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Enhanced propriospinal excitation from hand muscles to wrist flexors during reach-to-grasp in humans.
MedLine Citation:
PMID:  22031772     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
In humans, propriospinal neurones located at mid-cervical levels receive peripheral and corticospinal inputs and probably participate in the control of grip tasks, but their role in reaching movements, as observed in cats and primates, is still an open question. The effect of ulnar nerve stimulation on FCR MEP was tested during reaching tasks and tonic wrist flexion. Significant MEP facilitation was observed at the end of reach during reach-to-grasp but not during grasp, reach-to-point or tonic contractions. MEP facilitation occurred at a longer ISI than expected for convergence of corticospinal and afferent volleys at motoneurone level, and was not paralleled by a change in the H reflex. These findings suggest convergence of the two volleys at propriospinal level. Ulnar-induced MEP facilitation was observed when conditioning stimuli were at 0.75 MT, but not 1 MT. This favours an increased excitability of propriospinal neurones rather than depression of their feedback inhibition, as has been observed during tonic power grip tasks. It is suggested that the ulnar-induced facilitation of FCR MEP during reach may be due to descending activation of propriospinal neurones, assisting the early recruitment of large motoneurones for rapid movement. Because the feedback inhibitory control is still open, the excitation can be truncated by cutaneous inputs from the palmar side of the hand during grasp, thus assisting movement termination. It is concluded that the feed-forward activation of propriospinal neurones and their feedback control may be involved in the internal model, motor planning and online adjustments for reach-to-grasp movements in humans.
Authors:
Louis-Solas Giboin; Alexandra Lackmy-Vallée; David Burke; Veronique Marchand-Pauvert
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-10-26
Journal Detail:
Title:  Journal of neurophysiology     Volume:  -     ISSN:  1522-1598     ISO Abbreviation:  -     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1UPMC.
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