Spontaneous fluctuations in brain electrical activity and their role in movement initiation

Abstract

The article reports the results of an experimental research. A sample of 20 apparently healthy individuals performed reaching tasks toward a target either spontaneously or in response to an imperative signal with their EEG recorded. Six independent sources of EEG activity were identified: premotor areas, supplementary motor area, primary motor areas, and the posterior parietal cortex. We compared slow fluctuations in potential and desynchronization of EEG activity in the alpha and beta bands across the independent sources during the initiation of movement in two experimental conditions: cued and self-initiated reaching. Alpha desynchronization and beta desynchronization in the contralateral premotor areas was observed 3,000 ms and 600 ms prior to the start of self-initiated reaching, respectively. In contrast, during cued movement, beta desynchronization in the premotor areas was seen 2,000 ms before movement onset, exceeding the reaction time to the signal (about 800 ms). Additionally, alpha desynchronization in the posterior parietal cortex was recorded 1,300 ms before movement onset. These results suggest that activation of premotor areas and the posterior parietal cortex occurs even before the presentation of the imperative signal. The findings indicate that movement initiation is most likely triggered during a specific phase of spontaneous slow fluctuations in brain electrical activity.