Motor processing after movement execution as revealed by evoked and induced activity.

Event-related synchronization (ERS) in the beta frequency band following movement execution has shown that motor processing is not completed yet when a movement ends. It is known that induced and evoked activities reflect different aspects of cortical processing which may result in different time courses. In the current study, we analyzed topography of postimperative negative variation (PINV) in 39 healthy right-handed adolescents in an acoustic forewarned reaction time (contingent negative variation, CNV) task using a 64-electrode high-density sensor array. We dissociated different PINV components in their time course from postmovement beta ERS in order to provide fundamental knowledge about evoked and induced EEG components after movement execution as a basis for further analysis of postmovement processing. A postmovement negativity occurred from about 500 to 1200 ms after the imperative stimulus (peaking about 600 ms after a right-hand button press) at central electrodes, contralateral to the response movement side. Current source density (CSD) analysis confirmed the current sinks over motor areas [contralateral primary motor/premotor and supplementary/cingulate motor area]. The described DC component (motor PINV, mPINV) differed in time course and localization from later "classical" PINV (cPINV) which is thought to reflect contingency reappraisal. mPINV could also be distinguished topographically from a mere delayed CNV resolution. When mPINV and ERS at the same left central electrode were compared, both parameters showed different time courses. Left central mPINV rather paralleled ERS at midcentral electrodes. Therefore, we suggest that the topography of mPINV provides first hints towards an involvement of contralateral primary motor cortex in postmovement processing beyond a mere idling state as reflected by later beta ERS. mPINV could be a useful tool to investigate the role of primary motor cortex in motor-learning processes. The combined analysis of induced and evoked activities seems to be able to elucidate different aspects of cortical connectivity and motor processes following movement.