Electrophysiologic Mechanisms of Ketamine Antidepressant Response

This study aims to identify electrophysiologic biomarkers associated with antidepressant response to ketamine in adults with epilepsy undergoing clinically indicated stereo-electroencephalography (sEEG) monitoring who have at least mild depressive symptoms. Participants will receive a single subanesthetic intravenous ketamine infusion (0.5 mg/kg over 40 minutes) during their Epilepsy Monitoring Unit admission. Intracranial neural recordings and behavioral assessments will be collected before and approximately 24 hours after infusion to examine changes in neural circuits associated with rumination and anhedonia.

Inclusion Criteria: * Admitted to the Emory EMU for clinically indicated sEEG monitoring for epilepsy. * At least mild depressive symptoms at baseline, defined as MADRS ≥7 or BDI-II ≥14. * Electrode coverage that includes midline regions sufficient for enrollment and analyses. * Ability to provide informed consent and to complete bedside tasks/questionnaires in English. * Expected to remain under inpatient monitoring through the planned \~24-hour post-infusion follow-up unless clinical needs dictate otherwise. Exclusion Criteria: * Documented IQ \