The impact of transcutaneous vagus nerve stimulation on anterior cingulate cortex activity in a cognitive control task.

Transcutaneous vagus nerve stimulation (tVNS) offers a non-invasive method to enhance noradrenergic neurotransmission in the human brain, thereby increasing cognitive control. Here, we investigate if changes in cognitive control induced by tVNS are mediated through locus coeruleus-induced modifications of neural activity in the anterior cingulate cortex. Young healthy participants engaged in a simple cognitive control task focusing on response inhibition and a more complex task that involved both response inhibition and working memory, inside a magnetic resonance imaging scanner. The tasks were executed using a randomized within-subject design, with participants undergoing auricular tVNS and sham stimulation in separate sessions. tVNS significantly changed performance in the simple control task reflected in a greater propensity to respond. Furthermore, we observed a significant increase in neural activity in the anterior cingulate cortex during the simple cognitive control task under tVNS. Functional connectivity analyses revealed positive coupling between neural activity in the locus coeruleus and anterior cingulate cortex, however, this was not modulated by tVNS. The findings suggest that non-invasive stimulation of the vagus nerve can modulate neural activity in the anterior cingulate cortex. While these neural effects suggest an impact of tVNS in a key region involved in conflict monitoring and cognitive control, the behavioral effects are more indicative of a shift in response bias rather than enhanced cognitive control.