Abstract

• Simultaneous recordings of cortical activity, recorded as the magnetoencephalogram (MEG), and the electromyogram (EMG) of the ipsilateral and contralateral first dorsal interosseous muscles (1DI) were made during maintained voluntary contractions.
• The MEG recorded from a localized region of the sensorimotor cortex of the dominant hemisphere was coherent with the EMG from the contralateral 1DI muscle over a limited band of frequencies. The peak coherence was confined largely within the beta range of cortical activity (13-35 Hz). Significant cortical activity at 10 Hz and40-50 Hz was not correlated with motor output. The MEG and EMG from theipsilateral 1DI muscle were uncorrelated at all frequencies.
• Significant coherence between the MEG and the EMG was associated with synchronous behaviour between the MEG and EMG in the time domain.
• The results demonstrate that synchronized cortical activity contributing to MEG activity within the beta range of frequencies during maintained voluntary contractions is coupled to motor output at frequencies of motor-unit activity associated with motor-unit synchronization. This observation provides further evidence for the involvement of cortical neurones in the generation of motor-unit synchronization.
• We suggest that the coherence between MEG and contralateral EMG observed during maintained isometric contractions may provide an example of binding within the motor system

Abstract © 1995 The Physiological Society

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