Figure 1.
A, Experimental setup. Two pairs of surface electrodes were placed over the FDI and APB of the right hand, which is shown resting on a board. The tip of the index finger is resting on the force transducer. B, Time course of the task. Shown are the acoustic signal, which starts 200 ms after the begin of the recording, EMG in the FDI, the synergistic muscle, EMG in the APB, the surrounding muscle, and the forced produced. Stimuli were applied before the onset of the tone (rest, after 100 ms), during the premotor phase (20 ms before the onset of EMG in the FDI), the phasic phase (at the first peak of EMG in the FDI), and the tonic phase (1600 ms after the onset of the acoustic signal, maintenance phase of the contraction, steady state). C, Background EMG. Shown are the background EMG levels for the APB and FDI in all four different phases. Although there is no significant modulation of background EMG in APB, the EMG signal increases for the phasic and tonic phases in the FDI, reflecting its activation during the task. **p < 0.01; ***p < 0.005.