Abstract
Transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS) may accelerate fear extinction in healthy humans. Here, we aimed to investigate this hypothesis in healthy young participants in a prepared learning paradigm, using spider pictures as conditioned stimuli. After a fear conditioning phase, participants were randomly allocated to receive tVNS (final N = 42) or sham stimulation (final N = 43) during an extinction phase. Conditioned fear was assessed using US expectancy ratings, skin conductance and fear potentiated startle responses. After successful fear acquisition, participants in both groups showed a reduction of fear over the course of the extinction phase. There were no between-group differences in extinction rates for physiological indices of fear. Contrary to previous findings, participants in the tVNS condition also did not show accelerated declarative extinction learning. Participants in the tVNS condition did have lower initial US expectancy ratings for the CS− trials than those who received sham stimulation, which may indicate an enhanced processing of safety cues due to tVNS. In conclusion, the expected accelerated extinction due to tVNS was not observed. The results from this study call for more research on the optimal tVNS stimulation intensity settings.
Highlights
Increasing insights into the neurological underpinnings of fear have sparked an interest in neuromodulatory techniques aimed at enhancing fear extinction[1]
The analyses described in this article were performed on the data of the remaining 85 participants (NtVNS =, NSham =, Mage = 21.01 (SD = 1.87))
We tested the effects of transcutaneous VNS (tVNS) on fear extinction learning in humans in a single-day fear conditioning procedure
Summary
Increasing insights into the neurological underpinnings of fear have sparked an interest in neuromodulatory techniques aimed at enhancing fear extinction[1]. Promising extinction-modulating effects have been found for various neurostimulation techniques that target areas of the brain involved in extinction learning[2] Among these techniques, stimulation of the vagus nerve (VNS) is of particular interest, as preliminary evidence from animal models and human fear conditioning studies point towards treatment-augmenting effects of VNS during exposure therapy[3,4,5,6,7,8]. Recent studies have indicated that electrical stimulation of the concha of the left outer ear is a safe method to stimulate the auricular branch of the vagus nerve[9] This transcutaneous VNS (tVNS) has similar effects on brain activation patterns as invasive VNS10 and increases performance in memory tasks and other cognitive tasks[11,12]. One possible caveat of these studies was the limited sample size, which reduced the statistical power to detect meaningful differences
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