No history or clinical diagnosis of stroke within 1 year before or concurrent with onset of dementia; hydrocephalus, subdural hematoma, or mass lesion on screening MRI; current seizure disorder; head trauma with loss of consciousness and hospitalization within 1 year before or concurrent with onset of dementia; dementia onset within 1 year following cardiac arrest or surgery; Parkinson's disease (onset prior to or concurrent with dementia), Wilson's, Huntington's, Creutzfeldt-Jakob disease, Pick's disease, or Wernicke's encephalopathy; chronic CNS infection (positive RPR and/or FTA-ABS acceptable if luetic brain disease excluded by documented studies and/or treatment).