Hippocampal mean diffusivity and memory in healthy elderly individuals

Abstract

The relationship between age-related memory decline and hippocampal anatomic changes is a matter of debate. To investigate the relationship between age-related memory decline and MRI hippocampal anatomic changes in a cohort of healthy individuals. In this cross-sectional study, 76 healthy individuals (44 male and 32 female), ranging in age from 20 to 80 years, were recruited from universities, community recreational centers, hospital personnel, and patients' relatives from 2005 to 2008. These individuals were submitted to a 3-T MRI protocol with a whole-brain T1-weighted and diffusion-weighted scanning and a neuropsychological assessment. For each subject, we calculated the volumes of the total brain (gray + white matter) and hippocampi. The segmented hippocampi defined the binary masks where mean values of mean diffusivity (MD) and fractional anisotropy (FA) were calculated. Neuropsychological evaluation included tests of verbal memory (15 minutes delayed recall of a 15-word list) and visuospatial memory (20 minutes delayed reproduction of Rey complex figure). Hippocampal MD, but not hippocampal FA, hippocampal volume, or total brain volume, predicted performance of individuals beyond their 50s on tests of verbal and visuospatial memory. High mean diffusivity values in the hippocampal formation of healthy elderly individuals predict memory decline, as reflected by performance on tests of declarative verbal and visual-spatial memory.