Working memory enhancement using real-time phase-tuned transcranial alternating current stimulation.

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Transcranial alternating current stimulation (tACS) can modulate working memory (WM) by targeting alpha oscillations.
• Previous methods lacked real-time phase tracking due to stimulation artifacts.
• Real-time adaptation of tACS phase lag to endogenous oscillations is crucial for effective modulation.

Purpose of the Study:

• To develop a closed-loop system for real-time phase-tuned tACS targeting parietooccipital alpha oscillations.
• To investigate the hypothesis that real-time phase-tuned tACS enhances working memory performance.
• To determine the optimal phase lag for enhancing working memory.

Main Methods:

• Developed real-time phase-tuned closed-loop amplitude-modulated tACS (CLAM-tACS).
• Applied CLAM-tACS at six phase lags to participants performing a working memory task (N=21).
• Used a control group (N=25) receiving frontal stimulation to rule out sensory confounds.

Main Results:

• Working memory accuracy improved significantly with parietooccipital CLAM-tACS in a phase-lag-dependent manner (p=0.0350).
• The strongest enhancement was observed at a 330° phase lag (p=0.00273, d=0.976).
• Modulation of frontoparietal alpha oscillations correlated with WM accuracy changes; no effects were seen in the control group.

Conclusions:

• Demonstrated the feasibility and efficacy of real-time phase-tuned CLAM-tACS.
• Confirmed that CLAM-tACS can modulate brain activity and behavior.
• Opened avenues for investigating brain-behavior relationships and therapeutic applications.