Source analysis of scalp-recorded movement-related electrical potentials

We used brain electric source analysis to study the sources generating the movement-related cortical potentials during the interval from 200 msec before to 200 msec after the movement onset. Dipole solutions were obtained for the peak of the negative slope (pNS′) and the frontal peak of the motor potential (fpMP) on scalp-recorded movement-related electrical potentials elicited by self-paced, repetitive unilateral finger movements in 10 normal volunteers. Two sources in homologous areas on each side of a spherical head model provided a satisfactory solution for the activity occurring at the instant of the pNS′ in all subjects. The fpMP was modeled by a contralateral source and a midline source in 6 subjects and by a single contralateral source in the remaining 4 subjects. The percentage of the residual variance, or goodness-of-fit, over the interval from -200 to 200 msec, using the solutions derived at pNS′ and fpMP, was low. The results support the hypothesis that the NS′ originates from the activity of bilateral generators in the sensorimotor cortex, and the motor potential arises from the combined activity of sources in the contralateral postcentral regions and the supplementary motor area.