Age-related regional network of magnetic resonance imaging gray matter in the rhesus macaque.

Human structural neuroimaging studies have supported the preferential effects of healthy aging on frontal cortex, but reductions in other brain regions have also been observed. We investigated the regional network pattern of gray matter using magnetic resonance imaging (MRI) in young adult and old rhesus macaques (RMs) to evaluate age effects throughout the brain in a nonhuman primate model of healthy aging in which the full complement of Alzheimer's disease (AD) pathology does not occur. Volumetric T1 MRI scans were spatially normalized and segmented for gray matter using statistical parametric mapping (SPM2) voxel-based morphometry. Multivariate network analysis using the scaled subprofile model identified a linear combination of two gray matter patterns that distinguished the young from old RMs. The combined pattern included reductions in bilateral dorsolateral and ventrolateral prefrontal and orbitofrontal and superior temporal sulcal regions with areas of relative preservation in vicinities of the cerebellum, globus pallidus, visual cortex, and parietal cortex in old compared with young RMs. Higher expression of this age-related gray matter pattern was associated with poorer performance in working memory. In the RM model of healthy aging, the major regionally distributed effects of advanced age on the brain involve reductions in prefrontal regions and in the vicinity of the superior temporal sulcus. The age-related differences in gray matter reflect the effects of healthy aging that cannot be attributed to AD pathology, providing support for the targeted effects of aging on the integrity of frontal lobe regions and selective temporal lobe areas and their associated cognitive functions.