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The effect of ballistic thumb contractions on the excitability of the ipsilateral motor cortex
journal contribution
posted on 2023-05-17, 01:07 authored by Mark HinderMark Hinder, Matthew SchmidtMatthew Schmidt, Michael GarryMichael Garry, Jeffery SummersJeffery SummersWe investigated how ballistic contractions of the left thumb affect the excitability of the ipsilateral motor cortex using transcranial magnetic stimulation (TMS). TMS was applied at the motor hotspot for the right abductor pollicis brevis (APB) muscle. In ‘self-triggered’ trials, participants made targeted, isometric, contractions of the left APB. The right APB was either relaxed or maintained a tonic contraction. TMS was administered as soon as possible after electromyographic onset in the left APB. In ‘control’ trials, the left thumb remained quiescent and TMS was triggered by the computer. In each condition, 20–24 trials were conducted. Half these trials involved a single test stimulus, TS (130% APB resting motor threshold, RMT). In the other trials, short-interval intracortical inhibition (SICI) was investigated by applying a conditioning stimulus (70% APB RMT) 3 ms prior to the TS. SICI ratios were not significantly different in self-triggered and control trials. However, when the right APB was active, significantly shorter silent periods (SPs) were observed in self-triggered trials when compared with control trials. Our results support the view that SICI and SP are mediated by different inhibitory circuits, and that ipsilateral GABAB-ergic circuits (assessed by SP), but not GABAA-ergic circuits (assessed by SICI), are affected in the period immediately following voluntary ballistic contractions.
History
Publication title
Experimental Brain ResearchVolume
201Pagination
229-238ISSN
0014-4819Department/School
School of Psychological SciencesPublisher
Springer-VerlagPlace of publication
175 Fifth Ave, New York, USA, Ny, 10010Rights statement
The original publication is available at www.springerlink.comRepository Status
- Restricted