Neural Correlates of the Contextual Interference Effect in Motor Learning: A Transcranial Magnetic Stimulation Investigation

ABSTRACT The authors applied transcranial magnetic stimulation (TMS) to investigate the causal role of the primary motor cortex (M1) for the contextual-interference effect in motor learning. Previous work using a nonfocal TMS coil suggested a casual role for M1 during high-interference practice conditions, but this hypothesis has not yet been proven. In the 1st experiment, participants practiced 3 rapid elbow flexion–extension tasks in either a blocked or random order, with learning assessed by a delayed retention test. TMS was delivered immediately after feedback during practice using a circular coil, centered over the contralateral M1. Each participant practiced with 1 of 3 TMS conditions: no TMS, real TMS, or sham TMS. Although no significant differences were observed between groups during acquisition, retention of the random group was better than the blocked group. The learning benefits of random practice were attenuated in the real-TMS condition, but not in the sham-TMS or no-TMS conditions. In the 2...