Inclusion Criteria:  Healthy (absence of chronic medical conditions) individuals Aged 18-65. The lower limit is justified by the absence of safety studies involving DCS in pediatric studies, and the upper limit is justified by the increasing prevalence of chronic illness.  Exclusion Criteria:  Allergy to cycloserine Are currently pregnant, breast feeding or plan to become pregnant Have an alcohol or substance use disorder within the last 3 months Current psychiatric concerns are at a significant risk of harm to themselves or others Have any significant neurological disorder or insult including, but not limited to: any condition likely to be associated with increased intracranial pressure, space occupying brain lesion, any history of epilepsy, cerebral aneurysm, Parkinson's disease, Huntington's chorea, multiple sclerosis, significant head trauma with loss of consciousness for greater than or equal to 5 minutes Have concomitant major unstable medical illness, cardiac pacemaker or implanted medication pump Have an intracranial implant (e.g., aneurysm clips, shunts, stimulators, cochlear implants, or electrodes) or any other metal object within or near the head, excluding the mouth, that cannot be safely removed Conditions that may impair the ability to metabolize cycloserine including, but not limited to current Renal or Liver Disease. Inability to refrain from alcohol use for 24 hours prior to each session and following each session. Use of isoniazid or ethionamide Are currently (or in the last 4 weeks) using any benzodiazepine, cyclopyrrolone, gabapentin/pregabalin or anticonvulsant due to the potential to limit rTMS efficacy