Recording of movement-related potentials from the human cortex.

A patient with intractable epilepsy secondary to a brain tumor was evaluated with a chronically implanted array of 64 stainless-steel subdural electrodes covering the perirolandic area. Cortical potentials associated with voluntary, self-paced middle-finger extension were recorded simultaneously from subdural and scalp electrodes using a computer-assisted method for averaging movement-related potential (MRP) in relation to electromyographic (EMG) onset. A high-amplitude negative potential, Bereitschaftspotential/negative slope (BP/NS'), preceding the onset of the EMG activity by more than 1 sec was recorded in an extremely localized fashion exclusively from electrodes placed in the precentral hand motor area as well as in the more medial part of the somatosensory hand area. These results suggest that the hand motor and sensory areas have an essential participation in the generation of MRPs and, therefore, also in the preparation of voluntary finger movements.