Neurons in human epileptic cortex. Response to direct cortical stimulation.

During craniotomy for surgical treatment of medically intractable epilepsy, single neurons were recorded from the lateral temporal cortex of 11 awake patients. A total of 83 neurons were recorded, and their response to repetitive direct cortical stimulation with ascending and descending frequency ramps between 1 to 10 Hz was evaluated. More normal units from the suspected epileptogenic cortex responded to repetitive stimulation at frequencies between 5 to 20 Hz with augmented action potential bursts than did units from cortex thought not to be primarily epileptogenic. This burst response might persist for up to 30 seconds after the frequency ramp had descended from 10 to 1 Hz. Except in two cases, this augmentation of burst response was not accompanied by afterdischarge on electroencephalography. These data would indicate that neurons within the region of suspected epileptogenic cortex demonstrate a greater propensity for afterdischarge to repetitive stimuli than do neurons in more normal cortex.