Fig. 4.

Power changes around self-initiated left finger movements. Virtual electrode was placed at the right M1 (MNI coordinates: 37, − 18, 53) and time-series were extracted around the times when the subjects performed button presses with the fingers of his left hand. Time–frequency decomposition of the time-series shows ERD/ERS sequence in the alpha and beta bands and ERS in the high gamma band, which are well known features of movement-related cortical power dynamics. The rectangles show the time and frequency ranges that were used for volumetric beamformer analysis shown in Fig. 5. The dotted line corresponds to the high gamma range (55–80 Hz) and the dashed line to alpha and beta range (5 to 30 Hz). In the subtraction between two time windows the images corresponding to white rectangles entered with the positive sign and the images corresponding to black rectangles with the negative sign.