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.