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.