Department of Physiology, Semmelweis University, Budapest, Hungary.
Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Geroscience. 2024 Feb;46(1):473-489. doi: 10.1007/s11357-023-00836-z. Epub 2023 Jul 17.
Aging affects cognitive functions even in the absence of ongoing pathologies. The neurophysiological basis of age-related cognitive decline (CD), however, is not completely understood. Alterations in both functional brain connectivity and in the fractal scaling of neuronal dynamics have been linked to aging and cognitive performance. Recently, fractal connectivity (FrC) has been proposed - combining the two concepts - for capturing long-term interactions among brain regions. FrC was shown to be influenced by increased mental workload; however, no prior studies investigated how resting-state FrC relates to cognitive performance and plausible CD in healthy aging. We recruited 19 healthy elderly (HE) and 24 young control (YC) participants, who underwent resting-state electroencephalography (EEG) measurements and comprehensive cognitive evaluation using 7 tests of the Cambridge Neurophysiological Test Automated Battery. FrC networks were reconstructed from EEG data using the recently introduced multiple-resampling cross-spectral analysis (MRCSA). Elderly individuals could be characterized with increased response latency and reduced performance in 4-4 tasks, respectively, with both reaction time and accuracy being affected in two tasks. Auto- and cross-spectral exponents - characterizing regional fractal dynamics and FrC, respectively, - were found reduced in HE when compared to YC over most of the cortex. Additionally, fractal scaling of frontoparietal connections expressed an inverse relationship with task performance in visual memory and sustained attention domains in elderly, but not in young individuals. Our results confirm that the fractal nature of brain connectivity - as captured by MRCSA - is affected in healthy aging. Furthermore, FrC appears as a sensitive neurophysiological marker of age-related CD.
衰老会影响认知功能，即使没有持续的病理变化。然而，与年龄相关的认知能力下降（CD）的神经生理学基础尚未完全理解。功能性大脑连接和神经元动力学分形标度的改变都与衰老和认知表现有关。最近，分形连接（FrC）已经被提出-结合了这两个概念-用于捕捉大脑区域之间的长期相互作用。已经表明 FrC 受到增加的心理工作量的影响；然而，以前没有研究调查静息状态 FrC 与健康衰老中的认知表现和可能的 CD 之间的关系。我们招募了 19 名健康老年人（HE）和 24 名年轻对照组（YC）参与者，他们接受了静息状态脑电图（EEG）测量和使用剑桥神经生理测试自动化电池的 7 项测试的综合认知评估。FrC 网络是使用最近引入的多重采样互谱分析（MRCSA）从 EEG 数据中重建的。老年人在 4-4 项任务中分别表现出反应时间延长和表现下降，其中两项任务的反应时间和准确性都受到影响。与 YC 相比，HE 大脑皮层大部分区域的自谱和互谱指数-分别描述区域分形动力学和 FrC-均降低。此外，额叶顶叶连接的分形标度与老年人视觉记忆和持续注意力领域的任务表现呈负相关，但在年轻人中则没有。我们的结果证实，大脑连接的分形性质-如 MRCSA 所捕获的-在健康衰老中受到影响。此外，FrC 似乎是与年龄相关的 CD 的敏感神经生理学标志物。
