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Sub‐threshold transcranial magnetic stimulation applied after the go‐signal facilitates reaction time under control but not startle conditions
Author(s) -
Smith Victoria,
Carlsen Anthony N.
Publication year - 2018
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.13827
Subject(s) - transcranial magnetic stimulation , moro reflex , stimulus (psychology) , neuroscience , serial reaction time , motor cortex , startle reaction , psychology , stimulation , startle response , go/no go , audiology , medicine , cognition , computer science , reflex , cognitive psychology , machine learning
The presentation of a startling acoustic stimulus ( SAS ) in a simple reaction time ( RT ) task significantly reduces RT due to the involuntary early initiation of a prepared movement; however, the underlying neural mechanism remains unclear. It has been proposed that a SAS triggers a cortically stored motor program by involuntarily increasing initiation‐related activation. Sub‐threshold transcranial magnetic stimulation ( TMS ) can be used to investigate cortical processes, as it increases cortical excitability for 6–30 ms and significantly reduces RT . The purpose of the present experiments was to determine whether the application of sub‐threshold TMS over motor cortex in close temporal proximity to a SAS would facilitate startle RT in the same manner as control RT , providing evidence for cortical involvement in startle‐related RT s. Participants completed a simple RT task requiring targeted wrist extension in response to an auditory go‐signal, which was randomly replaced by a SAS on 25% of trials. On a subset of trials, sub‐threshold TMS was applied 30 ms following the go‐signal in control trials or at −15, 0, +15 or +30 ms with respect to the SAS in startle trials. In all three experiments, sham and real TMS significantly reduced RT in control trials, with real TMS having a larger effect, but there was no effect of either real or sham TMS on startle‐related RT . These results suggest that there may be limited cortical involvement in the initiation of movements in response to a SAS . As an alternative, startle may produce the fastest possible RT s, with little room for additional facilitation.