Abstract
Using high-density electroencephalography (EEG) , the brain regions involved in tapping of the index fingers were investigated. Subjects were requested to perform voluntary alternate tapping movements with both index fingers as fast as possible. During the task, the tapping mode in which both index fingers moved simultaneously was interlaced. The alternate tapping (A-mode) and simultaneous tapping (S-mode) groups were extracted using a histogram of the inter-tapping intervals. EEG coherence was used to evaluate functional connectivity between cortical regions. Compared with the S-mode, connectivity increased significantly in the A-mode in the mesial-central circuitry including the supplementary motor area (SMA) and the primary motor area (M1) , in the fronto-centroparietal circuitry including the primary somatosensory area (S1) and the premotor area (PM) , and in the fronto-central circuitry including the PM and M1 in the dominant hemisphere. In addition, interhemispheric connectivity increased in the PMs of both hemispheres. These findings indicate that the connectivity involved in the internal onset of the movement (SMA-M1) , in the sensori-motor integration (S1-PM, PM-M1) and in the phase planning (both PMs) is associated with the involuntary switching between A-mode and S-mode.
