The effects of amplitude modulated transcranial alternating current stimulation on working memory of college students

HENG WANG¹Yan Chen¹Ziyu Zhou²Rui Jiang¹Haowei Hu¹Yan Zhao^3,4K Dimyati⁵Shen Tong¹Ji Wang⁶Xiao Zhang^1,7*

• ¹Xuzhou Medical University, Xuzhou, China
• ²Chengdu Second People's Hospital, Chengdu, China
• ³Xuzhou Jiazhi Technology Co., Xuzhou, China
• ⁴Yantai Longchi Technologies Co., Yantai, China
• ⁵Universiti Malaya, Federal Territory of Kuala Lumpur, Malaysia
• ⁶Xuzhou Children's Hospital, Xuzhou, China
• ⁷Harbin Institute of Technology, Harbin, China

Background: Recent studies suggest that amplitude-modulated transcranial alternating current stimulation (AM-tACS) may enhance cognitive functions, but its mechanisms and optimal application remain unclear. Methods: Thirty-three healthy university students were randomly assigned to Sham, tACS (40 Hz, 1 mA, bilateral prefrontal cortex), or AM-tACS (200 Hz carrier frequency) groups, in AM-tACS, the baseband modulation frequency was individualized based on the pre-task phase-locking value (PLV) derived from occipitofrontal EEG. Working memory (WM) was assessed via a delayed-match-to-sample task (accuracy and sensitivity index d'). Results: Compared to Sham, the tACS group showed significant WM accuracy improvement (p<0.05). AM-tACS exhibited a smaller but statistically significant enhancement in d' (p<0.05). EEG analysis revealed no PLV increase between stimulated regions, but a trend toward heightened frontal-occipital functional connectivity. Conclusion: AM-tACS effectively enhances WM in college students, though physiological mechanisms require further investigation with multimodal approaches. The compatibility of AM-tACS with real-time EEG monitoring highlights its potential for closed-loop neuromodulation systems, where stimulation parameters could be dynamically adjusted based on neural feedback.