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Arya P, Kolodny NH, Gobes SMH. Tracing the development of learned song preferences in the female zebra finch brain with functional magnetic resonance imaging. Dev Neurobiol 2024; 84:47-58. [PMID: 38466218 PMCID: PMC11009042 DOI: 10.1002/dneu.22934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 01/31/2024] [Accepted: 02/07/2024] [Indexed: 03/12/2024]
Abstract
In sexually dimorphic zebra finches (Taeniopygia guttata), only males learn to sing their father's song, whereas females learn to recognize the songs of their father or mate but cannot sing themselves. Memory of learned songs is behaviorally expressed in females by preferring familiar songs over unfamiliar ones. Auditory association regions such as the caudomedial mesopallium (CMM; or caudal mesopallium) have been shown to be key nodes in a network that supports preferences for learned songs in adult females. However, much less is known about how song preferences develop during the sensitive period of learning in juvenile female zebra finches. In this study, we used blood-oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to trace the development of a memory-based preference for the father's song in female zebra finches. Using BOLD fMRI, we found that only in adult female zebra finches with a preference for learned song over novel conspecific song, neural selectivity for the father's song was localized in the thalamus (dorsolateral nucleus of the medial thalamus; part of the anterior forebrain pathway, AFP) and in CMM. These brain regions also showed a selective response in juvenile female zebra finches, although activation was less prominent. These data reveal that neural responses in CMM, and perhaps also in the AFP, are shaped during development to support behavioral preferences for learned songs.
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Affiliation(s)
- Payal Arya
- Neuroscience Department, Wellesley College, Wellesley, Massachusetts 02481, USA
| | - Nancy H. Kolodny
- Chemistry Department, Wellesley College, Wellesley, Massachusetts 02481, USA
| | - Sharon M. H. Gobes
- Neuroscience Department, Wellesley College, Wellesley, Massachusetts 02481, USA
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2
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Villalobos CA, Basso MA. Optogenetic activation of the inhibitory nigro-collicular circuit evokes contralateral orienting movements in mice. Cell Rep 2022; 39:110699. [PMID: 35443172 PMCID: PMC10144672 DOI: 10.1016/j.celrep.2022.110699] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 09/20/2021] [Accepted: 03/29/2022] [Indexed: 11/03/2022] Open
Abstract
We report that increasing inhibition from the basal ganglia (BG) to the superior colliculus (SC) through the substantia nigra pars reticulata (nigra) using in vivo optogenetic activation of GABAergic terminals in mice produces contralateral orienting movements. These movements are unexpected because decreases, and not increases, in nigral activity are generally associated with the initiation of orienting movements. We found that, in slice recordings, the same optogenetic stimulation of nigral terminals producing movements in vivo evokes post-inhibitory rebound depolarization followed by Na+ spikes in SC output neurons. Moreover, blocking T-type Ca2+ channels in slices prevent post-inhibitory rebound and subsequent Na+ spiking in SC output neurons and also reduce the likelihood of contralateral orienting in vivo. On the basis of these results, we propose that, in addition to the permissive role, the BG may play an active role in the generation of orienting movements in mice by driving post-inhibitory rebound depolarization in SC output neurons.
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Affiliation(s)
- Claudio A Villalobos
- Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, The Jane and Terry Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA.
| | - Michele A Basso
- Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, The Jane and Terry Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA.
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3
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Xiao L, Roberts TF. What Is the Role of Thalamostriatal Circuits in Learning Vocal Sequences? Front Neural Circuits 2021; 15:724858. [PMID: 34630047 PMCID: PMC8493212 DOI: 10.3389/fncir.2021.724858] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 08/23/2021] [Indexed: 11/13/2022] Open
Abstract
Basal ganglia (BG) circuits integrate sensory and motor-related information from the cortex, thalamus, and midbrain to guide learning and production of motor sequences. Birdsong, like speech, is comprised of precisely sequenced vocal elements. Learning song sequences during development relies on Area X, a vocalization related region in the medial striatum of the songbird BG. Area X receives inputs from cortical-like pallial song circuits and midbrain dopaminergic circuits and sends projections to the thalamus. It has recently been shown that thalamic circuits also send substantial projections back to Area X. Here, we outline a gated-reinforcement learning model for how Area X may use signals conveyed by thalamostriatal inputs to direct song learning. Integrating conceptual advances from recent mammalian and songbird literature, we hypothesize that thalamostriatal pathways convey signals linked to song syllable onsets and offsets and influence striatal circuit plasticity via regulation of cholinergic interneurons (ChIs). We suggest that syllable sequence associated vocal-motor information from the thalamus drive precisely timed pauses in ChIs activity in Area X. When integrated with concurrent corticostriatal and dopaminergic input, this circuit helps regulate plasticity on medium spiny neurons (MSNs) and the learning of syllable sequences. We discuss new approaches that can be applied to test core ideas of this model and how associated insights may provide a framework for understanding the function of BG circuits in learning motor sequences.
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Affiliation(s)
- Lei Xiao
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, United States
| | - Todd F Roberts
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, United States
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Magnusson JL, Leventhal DK. Revisiting the "Paradox of Stereotaxic Surgery": Insights Into Basal Ganglia-Thalamic Interactions. Front Syst Neurosci 2021; 15:725876. [PMID: 34512279 PMCID: PMC8429495 DOI: 10.3389/fnsys.2021.725876] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 08/06/2021] [Indexed: 11/13/2022] Open
Abstract
Basal ganglia dysfunction is implicated in movement disorders including Parkinson Disease, dystonia, and choreiform disorders. Contradicting standard "rate models" of basal ganglia-thalamic interactions, internal pallidotomy improves both hypo- and hyper-kinetic movement disorders. This "paradox of stereotaxic surgery" was recognized shortly after rate models were developed, and is underscored by the outcomes of deep brain stimulation (DBS) for movement disorders. Despite strong evidence that DBS activates local axons, the clinical effects of lesions and DBS are nearly identical. These observations argue against standard models in which GABAergic basal ganglia output gates thalamic activity, and raise the question of how lesions and stimulation can have similar effects. These paradoxes may be resolved by considering thalamocortical loops as primary drivers of motor output. Rather than suppressing or releasing cortex via motor thalamus, the basal ganglia may modulate the timing of thalamic perturbations to cortical activity. Motor cortex exhibits rotational dynamics during movement, allowing the same thalamocortical perturbation to affect motor output differently depending on its timing with respect to the rotational cycle. We review classic and recent studies of basal ganglia, thalamic, and cortical physiology to propose a revised model of basal ganglia-thalamocortical function with implications for basic physiology and neuromodulation.
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Affiliation(s)
| | - Daniel K Leventhal
- Department of Neurology, University of Michigan, Ann Arbor, MI, United States.,Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.,Parkinson Disease Foundation Research Center of Excellence, University of Michigan, Ann Arbor, MI, United States.,Department of Neurology, VA Ann Arbor Health System, Ann Arbor, MI, United States
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5
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Villalba RM, Behnke JA, Pare JF, Smith Y. Comparative Ultrastructural Analysis of Thalamocortical Innervation of the Primary Motor Cortex and Supplementary Motor Area in Control and MPTP-Treated Parkinsonian Monkeys. Cereb Cortex 2021; 31:3408-3425. [PMID: 33676368 PMCID: PMC8599722 DOI: 10.1093/cercor/bhab020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 12/29/2020] [Accepted: 01/19/2021] [Indexed: 12/15/2022] Open
Abstract
The synaptic organization of thalamic inputs to motor cortices remains poorly understood in primates. Thus, we compared the regional and synaptic connections of vGluT2-positive thalamocortical glutamatergic terminals in the supplementary motor area (SMA) and the primary motor cortex (M1) between control and MPTP-treated parkinsonian monkeys. In controls, vGluT2-containing fibers and terminal-like profiles invaded layer II-III and Vb of M1 and SMA. A significant reduction of vGluT2 labeling was found in layer Vb, but not in layer II-III, of parkinsonian animals, suggesting a potential thalamic denervation of deep cortical layers in parkinsonism. There was a significant difference in the pattern of synaptic connectivity in layers II-III, but not in layer Vb, between M1 and SMA of control monkeys. However, this difference was abolished in parkinsonian animals. No major difference was found in the proportion of perforated versus macular post-synaptic densities at thalamocortical synapses between control and parkinsonian monkeys in both cortical regions, except for a slight increase in the prevalence of perforated axo-dendritic synapses in the SMA of parkinsonian monkeys. Our findings suggest that disruption of the thalamic innervation of M1 and SMA may underlie pathophysiological changes of the motor thalamocortical loop in the state of parkinsonism.
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Affiliation(s)
- Rosa M Villalba
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Joseph A Behnke
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Jean-Francois Pare
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Yoland Smith
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
- Department of Neurology, School of Medicine, Emory University, Atlanta, GA 30329, USA
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Nejad MM, Rotter S, Schmidt R. Basal ganglia and cortical control of thalamic rebound spikes. Eur J Neurosci 2021; 54:4295-4313. [PMID: 33914390 DOI: 10.1111/ejn.15258] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 04/09/2021] [Accepted: 04/24/2021] [Indexed: 12/29/2022]
Abstract
Movement-related decreases in firing rate have been observed in basal ganglia output neurons. They may transmit motor signals to the thalamus, but the effect of these firing rate decreases on downstream neurons in the motor thalamus is not known. One possibility is that they lead to thalamic post-inhibitory rebound spikes. However, it has also been argued that the physiological conditions permitting rebound spiking are pathological, and primarily present in Parkinson's disease. As in Parkinson's disease neural activity becomes pathologically correlated, we investigated the impact of correlations in basal ganglia output on the transmission of motor signals using a Hodgkin-Huxley model of thalamocortical neurons. We found that such correlations disrupt the transmission of motor signals via rebound spikes by decreasing the signal-to-noise ratio and increasing the trial-to-trial variability. We further examined the role of sensory responses in basal ganglia output neurons and the effect of cortical excitation of motor thalamus in modulating rebound spiking. Interestingly, both could either promote or suppress the generation of rebound spikes depending on their timing relative to the motor signal. Finally, we determined parameter regimes, such as levels of excitation, under which rebound spiking is feasible in the model, and confirmed that the conditions for rebound spiking are primarily given in pathological regimes. However, we also identified specific conditions in the model that would allow rebound spiking to occur in healthy animals in a small subset of thalamic neurons. Overall, our model provides novel insights into differences between normal and pathological transmission of motor signals.
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Affiliation(s)
- Mohammadreza Mohagheghi Nejad
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg, Germany
- Department of Computational Science and Technology, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Stefan Rotter
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Robert Schmidt
- Department of Psychology, University of Sheffield, Sheffield, UK
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Schwab BC, Kase D, Zimnik A, Rosenbaum R, Codianni MG, Rubin JE, Turner RS. Neural activity during a simple reaching task in macaques is counter to gating and rebound in basal ganglia-thalamic communication. PLoS Biol 2020; 18:e3000829. [PMID: 33048920 PMCID: PMC7584254 DOI: 10.1371/journal.pbio.3000829] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 10/23/2020] [Accepted: 09/14/2020] [Indexed: 12/24/2022] Open
Abstract
Task-related activity in the ventral thalamus, a major target of basal ganglia output, is often assumed to be permitted or triggered by changes in basal ganglia activity through gating- or rebound-like mechanisms. To test those hypotheses, we sampled single-unit activity from connected basal ganglia output and thalamic nuclei (globus pallidus-internus [GPi] and ventrolateral anterior nucleus [VLa]) in monkeys performing a reaching task. Rate increases were the most common peri-movement change in both nuclei. Moreover, peri-movement changes generally began earlier in VLa than in GPi. Simultaneously recorded GPi-VLa pairs rarely showed short-time-scale spike-to-spike correlations or slow across-trials covariations, and both were equally positive and negative. Finally, spontaneous GPi bursts and pauses were both followed by small, slow reductions in VLa rate. These results appear incompatible with standard gating and rebound models. Still, gating or rebound may be possible in other physiological situations: simulations show how GPi-VLa communication can scale with GPi synchrony and GPi-to-VLa convergence, illuminating how synchrony of basal ganglia output during motor learning or in pathological conditions may render this pathway effective. Thus, in the healthy state, basal ganglia-thalamic communication during learned movement is more subtle than expected, with changes in firing rates possibly being dominated by a common external source.
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Affiliation(s)
- Bettina C. Schwab
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Technical Medical Center, University of Twente, Enschede, the Netherlands
| | - Daisuke Kase
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Andrew Zimnik
- Department of Neuroscience, Columbia University Medical Center, New York, New York, United States of America
| | - Robert Rosenbaum
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, South Bend, Indiana, United States of America
| | - Marcello G. Codianni
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Jonathan E. Rubin
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Robert S. Turner
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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8
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Abstract
Behavior is readily classified into patterns of movements with inferred common goals-actions. Goals may be discrete; movements are continuous. Through the careful study of isolated movements in laboratory settings, or via introspection, it has become clear that animals can exhibit exquisite graded specification to their movements. Moreover, graded control can be as fundamental to success as the selection of which action to perform under many naturalistic scenarios: a predator adjusting its speed to intercept moving prey, or a tool-user exerting the perfect amount of force to complete a delicate task. The basal ganglia are a collection of nuclei in vertebrates that extend from the forebrain (telencephalon) to the midbrain (mesencephalon), constituting a major descending extrapyramidal pathway for control over midbrain and brainstem premotor structures. Here we discuss how this pathway contributes to the continuous specification of movements that endows our voluntary actions with vigor and grace.
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Affiliation(s)
- Junchol Park
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA;
| | - Luke T Coddington
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA;
| | - Joshua T Dudman
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA;
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New Insights into the Avian Song System and Neuronal Control of Learned Vocalizations. THE NEUROETHOLOGY OF BIRDSONG 2020. [DOI: 10.1007/978-3-030-34683-6_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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10
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Pidoux L, Le Blanc P, Levenes C, Leblois A. A subcortical circuit linking the cerebellum to the basal ganglia engaged in vocal learning. eLife 2018; 7:32167. [PMID: 30044222 PMCID: PMC6112851 DOI: 10.7554/elife.32167] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 07/24/2018] [Indexed: 01/09/2023] Open
Abstract
Speech is a complex sensorimotor skill, and vocal learning involves both the basal ganglia and the cerebellum. These subcortical structures interact indirectly through their respective loops with thalamo-cortical and brainstem networks, and directly via subcortical pathways, but the role of their interaction during sensorimotor learning remains undetermined. While songbirds and their song-dedicated basal ganglia-thalamo-cortical circuitry offer a unique opportunity to study subcortical circuits involved in vocal learning, the cerebellar contribution to avian song learning remains unknown. We demonstrate that the cerebellum provides a strong input to the song-related basal ganglia nucleus in zebra finches. Cerebellar signals are transmitted to the basal ganglia via a disynaptic connection through the thalamus and then conveyed to their cortical target and to the premotor nucleus controlling song production. Finally, cerebellar lesions impair juvenile song learning, opening new opportunities to investigate how subcortical interactions between the cerebellum and basal ganglia contribute to sensorimotor learning.
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Affiliation(s)
- Ludivine Pidoux
- Center for Neurophysics, Physiology and Pathology (UMR CNRS 8119), Centre National de la Recherche Scientifique (CNRS), Institute for Neuroscience and Cognition, Paris Descartes University, Paris, France
| | - Pascale Le Blanc
- Center for Neurophysics, Physiology and Pathology (UMR CNRS 8119), Centre National de la Recherche Scientifique (CNRS), Institute for Neuroscience and Cognition, Paris Descartes University, Paris, France
| | - Carole Levenes
- Center for Neurophysics, Physiology and Pathology (UMR CNRS 8119), Centre National de la Recherche Scientifique (CNRS), Institute for Neuroscience and Cognition, Paris Descartes University, Paris, France
| | - Arthur Leblois
- Center for Neurophysics, Physiology and Pathology (UMR CNRS 8119), Centre National de la Recherche Scientifique (CNRS), Institute for Neuroscience and Cognition, Paris Descartes University, Paris, France
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Heston JB, Simon J, Day NF, Coleman MJ, White SA. Bidirectional scaling of vocal variability by an avian cortico-basal ganglia circuit. Physiol Rep 2018; 6:e13638. [PMID: 29687960 PMCID: PMC5913712 DOI: 10.14814/phy2.13638] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 01/31/2018] [Accepted: 02/02/2018] [Indexed: 12/14/2022] Open
Abstract
Behavioral variability is thought to be critical for trial and error learning, but where such motor exploration is generated in the central nervous system is unclear. The zebra finch songbird species offers a highly appropriate model in which to address this question. The male song is amenable to detailed measurements of variability, while the brain contains an identified cortico-basal ganglia loop that underlies this behavior. We used pharmacogenetic interventions to separately interrogate cortical and basal ganglia nodes of zebra finch song control circuitry. We show that bidirectional manipulations of each node produce near mirror image changes in vocal control: Cortical activity promotes song variability, whereas basal ganglia activity promotes song stability. Furthermore, female conspecifics can detect these pharmacogenetically elicited changes in song quality. Our results indicate that cortex and striatopallidum can jointly and reciprocally affect behaviorally relevant levels of vocal variability, and point to endogenous mechanisms for its control.
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Affiliation(s)
- Jonathan B. Heston
- Interdepartmental Program in NeuroscienceUniversity of CaliforniaLos AngelesCalifornia
| | - Joseph Simon
- Undergraduate Interdepartmental Program for NeuroscienceUniversity of CaliforniaLos AngelesCalifornia
| | - Nancy F. Day
- Department of Integrative Biology and PhysiologyUniversity of CaliforniaLos AngelesCalifornia
| | - Melissa J. Coleman
- W. M. Keck Science Department of Claremont McKenna CollegePitzer College, and Scripps CollegeClaremontCalifornia
| | - Stephanie A. White
- Interdepartmental Program in NeuroscienceUniversity of CaliforniaLos AngelesCalifornia
- Undergraduate Interdepartmental Program for NeuroscienceUniversity of CaliforniaLos AngelesCalifornia
- Department of Integrative Biology and PhysiologyUniversity of CaliforniaLos AngelesCalifornia
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12
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Effect of optogenetic modulation on entopeduncular input affects thalamic discharge and behavior in an AAV2-α-synuclein-induced hemiparkinson rat model. Neurosci Lett 2017; 662:129-135. [PMID: 29037791 DOI: 10.1016/j.neulet.2017.10.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 09/25/2017] [Accepted: 10/11/2017] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Neuromodulation of the globus pallidus internus(GPi) alleviates Parkinson's disease symptoms. The primate GPi is homologous to the rat entopeduncular nucleus (EP). The aim of the present study was to determine if optogenetic modulation of the EP could alter parkinsonian behavior or thalamic discharge in a hemiparkinson rat model. METHODS We injected an adeno-associated virus type-2 expressing α-synuclein (AAV2-α-syn) into the substantia nigra pars compacta (SNc) of the right hemisphere and confirmed parkinsonian behavior using an amphetamine-induced rotation test. Then we injected activated or inhibited neurons, using the channelrhodopsin2 (ChR2)/halorhodopsin (NpHR) system in the EP of the hemiparkinson rat model and examined downstream effects in vivo. We assessed alterations in parkinsonian behaviors using the stepping and cylinder tests before, during, and after optogenetic stimulation. RESULTS Importantly, optogenetic inhibition of the EP improved parkinsonian motor behaviors. When we monitored thalamic neuronal activity following optogenetic neuromodulation in vivo, and we observed alterations in thalamic discharge The thalamic neuronal activity is increased for optogenetic inhibition stimulation, whereas decreased for optogenetic activation stimulation. CONCLUSIONS Taken together, our data demonstrate that optical neuromodulation of the EP can successfully control contralateral forelimb movement and thalamic discharge in an AAV2-α-synuclein-induced hemiparkinson rat model.
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Tecuapetla F, Jin X, Lima SQ, Costa RM. Complementary Contributions of Striatal Projection Pathways to Action Initiation and Execution. Cell 2016; 166:703-715. [DOI: 10.1016/j.cell.2016.06.032] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/18/2016] [Accepted: 06/15/2016] [Indexed: 01/26/2023]
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14
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Kozloski J. Closed-Loop Brain Model of Neocortical Information-Based Exchange. Front Neuroanat 2016; 10:3. [PMID: 26834573 PMCID: PMC4716663 DOI: 10.3389/fnana.2016.00003] [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: 08/29/2015] [Accepted: 01/02/2016] [Indexed: 11/25/2022] Open
Abstract
Here we describe an “information-based exchange” model of brain function that ascribes to neocortex, basal ganglia, and thalamus distinct network functions. The model allows us to analyze whole brain system set point measures, such as the rate and heterogeneity of transitions in striatum and neocortex, in the context of neuromodulation and other perturbations. Our closed-loop model is grounded in neuroanatomical observations, proposing a novel “Grand Loop” through neocortex, and invokes different forms of plasticity at specific tissue interfaces and their principle cell synapses to achieve these transitions. By implementing a system for maximum information-based exchange of action potentials between modeled neocortical areas, we observe changes to these measures in simulation. We hypothesize that similar dynamic set points and modulations exist in the brain's resting state activity, and that different modifications to information-based exchange may shift the risk profile of different component tissues, resulting in different neurodegenerative diseases. This model is targeted for further development using IBM's Neural Tissue Simulator, which allows scalable elaboration of networks, tissues, and their neural and synaptic components toward ever greater complexity and biological realism.
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Affiliation(s)
- James Kozloski
- IBM Research Division, Computational Biology Center, IBM T.J. Watson Research Center Yorktown Heights, NY, USA
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15
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Agnesi F, Muralidharan A, Baker KB, Vitek JL, Johnson MD. Fidelity of frequency and phase entrainment of circuit-level spike activity during DBS. J Neurophysiol 2015; 114:825-34. [PMID: 26084905 DOI: 10.1152/jn.00259.2015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 06/16/2015] [Indexed: 11/22/2022] Open
Abstract
High-frequency stimulation is known to entrain spike activity downstream and upstream of several clinical deep brain stimulation (DBS) targets, including the cerebellar-receiving area of thalamus (VPLo), subthalamic nucleus (STN), and globus pallidus (GP). Less understood are the fidelity of entrainment to each stimulus pulse, whether entrainment patterns are stationary over time, and how responses differ among DBS targets. In this study, three rhesus macaques were implanted with a single DBS lead in VPLo, STN, or GP. Single-unit spike activity was recorded in the resting state in motor cortex during VPLo DBS, in GP during STN DBS, and in STN and pallidal-receiving area of motor thalamus (VLo) during GP DBS. VPLo DBS induced time-locked spike activity in 25% (n = 15/61) of motor cortex cells, with entrained cells following 7.5 ± 7.4% of delivered pulses. STN DBS entrained spike activity in 26% (n = 8/27) of GP cells, which yielded time-locked spike activity for 8.7 ± 8.4% of stimulus pulses. GP DBS entrained 67% (n = 14/21) of STN cells and 32% (n = 19/59) of VLo cells, which showed a higher fraction of pulses effectively inhibiting spike activity (82.0 ± 9.6% and 86.1 ± 16.6%, respectively). Latency of phase-locked spike activity increased over time in motor cortex (58%, VPLo DBS) and to a lesser extent in GP (25%, STN DBS). In contrast, the initial inhibitory phase observed in VLo and STN during GP DBS remained stable following stimulation onset. Together, these data suggest that circuit-level entrainment is low-pass filtered during high-frequency stimulation, most notably for glutamatergic pathways. Moreover, phase entrainment is not stationary or consistent at the circuit level for all DBS targets.
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Affiliation(s)
- Filippo Agnesi
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota
| | | | - Kenneth B Baker
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota
| | - Jerrold L Vitek
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota
| | - Matthew D Johnson
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota; Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Woolley S, Kao M. Variability in action: Contributions of a songbird cortical-basal ganglia circuit to vocal motor learning and control. Neuroscience 2015; 296:39-47. [DOI: 10.1016/j.neuroscience.2014.10.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 10/07/2014] [Accepted: 10/08/2014] [Indexed: 10/24/2022]
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Abstract
Starting with the work of Cajal more than 100 years ago, neuroscience has sought to understand how the cells of the brain give rise to cognitive functions. How far has neuroscience progressed in this endeavor? This Perspective assesses progress in elucidating five basic brain processes: visual recognition, long-term memory, short-term memory, action selection, and motor control. Each of these processes entails several levels of analysis: the behavioral properties, the underlying computational algorithm, and the cellular/network mechanisms that implement that algorithm. At this juncture, while many questions remain unanswered, achievements in several areas of research have made it possible to relate specific properties of brain networks to cognitive functions. What has been learned reveals, at least in rough outline, how cognitive processes can be an emergent property of neurons and their connections.
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Affiliation(s)
- John Lisman
- Biology Department and Volen Center for Complex Systems, Brandeis University, 415 South Street, Waltham, MA 02454-9110, USA.
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18
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Pidoux M, Bollu T, Riccelli T, Goldberg JH. Origins of basal ganglia output signals in singing juvenile birds. J Neurophysiol 2015; 113:843-55. [PMID: 25392171 DOI: 10.1152/jn.00635.2014] [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
Across species, complex circuits inside the basal ganglia (BG) converge on pallidal output neurons that exhibit movement-locked firing patterns. Yet the origins of these firing patterns remain poorly understood. In songbirds during vocal babbling, BG output neurons homologous to those found in the primate internal pallidal segment are uniformly activated in the tens of milliseconds prior to syllable onsets. To test the origins of this remarkably homogenous BG output signal, we recorded from diverse upstream BG cell types during babbling. Prior to syllable onsets, at the same time that internal pallidal segment-like neurons were activated, putative medium spiny neurons, fast spiking and tonically active interneurons also exhibited transient rate increases. In contrast, pallidal neurons homologous to those found in primate external pallidal segment exhibited transient rate decreases. To test origins of these signals, we performed recordings following lesion of corticostriatal inputs from premotor nucleus HVC. HVC lesions largely abolished these syllable-locked signals. Altogether, these findings indicate a striking homogeneity of syllable timing signals in the songbird BG during babbling and are consistent with a role for the indirect and hyperdirect pathways in transforming cortical inputs into BG outputs during an exploratory behavior.
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Affiliation(s)
- Morgane Pidoux
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
| | - Tejapratap Bollu
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
| | - Tori Riccelli
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
| | - Jesse H Goldberg
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
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19
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20
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Obeidat AZ, Nardelli P, Powers RK, Cope TC. Modulation of motoneuron firing by recurrent inhibition in the adult rat in vivo. J Neurophysiol 2014; 112:2302-15. [PMID: 25122713 PMCID: PMC4274916 DOI: 10.1152/jn.00358.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/12/2014] [Indexed: 11/22/2022] Open
Abstract
Recent reports show that synaptic inhibition can modulate postsynaptic spike timing without having strong effects on firing rate. Thus synaptic inhibition can achieve multiplicity in neural circuit operation through variable modulation of postsynaptic firing rate vs. timing. We tested this possibility for recurrent inhibition (RI) of spinal motoneurons. In in vivo electrophysiological studies of adult Wistar rats anesthetized by isoflurane, we examined repetitive firing of individual lumbosacral motoneurons recorded in current clamp and modulated by synchronous antidromic electrical stimulation of multiple motor axons and their centrally projecting collateral branches. Antidromic stimulation produced recurrent inhibitory postsynaptic potentials (RIPSPs) having properties similar to those detailed in the cat. Although synchronous RI produced marked short-term modulation of motoneuron spike timing and instantaneous firing rate, there was little or no suppression of average firing rate. The bias in firing modulation of timing over average rate was observed even for high-frequency RI stimulation (100 Hz), perhaps because of the brevity of RIPSPs, which were more than twofold shorter during motoneuron firing compared with rest. These findings demonstrate that RI in the mammalian spinal cord has the capacity to support and not impede heightened motor pool activity, possibly during rapid, forceful movements.
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Affiliation(s)
- Ahmed Z Obeidat
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio; and
| | - Paul Nardelli
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio; and
| | - Randall K Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Timothy C Cope
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio; and
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21
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Woolley SC, Rajan R, Joshua M, Doupe AJ. Emergence of context-dependent variability across a basal ganglia network. Neuron 2014; 82:208-23. [PMID: 24698276 DOI: 10.1016/j.neuron.2014.01.039] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2014] [Indexed: 10/25/2022]
Abstract
Context dependence is a key feature of cortical-basal ganglia circuit activity, and in songbirds the cortical outflow of a basal ganglia circuit specialized for song, LMAN, shows striking increases in trial-by-trial variability and bursting when birds sing alone rather than to females. To reveal where this variability and its social regulation emerge, we recorded stepwise from corticostriatal (HVC) neurons and their target spiny and pallidal neurons in Area X. We find that corticostriatal and spiny neurons both show precise singing-related firing across both social settings. Pallidal neurons, in contrast, exhibit markedly increased trial-by-trial variation when birds sing alone, created by highly variable pauses in firing. This variability persists even when recurrent inputs from LMAN are ablated. These data indicate that variability and its context sensitivity emerge within the basal ganglia network, suggest a network mechanism for this emergence, and highlight variability generation and regulation as basal ganglia functions.
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Affiliation(s)
- Sarah C Woolley
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Biology, McGill University, Montreal, QC H3A 1B1, Canada.
| | - Raghav Rajan
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA; Indian Institute of Science Education and Research, Pashan Road, Pune 411008, Maharashra, India
| | - Mati Joshua
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Neurobiology, Duke University, Durham, NC 27710, USA
| | - Allison J Doupe
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
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22
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Simmonds AJ, Leech R, Iverson P, Wise RJS. The response of the anterior striatum during adult human vocal learning. J Neurophysiol 2014; 112:792-801. [PMID: 24805076 DOI: 10.1152/jn.00901.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Research on mammals predicts that the anterior striatum is a central component of human motor learning. However, because vocalizations in most mammals are innate, much of the neurobiology of human vocal learning has been inferred from studies on songbirds. Essential for song learning is a pathway, the homolog of mammalian cortical-basal ganglia "loops," which includes the avian striatum. The present functional magnetic resonance imaging (fMRI) study investigated adult human vocal learning, a skill that persists throughout life, albeit imperfectly given that late-acquired languages are spoken with an accent. Monolingual adult participants were scanned while repeating novel non-native words. After training on the pronunciation of half the words for 1 wk, participants underwent a second scan. During scanning there was no external feedback on performance. Activity declined sharply in left and right anterior striatum, both within and between scanning sessions, and this change was independent of training and performance. This indicates that adult speakers rapidly adapt to the novel articulatory movements, possibly by using motor sequences from their native speech to approximate those required for the novel speech sounds. Improved accuracy correlated only with activity in motor-sensory perisylvian cortex. We propose that future studies on vocal learning, using different behavioral and pharmacological manipulations, will provide insights into adult striatal plasticity and its potential for modification in both educational and clinical contexts.
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Affiliation(s)
- Anna J Simmonds
- Computational, Cognitive and Clinical Neuroimaging Laboratory (C3NL), Division of Brain Sciences, Imperial College London, United Kingdom; and
| | - Robert Leech
- Computational, Cognitive and Clinical Neuroimaging Laboratory (C3NL), Division of Brain Sciences, Imperial College London, United Kingdom; and
| | - Paul Iverson
- Department of Speech, Hearing and Phonetic Sciences, Division of Psychology and Language Sciences, University College London, United Kingdom
| | - Richard J S Wise
- Computational, Cognitive and Clinical Neuroimaging Laboratory (C3NL), Division of Brain Sciences, Imperial College London, United Kingdom; and
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Edgerton JR, Jaeger D. Optogenetic activation of nigral inhibitory inputs to motor thalamus in the mouse reveals classic inhibition with little potential for rebound activation. Front Cell Neurosci 2014; 8:36. [PMID: 24574972 PMCID: PMC3920182 DOI: 10.3389/fncel.2014.00036] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 01/23/2014] [Indexed: 11/13/2022] Open
Abstract
The inhibitory output from the internal pallidum and substantia nigra to the thalamus forms an important link in the transmission of basal ganglia processing to cortex. Two hypotheses consider either inhibition of thalamic activity or thalamic excitation via post-inhibitory rebound burst firing as the functional mode of this link. We used optogenetics to characterize the synaptic properties of nigral input to motor thalamus in adult mouse brain slices, and to determine in what conditions the nigral inhibition of motor thalamus is transmitted via inhibition or rebound firing. Our results are more consistent with graded inhibition of spiking for conditions expected in normal awake animals, because inhibitory potentials from nigral input were generally not sufficient to elicit rebound spikes when the thalamic neurons were actively firing. However, with bursty or fast trains of nigral input low-threshold rebound spike bursts could be triggered for low levels of excitation. This may form the basis of pathological burst generation and transmission in parkinsonian conditions.
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Affiliation(s)
| | - Dieter Jaeger
- Department of Biology, Emory University Atlanta, GA, USA
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24
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Anderson ML, Finlay BL. Allocating structure to function: the strong links between neuroplasticity and natural selection. Front Hum Neurosci 2014; 7:918. [PMID: 24431995 PMCID: PMC3882658 DOI: 10.3389/fnhum.2013.00918] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Accepted: 12/15/2013] [Indexed: 11/23/2022] Open
Abstract
A central question in brain evolution is how species-typical behaviors, and the neural function-structure mappings supporting them, can be acquired and inherited. Advocates of brain modularity, in its different incarnations across scientific subfields, argue that natural selection must target domain-dedicated, separately modifiable neural subsystems, resulting in genetically-specified functional modules. In such modular systems, specification of neuron number and functional connectivity are necessarily linked. Mounting evidence, however, from allometric, developmental, comparative, systems-physiological, neuroimaging and neurological studies suggests that brain elements are used and reused in multiple functional systems. This variable allocation can be seen in short-term neuromodulation, in neuroplasticity over the lifespan and in response to damage. We argue that the same processes are evident in brain evolution. Natural selection must preserve behavioral functions that may co-locate in variable amounts with other functions. In genetics, the uses and problems of pleiotropy, the re-use of genes in multiple networks have been much discussed, but this issue has been sidestepped in neural systems by the invocation of modules. Here we highlight the interaction between evolutionary and developmental mechanisms to produce distributed and overlapping functional architectures in the brain. These adaptive mechanisms must be robust to perturbations that might disrupt critical information processing and action selection, but must also recognize useful new sources of information arising from internal genetic or environmental variability, when those appear. These contrasting properties of "robustness" and "evolvability" have been discussed for the basic organization of body plan and fundamental cell physiology. Here we extend them to the evolution and development, "evo-devo," of brain structure.
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Affiliation(s)
- Michael L. Anderson
- Department of Psychology, Franklin & Marshall CollegeLancaster, PA, USA
- Neuroscience and Cognitive Science Program, Institute for Advanced Computer Studies, University of MarylandCollege Park, MD, USA
| | - Barbara L. Finlay
- Behavioral and Evolutionary Neuroscience Group, Department of Psychology, Cornell UniversityIthaca, NY, USA
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Bosch-Bouju C, Hyland BI, Parr-Brownlie LC. Motor thalamus integration of cortical, cerebellar and basal ganglia information: implications for normal and parkinsonian conditions. Front Comput Neurosci 2013; 7:163. [PMID: 24273509 PMCID: PMC3822295 DOI: 10.3389/fncom.2013.00163] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/24/2013] [Indexed: 12/23/2022] Open
Abstract
Motor thalamus (Mthal) is implicated in the control of movement because it is strategically located between motor areas of the cerebral cortex and motor-related subcortical structures, such as the cerebellum and basal ganglia (BG). The role of BG and cerebellum in motor control has been extensively studied but how Mthal processes inputs from these two networks is unclear. Specifically, there is considerable debate about the role of BG inputs on Mthal activity. This review summarizes anatomical and physiological knowledge of the Mthal and its afferents and reviews current theories of Mthal function by discussing the impact of cortical, BG and cerebellar inputs on Mthal activity. One view is that Mthal activity in BG and cerebellar-receiving territories is primarily "driven" by glutamatergic inputs from the cortex or cerebellum, respectively, whereas BG inputs are modulatory and do not strongly determine Mthal activity. This theory is steeped in the assumption that the Mthal processes information in the same way as sensory thalamus, through interactions of modulatory inputs with a single driver input. Another view, from BG models, is that BG exert primary control on the BG-receiving Mthal so it effectively relays information from BG to cortex. We propose a new "super-integrator" theory where each Mthal territory processes multiple driver or driver-like inputs (cortex and BG, cortex and cerebellum), which are the result of considerable integrative processing. Thus, BG and cerebellar Mthal territories assimilate motivational and proprioceptive motor information previously integrated in cortico-BG and cortico-cerebellar networks, respectively, to develop sophisticated motor signals that are transmitted in parallel pathways to cortical areas for optimal generation of motor programmes. Finally, we briefly review the pathophysiological changes that occur in the BG in parkinsonism and generate testable hypotheses about how these may affect processing of inputs in the Mthal.
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Affiliation(s)
- Clémentine Bosch-Bouju
- 1Department of Anatomy, Otago School of Medical Science, University of Otago Dunedin, New Zealand ; 2Brain Health Research Centre, Otago School of Medical Science, University of Otago Dunedin, New Zealand
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26
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Goldberg JH, Farries MA, Fee MS. Basal ganglia output to the thalamus: still a paradox. Trends Neurosci 2013; 36:695-705. [PMID: 24188636 DOI: 10.1016/j.tins.2013.09.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 09/04/2013] [Accepted: 09/06/2013] [Indexed: 11/28/2022]
Abstract
The basal ganglia (BG)-recipient thalamus controls motor output but it remains unclear how its activity is regulated. Several studies report that thalamic activation occurs via disinhibition during pauses in the firing of inhibitory pallidal inputs from the BG. Other studies indicate that thalamic spiking is triggered by pallidal inputs via post-inhibitory 'rebound' calcium spikes. Finally excitatory cortical inputs can drive thalamic activity, which becomes entrained, or time-locked, to pallidal spikes. We present a unifying framework where these seemingly distinct results arise from a continuum of thalamic firing 'modes' controlled by excitatory inputs. We provide a mechanistic explanation for paradoxical pallidothalamic coactivations observed during behavior that raises new questions about what information is integrated in the thalamus to control behavior.
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Affiliation(s)
- Jesse H Goldberg
- McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
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27
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Person AL, Raman IM. Synchrony and neural coding in cerebellar circuits. Front Neural Circuits 2012; 6:97. [PMID: 23248585 PMCID: PMC3518933 DOI: 10.3389/fncir.2012.00097] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 11/16/2012] [Indexed: 11/18/2022] Open
Abstract
The cerebellum regulates complex movements and is also implicated in cognitive tasks, and cerebellar dysfunction is consequently associated not only with movement disorders, but also with conditions like autism and dyslexia. How information is encoded by specific cerebellar firing patterns remains debated, however. A central question is how the cerebellar cortex transmits its integrated output to the cerebellar nuclei via GABAergic synapses from Purkinje neurons. Possible answers come from accumulating evidence that subsets of Purkinje cells synchronize their firing during behaviors that require the cerebellum. Consistent with models predicting that coherent activity of inhibitory networks has the capacity to dictate firing patterns of target neurons, recent experimental work supports the idea that inhibitory synchrony may regulate the response of cerebellar nuclear cells to Purkinje inputs, owing to the interplay between unusually fast inhibitory synaptic responses and high rates of intrinsic activity. Data from multiple laboratories lead to a working hypothesis that synchronous inhibitory input from Purkinje cells can set the timing and rate of action potentials produced by cerebellar nuclear cells, thereby relaying information out of the cerebellum. If so, then changing spatiotemporal patterns of Purkinje activity would allow different subsets of inhibitory neurons to control cerebellar output at different times. Here we explore the evidence for and against the idea that a synchrony code defines, at least in part, the input–output function between the cerebellar cortex and nuclei. We consider the literature on the existence of simple spike synchrony, convergence of Purkinje neurons onto nuclear neurons, and intrinsic properties of nuclear neurons that contribute to responses to inhibition. Finally, we discuss factors that may disrupt or modulate a synchrony code and describe the potential contributions of inhibitory synchrony to other motor circuits.
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Affiliation(s)
- Abigail L Person
- Department of Physiology and Biophysics, University of Colorado School of Medicine Aurora, CO, USA
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