Alzheimer's disease (AD) is the most common cause of dementia among the elderly, affecting 5 percent of Americans over age 65, and 20 percent over age 80. At the histological level, an excess of senile plaques and neurofibrillary tangles, ventricular enlargement, and cortical atrophy characterizes AD. Diagnostic biomarkers for Alzheimer's are important in the early diagnosis of the disease. The introduction of in vivo brain imaging has allowed progress in the investigation of Alzheimer's disease, especially in the exclusion of other causes of dementia. The primary focus of my fellowship is to investigate abnormalities in cerebral blood flow in AD patients using SPECT imaging. Secondarily, I also plan to correlate other imaging techniques in the investigation of Alzheimer's, such as MRS and MRI to study biochemical markers, and PET to study cerebral glucose metabolism. Clinical evaluation, histopathologic correlation, and brain imaging are of greater AD diagnostic value when used together, as opposed to diagnosis made by any of the three alone. Thus, this research will concentrate on SPECT imaging, used in conjunction with other imaging and spectroscopic modalities, to characterize abnormal brain patterns of patients referred with a clinical diagnosis of probable or possible Alzheimer's disease. During my fellowship, I plan to participate in seminars and meetings relevant to imaging in the neurosciences. I also plan to take courses relevant to the study of brain disease and human physiology.