Cortical Control of Human Motoneuron Firing during Isometric Contraction.
Stephan Salenius, Karin Portin, Matti Kajola, Riitta Salmelin and Riitta Hari
Brain Research Unit, Low Temperature Laboratory, Helsinki University of
Technology, FIN-02150 Espoo (Finland).
APStracts 4:0067N, 1997.
ABSTRACT
1. We recorded whole-scalp magnetoencephalographic (MEG) signals
simultaneously with the electromyogram from upper and lower limb muscles of 6
healthy right-handed adults during voluntary isometric contraction. 2. The
15D33 Hz MEG signals, originating from the human motor cortex, were coherent
with motor unit firing in all subjects, and for all muscles. 3. The coherent
cortical rhythms originated in the hand motor area for upper limb muscles and
close to the foot area for lower limb muscles. The sites of origin
corresponding to different upper limb muscles did not differ significantly. 4.
The cortical signals preceded motor unit firing with time-lags ranging from 12
to 53 ms. The lags increased systematically with increasing cortico-muscular
distance. 5. We suggest that the motor cortex drives the motoneuronal pool
during sustained contractions, with the observed cortical rhythmic activity
influencing the timing of efferent commands.
Received 23 October 1996; accepted in final form 7 February 1997.
APS Manuscript Number J841-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 5 March 1997