Frangos et al. 2015

The aim of the study was to determine whether electrical stimulation applied to the ear could activate brain regions associated with vagus nerve pathways.

The researchers focused on the auricular branch of the vagus nerve, which provides a possible non-invasive access point for vagal stimulation through specific regions of the external ear.

The researchers used functional magnetic resonance imaging (fMRI) to measure brain activity during auricular vagus nerve stimulation.

Participants received electrical stimulation applied to specific ear regions believed to be innervated by the auricular branch of the vagus nerve.

Brain activity during stimulation was compared with control conditions in order to identify changes associated with vagal pathway activation.

The study found that stimulation of the auricular branch of the vagus nerve produced measurable activation in several brain regions associated with vagal pathways.

In particular, the researchers observed activation in the nucleus tractus solitarius and other brainstem regions involved in autonomic regulation.

These findings supported the idea that non-invasive stimulation through the ear may influence neural circuits associated with the vagus nerve.

The auricular branch of the vagus nerve provides sensory innervation to parts of the outer ear.

Because this branch is accessible through the skin, researchers have explored whether electrical stimulation applied to the ear may influence vagal signaling without requiring implanted devices.

This concept forms an important basis for transcutaneous auricular vagus nerve stimulation, often abbreviated as taVNS.

The Frangos et al. study provided important neuroimaging evidence supporting the idea that non-invasive vagus nerve stimulation may influence brain activity.

This helped strengthen scientific interest in auricular stimulation approaches and contributed to a rapidly expanding research area.

Since its publication, the study has been widely cited in research on taVNS, neuromodulation, autonomic regulation, and brainstem pathways associated with vagal signaling.

Following this study, researchers conducted many additional investigations into transcutaneous auricular vagus nerve stimulation.

Later studies explored how non-invasive stimulation may influence stress responses, autonomic balance, emotional regulation, and related physiological processes.

Although the field continues to evolve, this study remains one of the most important early pieces of evidence supporting auricular access to vagal pathways.

As with many early neuroimaging studies, the research involved a relatively small group of participants.

Further research has continued to explore stimulation parameters, target ear regions, mechanisms of action, and the relationship between neuroimaging findings and real-world physiological outcomes.

This means the study is best understood as an important early contribution rather than a final answer to how auricular vagus nerve stimulation works in all contexts.

The Frangos et al. study helped demonstrate that non-invasive stimulation applied to the ear may activate brain regions associated with vagus nerve pathways.

That finding made it much easier to take auricular stimulation research seriously as a legitimate area of investigation in neuroscience and neuromodulation.

Today, the paper remains one of the key references behind modern research on transcutaneous auricular vagus nerve stimulation.