The functional significance of motor-cortical oscillations for implicit and explicit motor learning

Objectives: Motor learning occurs during practice but also between practice sessions. A specific significance of the primary motor cortex (M1) for early consolidation has been suggested. We here investigate alterations of motor-cortical oscillations associated with acquisition and early consolidation of a newly learned motor sequence.

Methods: Fifteen healthy subjects were trained on a serial reaction time task. Data were compared with performance during a randomly varying sequence. Event-related desynchronization (ERD) as a measure of motor-cortical excitability at alpha (8 – 12 Hz) and beta (13 – 30 Hz) frequencies was investigated using a 306-channel whole-head magnetoencephalography (MEG) system. ERD was determined during initial motor learning and 10 minutes after skill acquisition (i.e. the post-training period).

Results: The data reveal s stepwise decrease of ERD amplitude at beta frequency from random presentation to initial sequence learning and the post-training period. This decrease was significantly correlated with reaction times. As a main result the analysis revealed differences between implicit and explicit learning: Subjects using an explicit learning strategy in the post-training period showed stronger beta power suppression already during initial sequence learning than subjects keeping an implicit strategy of skill acquisition.

Conclusion: The amount of motor-cortical beta power suppression during initial learning of a motor sequence may predict the switch from implicit to explicit learning after early consolidation.