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

## TL;DR

This study shows that amplitude-modulated transcranial alternating current stimulation can improve working memory in college students, with potential for real-time brain monitoring systems.

## Contribution

The study introduces individualized AM-tACS based on real-time EEG feedback to enhance working memory.

## Key findings

- AM-tACS significantly improved working memory sensitivity index (d') compared to sham.
- tACS at 40 Hz improved working memory accuracy compared to sham.
- EEG analysis showed a trend toward increased frontal-occipital connectivity but no change in phase-locking value.

## Abstract

Recent studies suggest that amplitude-modulated transcranial alternating current stimulation (AM-tACS) may enhance cognitive functions, but its mechanisms and optimal application remain unclear.

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’).

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.

Amplitude-modulated transcranial alternating current stimulation 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.