Neuromodulation of the Fear Extinction Circuit Using Temporally and Anatomically Specific TMS in Humans

Inclusion Criteria: * Willing and able to provide informed consent. * Inclusion Criteria for PTSD Subjects - Diagnosis of current PTSD * Inclusion Criteria: Healthy Controls (HC) - no current psychiatric disorders ("Axis I" disorders) Exclusion Criteria: * Lifetime history of seizure or significant head trauma or other significant neurologic disease (e.g., tic disorder) * History of serious/significant psychiatric diagnoses ("Axis I" diagnoses) * Current significant suicidal ideation, plan or intent or suicidal behavior in past 6 months based on CSSRS and clinical judgment or Self-injurious behavior that involves suicidal intent, requires medical attention, or occurs daily * Use of neuroleptics within one year prior to study * Current substance use * Pregnancy (to be ruled out by urine β-HCG). * Metallic implants or devices contraindicating magnetic resonance imaging. * Currently taking medications that lower the seizure threshold. These include antipsychotics, high dose theophylline or stimulants such as methylphenidate. Patients taking bupropion must be on a stable dose (\*last 3 months) and take less than or equal to 300 mg/day. * Implanted devices in subject's head (shunts, cochlear implants); metal in subject's head (other than dental implants). * High risk of adverse emotional or behavioral reaction, and/or an inability to understand study procedures or the informed consent process * Additional exclusion criteria for Healthy controls (HC) group: Current psychiatric diagnosis ("Axis I" diagnosis)