Multi-session transcranial alternating current stimulations facilitate working memory in older adults by synchronizing the parietal theta oscillation

Poster Session D - Monday, April 15, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Yun Zhong¹ (ceceliazy@163.com), Xiyue Chen¹, Ying Cai¹; ¹Zhejiang University

Recent studies have reported that multi-session theta transcranial alternative current stimulations (tACS) over the inferior parietal lobule (IPL) enhanced working memory (WM) in older adults. However, without direct examinations of untrained tasks and clarifications of the underlying neural plasticity mechanism, its further application remains unclear. Forty-four elders participated in the current study (50~61 years, 23 females). For 5 consecutive days, half participants received 20-minute 4-Hz tACS over the IPL during a word-learning task and others received 30-second sham stimulations. Electroencephalographs (EEG) were recorded 1-day before and after stimulations in both the resting state and during a change detection task for colors. Additional behavioral tests followed 1-month later. We found improvements in the word-learning recency effect (i.e., verbal WM) and the color WM accuracy only in the tACS group (ps < 0.001, BFs > 30), which were sustained for 1 month (ps < 0.01, BFs > 10). Meanwhile, we compared the neural changes between the two groups. In the resting state, tACS didn’t change the theta powers (4-7Hz) but increased the theta synchronizations between the stimulation site and the ipsilateral parietal sites and contralateral frontal sites (after multi-comparison corrections). Moreover, the parietal theta synchronization increases predicted both behavioral improvements in the tACS group (ps < 0.05, BFs > 1.9). Consistently, during the color WM maintenance, tACS increased event-related potentials and theta synchronizations in similar areas. Together, our study demonstrated that the multi-session tACS improved general WM ability by increasing the parietal theta synchronizations, and largely extended the future application of tACS.

Topic Area: EXECUTIVE PROCESSES: Working memory