 We aim to compare measures of memory and information processing speed at 2.5 hours and 5 hours after the administration of a 2 mg dose of lorazepam or placebo in cognitively normal, 50-65 year old APOE e4 carriers and noncarriers, and determine the differential impact of lorazepam on cognition at each time point. Twenty carriers and 20 noncarriers matched for age, sex, and education will be drawn from a database of persons who have already undergone genotyping for an ongoing study at the Mayo Clinic, excluding people with evidence of depression or cognitive impairment and other medical, neurological or psychiatric conditions. Using a double blind, crossover design, subjects will receive either placebo or a 2 mg dose of lorazepam after baseline testing. Equivalent tests will be repeated 2.5 and 5 hours post challenge. The data analysis will compare APOE e4 carriers to noncarriers. 