Motor training reduces surround inhibition in the motor cortex

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Surround inhibition (SI) is a neural mechanism thought to enhance focal muscle contractions by suppressing activity in adjacent muscles.
• Reduced SI has been observed in skilled pianists, suggesting it may not be critical for highly refined motor skills.

Purpose of the Study:

• To investigate whether repeated practice of focal muscle contractions in non-pianists can lead to a reduction in SI.
• To explore the role of attention in modulating SI during motor tasks.

Main Methods:

• Transcranial magnetic stimulation (TMS) was used to measure motor-evoked potentials in the abductor digiti minimi.
• Participants performed focal contractions of the first dorsal interosseous (FDI) muscle at 10% maximum voluntary contraction.
• SI was assessed at different intervals relative to FDI contractions over multiple practice blocks, with a final block manipulating attention.

Main Results:

• SI progressively declined over practice blocks as participants improved their FDI contraction performance.
• In a final block designed to increase attention, SI levels increased back towards baseline without impacting task performance.
• These findings indicate a dynamic modulation of SI based on learning and attentional demands.

Conclusions:

• SI is not strictly necessary for successful focal finger contractions, particularly in skilled individuals.
• The reduction of SI during practice suggests motor learning optimizes neural commands for precise muscle activation.
• Attention can reinstate SI, highlighting its potential role in adapting motor control under changing task conditions.