All participants will be patients with medically refractory epilepsy who have undergone depth electrode placement for stereo EEG monitoring for seizure localization. Participants will complete working memory tasks and EEG recordings will be concurrently collected from their depth electrodes. Some subjects will undergo macro-micro electrode implantation as a part of their SEEG implantation procedure for the purpose of EEG macro (local activity) and micro (single-unit) recordings. Some subjects will complete working memory tasks with stimulation applied during task completion.

Local field potential changes are from intracranial neural recordings taken while patients complete spatial working memory tasks. In the manual remember 1 remember 2 task, patients are instructed to hold down a cursor on a central location box colored one color or another on screen, while two boxes in locations sequentially flash on screen. Depending on the central location box color, the patient will drag their cursor to the first or second location box shown, after the central box has disappeared from screen. In the retro remember 1 remember 2 task, the color of the central box color is not shown until both location boxes have flashed onscreen. In the manual version, the central location box color is constant throughout the trial.

Single neuron spiking activity is recorded through SEEG micro neural recordings while patients complete working memory tasks.

Bipolar stimulation through pre-selected SEEG electrodes in the prefrontal cortex and surrounding areas will occur during the remember 1 remember 2 working memory tasks. Stimulation will be performed via the Ripple Neuromed Summit system. Stimulation will be tested with each patient prior to task to determine safety and tolerability, while patient is monitored by a neurosurgeon or neurologist.