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Handforth A, Singh RP, Kosoyan HP, Kadam PA. A Role for GABA A Receptor β3 Subunits in Mediating Harmaline Tremor Suppression by Alcohol: Implications for Essential Tremor Therapy. Tremor Other Hyperkinet Mov (N Y) 2024; 14:20. [PMID: 38681506 PMCID: PMC11049614 DOI: 10.5334/tohm.834] [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: 10/27/2023] [Accepted: 03/31/2024] [Indexed: 05/01/2024] Open
Abstract
Background Essential tremor patients may find that low alcohol amounts suppress tremor. A candidate mechanism is modulation of α6β3δ extra-synaptic GABAA receptors, that in vitro respond to non-intoxicating alcohol levels. We previously found that low-dose alcohol reduces harmaline tremor in wild-type mice, but not in littermates lacking δ or α6 subunits. Here we addressed whether low-dose alcohol requires the β3 subunit for tremor suppression. Methods We tested whether low-dose alcohol suppresses tremor in cre-negative mice with intact β3 exon 3 flanked by loxP, and in littermates in which this region was excised by cre expressed under the α6 subunit promotor. Tremor in the harmaline model was measured as a percentage of motion power in the tremor bandwidth divided by overall motion power. Results Alcohol, 0.500 and 0.575 g/kg, reduced harmaline tremor compared to vehicle-treated controls in floxed β3 cre- mice, but had no effect on tremor in floxed β3 cre+ littermates that have β3 knocked out. This was not due to potential interference of α6 expression by the insertion of the cre gene into the α6 gene since non-floxed β3 cre+ and cre- littermates exhibited similar tremor suppression by alcohol. Discussion As α6β3δ GABAA receptors are sensitive to low-dose alcohol, and cerebellar granule cells express β3 and are the predominant brain site for α6 and δ expression together, our overall findings suggest alcohol acts to suppress tremor by modulating α6β3δ GABAA receptors on these cells. Novel drugs that target this receptor may potentially be effective and well-tolerated for essential tremor. Highlights We previously found with the harmaline essential tremor model that GABAA receptors containing α6 and δ subunits mediate tremor suppression by alcohol. We now show that β3 subunits in α6-expressing cells, likely cerebellar granule cells, are also required, indicating that alcohol suppresses tremor by modulating α6β3δ extra-synaptic GABAA receptors.
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Affiliation(s)
- Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
| | - Ram P. Singh
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
| | - Hovsep P. Kosoyan
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
| | - Pournima A. Kadam
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
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Cetinkaya E, Lang EJ, Sahin M. Sensorimotor content of multi-unit activity recorded in the paramedian lobule of the cerebellum using carbon fiber microelectrode arrays. Front Neurosci 2024; 18:1232653. [PMID: 38486968 PMCID: PMC10937354 DOI: 10.3389/fnins.2024.1232653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 02/19/2024] [Indexed: 03/17/2024] Open
Abstract
The cerebellum takes in a great deal of sensory information from the periphery and descending signals from the cerebral cortices. It has been debated whether the paramedian lobule (PML) in the rat and its paravermal regions that project to the interpositus nucleus (IPN) are primarily involved in motor execution or motor planning. Studies that have relied on single spike recordings in behaving animals have led to conflicting conclusions regarding this issue. In this study, we tried a different approach and investigated the correlation of field potentials and multi-unit signals recorded with multi-electrode arrays from the PML cortex along with the forelimb electromyography (EMG) signals in rats during behavior. Linear regression was performed to predict the EMG signal envelopes using the PML activity for various time shifts (±25, ±50, ±100, and ± 400 ms) between the two signals to determine a causal relation. The highest correlations (~0.5 on average) between the neural and EMG envelopes were observed for zero and small (±25 ms) time shifts and decreased with larger time shifts in both directions, suggesting that paravermal PML is involved both in processing of sensory signals and motor execution in the context of forelimb reaching behavior. EMG envelopes were predicted with higher success rates when neural signals from multiple phases of the behavior were utilized for regression. The forelimb extension phase was the most difficult to predict while the releasing of the bar phase prediction was the most successful. The high frequency (>300 Hz) components of the neural signal, reflecting multi-unit activity, had a higher contribution to the EMG prediction than did the lower frequency components, corresponding to local field potentials. The results of this study suggest that the paravermal PML in the rat cerebellum is primarily involved in the execution of forelimb movements rather than the planning aspect and that the PML is more active at the initiation and termination of the behavior, rather than the progression.
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Affiliation(s)
- Esma Cetinkaya
- Biomedical Engineering Department, New Jersey Institute of Technology, Newark, NJ, United States
- Department of Neuroscience and Physiology, NYU Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, United States
| | - Eric J. Lang
- Department of Neuroscience and Physiology, NYU Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, United States
| | - Mesut Sahin
- Biomedical Engineering Department, New Jersey Institute of Technology, Newark, NJ, United States
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Handforth A, Singh RP, Treven M, Ernst M. Search for Novel Therapies for Essential Tremor Based on Positive Modulation of α6-Containing GABA A Receptors. Tremor Other Hyperkinet Mov (N Y) 2023; 13:39. [PMID: 37900009 PMCID: PMC10607569 DOI: 10.5334/tohm.796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 10/10/2023] [Indexed: 10/31/2023] Open
Abstract
Background Prior work using GABAA receptor subunit knockouts and the harmaline model has indicated that low-dose alcohol, gaboxadol, and ganaxolone suppress tremor via α6βδ GABAA receptors. This suggests that drugs specifically enhancing the action of α6βδ or α6βγ2 GABAA receptors, both predominantly expressed on cerebellar granule cells, would be effective against tremor. We thus examined three drugs described by in vitro studies as selective α6βδ (ketamine) or α6βγ2 (Compound 6, flumazenil) receptor modulators. Methods In the first step of evaluation, the maximal dose was sought at which 6/6 mice pass straight wire testing, a sensitive test for psychomotor impairment. Only non-impairing doses were used to evaluate for anti-tremor efficacy in the harmaline model, which was assessed in wildtype and α6 subunit knockout littermates. Results Ketamine, in maximally tolerated doses of 2.0 and 3.5 mg/kg had minimal effect on harmaline tremor in both genotypes. Compound 6, at well-tolerated doses of 1-10 mg/kg, effectively suppressed tremor in both genotypes. Flumazenil suppressed tremor in wildtype mice at doses (0.015-0.05 mg/kg) far lower than those causing straight wire impairment, and did not suppress tremor in α6 knockout mice. Discussion Modulators of α6βδ and α6βγ2 GABAA receptors warrant attention for novel therapies as they are anticipated to be effective and well-tolerated. Ketamine likely failed to attain α6βδ-active levels. Compound 6 is an attractive candidate, but further study is needed to clarify its mechanism of action. The flumazenil results provide proof of principle that targeting α6βγ2 receptors represents a worthy strategy for developing essential tremor therapies. Highlights We tested for harmaline tremor suppression drugs previously described as in vitro α6βδ or α6βγ2 GABAA receptor-selective modulators. Well-tolerated flumazenil doses suppressed tremor in α6-wildtype but not α6-knockout mice. Compound 6 and ketamine failed to display this profile, likely from off-target effects. Selective α6 modulators hold promise as tremor therapy.
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Affiliation(s)
- Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Ram P. Singh
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Marco Treven
- Department of Neurology, Medical Neuroscience Cluster, Medical University of Vienna, Vienna, Austria
| | - Margot Ernst
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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Handforth A, Kosoyan HP, Kadam PA, Singh RP. Alcohol and Ganaxolone Suppress Tremor via Extra-Synaptic GABA A Receptors in the Harmaline Model of Essential Tremor. Tremor Other Hyperkinet Mov (N Y) 2023; 13:18. [PMID: 37214542 PMCID: PMC10198231 DOI: 10.5334/tohm.760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 05/06/2023] [Indexed: 05/24/2023] Open
Abstract
Background A long-standing question is why essential tremor often responds to non-intoxicating amounts of alcohol. Blood flow imaging and high-density electroencephalography have indicated that alcohol acts on tremor within the cerebellum. As extra-synaptic δ-subunit-containing GABAA receptors are sensitive to low alcohol levels, we wondered whether these receptors mediate alcohol's anti-tremor effect and, moreover, whether the δ-associated GABAA receptor α6 subunit, found abundantly in the cerebellum, is required. Methods We tested the hypotheses that low-dose alcohol will suppress harmaline-induced tremor in wild-type mice, but not in littermates lacking GABAA receptor δ subunits, nor in littermates lacking α6 subunits. As the neurosteroid ganaxolone also activates extra-synaptic GABAA receptors, we similarly assessed this compound. The harmaline mouse model of essential tremor was utilized to generate tremor, measured as a percentage of motion power in the tremor bandwidth (9-16 Hz) divided by background motion power at 0.25-32 Hz. Results Ethanol, 0.500 and 0.575 g/kg, and ganaxolone, 7 and 10 mg/kg, doses that do not impair performance in a sensitive psychomotor task, reduced harmaline tremor compared to vehicle-treated controls in wild-type mice but failed to suppress tremor in littermates lacking the δ or the α6 GABAA receptor subunit. Discussion As cerebellar granule cells are the predominant brain site intensely expressing GABAA receptors containing both α6 and δ subunits, these findings suggest that this is where alcohol acts to suppress tremor. It is anticipated that medications designed specifically to target α6βδ-containing GABAA receptors may be effective and well-tolerated for treating essential tremor. Highlights How does alcohol temporarily ameliorate essential tremor? This study with a mouse model found that two specific kinds of GABA receptor subunits were needed for alcohol to work. As receptors with both these subunits are found mainly in cerebellum, this work suggests this is where alcohol acts to suppress tremor.
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Affiliation(s)
- Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Hovsep P. Kosoyan
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Pournima A. Kadam
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Ram P. Singh
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
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Romano V, Zhai P, van der Horst A, Mazza R, Jacobs T, Bauer S, Wang X, White JJ, De Zeeuw CI. Olivocerebellar control of movement symmetry. Curr Biol 2022; 32:654-670.e4. [PMID: 35016009 DOI: 10.1016/j.cub.2021.12.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 10/26/2021] [Accepted: 12/08/2021] [Indexed: 01/02/2023]
Abstract
Coordination of bilateral movements is essential for a large variety of animal behaviors. The olivocerebellar system is critical for the control of movement, but its role in bilateral coordination has yet to be elucidated. Here, we examined whether Purkinje cells encode and influence synchronicity of left-right whisker movements. We found that complex spike activity is correlated with a prominent left-right symmetry of spontaneous whisker movements within parts, but not all, of Crus1 and Crus2. Optogenetic stimulation of climbing fibers in the areas with high and low correlations resulted in symmetric and asymmetric whisker movements, respectively. Moreover, when simple spike frequency prior to the complex spike was higher, the complex spike-related symmetric whisker protractions were larger. This finding alludes to a role for rebound activity in the cerebellar nuclei, which indeed turned out to be enhanced during symmetric protractions. Tracer injections suggest that regions associated with symmetric whisker movements are anatomically connected to the contralateral cerebellar hemisphere. Together, these data point toward the existence of modules on both sides of the cerebellar cortex that can differentially promote or reduce the symmetry of left and right movements in a context-dependent fashion.
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Affiliation(s)
- Vincenzo Romano
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands.
| | - Peipei Zhai
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | | | - Roberta Mazza
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - Thomas Jacobs
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - Staf Bauer
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - Xiaolu Wang
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - Joshua J White
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - C I De Zeeuw
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands; Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, Amsterdam, the Netherlands.
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Stevens SR, van der Heijden ME, Ogawa Y, Lin T, Sillitoe RV, Rasband MN. Ankyrin-R Links Kv3.3 to the Spectrin Cytoskeleton and Is Required for Purkinje Neuron Survival. J Neurosci 2022; 42:2-15. [PMID: 34785580 PMCID: PMC8741159 DOI: 10.1523/jneurosci.1132-21.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 10/26/2021] [Accepted: 10/31/2021] [Indexed: 11/21/2022] Open
Abstract
Ankyrin scaffolding proteins are critical for membrane domain organization and protein stabilization in many different cell types including neurons. In the cerebellum, Ankyrin-R (AnkR) is highly enriched in Purkinje neurons, granule cells, and in the cerebellar nuclei (CN). Using male and female mice with a floxed allele for Ank1 in combination with Nestin-Cre and Pcp2-Cre mice, we found that ablation of AnkR from Purkinje neurons caused ataxia, regional and progressive neurodegeneration, and altered cerebellar output. We show that AnkR interacts with the cytoskeletal protein β3 spectrin and the potassium channel Kv3.3. Loss of AnkR reduced somatic membrane levels of β3 spectrin and Kv3.3 in Purkinje neurons. Thus, AnkR links Kv3.3 channels to the β3 spectrin-based cytoskeleton. Our results may help explain why mutations in β3 spectrin and Kv3.3 both cause spinocerebellar ataxia.SIGNIFICANCE STATEMENT Ankyrin scaffolding proteins localize and stabilize ion channels in the membrane by linking them to the spectrin-based cytoskeleton. Here, we show that Ankyrin-R (AnkR) links Kv3.3 K+ channels to the β3 spectrin-based cytoskeleton in Purkinje neurons. Loss of AnkR causes Purkinje neuron degeneration, altered cerebellar physiology, and ataxia, which is consistent with mutations in Kv3.3 and β3 spectrin causing spinocerebellar ataxia.
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Affiliation(s)
- Sharon R Stevens
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | | | - Yuki Ogawa
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | - Tao Lin
- Department Pathology and Immunology, Baylor College of Medicine, Houston, Texas 77030
| | - Roy V Sillitoe
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
- Department Pathology and Immunology, Baylor College of Medicine, Houston, Texas 77030
| | - Matthew N Rasband
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
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Lang EJ, Handforth A. Is the inferior olive central to essential tremor? Yes. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:133-165. [PMID: 35750361 DOI: 10.1016/bs.irn.2022.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We consider the question whether the inferior olive (IO) is required for essential tremor (ET). Much evidence shows that the olivocerebellar system is the main system capable of generating the widespread synchronous oscillatory Purkinje cell (PC) complex spike (CS) activity across the cerebellar cortex that would be capable of generating the type of bursting cerebellar output from the deep cerebellar nuclei (DCN) that could underlie tremor. Normally, synchronous CS activity primarily reflects the effective electrical coupling of IO neurons by gap junctions, and traditionally, ET research has focused on the hypothesis of increased coupling of IO neurons as the cause of hypersynchronous CS activity underlying tremor. However, recent pathology studies of brains from humans with ET and evidence from mutant mice, particularly the hotfoot17 mouse, that largely replicate the pathology of ET, suggest that the abnormal innervation of multiple Purkinje cells (PCs) by climbing fibers (Cfs) is related to tremor. In addition, ET brains show partial PC loss and axon terminal sprouting by surviving PCs. This may provide another mechanism for tremor. It is proposed that in ET, these three mechanisms may promote tremor. They all involve hypersynchronous DCN activity and an intact IO, but the level at which excessive synchronization occurs may be at the IO level (from abnormal afferent activity to this nucleus), the PC level (via aberrant Cfs), or the DCN level (via terminal PC collateral innervation).
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Zahra O, Navarro-Alarcon D, Tolu S. A Neurorobotic Embodiment for Exploring the Dynamical Interactions of a Spiking Cerebellar Model and a Robot Arm During Vision-Based Manipulation Tasks. Int J Neural Syst 2021; 32:2150028. [PMID: 34003083 DOI: 10.1142/s0129065721500283] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
While the original goal for developing robots is replacing humans in dangerous and tedious tasks, the final target shall be completely mimicking the human cognitive and motor behavior. Hence, building detailed computational models for the human brain is one of the reasonable ways to attain this. The cerebellum is one of the key players in our neural system to guarantee dexterous manipulation and coordinated movements as concluded from lesions in that region. Studies suggest that it acts as a forward model providing anticipatory corrections for the sensory signals based on observed discrepancies from the reference values. While most studies consider providing the teaching signal as error in joint-space, few studies consider the error in task-space and even fewer consider the spiking nature of the cerebellum on the cellular-level. In this study, a detailed cellular-level forward cerebellar model is developed, including modeling of Golgi and Basket cells which are usually neglected in previous studies. To preserve the biological features of the cerebellum in the developed model, a hyperparameter optimization method tunes the network accordingly. The efficiency and biological plausibility of the proposed cerebellar-based controller is then demonstrated under different robotic manipulation tasks reproducing motor behavior observed in human reaching experiments.
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Affiliation(s)
- Omar Zahra
- The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | | | - Silvia Tolu
- Technical University of Denmark, Kongens Lyngby, Denmark
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van der Heijden ME, Kizek DJ, Perez R, Ruff EK, Ehrlich ME, Sillitoe RV. Abnormal cerebellar function and tremor in a mouse model for non-manifesting partially penetrant dystonia type 6. J Physiol 2021; 599:2037-2054. [PMID: 33369735 PMCID: PMC8559601 DOI: 10.1113/jp280978] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/16/2020] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Loss-of-function mutations in the Thap1 gene cause partially penetrant dystonia type 6 (DYT6). Some non-manifesting DYT6 mutation carriers have tremor and abnormal cerebello-thalamo-cortical signalling. We show that Thap1 heterozygote mice have action tremor, a reduction in cerebellar neuron number, and abnormal electrophysiological signals in the remaining neurons. These results underscore the importance of Thap1 levels for cerebellar function. These results uncover how cerebellar abnormalities contribute to different dystonia-associated motor symptoms. ABSTRACT Loss-of-function mutations in the Thanatos-associated domain-containing apoptosis-associated protein 1 (THAP1) gene cause partially penetrant autosomal dominant dystonia type 6 (DYT6). However, the neural abnormalities that promote the resultant motor dysfunctions remain elusive. Studies in humans show that some non-manifesting DYT6 carriers have altered cerebello-thalamo-cortical function with subtle but reproducible tremor. Here, we uncover that Thap1 heterozygote mice have action tremor that rises above normal baseline values even though they do not exhibit overt dystonia-like twisting behaviour. At the neural circuit level, we show using in vivo recordings in awake Thap1+/- mice that Purkinje cells have abnormal firing patterns and that cerebellar nuclei neurons, which connect the cerebellum to the thalamus, fire at a lower frequency. Although the Thap1+/- mice have fewer Purkinje cells and cerebellar nuclei neurons, the number of long-range excitatory outflow projection neurons is unaltered. The preservation of interregional connectivity suggests that abnormal neural function rather than neuron loss instigates the network dysfunction and the tremor in Thap1+/- mice. Accordingly, we report an inverse correlation between the average firing rate of cerebellar nuclei neurons and tremor power. Our data show that cerebellar circuitry is vulnerable to Thap1 mutations and that cerebellar dysfunction may be a primary cause of tremor in non-manifesting DYT6 carriers and a trigger for the abnormal postures in manifesting patients.
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Affiliation(s)
- Meike E. van der Heijden
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, Texas, USA
| | - Dominic J. Kizek
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, Texas, USA
| | - Ross Perez
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, Texas, USA
| | - Elena K. Ruff
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, Texas, USA
| | - Michelle E. Ehrlich
- Department of Neurology and Pediatrics, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
| | - Roy V. Sillitoe
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
- Development, Disease Models & Therapeutics Graduate Program, Baylor College of Medicine, Houston, Texas, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, Texas, USA
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Handforth A, Lang EJ. Increased Purkinje Cell Complex Spike and Deep Cerebellar Nucleus Synchrony as a Potential Basis for Syndromic Essential Tremor. A Review and Synthesis of the Literature. THE CEREBELLUM 2020; 20:266-281. [PMID: 33048308 DOI: 10.1007/s12311-020-01197-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/29/2020] [Indexed: 12/19/2022]
Abstract
We review advances in understanding Purkinje cell (PC) complex spike (CS) physiology that suggest increased CS synchrony underlies syndromic essential tremor (ET). We searched PubMed for papers describing factors that affect CS synchrony or cerebellar circuits potentially related to tremor. Inferior olivary (IO) neurons are electrically coupled, with the degree of coupling controlled by excitatory and GABAergic inputs. Clusters of coupled IO neurons synchronize CSs within parasagittal bands via climbing fibers (Cfs). When motor cortex is stimulated in rats at varying frequencies, whisker movement occurs at ~10 Hz, correlated with synchronous CSs, indicating that the IO/CS oscillatory rhythm gates movement frequency. Intra-IO injection of the GABAA receptor antagonist picrotoxin increases CS synchrony, increases whisker movement amplitude, and induces tremor. Harmaline and 5-HT2a receptor activation also increase IO coupling and CS synchrony and induce tremor. The hotfoot17 mouse displays features found in ET brains, including cerebellar GluRδ2 deficiency and abnormal PC Cf innervation, with IO- and PC-dependent cerebellar oscillations and tremor likely due to enhanced CS synchrony. Heightened coupling within the IO oscillator leads, through its dynamic control of CS synchrony, to increased movement amplitude and, when sufficiently intense, action tremor. Increased CS synchrony secondary to aberrant Cf innervation of multiple PCs likely also underlies hotfoot17 tremor. Deep cerebellar nucleus (DCN) hypersynchrony may occur secondary to increased CS synchrony but might also occur from PC axonal terminal sprouting during partial PC loss. Through these combined mechanisms, increased CS/DCN synchrony may plausibly underlie syndromic ET.
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Affiliation(s)
- Adrian Handforth
- Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Blvd., Los Angeles, CA, 90073, USA.
| | - Eric J Lang
- Department of Neuroscience and Physiology, New York University, School of Medicine, New York, NY, USA
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Climbing fiber synapses rapidly and transiently inhibit neighboring Purkinje cells via ephaptic coupling. Nat Neurosci 2020; 23:1399-1409. [PMID: 32895566 PMCID: PMC7606706 DOI: 10.1038/s41593-020-0701-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 07/31/2020] [Indexed: 12/30/2022]
Abstract
Climbing fibers (CFs) from the inferior olive (IO) make strong excitatory synapses onto cerebellar Purkinje cell (PC) dendrites, and trigger distinctive responses known as complex spikes (CSs). We find that in awake mice, a CS in one PC suppresses conventional simple spikes (SSs) in neighboring PCs for several milliseconds. This involves a novel ephaptic coupling, in which an excitatory synapse generates large negative extracellular signals that nonsynaptically inhibit neighboring PCs. The distance dependence of CS-SS ephaptic signaling, combined with the known CF divergence, allows a single IO neuron to influence the output of the cerebellum by synchronously suppressing the firing of potentially over one hundred PCs. Optogenetic studies in vivo, and dynamic clamp studies in slice, indicate that such brief PC suppression, either as a result of ephaptic signaling or other mechanisms, can effectively promote firing in neurons in the deep cerebellar nuclei with remarkable speed and precision.
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12
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Electrical coupling controls dimensionality and chaotic firing of inferior olive neurons. PLoS Comput Biol 2020; 16:e1008075. [PMID: 32730255 PMCID: PMC7419012 DOI: 10.1371/journal.pcbi.1008075] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 08/11/2020] [Accepted: 06/18/2020] [Indexed: 01/15/2023] Open
Abstract
We previously proposed, on theoretical grounds, that the cerebellum must regulate the dimensionality of its neuronal activity during motor learning and control to cope with the low firing frequency of inferior olive neurons, which form one of two major inputs to the cerebellar cortex. Such dimensionality regulation is possible via modulation of electrical coupling through the gap junctions between inferior olive neurons by inhibitory GABAergic synapses. In addition, we previously showed in simulations that intermediate coupling strengths induce chaotic firing of inferior olive neurons and increase their information carrying capacity. However, there is no in vivo experimental data supporting these two theoretical predictions. Here, we computed the levels of synchrony, dimensionality, and chaos of the inferior olive code by analyzing in vivo recordings of Purkinje cell complex spike activity in three different coupling conditions: carbenoxolone (gap junctions blocker), control, and picrotoxin (GABA-A receptor antagonist). To examine the effect of electrical coupling on dimensionality and chaotic dynamics, we first determined the physiological range of effective coupling strengths between inferior olive neurons in the three conditions using a combination of a biophysical network model of the inferior olive and a novel Bayesian model averaging approach. We found that effective coupling co-varied with synchrony and was inversely related to the dimensionality of inferior olive firing dynamics, as measured via a principal component analysis of the spike trains in each condition. Furthermore, for both the model and the data, we found an inverted U-shaped relationship between coupling strengths and complexity entropy, a measure of chaos for spiking neural data. These results are consistent with our hypothesis according to which electrical coupling regulates the dimensionality and the complexity in the inferior olive neurons in order to optimize both motor learning and control of high dimensional motor systems by the cerebellum. Computational theory suggests that the cerebellum must decrease the dimensionality of its neuronal activity to learn and control high dimensional motor systems effectively, while being constrained by the low firing frequency of inferior olive neurons, one of the two major source of input signals to the cerebellum. We previously proposed that the cerebellum adaptively controls the dimensionality of inferior olive firing by adjusting the level of synchrony and that such control is made possible by modulating the electrical coupling strength between inferior olive neurons. Here, we developed a novel method that uses a biophysical model of the inferior olive to accurately estimate the effective coupling strengths between inferior olive neurons from in vivo recordings of spike activity in three different coupling conditions. We found that high coupling strengths induce synchronous firing and decrease the dimensionality of inferior olive firing dynamics. In contrast, intermediate coupling strengths lead to chaotic firing and increase the dimensionality of the firing dynamics. Thus, electrical coupling is a feasible mechanism to control dimensionality and chaotic firing of inferior olive neurons. In sum, our results provide insights into possible mechanisms underlying cerebellar function and, in general, a biologically plausible framework to control the dimensionality of neural coding.
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Why do we move to the beat? A multi-scale approach, from physical principles to brain dynamics. Neurosci Biobehav Rev 2020; 112:553-584. [DOI: 10.1016/j.neubiorev.2019.12.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 10/20/2019] [Accepted: 12/13/2019] [Indexed: 01/08/2023]
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Ten Brinke MM, Boele HJ, De Zeeuw CI. Conditioned climbing fiber responses in cerebellar cortex and nuclei. Neurosci Lett 2018; 688:26-36. [PMID: 29689340 DOI: 10.1016/j.neulet.2018.04.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 04/17/2018] [Accepted: 04/18/2018] [Indexed: 11/30/2022]
Abstract
The eyeblink conditioning paradigm captures an elementary form of associative learning in a neural circuitry that is understood to an extraordinary degree. Cerebellar cortical Purkinje cell simple spike suppression is widely regarded as the main process underlying conditioned responses (CRs), leading to disinhibition of neurons in the cerebellar nuclei that innervate eyelid muscles downstream. However, recent work highlights the addition of a conditioned Purkinje cell complex spike response, which at the level of the interposed nucleus seems to translate to a transient spike suppression that can be followed by a rapid spike facilitation. Here, we review the characteristics of these responses at the cerebellar cortical and nuclear level, and discuss possible origins and functions.
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Affiliation(s)
- M M Ten Brinke
- Department of Neuroscience, Erasmus Medical Center, 3000 DR Rotterdam, The Netherlands.
| | - H J Boele
- Department of Neuroscience, Erasmus Medical Center, 3000 DR Rotterdam, The Netherlands
| | - C I De Zeeuw
- Department of Neuroscience, Erasmus Medical Center, 3000 DR Rotterdam, The Netherlands; Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences (KNAW), 1105 BA Amsterdam, The Netherlands.
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Benagiano V, Rizzi A, Lorusso L, Flace P, Saccia M, Cagiano R, Ribatti D, Roncali L, Ambrosi G. The functional anatomy of the cerebrocerebellar circuit: A review and new concepts. J Comp Neurol 2017; 526:769-789. [PMID: 29238972 DOI: 10.1002/cne.24361] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 11/03/2017] [Accepted: 11/06/2017] [Indexed: 12/19/2022]
Abstract
The cerebrocerebellar circuit is a feedback circuit that bidirectionally connects the neocortex and the cerebellum. According to the classic view, the cerebrocerebellar circuit is specifically involved in the functional regulation of the motor areas of the neocortex. In recent years, studies carried out in experimental animals by morphological and physiological methods, and in humans by magnetic resonance imaging, have indicated that the cerebrocerebellar circuit is also involved in the functional regulation of the nonmotor areas of the neocortex, including the prefrontal, associative, sensory and limbic areas. Moreover, a second type of cerebrocerebellar circuit, bidirectionally connecting the hypothalamus and the cerebellum, has been detected, being specifically involved in the regulation of the hypothalamic functions. This review analyzes the morphological features of the centers and pathways of the cerebrocerebellar circuits, paying particular attention to their organization in different channels, which separately connect the cerebellum with the motor areas and nonmotor areas of the neocortex, and with the hypothalamus. Actually, a considerable amount of new data have led, and are leading, to profound changes on the views on the anatomy, physiology, and pathophysiology of the cerebrocerebellar circuits, so much they may be now considered to be essential for the functional regulation of many neocortex areas, perhaps all, as well as of the hypothalamus and of the limbic system. Accordingly, clinical studies have pointed out an involvement of the cerebrocerebellar circuits in the pathophysiology of an increasing number of neuropsychiatric disorders.
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Affiliation(s)
- Vincenzo Benagiano
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Anna Rizzi
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Loredana Lorusso
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Paolo Flace
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Matteo Saccia
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Raffaele Cagiano
- Department of Biomedical Sciences and Human Oncology, University of Bari, Bari, Italy
| | - Domenico Ribatti
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy.,National Cancer Institute 'Giovanni Paolo II', Bari, Italy
| | - Luisa Roncali
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
| | - Glauco Ambrosi
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs, University of Bari, Bari, Italy
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The Roles of the Olivocerebellar Pathway in Motor Learning and Motor Control. A Consensus Paper. THE CEREBELLUM 2017; 16:230-252. [PMID: 27193702 DOI: 10.1007/s12311-016-0787-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
For many decades, the predominant view in the cerebellar field has been that the olivocerebellar system's primary function is to induce plasticity in the cerebellar cortex, specifically, at the parallel fiber-Purkinje cell synapse. However, it has also long been proposed that the olivocerebellar system participates directly in motor control by helping to shape ongoing motor commands being issued by the cerebellum. Evidence consistent with both hypotheses exists; however, they are often investigated as mutually exclusive alternatives. In contrast, here, we take the perspective that the olivocerebellar system can contribute to both the motor learning and motor control functions of the cerebellum and might also play a role in development. We then consider the potential problems and benefits of it having multiple functions. Moreover, we discuss how its distinctive characteristics (e.g., low firing rates, synchronization, and variable complex spike waveforms) make it more or less suitable for one or the other of these functions, and why having multiple functions makes sense from an evolutionary perspective. We did not attempt to reach a consensus on the specific role(s) the olivocerebellar system plays in different types of movements, as that will ultimately be determined experimentally; however, collectively, the various contributions highlight the flexibility of the olivocerebellar system, and thereby suggest that it has the potential to act in both the motor learning and motor control functions of the cerebellum.
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Tang T, Xiao J, Suh CY, Burroughs A, Cerminara NL, Jia L, Marshall SP, Wise AK, Apps R, Sugihara I, Lang EJ. Heterogeneity of Purkinje cell simple spike-complex spike interactions: zebrin- and non-zebrin-related variations. J Physiol 2017; 595:5341-5357. [PMID: 28516455 DOI: 10.1113/jp274252] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 05/16/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cerebellar Purkinje cells (PCs) generate two types of action potentials, simple and complex spikes. Although they are generated by distinct mechanisms, interactions between the two spike types exist. Zebrin staining produces alternating positive and negative stripes of PCs across most of the cerebellar cortex. Thus, here we compared simple spike-complex spike interactions both within and across zebrin populations. Simple spike activity undergoes a complex modulation preceding and following a complex spike. The amplitudes of the pre- and post-complex spike modulation phases were correlated across PCs. On average, the modulation was larger for PCs in zebrin positive regions. Correlations between aspects of the complex spike waveform and simple spike activity were found, some of which varied between zebrin positive and negative PCs. The implications of the results are discussed with regard to hypotheses that complex spikes are triggered by rises in simple spike activity for either motor learning or homeostatic functions. ABSTRACT Purkinje cells (PCs) generate two types of action potentials, called simple and complex spikes (SSs and CSs). We first investigated the CS-associated modulation of SS activity and its relationship to the zebrin status of the PC. The modulation pattern consisted of a pre-CS rise in SS activity, and then, following the CS, a pause, a rebound, and finally a late inhibition of SS activity for both zebrin positive (Z+) and negative (Z-) cells, though the amplitudes of the phases were larger in Z+ cells. Moreover, the amplitudes of the pre-CS rise with the late inhibitory phase of the modulation were correlated across PCs. In contrast, correlations between modulation phases across CSs of individual PCs were generally weak. Next, the relationship between CS spikelets and SS activity was investigated. The number of spikelets/CS correlated with the average SS firing rate only for Z+ cells. In contrast, correlations across CSs between spikelet numbers and the amplitudes of the SS modulation phases were generally weak. Division of spikelets into likely axonally propagated and non-propagated groups (based on their interspikelet interval) showed that the correlation of spikelet number with SS firing rate primarily reflected a relationship with non-propagated spikelets. In sum, the results show both zebrin-related and non-zebrin-related physiological heterogeneity in SS-CS interactions among PCs, which suggests that the cerebellar cortex is more functionally diverse than is assumed by standard theories of cerebellar function.
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Affiliation(s)
- Tianyu Tang
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
| | - Jianqiang Xiao
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
| | - Colleen Y Suh
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
| | - Amelia Burroughs
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Nadia L Cerminara
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Linjia Jia
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
| | - Sarah P Marshall
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
| | - Andrew K Wise
- Bionics Institute, East Melbourne, Victoria, Australia
| | - Richard Apps
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Izumi Sugihara
- Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, and Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan
| | - Eric J Lang
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, USA
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Abstract
The control of deep cerebellar nuclear (DCN) neuronal firing is central to cerebellar function but is not well understood. The large majority of synapses onto DCN neurons derive from Purkinje cells (PCs), suggesting that PC activity is an important determinant of DCN firing; however, PCs fire both simple and complex spikes (CSs), and little is known about how the latter's action affects DCN activity. Thus, here, we explored the effects of CSs on DCN activity. CSs were recorded from PC arrays along with individual DCN neurons. Presumed synaptically connected PC-DCN cell pairs were identified using CS-triggered correlograms of DCN activity, which also showed that CS activity was associated with a predominantly inhibitory effect on DCN activity. The strength of the CS effect varied as a function of synchrony, such that isolated CSs produced only weak inhibition of DCN activity, whereas highly synchronous CSs caused a larger drop in firing levels. Although the present findings were obtained in anesthetized animals, similar CS synchrony levels exist in awake animals, and changes in synchrony level have been observed in association with movements in awake animals. Thus, the present data suggest that synchronous CS activity may be a mechanism for shaping DCN output related to motor commands.
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Lang EJ, Tang T, Suh CY, Xiao J, Kotsurovskyy Y, Blenkinsop TA, Marshall SP, Sugihara I. Modulation of Purkinje cell complex spike waveform by synchrony levels in the olivocerebellar system. Front Syst Neurosci 2014; 8:210. [PMID: 25400556 PMCID: PMC4214199 DOI: 10.3389/fnsys.2014.00210] [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: 06/06/2014] [Accepted: 10/06/2014] [Indexed: 11/13/2022] Open
Abstract
Purkinje cells (PCs) generate complex spikes (CSs) when activated by the olivocerebellar system. Unlike most spikes, the CS waveform is highly variable, with the number, amplitude, and timing of the spikelets that comprise it varying with each occurrence. This variability suggests that CS waveform could be an important control parameter of olivocerebellar activity. The origin of this variation is not well known. Thus, we obtained extracellular recordings of CSs to investigate the possibility that the electrical coupling state of the inferior olive (IO) affects the CS waveform. Using multielectrode recordings from arrays of PCs we showed that the variance in the recording signal during the period when the spikelets occur is correlated with CS synchrony levels in local groups of PCs. The correlation was demonstrated under both ketamine and urethane, indicating that it is robust. Moreover, climbing fiber reflex evoked CSs showed an analogous positive correlation between spikelet-related variance and the number of cells that responded to a stimulus. Intra-IO injections of GABA-A receptor antagonists or the gap junction blocker carbenoxolone produced correlated changes in the variance and synchrony levels, indicating the presence of a causal relationship. Control experiments showed that changes in variance with synchrony were primarily due to changes in the CS waveform, as opposed to changes in the strength of field potentials from surrounding cells. Direct counts of spikelets showed that their number increased with synchronization of CS activity. In sum, these results provide evidence of a causal link between two of the distinguishing characteristics of the olivocerebellar system, its ability to generate synchronous activity and the waveform of the CS.
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Affiliation(s)
- Eric J Lang
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Tianyu Tang
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Colleen Y Suh
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Jianqiang Xiao
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Yuriy Kotsurovskyy
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Timothy A Blenkinsop
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Sarah P Marshall
- Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Izumi Sugihara
- Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University Tokyo, Japan ; Center for Brain Integration Research, Tokyo Medical and Dental University Tokyo, Japan
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Courtemanche R, Robinson JC, Aponte DI. Linking oscillations in cerebellar circuits. Front Neural Circuits 2013; 7:125. [PMID: 23908606 PMCID: PMC3725427 DOI: 10.3389/fncir.2013.00125] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 07/11/2013] [Indexed: 11/13/2022] Open
Abstract
In many neuroscience fields, the study of local and global rhythmicity has been receiving increasing attention. These network influences could directly impact on how neuronal groups interact together, organizing for different contexts. The cerebellar cortex harbors a variety of such local circuit rhythms, from the rhythms in the cerebellar cortex per se, or those dictated from important afferents. We present here certain cerebellar oscillatory phenomena that have been recorded in rodents and primates. Those take place in a range of frequencies: from the more known oscillations in the 4-25 Hz band, such as the olivocerebellar oscillatory activity and the granule cell layer oscillations, to the more recently reported slow (<1 Hz oscillations), and the fast (>150 Hz) activity in the Purkinje cell layer. Many of these oscillations appear spontaneously in the circuits, and are modulated by behavioral imperatives. We review here how those oscillations are recorded, some of their modulatory mechanisms, and also identify some of the cerebellar nodes where they could interact. A particular emphasis has been placed on how these oscillations could be modulated by movement and certain neuropathological manifestations. Many of those oscillations could have a definite impact on the way information is processed in the cerebellum and how it interacts with other structures in a variety of contexts.
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Affiliation(s)
- Richard Courtemanche
- Department of Exercise Science, Groupe de Recherche en Neurobiologie Comportementale/Center for Studies in Behavioral Neurobiology, Concordia UniversityMontréal, QC, Canada
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Craner MJ, Fugger L. Misfiring in multiple sclerosis. Ann Neurol 2012; 71:437-8. [DOI: 10.1002/ana.23537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Uusisaari M, De Schutter E. The mysterious microcircuitry of the cerebellar nuclei. J Physiol 2011; 589:3441-57. [PMID: 21521761 PMCID: PMC3167109 DOI: 10.1113/jphysiol.2010.201582] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 04/20/2011] [Indexed: 11/08/2022] Open
Abstract
The microcircuitry of cerebellar cortex and, in particular, the physiology of its main element, the Purkinje neuron, has been extensively investigated and described. However, activity in Purkinje neurons, either as single cells or populations, does not directly mediate the cerebellar effects on the motor effector systems. Rather, the result of the entire cerebellar cortical computation is passed to the relatively small cerebellar nuclei that act as the final, integrative processing unit in the cerebellar circuitry. The nuclei ultimately control the temporal and spatial features of the cerebellar output. Given this key role, it is striking that the internal organization and the connectivity with afferent and efferent pathways in the cerebellar nuclei are rather poorly known. In the present review, we discuss some of the many critical shortcomings in the understanding of cerebellar nuclei microcircuitry: the extent of convergence and divergence of the cerebellar cortical pathway to the various cerebellar nuclei neurons and subareas, the possible (lack of) conservation of the finely-divided topographical organization in the cerebellar cortex at the level of the nuclei, as well as the absence of knowledge of the synaptic circuitry within the cerebellar nuclei. All these issues are important for predicting the pattern-extraction and encoding capabilities of the cerebellar nuclei and, until resolved, theories and models of cerebellar motor control and learning may err considerably.
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Affiliation(s)
- Marylka Uusisaari
- Theoretical and Experimental Neurobiology Unit, Okinawa Institute of Science and Technology, 7542 Onna, Onna-son, Okinawa 904-0411, Japan.
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