- Visit 1 (screening visit): Study candidates will have a medical history, physical and neurological examinations, electrocardiogram (EKG), and possibly blood tests. They will also undergo neuropsychological testing (tests of memory, language, mood and, other brain functions) and fill out a quality of life questionnaire. Those enrolled will be randomly assigned to receive either donepezil (5 mg per day) or placebo-a look-alike pill with no active ingredients. After 4 weeks, the dose of donepezil will be increased to 10 mg per day. Patients who do not tolerate the higher dose will have it reduced to 5 mg. Those who do not tolerate the 5-mg dose will be taken off medication but will continue to be followed and tested.