Two brakes are better than one: the neural bases of inhibitory control of motor memory traces.

Inhibitory control of actions is one important aspect in daily life to warrant adequate context related behavior. Alpha activity (oscillatory brain activity around 10Hz) has been suggested to play a major role for the implementation of inhibitory control. In the present study electrophysiological correlates of voluntary suppression of acquired, memorized motor actions have been compared to the suppression of novel motor actions. Multichannel EEG analyses of alpha power and alpha phase coherence were used. Healthy subjects were asked to inhibit the execution of either well-trained, memorized or untrained, novel sequential finger movements depending on the respective context. An increase of focal upper alpha activity at bilateral sensorimotor cortices was found during suppression of movements independent of whether these were memorized or novel. This represents a memory unspecific mechanism of motor cortical inhibition. In contrast, interregional phase synchronization between frontal and (left) central recording sites showed a differential effect with decoupling during suppression of memorized movements which was not the case with novel ones. Increase of fronto-central coupling at upper alpha frequency during retrieval of the memory trace and decrease during suppression of retrieval were obtained. This further supports the view of the functional relevance of upper alpha oscillations as a mechanism of context-dependent sustained inhibition of memory contents.