Posterior Cingulate Connectivity in Individuals at Risk for Alzheimer’s Disease

This study will evaluate individuals with high- and low-risk of Alzheimer’s disease. Diffusion tensor imaging (DTI) will be used to determine differences in structural connectivity between the posterior cingulate cortex (PCC) and the mesial temporal lobe (MTL) in individuals with varying risk for AD. Also, fMRI will be used to determine differences in resting state functional connectivity between the PCC and MTL in these same individuals.
Alzheimer’s disease (AD) may have a prolonged preclinical phase characterized by asymptomatic brain changes in specific brain regions. The PCC and MTL are two brain regions that show some of the earliest signs of changes associated with AD. Our lab has been studying these regions with functional imaging during cognitive tasks and we have found differences in brain activation as a function of family history of AD and APOE status. We have replicated the phenomenon in all three studies we have undertaken: two of the studies found differences in the MTL, and one study found a difference in the PCC. It appears that the phenomenon is indeed real and now our attention is beginning to turn toward understanding mechanisms of the family history by APOE interaction. Through structural and functional connectivity analysis, progression of AD pathology may be understood in terms of the breakdown of a network of regions that subserve memory and related functions. The current investigation will examine connectivity between PCC and MTL in middle-aged individuals who have normal memory, but have family history and genetic risk factors for AD.