In this study, the researchers used the technique I’m experimenting with, transcutaneous auricular vagal nerve stimulation, or TaVNS, in patients with depression to correlate with their fMRI results. The procedure was similar to what I’ve been using in the clinic. The patients apply the electrode via a clip to the Left ear in the cymba concha region and turn it up so the sensation is strong but not painful. They leave it on for 30 minutes and do this twice a day at least 5 days a week for four weeks. The tVNS or TAVNS lead to better reduction in depression scores than the sham treatment. Interestingly, they also found that a spike in activity in the insula during the initial tVNS treatment correlated with successful outcome. This is of great interest to me, since I’m always looking for physiological biomarkers for successful clinical results. Strangely, they do not study any autonomic measures in this study, even though they are targeting the vagus nerve in the ear.
Early cortical biomarkers of longitudinal transcutaneous vagus nerve stimulation treatment success in depression
Transcutaneous vagus nerve stimulation (tVNS), a non-invasive method of brain stimulation through the auricular branch of the vagus nerve, has shown promising results in treating major depressive disorder (MDD) in several pilot studies. However, the neural mechanism by which the effect on depression might be achieved has not been fully investigated, with only a few neuroimaging studies demonstrating tVNS-induced changes in the brains of healthy volunteers. Identifying specific neural pathways, which are influenced by tVNS compared with sham in depressed individuals, as well as determining neurobiomarkers of tVNS treatment success are needed to advance the application of tVNS for MDD. In order to address these questions, we measured fMRI brain activity of thirty-eight depressed patients assigned to undergo tVNS (n = 17) or sham (n = 21) treatment for 4 weeks, during the first stimulation session. The results showed significant fMRI signal increases in the left anterior insula, revealed by a direct comparison of tVNS and sham stimulation. Importantly, the insula activation level during the first stimulation session in the tVNS group was significantly associated with the clinical improvement at the end of the four-week treatment, as indicated by the Hamilton Depression Rating Scale (HAM-D) score. Our findings suggest that anterior insula fMRI activity could serve as a potential cortical biomarker and an early predictor of tVNS longitudinal treatment success.
if you get a spike in the insula on the first treatment, it correlates with clinical outcome…