Related Experiment Video
Updated: May 19, 2026
07:33
Measuring Contralateral Silent Period Induced by Single-Pulse Transcranial Magnetic Stimulation to Investigate M1 Corticospinal Inhibition
Published on: August 23, 2022
Interhemispheric inhibition in human wrist muscles
V Sattler1, M Dickler, M Michaud
1Service de Neurologie, Centre Hospitalier Universitaire de Toulouse, Pôle Neurosciences, CHU Purpan, Place du Dr Baylac, TSA40031, 31059 Toulouse Cedex 9, France.
Experimental Brain Research
|August 28, 2012
Summary
Interhemispheric inhibition (IHI) between primary motor cortices (M1) controlling wrist muscles is reduced during unilateral movement. This suppression, particularly at short intervals, aids in controlling voluntary actions and inhibiting the opposite limb.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Interhemispheric interactions between homologous muscle representations in the left and right primary motor cortex (M1) are crucial for motor control.
- Transcranial magnetic stimulation (TMS) is a key tool for investigating these interactions, particularly interhemispheric inhibition (IHI).
Purpose of the Study:
- To investigate the magnitude and directionality of IHI between wrist extensor and flexor muscle representations in the human M1.
- To examine how unimanual voluntary contraction affects IHI at different interstimulus intervals (ISIs).
Main Methods:
- Paired-pulse TMS was used in 9 healthy subjects to assess IHI at short (10 ms, SIHI) and long (40 ms, LIHI) ISIs.
- Stimulation was applied between motor cortices controlling homologous wrist muscles, comparing rest and unimanual tonic contraction conditions.
- IHI was measured during stimulation from dominant to non-dominant cortex and vice versa.
Main Results:
- A bidirectional IHI was observed for both wrist extensors and flexors at rest for both SIHI and LIHI.
- Short-interval IHI (SIHI) was significantly reduced during unimanual contraction of the contralateral hand, while long-interval IHI (LIHI) was not.
- IHI magnitude did not differ between stimulation of the dominant versus non-dominant hemisphere.
Conclusions:
- Unilateral muscle activity globally and bidirectionally reduces IHI between homologous M1 representations, with a more pronounced effect on SIHI.
- These findings suggest that modulation of interhemispheric interactions in M1 is vital for controlling unilateral movements and suppressing unwanted activity in the contralateral limb.
