Overview

The purpose of this study is to use a non-invasive brain stimulation technique, transcranial direct current stimulation (tDCS), to test a set of hypotheses about the role of the prefrontal cortex in behavioral and neural correlates of cognition in schizophrenia. Behavioral, electrophysiological (EEG) and neuroimaging measures will be used to assess cognitive performance. This study has three main goals: (1) To compare the effects of task-engaged versus resting tDCS in order to optimize the impact of tDCS on goal maintenance related neural oscillatory activity and task performance in schizophrenia; (2) To establish the regional specificity of the impact of DLPFC tDCS (compared to Occipital tDCS) effects on brain circuitry underlying goal maintenance in schizophrenia; (3) To examine relationships between tDCS effects on DLPFC GABA levels, DLPFC-related oscillatory activity and cognitive performance in schizophrenia. This study is solely intended as basic research in order to understand brain function in healthy individuals and individuals with schizophrenia. This study is not intended to diagnose, cure or treat schizophrenia or any other disease.

Eligibility

Inclusion Criteria:

• Participants must be able to sufficiently speak and understand English so as to be able to understand and complete cognitive tasks.
• All subjects must have the ability to give valid informed consent.

Inclusion Criteria for Patients with Schizophrenia Only:

• Diagnosis of schizophrenia, schizophreniform or schizoaffective disorder
• No medication changes in the prior month
• No medication changes anticipated in the upcoming month
• Stable outpatient or partial hospital status
• Normal IQ (>70; IQ will be measured by administering the Wechsler Abbreviated Scale of
• Intelligence (WASI) test)
• Must not be currently taking the antipsychotic clozapine

Exclusion Criteria:

• Pacemakers
• Implanted electrical (brain and spinal) stimulators
• Implanted defibrillator
• Metallic implants
• Skin damage or skin conditions such as eczema at the sites where electrodes will be placed
• Hair styles hindering the placement of electrodes
• Cranial pathologies
• Head trauma
• Epilepsy
• Mental retardation
• Any known history of neurological disorders (including epilepsy, amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), stroke, cerebral palsy, any DSM-5 axis I psychiatric disorder (for healthy control subjects), autism)
• Uncorrected vision problems that would hinder cognitive testing (this also pertains to subjects with color blindness in tasks where discriminating colored objects/items is necessary for successful performance)
• Pregnancy
• Substance dependence in the past six months
• Substance abuse in the past month