Motor training reduces surround inhibition in the motor cortex

• Surround inhibition (SI) is not necessary for the generation of skilled isolated finger movement.
• SI may be utilised during the early stages of motor learning.
• Attention may play a role in modulating SI; increased attention appears to engage a stronger SI.

ObjectiveSurround inhibition (SI) is thought to facilitate focal contraction of a hand muscle by keeping nearby muscles silent. Unexpectedly, SI is reduced in skilled pianists. We tested whether repeated practice of focal contraction in non-pianists could reduce SI.MethodsMotor-evoked potentials were elicited by transcranial magnetic stimulation in the relaxed abductor digiti minimi randomly at the onset and 5 s after offset of a 2 s focal contraction (10% maximum) of the first dorsal interosseous (FDI). Over 5 blocks of 40 trials participants obtained points for increasing contraction speed and stability in FDI. In a final block, the interval between contractions was varied randomly to increase attention to the task.ResultsOver the first 5 blocks, SI declined as performance (points scored) improved. In the final “attention” block SI increased towards baseline without affecting performance.ConclusionsAlthough SI may be useful during the early stages of learning, skilled focal finger movement does not require SI to prevent activity in non-involved muscles. This could be due to better targeting of the excitatory command to move. Results from the final block suggest that increased attention can re-engage SI when task parameters change.SignificanceSI is not necessary for successful focal contraction, but may contribute during learning and during attention to task.