Open AccessCorticospinal control from M1 and PMv areas on inhibitory cervical propriospinal neurons in humans
Author(s) -
Giboin LouisSolal,
Sangari Sina,
LackmyVallée Alexandra,
Messé Arnaud,
PradatDiehl Pascale,
MarchandPauvert Véronique
Publication year - 2017
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13387
Subject(s) - inhibitory postsynaptic potential , neuroscience , ctbs , transcranial magnetic stimulation , stimulation , facilitation , corticospinal tract , primary motor cortex , biology , medicine , radiology , diffusion mri , magnetic resonance imaging
Inhibitory propriospinal neurons with diffuse projections onto upper limb motoneurons have been revealed in humans using peripheral nerve stimulation. This system is supposed to mediate descending inhibition to motoneurons, to prevent unwilling muscle activity. However, the corticospinal control onto inhibitory propriospinal neurons has never been investigated so far in humans. We addressed the question whether inhibitory cervical propriospinal neurons receive corticospinal inputs from primary motor (M1) and ventral premotor areas ( PM v) using spatial facilitation method. We have stimulated M1 or PM v using transcranial magnetic stimulation ( TMS ) and/or median nerve whose afferents are known to activate inhibitory propriospinal neurons. Potential input convergence was evaluated by studying the change in monosynaptic reflexes produced in wrist extensor electromyogram ( EMG ) after isolated and combined stimuli in 17 healthy subjects. Then, to determine whether PM v controlled propriospinal neurons directly or through PM v‐M1 interaction, we tested the connectivity between PM v and propriospinal neurons after a functional disruption of M1 produced by paired continuous theta burst stimulation ( cTBS ). TMS over M1 or PM v produced reflex inhibition significantly stronger on combined stimulations, compared to the algebraic sum of effects induced by isolated stimuli. The extra‐inhibition induced by PM v stimulation remained even after cTBS which depressed M1 excitability. The extra‐inhibition suggests the existence of input convergence between peripheral afferents and corticospinal inputs onto inhibitory propriospinal neurons. Our results support the existence of direct descending influence from M1 and PM v onto inhibitory propriospinal neurons in humans, possibly though direct corticospinal or via reticulospinal inputs.