Does tDCS Change Synaptic Density in the Brains of Patients With Schizophrenia

This study is using a special brain scan (called an SV2A PET scan) to examine whether a brain stimulation treatment called tDCS (transcranial direct current stimulation) changes the density of connections between brain cells (synapses) in people with schizophrenia or schizoaffective disorder. It is a sub-study of a larger research program. **You may be eligible if:** - You are already enrolled in the parent tDCS-adherence study - You are 18 or older with a diagnosis of schizophrenia or schizoaffective disorder - You have been on a stable dose of antipsychotic medication for at least 2 months - You are capable of consenting to the research **You may NOT be eligible if:** - You are not enrolled in the parent study - You are unable or unwilling to consent - Your medical or psychiatric condition is unstable - You have conditions that prevent safe participation in the brain scanning procedure Talk to your doctor to see if this trial is right for you.