From the initial pool of families, a subset of families with at least two affected first degree adult relatives in addition to the proband was selected for intensive study. In these families, data collection was expanded to individuals in other branches of the family. For all available consenting members of these extended, densely affected pedigrees, the core protocol was supplemented with neurophysiological (EEG/ERP) and neuropsychological evaluations and blood was collected for DNA and cell lines (see 4. Genetics and 3. Brain function) (in Table 1, specific components of the brain function protocol in the initial data collection are displayed; additional details about these tests may be found in 3. Brain function.) This approach thus identified densely affected families that were suitable for the planned genetic linkage and association studies (see 4. Genetics). Probands and their relatives constituted “case” families. In addition to the case families, a set of families, called “comparison” families, were recruited from a variety of community sources (e.g., dental clinic admissions and state drivers' registries) and assessed with the identical expanded protocol. Extensions to other family branches
