Brain neural networks undergo relevant changes during physiological aging, which affect cognitive and behavioral functions. Currently, non-invasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), are proposed as tools able to modulate cognitive functions in brain aging, acting on networks properties and connectivity. Segregation and integration measures are used and evaluated by means of local clustering (segregation) and path length (integration). Moreover, to assess the balancing between them, the Small World (SW) parameter is employed, evaluating functional coupling in normal brain aging and in pathological conditions including neurodegeneration. The aim of this study was to systematically investigate the tDCS-induced effects on brain network proprieties in physiological aging. In order to reach this aim, cortical activity was acquired from healthy young and elderly subjects by means of EEG recorded before, during, and after anodal, cathodal, and sham tDCS sessions. Specifically, the aim to exploring tDCS polarity-dependent changes in the age-dependent network dynamics was based on a network graph theory application on two groups divided in young and elderly subjects. Eighteen healthy young (9 females; mean age = 24.7, SD = 3.2) and fifteen elderly subjects (9 females; mean = 70.1, SD = 5.1) were enrolled. Each participant received anodal, cathodal, or sham tDCS over the left prefrontal cortex (PFC) in three separate experimental sessions performed 1 week apart. SW was computed to evaluate brain network organization. The present study demonstrates that tDCS delivered in PFC can change brain network dynamics, and tDCS-EEG coregistration data can be analyzed using graph theory to understand the induced effects of different tDCS polarities in physiological and pathological brain aging.

脑神经网络在生理衰老过程中会发生相关变化，从而影响认知和行为功能。目前，提出了非侵入性脑刺激技术，例如经颅直流电刺激 (tDCS)，作为能够调节大脑衰老过程中的认知功能、作用于网络特性和连接性的工具。通过局部聚类（隔离）和路径长度（积分）来使用和评估隔离和整合措施。此外，为了评估它们之间的平衡，使用小世界 (SW) 参数，评估正常脑老化和包括神经退行性变在内的病理条件下的功能耦合。本研究的目的是系统地研究 tDCS 诱导的生理衰老对大脑网络特性的影响。为了达到这个目标，通过在阳极、阴极和假 tDCS 会议之前、期间和之后记录的脑电图从健康的年轻和老年受试者中获得皮质活动。具体来说，探索年龄相关网络动态中 tDCS 极性相关变化的目的是基于网络图论对分为年轻和老年受试者的两组的应用。招募了 18 名健康的年轻人（9 名女性；平均年龄 = 24.7，SD = 3.2）和 15 名老年受试者（9 名女性；平均 = 70.1，SD = 5.1）。每个参与者在相隔 1 周的三个单独的实验会话中接受左侧前额叶皮层 (PFC) 的阳极、阴极或假 tDCS。计算 SW 以评估大脑网络组织。本研究表明，在 PFC 中传递的 tDCS 可以改变大脑网络动态，