McDonough Ian M, Madan Christopher R
Department of Psychology, The University of Alabama, Tuscaloosa, AL, USA.
School of Psychology, University of Nottingham, Nottingham, UK.
Neurobiol Aging. 2021 Feb;98:185-196. doi: 10.1016/j.neurobiolaging.2020.10.023. Epub 2020 Nov 14.
Fractal dimensionality (FD) measures the complexity within the folds and ridges of cortical and subcortical structures. We tested the degree that FD might provide a new perspective on the atrophy-compensation hypothesis: age or disease-related atrophy causes a compensatory neural response in the form of increased brain activity in the prefrontal cortex to maintain cognition. Brain structural and functional data were collected from 63 middle-aged and older adults and 18 young-adult controls. Two distinct patterns of FD were found that separated cortical from subcortical structures. Subcortical FD was more strongly negatively correlated with age than cortical FD, and cortical FD was negatively associated with brain activity during memory retrieval in medial and lateral parietal cortices uniquely in middle-aged and older adults. Multivariate analyses revealed that the lower FD/higher brain activity pattern was associated with poorer cognition-patterns not present in young adults, consistent with compensation. Bayesian analyses provide further evidence against the modal interpretation of the atrophy-compensation hypothesis in the prefrontal cortex-a key principle found in some neurocognitive theories of aging.
分形维数（FD）衡量皮质和皮质下结构褶皱和脑回内的复杂性。我们测试了FD在多大程度上可能为萎缩 - 补偿假说提供新的视角：与年龄或疾病相关的萎缩会引发一种补偿性神经反应，表现为前额叶皮质脑活动增加，以维持认知功能。我们收集了63名中老年成年人和18名年轻成年人对照组的脑结构和功能数据。发现了两种不同的FD模式，将皮质结构与皮质下结构区分开来。与皮质FD相比，皮质下FD与年龄的负相关性更强，并且仅在中老年成年人中，皮质FD与内侧和外侧顶叶皮质记忆检索期间的脑活动呈负相关。多变量分析显示，较低的FD/较高的脑活动模式与较差的认知相关——这种模式在年轻人中不存在，这与补偿作用相符。贝叶斯分析进一步证明了前额叶皮质中萎缩 - 补偿假说的模态解释不成立——这是一些衰老神经认知理论中的一个关键原则。
