Darwin revisited: the vagus nerve is a causal element in controlling recognition of other's emotions

Abstract

This Expression of Concern comes after a thorough and time-consuming analysis of the published article and the data it reports, following an investigation from the University of Leiden.

On 17th November 2021 Cortex received advice from the University of Leiden, containing allegations of misconduct concerning the data reported in this article. Due to the nature of the concerns raised about this paper, the Editor-in-Chief, in consultation with the Co-Editor, examined all documents provided, all aspects of the peer review and editorial process and requested the view of each of the authors. The Editor-in-Chief wishes to acknowledge the co-operation of all parties.

The Editor-in-Chief found no evidence of fraud. However, there is a legitimate cause for concern due to the authors dropping a small number of participants' performances without reporting it, which however does not invalidate the conclusions of the article. The Editor-in-Chief commends the authors for their willingness in participating in this dialogue. The Editor-in-Chief, the Co-Editor and the entire editorial board will use this case as a reminder to be as diligent as possible in the peer review process and to support transparency and openness in data sharing. Charles Darwin proposed that via the vagusnerve, the tenth cranial nerve, emotional facial expressions are evolved, adaptive and serve a crucial communicative function. In line with this idea, the later-developed polyvagal theory assumes that the vagus nerve is the key phylogenetic substrate that regulates emotional and social behavior. The polyvagal theory assumes that optimal social interaction, which includes the recognition of emotion in faces, is modulated by the vagus nerve. So far, in humans, it has not yet been demonstrated that the vagus plays a causal role in emotion recognition. To investigate this we employed transcutaneous vagus nerve stimulation (tVNS), a novel non-invasive brain stimulation technique that modulates brain activity via bottom-up mechanisms. A sham/placebocontrolled, randomized cross-over within-subjects design was used to infer a causal relation between the stimulated vagus nerve and the related ability to recognize emotions as indexed by the Reading the Mind in the Eyes Test in 38 healthy young volunteers. Active tVNS, compared to sham stimulation, enhanced emotion recognition for easy items, suggesting that it promoted the ability to decode salient social cues. Our results confirm that the vagus nerve is causally involved in emotion recognition, supporting Darwin's argumentation.