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Beta-Adrenergic Modulation of Tremor and Corticomuscular Coherence in Humans

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

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Abstract

Coherence between the bioelectric activity of sensorimotor cortex and contralateral muscles can be observed around 20 Hz. By contrast, physiological tremor has a dominant frequency around 10 Hz. Although tremor has multiple sources, it is partly central in origin, reflecting a component of motoneuron discharge at this frequency. The motoneuron response to similar to 20 Hz descending input could be altered by non-linear interactions with similar to 10 Hz motoneuron firing. We investigated this further in eight healthy human subjects by testing the effects of the beta-adrenergic agents propranolol (non-selective beta-antagonist) and salbutamol (beta(2)-agonist), which are known to alter the size of physiological tremor. Corticomuscular coherence was assessed during an auxotonic precision grip task; tremor was quantified using accelerometry during index finger extension. Experiments with propranolol used a double-blind, placebo-controlled crossover design. A single oral dose of propranolol (40 mg) significantly increased beta band (15.3-32.2 Hz) corticomuscular coherence compared with placebo, but reduced tremor in the 6.2-11.9 Hz range. Salbutamol (2.5 mg) was administered by inhalation. Whilst salbutamol significantly increased tremor amplitude as expected, it did not change corticomuscular coherence. The opposite direction of the effects of propranolol on corticomuscular coherence and tremor, and the fact that salbutamol enhances tremor but does not affect coherence, implies that the magnitude of corticomuscular coherence is little influenced by non-linear interactions with 10 Hz oscillations in motoneurons or the periphery. Instead, we suggest that propranolol and salbutamol may affect both tremor and corticomuscular coherence partly via a central site of action.


Publication metadata

Author(s): Baker MR, Baker SN

Publication type: Article

Publication status: Published

Journal: PLoS One

Year: 2012

Volume: 7

Issue: 11

Print publication date: 20/11/2012

Date deposited: 04/02/2013

ISSN (electronic): 1932-6203

Publisher: Public Library of Science

URL: http://dx.doi.org/10.1371/journal.pone.0049088

DOI: 10.1371/journal.pone.0049088


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