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Renshaw Cell Recurrent Inhibition Improves Physiological Tremor by Reducing Corticomuscular Coupling at 10 Hz

Lookup NU author(s): Dr Elizabeth Williams, Professor Stuart Baker

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Abstract

Corticomuscular coherence between the primary motor cortex (M1) and hand muscle electromyograms (EMG) occurs at similar to 20 Hz but is rarely seen at similar to 10 Hz. This is unexpected, because M1 has oscillations at both frequencies, which are effectively transmitted to the spinal cord via the corticospinal tract. We have previously speculated that a specific "neural filter" may selectively reduce coherence at similar to 10 Hz. This would have functional utility in minimizing physiological tremor, which often has a dominant component around this frequency. Recurrent inhibition via Renshaw cells in the spinal cord is a putative neural substrate for such a filter. Here we investigate this system in more detail with a biophysically based computational model. Renshaw cell recurrent inhibition reducedEMGoscillations at similar to 10 Hz, and also reduced corticomuscular coherence at this frequency (from 0.038 to 0.014). Renshaw cell inhibitory feedback also generated synchronous oscillations in the motoneuron pool at similar to 30 Hz. We show that the effects at 10 Hz and 30 Hz can both be understood from the dynamics of the inhibitory feedback loop. We conclude that recurrent inhibition certainly plays an important role in reducing 10 Hz oscillations in muscle, thereby decreasing tremor amplitude. However, our quantitative results suggest it is unlikely to be the only system for tremor reduction, and probably acts in concert with other neural circuits which remain to be elucidated.


Publication metadata

Author(s): Williams ER, Baker SN

Publication type: Article

Publication status: Published

Journal: Journal of Neuroscience

Year: 2009

Volume: 29

Issue: 20

Pages: 6616-6624

Date deposited: 04/08/2010

ISSN (print): 0270-6474

ISSN (electronic): 1529-2401

Publisher: Society for Neuroscience

URL: http://dx.doi.org/10.1523/JNEUROSCI.0272-09.2009

DOI: 10.1523/JNEUROSCI.0272-09.2009


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