Enhancing episodic memory in older adults through modulating oscillatory activities in the fronto-posterior network using transcranial alternating current stimulation (MEMTACS)

前后脑网络中的Theta振荡活动在成功实现情景记忆过程中起着至关重要的作用。与年龄相关的额叶theta能力和前后相同步的变化与老年人的认知障碍有关。在过去的几年里，第一个有希望的证据表明，在theta频率范围内的经颅交流电刺激(Tacs)应用于额叶和后部部位可能会增加区域间的theta相同步，并增强年轻人的认知过程。这为使用TAC来调节与衰老相关的振荡活动的下降提供了可能性，从而改善了老年人的认知功能。到目前为止，Tacs对年轻人认知功能和相关大脑振荡的影响已经被证明，而对老年人的研究以及关于刺激效果潜在的年龄相关变化的知识仍然缺乏。此外，Tacs诱导效应的神经机制，以及它调节老年人振荡活动和增强情景记忆功能的潜力，尚未被探索。为此，我们将表征老年人连续情节记忆过程的电生理相关性，并检查成功表现的决定因素。对功能和结构网络的额外分析以及对电流的生物物理建模将有助于阐明记忆过程与神经完整性的关系，并探索诱导电流在老年人大脑中的个体分布。随后，我们将测试Tacs对老年人记忆功能和前后角振荡的调节作用。该项目将为Tacs在健康衰老过程中对海马区依赖记忆过程的诱导作用机制提供新的见解。该项目的成果将有助于开发适合年龄的刺激方案，以成功地抵消老年人的认知衰退。

Theta oscillatory activity in the fronto-posterior network plays a crucial role in successful implementation of episodic memory processes. Aging-related changes in frontal theta power and fronto-posterior phase synchronization have been linked to cognitive deficits in older adults. Over the past few years, first promising evidence indicates that transcranial alternating current stimulation (tACS) in the theta frequency range applied to frontal and posterior sites may increase inter-regional theta-phase synchronization and augment cognitive processes in younger adults. This opens up the possibility of using tACS to modulate aging-related declines in oscillatory activity and consequently improve cognitive function in older adults. So far, tACS-induced effects on cognitive functions and associated brain oscillations have been shown for younger adults, whereas studies in older adults as well as knowledge about potential age-dependent variations in stimulation effects are still missing. Furthermore, the neural mechanisms underlying tACS-induced effects, and its potential to modulate oscillatory activity and enhance episodic memory functions in older adults, have not been explored. To this end, we will characterize electrophysiological correlates of sequential episodic memory processes in older adults and examine determinants of successful performance. Additional analyses of functional and structural networks and biophysical modeling of current flow will help to elucidate relationships of memory processes with neural integrity and explore individual distribution of induced electric currents in older brains. Subsequently, we will test tACS-induced modulation of memory functions and fronto-posterior theta oscillations in older adults. The project will provide novel insights into the mechanisms of tACS-induced effects on hippocampus-dependent memory processes in the course of healthy aging. Outcomes of the project will help to develop age-appropriate stimulation protocols to successfully counteract cognitive decline in older adults.