Interoceptive attention (IAt), the process of selectively focusing on internal bodily signals, plays a critical role in mental health and can be influenced by bottom-up interventions. One such intervention is transcutaneous auricular vagus nerve stimulation (taVNS), a non-invasive neuromodulation technique that activates vagal afferent pathways through electrical stimulation of the external ear. Heartbeat-evoked potentials (HEPs) provide a neurophysiological measure of how cardiac afferent signals are represented in the cortex and serve as an index of IAt. While several brain regions involved in interoception, such as the anterior cingulate cortex, insula, and prefrontal cortex, may be activated by taVNS, direct evidence linking taVNS to HEPs is limited. In this study, 41 healthy participants completed two laboratory sessions, separated by one week, during which they received active taVNS at the cymba conchae and sham stimulation at the earlobe. In each session, participants were exposed to different combinations of stimulation frequency and pulse width. Continuous ECG and EEG recordings were taken, and heart rate (HR) and HEPs were assessed during baseline, stimulation, and recovery periods. Active taVNS significantly enhanced HEP amplitudes, regardless of stimulation parameters, indicating a stronger cortical representation of cardiac afferent signals during taVNS stimulation. These findings suggest that taVNS might be a promising neurostimulation approach to treat disorders characterized by impaired IAt and improve mental health.

The vagus nerve is a critical body–brain communication channel, with ascending signals innervating neuromodulatory nuclei that regulate brain-wide processing and sympathetic arousal. Using a multimodal and multi MRI contrast acquisition, we tested whether transcutaneous vagus nerve stimulation can be used as a tool to experimentally modulate neuromodulatory activity.

Participants (n=64; 25.7±5.9y; 31M/33F) completed two stimulation sessions with concurrent fMRI, pupillometry, respiration, and heart rate measurements. On each trial, participants received a brief (1 s) electrical stimulation to either the ear’s cymba conchae (active site with ascending vagal projections) or the earlobe (control), on separate days in counterbalanced order. Stimulation intensity was calibrated per site, with three amplitude levels (40%, 60%, 80% of individual maximum) administered in a parametric design. Additional quantitative structural MRI enabled delineation of neuromodulatory nuclei based on their tissue properties.

Stimulation rapidly dilated participants’ pupils, an established marker of neuromodulatory activation, with pupil size scaling with stimulation amplitude on a trial-by-trial basis. Differences between active and control stimulation in pupil-indexed neuromodulation were modulated by stimulation order and site-specific calibration, highlighting important contextual factors. Integrating pupil and fMRI data, we found that stimulation-related increases in pupil size were coupled to robust activation of brainstem–midbrain neuromodulatory centers. Quantitative MRI enabled reliable visualization of neuromodulatory nuclei of interest, including the noradrenergic locus coeruleus and dopaminergic substantia nigra, providing an anatomical framework for ongoing structure–function analyses.

This work provides foundational evidence for how vagal signaling modulates neuromodulatory activity and physiological responses, and informs its potential for experimental and clinical applications.

Interoception is crucially involved in mental and physical health. Two major facets of cardiac interoception, interoceptive accuracy (IAc) and interoceptive attention (IAt), show a specific alteration in mental disorders, such as depression, somatic symptom or eating disorders. We developed two novel modification techniques to enhance cardiac IAc and IAt as potential future treatment approaches for mental disorders with interoceptive dysfunction. In Study I, N=96 (80 w/age: 20.1 years) healthy adults underwent either a heartbeat perception training (HBPT) or a visual perception training (VPT), followed by either a post-learning stress test (‘socially-evaluated cold pressor test’/SECPT) or a control test (randomly assigned). IAc was assessed using a heartbeat counting (HCT) and a heartbeat discrimination task (HDT). We observed an increase of IAc in the HCT for the HBPT+stress group only. In Study II, N=22 healthy adults (16 w/age: 27.3 years) received three protocols of transcranial magnetic stimulation of their right supramarginal gyrus (rSMG), a brain structure with high functional correlation with the interoceptive brain network. We used a continuous (cTBS: inhibition), intermittent (iTBS: stimulation) and an intermediate (imTBS) theta burst stimulation protocol. IAc based on the HCT/HDT and heartbeat-evoked potentials (HEPs) as indicators of IAt were assessed. The iTBS protocol selectively enhanced HEPs, but did not affect IAc in the HCT/HDT. Interoceptive perceptual learning plus post-learning stress may be used as technique to enhance cardiac IAc, whereas iTBS of the rSMG selectively increases IAt. These techniques may be used to normalize dysfunctional interoception in specific mental disorders in the future.

Ideomotor theory explains how people can gain voluntary or goal-directed control over external somatomotor actions, such as grasping an object (i.e., “exteroaction”). The theory states that control operates through the anticipation of exteroceptive feedback associated with the motor command (e.g., seeing your arm move). In contrast, there is currently no clear explanation for how people can acquire voluntary control over internal visceromotor actions, such as changes in heart rate (i.e., “interoaction”). As ideomotor theory is in principle compatible with any action that provides sensory feedback, the question arises whether people can similarly learn to control interoactions through the anticipation of interoceptive feedback. To test this hypothesis, we recruited 20 participants for a six-week autogenic training course, where they learned to anticipate the interoceptive feedback associated with reductions in heart rate. We found that participants were able to voluntary reduce their heart rate (and increase heart rate variability) compared to baseline only after training. We further tested the role of response specification, i.e., whether or not participants were able to directly control their heart rate or relied on an indirect pathways for which prior control exists, by testing the synchronization between heart- and respiration rate in post- vs. pre-training. Together, our results provide initial support for the ideomotor hypothesis of voluntary interoaction, but future research should more directly test the role of central theoretical mechanisms of ideomotor theory in this context, such as the role of the response image and ideomotor compatibility.

Background: Impaired interoceptive abilities in clinical samples point out the relevance to improve interoception. While an impact of a body scan meditation on cognitive and physiological variables was shown, there is a lack of knowledge regarding effects on interoception. This study aimed to enhance interoceptive dimensions, including the heartbeat-evoked brain potential (HEP), with a body scan.

Methods: 49 healthy students were randomized to an intervention group (n = 25) or to a control group (n = 24). The intervention group conducted a 20-min audio-guided body scan for 8 weeks. The control group listened to an audio book. Interoceptive accuracy, assessed by a heartbeat detection task, sensibility, acquired by confidence ratings, and the HEP, measured by EEG, were ascertained before and after the intervention.

Findings: There was no difference between the groups in interoceptive accuracy, sensibility and the HEP after the intervention. For both groups, an improvement over time was observed in accuracy, F(1, 47) = 18.4, p < .001, η²_p = .28, and sensibility, F(1, 47) = 13.9, p < .001, η²_p = .23. While accuracy predicted centroparietooccipital HEPs at t1 (ß = 1.8, p = .02), sensibility predicted HEPs at t2 (ß = - .23, p = .02).

Discussion: The findings indicate an improvement of interoceptive abilities by training, although the body scan might have been too unspecific. The potential of the HEP as an additional marker of interoceptive processing is underlined. Future studies should target improvements of interoception in clinical samples using trainings of concrete interoceptive modalities.