Temporal activation pattern of parietal and premotor areas related to praxis movements

We sought to determine the cortical physiology underlying praxis movements in normal subjects using electroencephalography (EEG). Eight normal subjects were instructed to perform six types of self-paced tool-use pantomime and communicative gesture movements with the right hand. We recorded 64-channel EEG using a linked ear reference and electromyogram (EMG) from right thumb and forearm flexors. Data revealed early slow wave components of the movement-related cortical potential (MRCP) beginning over the left parietal area about 3 s before movement onset, similarly for both movement types. At movement onset, maximal amplitude was present over central and bilateral sensorimotor areas. Event-related desynchronization (ERD) in the beta band was seen over the left parietal and sensorimotor cortices during preparation, later spreading to the homologous area of the right hemisphere. Alpha ERD was mainly in the left sensorimotor cortex about 1.5 s before movement onset. Beta ERD in mesial frontal areas was greater during preparation for tool use compared to communicative gesture movements. Mesial frontal beta event-related synchronization (ERS) developed more rapidly after communicative gestures than tool-use. The dynamics of parietal and frontal activities indicates the timing of these areas in the production of praxis. The posterior parietal cortex contributes to the early slow wave negativity of the MRCP. Planning self-paced praxis movements begins as early as 3 s before movement in the left parietal area and subsequently engages frontal cortical regions.