Jul 2026· American Journal of Primatology· Vol 88· 0 citations· 72 references
Medicine
TL;DR
It is found that variation in primate social systems and/or reproductive aging may influence sex and species differences in brain aging, and within the baboons but not the chimpanzees, significant sex differences were found in age‐related differences in cortical folding.
Abstract
In light of the evidence that nonhuman primates naturally develop Alzheimer's disease neuropathologies, there is a renewed interest in research on the comparative biology of aging, including neurological changes across the age groups in species with diverse lifespans. In this paper, we examined age‐related differences in two measures of cortical folding, mean depth and fold opening, in a sample of chimpanzees (Pan troglodytes) and olive baboons (Papio anubis). We found significant species differences in the slope and pattern of age‐related changes in cortical folding. As predicted, chimpanzees showed negative linear associations between age and mean depth and positive linear associations between age and fold opening, as we see in humans. However, contrary to our hypotheses, baboons showed positive quadratic associations between age and mean depth and negative quadratic associations between age and fold opening. Additionally, within the baboons but not the chimpanzees, significant sex differences were found in age‐related differences in cortical folding. Here, male baboons showed significant linear associations between age, sulci depth, and fold opening, much like male and female chimpanzees. However, for female baboons, slopes of age‐related differences in fold opening were flat or showed slight quadratic associations. It is possible that variation in primate social systems and/or reproductive aging may influence sex and species differences in brain aging. Longitudinal studies on primate brain aging, as well as comparative research with additional taxa, could shed light on the causes and implications of these differences.
BACKGROUND
Global population aging highlights the need to explore age-related limbic system alterations, which are closely linked to emotion, memory, and cognition. Heterogeneous volume changes of limbic subregions and their memory-related impacts in healthy aging remain poorly understood.
METHODS
A total of 315 cognitively normal adults aged 20-89 years were divided into four age cohorts. T1-weighted MRI was applied to quantify volumes of core limbic subregions. Memory and general cognition were evaluated via the Mini-Mental State Examination (MMSE) and Hopkins Verbal Learning (HOP), covering immediate recall, delayed recall, and delayed recognition. Associations between regional brain volumes and memory performance were analyzed.
RESULTS
Most regions of the limbic system exhibited a trend of volume reduction across all four age groups. The right anterior basal forebrain atrophied starting from young adulthood, while the fornix, left basal forebrain, and bilateral hypothalamus shrank significantly in late middle-aged and older adults, respectively. Uniquely, the volume of the left septal nucleus exhibits an abnormal increase. MMSE scores declined gradually, with accelerated loss after 65 years. Older adults exhibited lower immediate and delayed recall scores, positively correlated with the volumes of the nucleus accumbens, hypothalamus, fornix, and basal forebrain. No correlation existed between left septal nucleus volume and memory.
CONCLUSION
Healthy aging causes heterogeneous limbic structural changes, which are essential for sustaining immediate and delayed memory. This advances understanding of the neural mechanisms underlying normal cognitive aging.
Abstract The baboon (Papio) is an invaluable resource within nonhuman primate research, having the advantage of being a cercopithecoid (Old World monkey) with one of the largest brains among non-hominid primates. In order to facilitate comparative developmental neuroscience research, we present the BABACOOL (BAby Brain Atlas COnstruction for Optimized Labeled segmentation) approach for creating multi-modal developmental atlases, which we used to produce BaBa21, a population-based longitudinal developmental baboon template. BaBa21 is a spatio-temporal template that consists of structural (T1- and T2-weighted) images and tissue probability maps from a population of 21 baboons (Papio anubis) scanned at 4 timepoints beginning from about 2 weeks after birth and continuing to sexual maturity (5 years). Further, this study offers a fully automatic method for generating a template at any intermediate age for future age-specific group studies. This resource is made available to provide a normalization target for baboon data across the lifespan, including intermediate timepoints, and moreover facilitate neuroimaging research in baboons, comparative research with humans and nonhuman primate species for which developmental templates are available (e.g., macaques).
Katherine L. Bryant, A. Le Troter, D. Meunier et al.· Imaging neuroscience· 0 citations
INTRODUCTION: Brain age gap (BAG) is the difference between a person's chronological age and the age predicted from the structural appearance of their brain on MRI. A higher BAG indicates an older-appearing brain and provides a global marker of structural brain aging across the Alzheimer's disease continuum. Prior studies suggest that females may show greater Alzheimer's disease-related pathology or faster late-stage neurodegeneration than males. We tested whether sex was associated with baseline BAG or longitudinal BAG change after accounting for APOE {epsilon}4 genetic risk, amyloid positivity, cognitive severity, and disease stage. METHODS: We developed a domain-adaptive deep learning model to estimate BAG from T1-weighted MRIs, training it on 26,512 neurologically healthy UK Biobank data and fine-tuning it on 2,974 amyloid-negative cognitively normal samples from Mayo Clinic Study of Aging and OASIS-3 cohorts. We applied the model to ADNI and used hierarchical mixed-effects models to test whether sex was associated with BAG trajectories after adjusting for Alzheimer's disease risk factors. RESULTS: After adjustment for Alzheimer's disease risk factors, there was no baseline sex differences in BAG. Longitudinally, females showed greater BAG acceleration than males, but this effect was moderated by APOE {epsilon}4 status. APOE {epsilon}4 accelerated brain aging in a dose-dependent manner, independent of amyloid burden. DISCUSSION: Sex differences in BAG across the AD continuum were largely explained by APOE {epsilon}4-related acceleration rather than by an independent effect of sex alone. These findings suggest that females may be more vulnerable to APOE {epsilon}4-associated structural brain aging over time.
R. Rajabli, M. Soltaninejad, S. Villeneuve et al.· medRxiv· 0 citations