Interhemispheric inhibition during mental actions of different complexity

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Actual and mental actions are known to activate similar neural substrates.
• Limited neurophysiological evidence exists regarding interhemispheric interactions during mental movements.

Purpose of the Study:

• To investigate if task complexity in mental imagery is reflected in inhibitory interactions between the primary motor cortices (M1s).
• To explore the neurophysiological basis of shared neural circuits for actual and mental movements.

Main Methods:

• Transcranial magnetic stimulation (TMS) applied to the left primary motor cortex (M1).
• Subjects performed actual and mental movements of increasing complexity with the right hand.
• Corticospinal excitability and ipsilateral silent period (iSP) in the left opponent pollicis muscle (OP) were measured.

Main Results:

• Corticospinal excitability in the right OP increased during both actual and mental movements, with complexity-dependent changes only in actual movements.
• Interhemispheric motor inhibition, measured by iSP in the left OP, was similarly modulated by task complexity in both actual and mental movements.
• The duration and area of the iSP increased with task complexity across both movement conditions.

Conclusions:

• Mental and actual movements share similar inhibitory neural circuits between homologous primary motor cortex areas.
• Task complexity influences interhemispheric motor inhibition in a comparable manner for both real and imagined movements.