Scientists scan young brains to map how connections are pruned

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Males or females between 18-26 years of age, AND currently enrolled in the Parent Project (R01MH067924) Exclusion Criteria: (these exclusion criteria are outlined in the Parent Project) * Head injury with loss of consciousness over an hour. * A vision problem or eye movement problem (such as lazy eye, double vision, blurred vision, or color blindness). * A learning disability and/or ever had an Individualized Education Plan (IEP) in school. * Significant neurological or metabolic illness: Epilepsy, Meningitis, Encephalitis, Diabetes, Huntington's disease. * Diagnosed with a psychiatric disorder. * Participants with, or with a first degree relative, having a DSM IV Axis l psychiatricdisorder. * Metal implants or ferromagnetic objects contained within the body which may interfere with the MRI scan (but not limited to, those with a pacemaker, presence of metallic fragments near the eyes or spinal cord, or cochlear implant.) Dental fillings do not present a risk for MRI. If there is a possibility of metal being present in the participant's body, the participant will be excluded from the study. * Weight more than 250 pounds. * Claustrophobia or uncomfortable in small spaces. * \<70% on the Achenbach scale (either from Youth Self Report (YSR) or Adult Self Report (ASR)). * IQ \< 80 or IQ \> 130. * Pregnancy or lactation, lack of effective birth control during 15 days before the scans. * Currently employed as radiation worker; or participation in radioactive drug research protocols within the previous year such that the total cumulative annual radiation dose (i.e., from participation in the previous radioactive drug study \[studies\] and this study) would exceed the radiation dose limits specified in the FDA regulations (i.e., 21 CFR 361.1) that govern the research use of \[C-11\]UCB-J * History of drug or alcohol abuse (from parent study eligibility).