Alpha, Beta, and Gamma Oscillations in Cortical Communication During Motor Preparation

Motor cortices prepare movements by rotating activity from one region into another via synchronized firing at different frequencies, primarily involving α, β and γ bands. Previous results in non-disabled participants showed that although within β-band couplings in contralateral motor cortices dominant cortical activities for hand opening task, α-β and γ-β couplings are presented for more complex tasks. These findings raise the question whether α and γ bands play a modulation role on the β-oscillation during the motor preparation for an “un-established” task. To test this question, we compared the cortico-cortical-communication during motor preparation for hand opening between the non-disabled and stroke groups. Twelve stroke individuals who cannot open hand sufficiently and eleven age-matched non-disabled individuals performed a maximal hand opening with a high-density EEG measure. The non-disabled group expressed the exclusive within-β communications primarily within contralateral motor areas. Differently, the stroke group showed complex couplings across both hemispheres involving α, β and Gamma bands. These findings suggest that a cortical preparatory β communication may reflect using a well-established internal model. However, when the internal model does not work sufficiently, bilateral α and γ-band modulation to the β oscillation occurs, demonstrating the learning and adjustment to the motor plan.