Open AccessModulation of motor cortex inhibition during motor imagery
Author(s) -
Benjamin Chong,
Cathy M. Stinear
Publication year - 2017
Publication title -
journal of neurophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 245
eISSN - 1522-1598
pISSN - 0022-3077
DOI - 10.1152/jn.00549.2016
Subject(s) - transcranial magnetic stimulation , disinhibition , inhibitory postsynaptic potential , neuroscience , motor cortex , primary motor cortex , excitatory postsynaptic potential , psychology , postsynaptic potential , silent period , stimulation , medicine , receptor
Motor imagery (MI) is similar to overt movement, engaging common neural substrates and facilitating the corticomotor pathway; however, it does not result in excitatory descending motor output. Transcranial magnetic stimulation (TMS) can be used to assess inhibitory networks in the primary motor cortex via measures of 1-ms short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI), and late cortical disinhibition (LCD). These measures are thought to reflect extrasynaptic GABA A tonic inhibition, postsynaptic GABA B inhibition, and presynaptic GABA B disinhibition, respectively. The behavior of 1-ms SICI, LICI, and LCD during MI has not yet been explored. This study aimed to investigate how 1-ms SICI, LICI, and LCD are modulated during MI and voluntary relaxation (VR) of a target muscle. Twenty-five healthy young adults participated. TMS was used to assess nonconditioned motor evoked potential (MEP) amplitude, 1-ms SICI, 100- (LICI 100 ) and 150-ms LICI, and LCD in the right abductor pollicis brevis (APB) and right abductor digiti minimi during rest, MI, and VR of the hand. Compared with rest, MEP amplitudes were facilitated in APB during MI. SICI was not affected by task or muscle. LICI 100 decreased in both muscles during VR but not MI, whereas LCD was recruited in both muscles during both tasks. This indicates that VR modulates postsynaptic GABA B inhibition, whereas both tasks modulate presynaptic GABA B inhibition in a non-muscle-specific way. This study highlights further neurophysiological parallels between actual and imagined movement, which may extend to voluntary relaxation. NEW & NOTEWORTHY This is the first study to investigate how 1-ms short-interval intracortical inhibition, long-interval intracortical inhibition, and late cortical disinhibition are modulated during motor imagery and voluntary muscle relaxation. We present novel findings of decreased 100-ms long-interval intracortical inhibition during voluntary muscle relaxation and increased late cortical disinhibition during both motor imagery and voluntary muscle relaxation.