Transcutaneous Auricular Vagus Nerve Stimulation Selectively Improves Executive Control and Cognitive Flexibility Following Sustained High Cognitive Load: A Randomized, Single-Blind, Sham-Controlled Study

OBJECTIVES: Acute exposure to sustained high cognitive load rapidly depletes executive functions, yet rapid, field-compatible countermeasures remain scarce. This study examined whether transcutaneous auricular vagus nerve stimulation (taVNS) improves cognitive functions across multiple domains-including the attention networks, cognitive flexibility, and working memory-following sustained high cognitive load. METHODS: Healthy young men completed a 1 h dual task combining spatial 1-back and color-word Stroop judgments (the BS task) to induce a high-cognitive-load state; 65 participants were randomized to receive 30 min of active taVNS (left cymba conchae; 25 Hz; 500-μs pulse width; 30 s on/30 s off) or sham stimulation under a single-blind design, and 62 provided complete data and were analyzed. Cognitive performance was assessed with the Attention Network Test, Cued Switching Task, and spatial 2-back task immediately after the intervention and after 1, 2, 4, and 8 h; baseline-corrected change scores were analyzed with linear mixed-effects models. RESULTS: The induction task reliably increased subjective workload and degraded task accuracy. Immediately after the intervention, taVNS significantly reduced the conflict effect relative to sham (b = -16.43 ms, 95% CI [-32.03, -0.82], F(1, 127.5) = 4.34, p = 0.039, d = 0.64) and the switch cost (b = -59.79 ms, 95% CI [-109.66, -9.92], F(1, 81.8) = 5.69, p = 0.019, d = 0.53); both immediate effects remained significant after Holm correction. Group × time interactions were nonsignificant, and the temporal course of the between-group differences should therefore be interpreted cautiously. No significant effects were observed for alerting, orienting, or working memory. CONCLUSIONS: These findings indicate that taVNS selectively and immediately improves executive control and cognitive flexibility following sustained high cognitive load, supporting its potential as a portable, rapid-acting cognitive countermeasure for high-demand operational settings.