Premium
TMS reveals a direct influence of spinal projections from human SMA p on precise force production
Author(s) -
Entakli Jonathan,
Bonnard Mireille,
Chen Sophie,
Berton Eric,
Graaf Jozina B.
Publication year - 2014
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.12392
Subject(s) - isometric exercise , transcranial magnetic stimulation , primary motor cortex , neuroscience , stimulation , sma* , supplementary motor area , motor cortex , silent period , inhibitory postsynaptic potential , computer science , psychology , biology , functional magnetic resonance imaging , physiology , algorithm
The corticospinal ( CS ) system plays an important role in fine motor control, especially in precision grip tasks. Although the primary motor cortex (M1) is the main source of the CS projections, other projections have been found, especially from the supplementary motor area proper ( SMA p). To study the characteristics of these CS projections from SMA p, we compared muscle responses of an intrinsic hand muscle ( FDI ) evoked by stimulation of human M1 and SMA p during an isometric static low‐force control task. Subjects were instructed to maintain a small cursor on a target force curve by applying a pressure with their right precision grip on a force sensor. Neuronavigated transcranial magnetic stimulation was used to stimulate either left M1 or left SMA p with equal induced electric field values at the defined cortical targets. The results show that the SMA p stimulation evokes reproducible muscle responses with similar latencies and amplitudes as M1 stimulation, and with a clear and significant shorter silent period. These results suggest that (i) CS projections from human SMA p are as rapid and efficient as those from M1, (ii) CS projections from SMA p are directly involved in control of the excitability of spinal motoneurons and (iii) SMA p has a different intracortical inhibitory circuitry. We conclude that human SMA p and M1 both have direct influence on force production during fine manual motor tasks.