Atrophy of posteromedial sulci in aging and Alzheimer’s disease differs by sulcal type and location

Abstract

AbstractBackgroundRecent work has shown that the morphology of tertiary sulci — small, evolutionarily‐newer sulci that emerge last in gestation — is associated with individual differences in cognitive development and symptoms of neuropsychiatric disorders, but these sulci have not been investigated in aging. Here we extend these findings on tertiary sulci to the aging brain.MethodWe manually defined sulci on cortical surface reconstructions of T1 MRI scans in FreeSurfer and extracted the cortical thickness and mean anterior coordinate of each sulcus. We defined sulci in posteromedial cortex (PMC) in 72 younger adults (YA; age 18‐35) from the Human Connectome Project, 72 cognitively normal older adults (OA; age 65‐90) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), and 72 age‐matched amyloid positive older adults with AD from ADNI: 4,341 sulci total. We used a mixed‐effects ANOVA to examine the effects of group (YA, OA, AD) as a between‐subject variable, and sulcal type (tertiary or non‐tertiary) and hemisphere (left/right) as within‐subject variables on sulcal cortical thickness. We used LASSO regression with nested cross‐validation for feature selection to determine which sulcal measures are most related to ADNI Memory Composite (MEM) scores, and LOOCV linear regression to predict MEM scores from the best model. Because not all sulci are found in all participants, only the most consistent were included in the LASSO models.ResultIn PMC, tertiary sulci show more age‐ and AD‐related thinning compared to non‐tertiary (group x sulcal type interaction p<.0001; Fig. 1). Additionally, atrophy in PMC shows a more anterior bias in aging that is absent in AD (Fig. 2). The best model for predicting ADNI‐MEM scores relies on a subset of mostly posterior sulci, suggesting a posterior shift in atrophy may be more related to cognitive decline (Fig. 3).ConclusionThis is the first study to investigate tertiary sulci in aging and AD. Results show tertiary sulci in PMC are especially vulnerable to atrophy in aging and that a subset of PMC sulci are particularly associated with memory. The results provide insight into the anatomical specificity of age‐ and AD‐related atrophy in PMC and its association with cognitive decline.