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.

中文翻译：

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结构复杂性与大脑活动呈负相关：衰老补偿理论的新多模态测试

分形维数 (FD) 测量皮层和皮层下结构的褶皱和脊内的复杂性。我们测试了 FD 可能为萎缩补偿假说提供新视角的程度：年龄或与疾病相关的萎缩导致前额叶皮层大脑活动增加以维持认知的形式的补偿性神经反应。从 63 名中老年人和 18 名青年对照中收集了大脑结构和功能数据。发现两种不同的 FD 模式将皮质与皮质下结构分开。与皮质 FD 相比，皮质下 FD 与年龄的负相关性更强，并且皮质 FD 与中年和老年人独特的内侧和外侧顶叶皮质记忆提取过程中的大脑活动呈负相关。多变量分析显示，较低的 FD/较高的大脑活动模式与年轻人不存在的较差的认知模式相关，这与补偿一致。贝叶斯分析为前额叶皮层中的萎缩补偿假说的模态解释提供了进一步的证据，这是在一些衰老的神经认知理论中发现的一个关键原则。