All participants completed magnetic resonance imaging (MRI) scans of the brain as well as a battery of behavioral tasks. Two years after initial enrollment and testing, all were invited back for retesting. Retention was excellent with 90% of participants returning for the follow-up assessment. Follow-up intervals were close to two years for all participants, as indicated in Table 1. This report focuses on analysis of MRI data from two assessment waves (baseline and follow-up).
