Task-dependent effects of interhemispheric inhibition on motor control

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Interhemispheric communication involves a balance of facilitation and inhibition.
• Task-dependent modulation of this balance is known, but its relation to individual motor performance differences is unclear.

Purpose of the Study:

• To investigate the relationship between individual differences in interhemispheric inhibition (IHI) and motor performance.
• To assess the role of IHI in unimanual and bimanual tasks.

Main Methods:

• Used the ipsilateral silent period (iSP) technique, a measure of interhemispheric inhibition, via transcranial magnetic stimulation.
• Participants performed three tasks: unimanual (right hand) constant force, simultaneous bimanual constant force, and independent bimanual (right hand constant force, left hand sine wave tracking).

Main Results:

• Greater IHI capacity correlated with reduced mirror electromyography (EMG) activity in the non-dominant hand during unimanual contractions.
• Individuals with higher IHI capacity performed worst on the independent bimanual task.

Conclusions:

• High IHI capacity effectively suppresses motor overflow during unimanual tasks.
• However, strong IHI may impede necessary interhemispheric cooperation for independently controlled bimanual tasks.