HUMAN BRAIN CORTICAL ELECTRIC-CURRENT SOURCE LOCALIZATION FROM THE SURFACE LAPLACIAN OF A VISUAL AND MOTOR EVENT-RELATED POTENTIAL

The surface Laplacian of the human-brain event-related potential were applied to an experiment designed to compare the known cognitive sites for mental tasks with the peak positions of the surface Laplacians of the subject's cortical electric potentials at each instant during a t ask. The computer was programmed to present randomly a letter 'L' or ' R' On a computer screen. When the monitor commands the subject to pres s the keyboard with subject's left (right) index finger depending on ' L' ('R'), the subject presses the left (right) shift-key on the keyboa rd. Multichannel event-related potentials were used to estimate the di stributions of the surface Laplacians of cortically generated electric potentials on the scalp. The locus of the surface Laplacian peak corr esponds to the sites and the stages of cortical source localization of the neural activity in both the visual and the motor area. The locus of the surface Laplacian peak seems to track the sequence of known cor tical localization of cognitive process.