Memory and MRI-based hippocampal volumes in aging and AD.

To demonstrate structural-functional relationships between MRI-based volumetric measurements of medial temporal lobe structures and cognitive function. Previous work has documented the ability of MRI-based measurements of the hippocampus to discriminate between age-matched control subjects and patients with very mild AD. Relatively less is known about the correlation between medial temporal lobe structures and cognitive functions. We evaluated structural-functional relationships among the hippocampal formation, parahippocampal gyrus, and amygdala, and measures of memory, language, and general cognitive performance in 220 probable AD patients and normal control subjects. Standardized instruments of memory and general cognitive function were used to assess subjects enrolled in a longitudinal study of aging and dementia. The volume of the hippocampal formation predicted performance on most acquisition and recall measures across the spectrum of normal aging and AD. If the groups were segregated, most of the expected associations between medial temporal lobe structures and memory measures were observed in the AD patients. MRI-based hippocampal volumetry accurately depicts the structural-functional relationships between memory loss and hippocampal damage across the spectrum from normal aging to dementia.