Resting hippocampal blood flow, spatial memory and aging.

Aging is accompanied by a general deterioration of fluid cognitive processes and a reduction in resting cerebral blood flow (CBF). While the two phenomena have been observed independently, it is uncertain whether individual differences in cerebral blood flow are reliably associated with cognitive functioning in older adults. Furthermore, previous studies have concentrated primarily on gross measures of cognition and global gray matter CBF, leaving open the possibility that perfusion of specific brain regions may relate differentially to distinct cognitive domains. The present study sought to provide a more focused treatment of CBF and cognitive function in the context of aging by investigating the relationships among aging, spatial memory and resting hippocampal blood flow, both between and within younger and older adult groups. Blood flow was quantified using a novel Flow-Enhanced Signal Intensity (FENSI) technique which provides a localized, functionally relevant measure of volumetric flow across a given unit area. As expected, we found that aging was associated with poorer spatial memory and reduced resting CBF. Moreover, hippocampal blood flow was positively correlated with spatial memory performance in the older adult group, suggesting that increased blood flow to the hippocampus is associated with superior memory performance in older adults. These results demonstrate a region-specific CBF-cognition relationship and thereby offer new insight into the complex connection between the aging brain and behavior.