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Task‐dependent changes in late inhibitory and disinhibitory actions within the primary motor cortex in humans
Author(s) -
CauxDedeystère Alexandre,
Rambour Mélanie,
Duhamel Alain,
Cassim François,
Derambure Philippe,
Devanne Hervé
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.12505
Subject(s) - disinhibition , transcranial magnetic stimulation , neuroscience , inhibitory postsynaptic potential , silent period , index finger , interstimulus interval , psychology , motor cortex , evoked potential , pulse (music) , primary motor cortex , stimulation , medicine , anatomy , physics , detector , optics
The objective of the present study was to investigate the time course of long‐interval intracortical inhibition ( LICI ) and late cortical disinhibition ( LCD ) as a function of the motor task (index abduction, thumb–index precision grip). Motor‐evoked potentials were recorded from the first dorsal interosseus ( FDI ) muscle of the dominant limb in 13 healthy subjects. We used paired‐pulse transcranial magnetic stimulation ( TMS ) paradigms in which a test pulse was preceded by a suprathreshold priming pulse (130% of the resting motor threshold) with varying interstimulus intervals ( ISI s). In each task, double pulses were delivered with ISI s ranging from 30% of the corresponding silent period ( SP ; ~ 45 ms) to 220% of the SP (~ 330 ms). In both tasks, we found that LICI was followed by LCD (namely a period of increased cortical excitability lasting until ~ 200% of the SP ). The time‐dependent modulation of LICI and LCD differed in the two tasks; LICI was shorter (i.e. disinhibition occurred earlier) and LCD was more intense during precision grip than during index abduction. Long‐interval intracortical inhibition disappeared well before the end of the SP in the precision grip task, suggesting that the mechanisms underlying these two inhibitory phenomena are distinct. Our data suggest that disinhibition might reflect adaptation of neural circuit excitability to the functional requirements of the motor task.