Changes in interhemispheric inhibition from active to resting primary motor cortex during a fine-motor manipulation...

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Interhemispheric inhibition (IHI) modulates motor cortex excitability.
• The influence of sensorimotor task complexity on IHI from the active to the resting primary motor cortex (M1) is not fully understood.

Purpose of the Study:

• To investigate how performing a fine-motor manipulation (FM) task versus an isometric abduction (IA) task affects IHI.
• To determine if IHI changes are task-dependent and related to motor cortex activity.

Main Methods:

• Used transcranial magnetic stimulation (TMS) to assess IHI between the left and right primary motor cortices (M1) in 10 right-handed subjects.
• Measured motor evoked potentials (MEPs) in the first dorsal interosseous (FDI) muscle.
• Compared IHI during a complex FM task (chopsticks) and a simpler IA task, both performed with the left hand.

Main Results:

• Interhemispheric inhibition (IHI) from the active to the resting M1 was significantly increased during the FM task compared to the IA task.
• This increase in IHI was independent of the motor evoked potential (MEP) amplitude in the active M1.
• Findings suggest a reduction in ipsilateral intracortical inhibition during complex motor tasks.

Conclusions:

• Complex sensorimotor tasks, like fine-motor manipulation, enhance IHI between primary motor cortices.
• The observed increase in IHI during complex tasks may be linked to altered intracortical inhibitory circuit activity.
• Task-specific modulation of interhemispheric communication is crucial for motor control.