Closed-Loop Deep Brain Stimulation for Treatment-Resistant Bipolar Depression

Inclusion Criteria: * Age 22-70 * Meet Diagnostic and Statistical Manual-V (DSM-V) diagnostic criteria for Bipolar II Disorder, with an episode of depression lasting at least 1 year that is treatment resistant as defined above, without a manic or hypomanic episode in the last 2 years; patients must be taking a mood stabilizer (lithium \>0.6 mEq/L or valproate \>350 mM/L), an atypical antipsychotic, or a combination of a mood stabilizer and an atypical antipsychotic for at least 2 weeks at a stable dosage before starting the study and must continue taking anti-manic medication throughout their participation in the study unless discontinuation is necessary because of patient safety/health considerations. * Must have either failed ECT (it was effective but not tolerated due to side effects; it was effective, but patients could not achieve a sustained response), not been able to complete a course of ECT due to side effects, or have been medically advised to receive ECT and have been unwilling or unable to obtain ECT. * Has MADRS score of \> 26 at two baseline visits * Ability to complete repeated administrations of MDD rating scales. * If patient is on a regimen of psychotropic medication, no changes in this regimen should be expected during the 4 weeks prior to entry into and the duration of the study. * Willing and able to undergo invasive brain recording/stimulation study * Willing and able to attend multiple research visits and perform at-home research protocol * Willing and able to provide informed consent * Ability to speak and read English Exclusion Criteria: * Meets DSM-V criteria for a psychotic disorder, eating disorder, panic disorder, posttraumatic stress disorder, obsessive compulsive disorder, tic disorder, or another comorbid psychiatric disorder other than MDD or generalized anxiety disorder based on a SCID * Generalized anxiety disorder is the primary DSM-V disorder during the current MDD episode * Active suicidal ideation with intent and plan as defined by a score of 5 on the Columbia-Suicide Severity Rating Scale (C-SSRS) * History of suicide attempt requiring hospitalization in previous 2 years. * Meets criteria for alcohol or substance abuse or dependence (other than caffeine) in previous 6 months, determined by the SCID * Has a personality disorder based on the investigator's assessment that the investigator believes will adversely impact subject compliance or safety * Fibromyalgia or chronic fatigue syndrome * Current condition requiring chronic narcotic use * History of traumatic brain injury, another neurological disorder, or developmental delay * History of seizures * MRI (done within one year of the first visit) with significant abnormalities * Previous ablative intracranial surgery or previously implanted deep brain stimulation system or any previously implanted device treatment involving brain stimulation * Implantable hardware not compatible with MRI or with the study * Major medical co-morbidities increasing the risk of surgery including severe diabetes, major organ system failure, history of hemorrhagic stroke, need for chronic anticoagulation other than aspirin, active infection, intracranial space occupying lesion, increased intracranial pressure, cardiovascular accident within the last month, aneurysm/abnormality, retinal detachment, unstable cardiovascular disease (recent myocardial infarction, severe ischemia, severe or uncontrolled hypertension), immunocompromised state, or malignancy with \< 5 years life expectancy * Inability to stop Coumadin or platelet anti-aggregation therapy for surgery and after surgery. - Patients taking these medications will need to discuss the need/risk of continuing these medications with their physicians and the PI or study personnel may contact the treating physician(s) to discuss the risks of anticoagulation/antiaggregation therapy discontinuation * Coagulopathy. Patients will be excluded unless assessed and cleared by hematology * Allergies or known hypersensitivity to materials in the NeuroPace RNS® System (i.e. titanium, polyurethane, silicone, polyetherimide, stainless steel) * Subject lives alone without possibility of caregiver support post-hospital stay * Inability to comply with study follow-up visits