Electrochemical and Electrophysiological Study

This study will utilize computerized algorithms in combination with real-time intracranial neurophysiological and neurochemical recordings and microstimulation to measure cognitive and affective behavior in humans. Questionnaires or simple behavioral tasks (game-like tasks on a computer or an iPad) may also be given to additionally characterize subjects on related cognitive or affective components. Importantly, for the purposes of understanding the function of the human brain, neural activity can be recorded and probed (i.e. microstimulation) while subjects are performing the same computerized cognitive and affective tasks. These surgeries allow for the in vivo examination of human neurophysiology and are a rare opportunity for such research. In addition to computerized testing, the investigators plan to characterize subjects' behavior on related cognitive or affective components. Some neuropsychological questionnaires, many of which are administered for clinical reasons (listed below under study population), may also be given to patients and healthy control subjects. All patients undergoing epilepsy surgery (the population from which subjects will be selected) undergo a standard clinical neuropsychological battery to assess aspects of cognitive function. This is a regular aspect of their clinical assessment carried out prior to consideration for study inclusion. All participants are selected uniformly because they are undergoing surgery for subdural electrode implantation. No particular ethnic group or population is targeted by or excluded from the study. Those to be considered for inclusion in the proposed study performing more than 2 standard deviations below the mean on any aspect of cognitive functioning as determined by standard preoperative neuropsychological testing will be excluded from the study. No additional neuropsychological testing will be necessary as part of the study itself.