/j.heares.2006.12.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 12/07/2006] [Accepted: 12/07/2006] [Indexed: 10/23/2022]
Abstract
Our knowledge of the function of the auditory nervous system is based upon a wealth of data obtained, for the most part, in anaesthetised animals. More recently, it has been generally acknowledged that factors such as attention profoundly modulate the activity of sensory systems and this can take place at many levels of processing. Imaging studies, in particular, have revealed the greater activation of auditory areas and areas outside of sensory processing areas when attending to a stimulus. We present here a brief review of the consequences of such non-passive listening and go on to describe some of the experiments we are conducting to investigate them. In imaging studies, using fMRI, we can demonstrate the activation of attention networks that are non-specific to the sensory modality as well as greater and different activation of the areas of the supra-temporal plane that includes primary and secondary auditory areas. The profuse descending connections of the auditory system seem likely to be part of the mechanisms subserving attention to sound. These are generally thought to be largely inactivated by anaesthesia. However, we have been able to demonstrate that even in an anaesthetised preparation, removing the descending control from the cortex leads to quite profound changes in the temporal patterns of activation by sounds in thalamus and inferior colliculus. Some of these effects seem to be specific to the ear of stimulation and affect interaural processing. To bridge these observations we are developing an awake behaving preparation involving freely moving animals in which it will be possible to investigate the effects of consciousness (by contrasting awake and anaesthetized), passive and active listening.
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Affiliation(s)
- A R Palmer
- MRC Institute of Hearing Research, University Park, Nottingham, UK.
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Anderson LA, Wallace MN, Palmer AR. Identification of subdivisions in the medial geniculate body of the guinea pig. Hear Res 2007; 228:156-67. [PMID: 17399924 DOI: 10.1016/j.heares.2007.02.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 02/07/2007] [Accepted: 02/09/2007] [Indexed: 11/17/2022]
Abstract
The accurate and reliable identification of subdivisions within the auditory thalamus is important for future studies of this nucleus. However, in the guinea pig, there has been no agreement on the number or nomenclature of subdivisions within the main nucleus of the auditory thalamus, the medial geniculate body (MGB). Thus, we assessed three staining methods in the guinea pig MGB and concluded that cytochrome oxidase (CYO) histochemistry provides a clear and reliable method for defining MGB subdivisions. By combining CYO with acetylcholinesterase staining and extensive physiological mapping we defined five separate divisions, all of which respond to auditory stimuli. Coronal sections stained for CYO revealed a moderate to darkly-stained oval core. This area (the ventral MGB) contained a high proportion (61%) of V-shaped tuning curves and a tonotopic organisation of characteristic frequencies. It was surrounded by four smaller areas that contained darkly stained somata but had a paler neuropil. These areas, the dorsolateral and suprageniculate (which together form the dorsal MGB), the medial MGB and the shell MGB, did not have any discernable tonotopic frequency gradient and contained a smaller proportion of V-shaped tuning curves. This suggests that CYO permits the identification of core and belt areas within the guinea pig MGB.
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Affiliation(s)
- L A Anderson
- MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, UK.
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