tcVNS Alters EEG and Heart Rate Variability in Healthy Dogs

Transcutaneous cervical vagus nerve stimulation (tcVNS) produces measurable shifts in scalp electroencephalogram (EEG) recordings and heart rate variability (HRV) in healthy dogs, according to a pilot study published in Frontiers. The publication adds to a small but growing literature on non-invasive vagal modulation in veterinary species.

The work is preliminary by design. Investigators delivered electrical current through surface electrodes placed over the cervical course of the vagus nerve while recording concurrent EEG and cardiac autonomic metrics. The protocol was framed as a proof of concept.

The methodology follows a translational logic. Implanted vagus nerve stimulation has established indications in drug-resistant epilepsy and treatment-resistant depression in humans. The standard devices require surgical implantation of a pulse generator in the chest and a helical electrode wrapped around the left cervical vagus.

A transcutaneous cervical approach uses skin-contact electrodes positioned over the same nerve branch in the neck, eliminating the operative step and its associated morbidity. The shift also lowers the barrier to sham-controlled trials, since participants or animals can receive apparent stimulation without active current.

For the canine cohort, the recording method carries specific technical constraints. EEG in dogs requires adapted montages because of differences in skull morphology and temporal muscle mass compared with humans.

Sedation, where used, alters background rhythms and must be accounted for in spectral analysis. The study treats EEG and HRV as paired readouts of central and autonomic nervous system activity during stimulation.

HRV in this context derives from a surface electrocardiogram (ECG). Time-domain indices include SDNN (standard deviation of normal-to-normal intervals) and RMSSD (root mean square of successive differences). Frequency-domain indices partition total power into high-frequency and low-frequency bands associated with parasympathetic and sympathetic modulation.

The combined indices serve as a peripheral complement to the cortical EEG signal. Prior work in humans receiving implanted vagus nerve stimulation has documented acute shifts in alpha and gamma band power and HRV modulation consistent with parasympathetic engagement.

What does this change for veterinary neurology and human neuromodulation?

At minimum, the pilot supports the feasibility of running combined tcVNS, EEG, and HRV paradigms in dogs. The work establishes that the modalities can be acquired simultaneously and that stimulation produces detectable signal changes. Whether the EEG signatures mirror those reported in human recipients of implanted vagus nerve stimulators remains an open empirical question.

For laboratories studying non-invasive neuromodulation, the methodological lesson is practical. Pairing scalp EEG with HRV during transcutaneous vagal stimulation offers central and peripheral readouts in a single recording session. Researchers can test whether cortical signal shifts correlate with autonomic signal shifts and at what latency after stimulation onset.

The combined approach also supports dose-finding work, since HRV provides a near-instantaneous index of autonomic engagement. The Frontiers publication positions the canine model as a translational bridge. Dogs share substantial neuroanatomical and autonomic physiology with humans, and a non-invasive platform permits repeated sessions without surgical recovery.

Animal data, however, does not extrapolate directly to human outcomes, and pilot findings require independent replication in larger cohorts with sham controls. For veterinary clinical practice, the implications remain distant. tcVNS is investigational in dogs; no FDA-cleared or equivalently approved canine indication has been established.

Any therapeutic application would require controlled efficacy and safety data, including behavioral monitoring, repeated-session tolerance, and long-term follow-up. Canine-specific stimulation parameters, electrode geometry, and tolerable current densities are not yet standardized.

The investigators will need to publish the full numerical results before the field can weigh the magnitude and clinical relevance of the reported changes. Forthcoming work will determine whether the EEG and HRV shifts are reproducible, dose-dependent, and clinically actionable across species. Until then, the study stands as a methodological foundation rather than a treatment claim.