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Open Access Research article

Corticospinal interaction during isometric compensation for modulated forces with different frequencies

José R Naranjo1, Xi Wang1, Jürgen Schulte-Mönting2, Frank Huethe1, Christoph Maurer1, Marie-Claude Hepp-Reymond3* and Rumyana Kristeva1

Author Affiliations

1 Neurological Clinic, University Freiburg, Breisacherstraße 64, 79106 Freiburg, Germany

2 Institute for Medical Biometry and Medical Informatics, Freiburg, Germany

3 Institute of Neuroinformatics, University of Zürich and ETH Zürich, Switzerland

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BMC Neuroscience 2010, 11:157  doi:10.1186/1471-2202-11-157

Published: 31 December 2010

Abstract

Background

During isometric compensation of modulated low-level forces corticomuscular coherence (CMC) has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger. The effect of three frequencies of force modulation (0.6, 1.0 and 1.6 Hz) was tested. EEG, EMG from first dorsal interosseus, hand flexor and extensor muscles, and finger position were recorded in eight right-handed women.

Results

Five subjects showed CMC in gamma- (28-45 Hz) and three in beta-range (15-30 Hz). Beta- and gamma-range CMC and cortical motor spectral power were not modulated by the various frequencies. However, a sharp bilateral CMC peak at 1.6 Hz was observed, but only in the five gamma-range CMC subjects. The performance error increased linearly with the frequency.

Conclusions

Our findings suggest that the frequency of force modulation has no effect on the beta- and gamma-range CMC during isometric compensation for modulated forces at 8% MVC. The beta- and gamma-range CMC may be related to interindividual differences and possibly to strategy differences.