Motor sequence learning elicits mu peak-specific corticospinal plasticity.

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Transcranial magnetic stimulation (TMS) interventions targeting the motor cortex (M1) can enhance corticospinal output and motor learning.
• Previous research suggests optimal timing for TMS during sensorimotor mu rhythm trough phases, not peak phases, for motor learning benefits.
• This implies that neural mechanisms supporting motor learning are potentially more active during mu rhythm trough phases.

Purpose of the Study:

• To investigate whether motor sequence learning-related corticospinal plasticity is most evident when measured during mu trough phases.
• To test the hypothesis that motor sequence learning preferentially recruits mu phase-dependent plasticity.

Main Methods:

• Healthy adults participated in either a sequence or no-sequence group, practicing the serial reaction time task (SRTT).
• EEG-informed single-pulse TMS was used to measure mu phase-independent and mu phase-dependent motor evoked potential (MEP) amplitudes.
• MEP amplitudes were recorded before, immediately after, and 30 minutes post-SRTT, with a retention test one hour later.

Main Results:

• Both groups showed increased mu phase-independent MEP amplitudes post-SRTT.
• The sequence group exhibited greater peak-specific MEP amplitude increases 30 minutes after SRTT acquisition compared to the no-sequence group.
• The magnitude of these peak-specific MEP increases was inversely correlated with the degree of sequence learning.

Conclusions:

• Contrary to the initial hypothesis, motor sequence learning induces peak-specific corticospinal plasticity.
• This study provides the first direct evidence that motor sequence learning engages mu phase-dependent neurophysiological processes.
• Findings suggest a novel understanding of the neural mechanisms underlying motor learning and brain plasticity.