Somatosensory evoked potentials during the ideation and execution of individual finger movements

Scalp somatosensory evoked potentials (SEPs) were recorded in 10 volunteers after median nerve stimulation, in four experimental conditions of hand movements performance/ideation, and compared with the baseline condition of full relaxation. The experimental conditions were (a) self-improvised hand-finger sequential movements; (b) the same movements according to a read sequence of numbers; (c) mental ideation of finger movements; and (d) passive displacement of fingers in complete relaxation. Latencies and amplitudes of the parietal (N20, P25, N33, and P45) and frontal peaks (P20-22, N30, and P40) were analyzed. Latencies did not vary in any of the paradigms. Among the parietal complexes, only the P25-N33 amplitude was significantly reduced in (a), (b), (c), and (d) and the N20-P25 was reduced in (a) and (d); among frontal waves, N30 and P40 were significantly reduced (20-75%) in (a) and (b). Coronal electrodes showed amplitude decrements maximal at the frontal-rolandic positions contralateral to the stimulated side.