Beneficial Effects of Transcutaneous Auricular Vagus Nerve Stimulation on the Emotional State and Cognitive Functioning: A Pilot Study

Vagus nerve stimulation as a modern effective neuromodulation method produces therapeutic effects for treating psychiatric disorders, neuralgia, heart failure, and others. Auricular vagus nerve stimulation reduces anxiety, alleviates stress and emotional burnout, and improves cognitive function. The objectives of the current study were to evaluate the effects of transcutaneous auricular vagus nerve stimulation (taVNS) and sham stimulation (SHAM) on emotional state, and emotional burnout and reveal a causal relation between taVNS and a related cognitive function. 6 right-handed male volunteers aged 18–22 years (Mage= 18.00) participated in the taVNS study. 5 right-handed male volunteers aged 18–22 years (Mage= 18.00) participated in SHAM study. We used the combination of pleasant meditative classical music and a slow bi-polar wave (0.1-0.2 Hz) of electrical non-invasive transcutaneous auricular vagus nerve stimulation for 5 minutes. The set of 4 VNS was performed at intervals of 3 days. EEG was registered during the rest state before and after taVNS (3 min, closed eyes condition). To measure the severity of emotional burnout, we used the 22-items Maslach Burnout Inventory (MBI). To determine the development of short-term memory we used 2 computer subtests. taVNS attenuated emotional burnout (the depersonalization and reduction of personal achievements). The results of the test indicate the improving effect of the set of VNS on short-term memory. Changes in the psychoemotional state of the respondents accompanied increases in the ratio of beta /alpha rhythms, the theta-Fz/alpha-Pz ratio that reflects an enhancement of the activation level, and the amount of brain resources involved in processing the perceived information. The observed increase in the power of the alpha rhythm may relate to improving of mental processes and internally oriented attention in creative activities. A higher left frontal activity under the cognitive test points to a positive emotional attitude toward the task. The detected focus of beta, gamma, and theta activities in the vertex (Cz) reflected the effect of taVNS on learning at the level of the sensorimotor cortex. Activation of the right dorsolateral prefrontal cortex reflects the taVNS effects on the attention processes. The increase in the theta activity in the left occipital cortex indicated the involvement of the visual cortex. The obtained data suggest that the taVNS have prolonged beneficial effects on emotional state and stimulating effect on the brain processes, enhancement of the cognitive process.