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The Effects of Motor Cortical Stimulation on the Excitability of Spinal Motoneurons in Man

Published online by Cambridge University Press:  18 September 2015

S.H. Milner-Brown ,
J.P. Girvin  and
W.F. Brown
S.H. Milner-Brown
Affiliation:
Department of Clinical Neurological Sciences, University Hospital, London, Ontario, Canada
J.P. Girvin
Affiliation:
Department of Clinical Neurological Sciences, University Hospital, London, Ontario, Canada
W.F. Brown*
Affiliation:
Department of Clinical Neurological Sciences, University Hospital, London, Ontario, Canada
*
Dept. of Clinical Neurol. Sciences,University Hospital, 339 Windermere Rd., London, Ontario, Canada N6G 2K3
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The pyramidal tract and particularly the direct corticomotoneuronal components (DCM) have become increasingly important in the higher primates. Minimal single pulse precentral stimulation in man evokes EMG discharges from the contralateral hand muscles with a latency of 18-21 milliseconds. The excitability changes produced by such cortical stimulation on the upper limb H-reflex has been observed to include a short duration early facilitation probably corresponding to the DCM input and a later, longer lasting facilitation mediated by the same and probably other corticofugal projections. Potentiation of the H-reflex in the upper limbs by means of postcentral excitation required much higher single pulse stimulus intensities and the changes in excitability produced on the spinal motoneurons could have been explained by physical extension of the stimulus current to the precentral region. Isometric contraction potentiated the H-reflex produced by combinations of precentral cortical and peripheral nerve stimulation but no direct evidence was found to support a possible transcortical basis for the V2 stretch reflex.

Type
Research Article
Information
Canadian Journal of Neurological Sciences , Volume 2 , Issue 3 , August 1975 , pp. 245 - 253
Copyright
Copyright © Canadian Neurological Sciences Federation 1975

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