Alpha band power changes in unimanual and bimanual sequential movements, and during motor transitions

Objective: To investigate the cortical activation during execution of unimanual and bimanual synchronous and asynchronous finger sequences, as well as during transitions between those sequences. Methods: Task-related power (TRPow) analysis of multichannel surface EEG was used to examine the regional oscillatory brain activity in the lower (7.8–9.8 Hz) and upper (10.8–11.8 Hz) alpha band. Unimanual to bimanual, bimanual to unimanual, and unimanual to unimanual transitions, prompted by visual cues, were studied in 10 right handed subjects. Results: (1) Execution of unimanual and bimanual movements was accompanied by a bilateral activation over the central regions. (2) The 7.8–9.8 Hz TRPow decrease was more prominent for left and bimanual movements, suggesting sensitivity of the lower alpha band to task difficulty. (3) No difference in alpha oscillatory activity was found between bimanual synchronous and asynchronous sequences. (4) Transitions between motor sequences were invariably accompanied by a mesioparietal TRPow decrease in the lower alpha band. (5) This mesioparietal activation was contingent to the change of motor program, and could not be accounted for by the change of visual cue, or related attentional processes. Conclusion: The 7.8–9.8 Hz mesioparietal activation most likely reflects a posterior parietal motor command initiating transition between motor programs.