Transcutaneous Acupoint Electrical Stimulation Ameliorates Working Memory Impairment in Nap-deprived Interns: The Mediating Role of Augmented Brain-Heart Interaction

Background ​ Working memory (WM) decrement due to circadian dips and sleep restriction is a prevalent issue among interns, potentially impacting clinical decision-making. Non-invasive neuromodulation techniques, such as transcutaneous electrical acupoint stimulation (TEAS), offer a promising approach to mitigate cognitive fatigue. This study investigates the efficacy and underlying neurophysiological mechanism of TEAS at the Yintang (EX-HN3) acupoint in counteracting WM impairment induced by nap deprivation. Methods We enrolled 90 interns with habitual napping behavior, who were randomly assigned to one of three groups: normal control group (NC), nap deprivation group (ND), and nap deprivation group receiving TEAS intervention (ND+TEAS). Cognitive performance was assessed using a 3-back WM task at baseline (12:00) and post-intervention (15:00). Concurrently, prefrontal cerebral hemodynamics and autonomic nervous system activity were monitored via functional near-infrared spectroscopy (fNIRS) and heart rate variability (HRV), respectively. Subjective cognitive load was evaluated using the NASA-Task Load Index (NASA-TLX). Results Compared to the NC group, the ND group exhibited significant deterioration in WM accuracy and speed, accompanied by reduced prefrontal cortex (PFC) activation and attenuated parasympathetic activity (reflected by decreased HRV high-frequency power). The ND+TEAS group demonstrated a reversal of these effects, showing superior WM performance, enhanced PFC oxygenation, and increased vagally-mediated HRV indices relative to the ND group. Crucially, mediation analysis revealed that the improvement in WM performance following TEAS was mediated by its effect on augmenting PFC activation, which in turn was associated with increased parasympathetic tone. Conclusions TEAS at the Yintang acupoint effectively alleviates nap deprivation-induced WM impairment. The mechanism appears to involve the enhancement of parasympathetic nervous activity and the subsequent facilitation of prefrontal cortical function. These findings provide novel experimental evidence for the brain-heart interaction as a pathway for cognitive enhancement and position TEAS as a viable, non-invasive strategy to bolster cognitive resilience in populations susceptible to circadian fatigue, such as clinical staff.