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Fatigue suppresses ipsilateral intracortical facilitation
T Bäumer1, A Münchau, C Weiller
1Department of Neurology, University of Hamburg, Martinistrasse 52, 20246 Hamburg, Germany. baeumer@uke.uni-hamburg.de
Experimental Brain Research
|October 2, 2002
Summary
Fatigue in one hand temporarily reduces motor cortex facilitation in the opposite hand. This interhemispheric effect, studied using transcranial magnetic stimulation (TMS), shows task-specific suppression of intracortical facilitation.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- The motor cortices of the right and left hemispheres are interconnected.
- Interactions between these areas can be investigated using transcranial magnetic stimulation (TMS).
- Fatigue's impact on interhemispheric motor cortex communication is not fully understood.
Purpose of the Study:
- To investigate the interhemispheric effects of fatigue on intracortical facilitation (ICF) and inhibition (ICI).
- To explore how fatigue in one hand influences motor cortex excitability in the contralateral homologous muscle.
Main Methods:
- Paired-pulse TMS was used to assess ICF and ICI.
- Ten healthy subjects performed fatiguing pinch grips with their left hand (50% MVC).
- Motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles.
Main Results:
- Fatigue significantly reduced ICF in the right FDI (P=0.0008).
- This reduction in ICF was temporary, returning to baseline within 15 minutes.
- No significant changes were observed in the right ADM or in control experiments without fatigue.
Conclusions:
- Fatigue induces a short-lasting, task-specific suppression of intracortical facilitation in the contralateral motor cortex.
- These findings highlight effective interhemispheric interactions between motor cortices, persisting even after movement cessation.