Maintenance of Gray Matter Diffusion in Older Adults Relates to Better Episodic Memory

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Danielle L Greenman¹, Ilana Bennett¹; ¹University of California Riverside

The brain maintenance theory suggests that the more “young-like” a person’s brain is, the better they perform on cognitive tasks. Using diffusion-weighted magnetic resonance imaging, studies have found that older adults whose diffusivity in white matter is more similar to younger adults, indicating preservation of tissue microstructure, have better memory performance. Prior work has also supported the brain maintenance model using diffusivity in gray matter, but not using biophysical diffusion models that may better capture its less coherent underlying tissue properties. To test this, we used neurite orientation dispersion and density imaging (NODDI) to estimate diffusion in the hippocampus and dorsal and ventral striatum in 75 younger and 64 older adults who also completed the Rey Auditory Verbal Learning Task (RAVLT). For each participant, each NODDI metric in each region was subtracted from the younger adult group average, thus smaller difference scores indicated more young-like diffusion. Results revealed that, independent of age group, smaller diffusion difference scores in the hippocampus and dorsal striatum, but not the ventral striatum, related to better RAVLT total recall. This finding supports the brain maintenance theory. Moreover, whereas the negative diffusion-memory relationships were seen for all NODDI metrics in the hippocampus, they were only significant for intracellular and free diffusion in the caudate and putamen, providing clues about which tissue properties need to be preserved for better episodic memory in aging.

Topic Area: LONG-TERM MEMORY: Development & aging