Learning of new associations invokes a major change in modulations of cortical beta oscillations in human adults

Abstract

Large-scale cortical beta (β) oscillations have been implicated in the learning processes but their exact role is debated. We explored the dynamics of β-oscillations while 25 adult participants learned, through trial and error, novel associations between four auditory pseudowords and movements of four body extremities. We used MEG to evaluate learninginduced changes in beta modulation accompanying cue-triggered movements.Our findings showed that spatial-temporal characteristics of movement-related β-oscillations underwent a major transition as learning proceeded. Early in learning, suppression of β-power in multiple cortical areas occurred long before movement initiation and sustained throughout the whole behavioral trial. As learning advanced and task performance reached asymptote, βsuppression was replaced by a widespread and prolonged rise in β-power. The β-power rise started shortly after the initiation of correct motor response and mainly comprised the prefrontal and medial temporal regions of the left hemisphere. This post-decision β-power predicted trial-by-trial response times (RT) at both stages of learning (before and after the rules become familiar) but in opposite ways. When a subject started to acquire associative rules and gradually improved task performance, a decrease in RT was correlated with the increase in the post-decision β-band power. Repeatedly correct implementation of the learned rules reversed this correlation in the opposite direction with faster (more confident) responses associated with the weaker post-decision β-band synchronization.Our findings suggest that maximal beta activity is pertinent to a distinct stage of learning and may serve to strengthen the newly learned association in a distributed memory network.