 7. Participant is off all psychotropic and other types of drugs likely to interact with glutamate for at least 14 days before starting the study. The exceptions are SRI medications and short acting benzodiazepines for distressing anxiety or insomnia which can be taken up to 24 hours prior to ketamine infusion. Participants will be off neuroleptics for 1 month and off fluoxetine for 6 weeks prior to the study. 