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

额-后叶网络中的θ波振荡活动在情景记忆过程的成功实施中起着至关重要的作用。与衰老相关的额波功率和额-后相同步的变化与老年人的认知缺陷有关。在过去的几年里，第一个有希望的证据表明，在θ波频率范围内的经颅交流电刺激（tACS）应用于额叶和后部可能会增加区域间的θ波相同步，并增强年轻人的认知过程。这开启了使用tACS来调节与衰老相关的振荡活动下降的可能性，从而改善老年人的认知功能。到目前为止，tacs诱导的对认知功能和相关大脑振荡的影响已经在年轻人中得到证实，而对老年人的研究以及对刺激效应中潜在的年龄依赖性变化的了解仍然缺失。此外，tacs诱导的神经机制及其调节振荡活动和增强老年人情景记忆功能的潜力尚未得到探讨。为此，我们将描述老年人连续情景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进一步分析以及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，并探索老年人大脑中感应电流的个体分布。随后，我们将测试tacs诱导的老年人记忆功能和额-后θ波振荡的调节。该项目将为tacs诱导的海马体依赖性记忆过程在健康衰老过程中的作用机制提供新的见解。该项目的结果将有助于制定适合年龄的刺激方案，以成功地抵消老年人的认知能力下降。

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.