Because the P3 (P300) event-related brain potential (ERP) indexes the information processing events associated with memory function, attempts have been made to use the P3 as a measure of the cognitive changes found in Alzheimer's disease and other dementing illnesses. However, the clinical utility of the P3 as a diagnostic tool for neurological disorders has been hampered by the variability observed for its amplitude and latency in normal subjects. Recent findings suggest that this variability stems in part from a number of biological and psychological variables (body temperature, recency of food consumption, and cognitive ability) which have not been controlled since little was known about the effects of such factors on the ERP. Because previous studies may have been confounded by these extraneous variables, the present proposal seeks to re-evaluate the utility of the P3 as a non-invasive measure of cognitive function in Alzheimer's disease. The proposed studies have been designed so that they will: (1) facilitate the development of the P3 as a clinical measure of mental function by assessing Alzheimer patients in the early stages of the disease and normal elderly controls with ERP procedures designed to tap specific cognitive functions, and (2) permit a systematic determination of how effective the P3 component can be as an index for the mental decline found Alzheimer's disease. These procedures should enhance the sensitivity of ERPs as measures of the cognitive deterioration observed in Alzheimer's disease through the use of focused paradigms and experimental control of factors now known to affect P3 measures. Thus, the results will provide a much needed data base that will guide accurately the development of ERPs as a diagnostic and prognostic tool for the assessment of Alzheimer's disease.