Rhythm of the body, rhythm of the brain: exploring the relationship between interoception and time perception through auricular vagus nerve stimulation (taVNS)

Integration of visceral-interoceptive signals seems to underlie our physiological experience of time. To further investigate this relationship, we used the non-invasive stimulation of the auricular branch of the vagus nerve (taVNS), which, as has been highlighted, has a modulatory effect on several high-level cognitive processes. The vagal system is crucial in regulating the organism's homeostasis and it has broad connections with various cortical and subcortical regions. In our study, healthy subjects were engaged in explicit and implicit temporal tasks across two separate experimental sessions involving taVNS (active stimulation and sham conditions). Particularly in the prediction temporal task, a white circle was shown on a gray background, with a superimposed circular band acting as an occluder. In each trial, a ball moved from the center of the display toward the periphery in a fixed direction and at a constant speed, undergoing a change of velocity under the occluder. Thus, participants were asked whether the ball re-emerged earlier or later than expected. Meanwhile, interoception was measured using a heartbeat counting task (HCT). Preliminary results obtained through a Wilcoxon-Mann-Whitney test show an improved performance during the active stimulation condition, particularly for predictive temporal tasks. Meanwhile, we found that the positive correlation between timing abilities and interoception disappears in the active stimulation condition. TaVNS may enhance brain activity in areas crucial particularly for implicit timing (e.g. upper temporal cortex, low parietal cortex). At the same time, it seems to interfere with the interoceptive sphere mitigating its link with time experience.