Structural complexity is negatively associated with brain activity: a novel multimodal test of compensation theories of aging

Fractal dimensionality (FD) measures the complexity within folds and ridges of cortical subcortical structures. We tested degree that FD might provide a new perspective on atrophy-compensation hypothesis: age or disease-related atrophy causes compensatory neural response in form increased brain activity prefrontal cortex to maintain cognition. Brain structural functional data were collected from 63 middle-aged older adults 18 young-adult controls. Two distinct patterns found separated Subcortical was more strongly negatively correlated with than FD, associated during memory retrieval medial lateral parietal cortices uniquely adults. Multivariate analyses revealed lower FD/higher pattern poorer cognition—patterns not present young adults, consistent compensation. Bayesian further evidence against modal interpretation hypothesis cortex—a key principle some neurocognitive theories aging.