Brain Imaging in Alzheimer's Disease

The purpose of this study is to use brain imaging technology to examine the role of certain brain chemicals in individuals with Alzheimer's disease (AD) and in healthy volunteers.

Cognitive dysfunction in people with AD is thought to arise from decreased chemical activity in specific parts of the brain. Decreases in alpha4beta2 nicotinic acetycholine receptors (nAChRs) have been found in the brains of people who died with AD; however, the status of this receptor system in living brains remains unclear. This study will use single photon emission computed tomography (SPECT) to study this receptor system in people with AD who have mild to moderate dementia and in healthy volunteers. In addition, this study will examine the relationship between cognitive dysfunction and nAChR deficits in the brains of individuals with AD.

Participants with AD will have four clinic visits; healthy volunteers will have three visits. At Visit 1, participants will undergo a medical history, physical examination, and laboratory tests. Healthy volunteers will have a Mini-Mental State Examination (MMSE) cognitive function test. Participants with AD will have a MMSE and measurement of the severity of their dementia.

During Visit 2, participants will undergo a magnetic resonance imaging (MRI) scan of the brain.

At Visit 3, participants will undergo SPECT imaging.

Only participants with AD will participate in Visit 4. During this visit, cognitive testing will be performed.