AGE-RELATED REGIONAL NETWORK PATTERN OF MRI GRAY MATTER IN THE RHESUS MACAQUE

G.E. Alexander ^1,6 , K. Chen ^2,6, L.E. Santerre-Lemmon ^1,6, M. Aschenbrenner ^1,6, P.R. Rapp ³, M.H. Buonocore ⁴, C.A. Barnes ^5,6

1. Psychol, Arizona State Univ, Tempe , AZ , USA
2. Banner, Phoenix , AZ , USA
3. Neurobiol, Mt Sinai, New York , NY , USA
4. Radiol, Univ Cal , Sacramento , CA , USA
5. NSMA , Univ Arizona , Tucson , AZ , USA
6. AZ ADC, Phoenix , AZ , USA

Human studies of cognition have suggested that the frontal cortex may be preferentially affected in healthy aging. Such studies, however, cannot exclude brain changes related to underlying Alzheimer’s disease (AD) pathology. We investigated regional patterns of gray matter using MRI in 7 young (age=10±2 yrs; 2F/5M) and 12 old (age=24±3 yrs; 4F/8M) healthy rhesus macaques (RM) on a voxel basis to evaluate the effects of aging in a non-human primate model in which the pathology of AD does not occur. We hypothesized that older age in the RM would be associated with reductions in gray matter in frontal brain regions thought to decline in healthy aging in humans. Volumetric T1 MRI scans were acquired on a 1.5T scanner. For each scan, the brain was manually segmented from non-brain tissue and SPM2 voxel-based morphometry was used to spatially normalize and segment gray matter with a customized template for the RM. Multivariate network analysis using the scaled subprofile model (SSM) identified a linear combination of 3 gray matter patterns that distinguished the young from old RM (R 2=0.69, p≤0.001). The combined pattern included reductions mainly in bilateral medial and lateral frontal cortices with areas of relative preservation in basal ganglia, cerebellum, and a primary motor region in the old compared to young RM. Follow up univariate analyses showed similar age group reductions in frontal cortex. The results suggest that advanced aging in RM is associated with a regionally distributed pattern of gray matter that includes reductions in frontal cortex. The age-related differences in gray matter reflect the effects of healthy aging that cannot be attributed to AD pathology, providing support for the effects of aging on frontal lobe integrity and its associated cognitive functions.

Support Contributed By: AG003376, AG019610 & AARC DHS 211002

Key words: aging, neuroimaging, frontal cortex, monkey