Maintenance of Auditory Deviance Processing Following Auricular Vagal Neuromodulation Therapy in Disorders of Consciousness

Background/Objectives: Auricular Vagal Neuromodulation Therapy (AVNT) constitutes a promising non-invasive therapeutic approach for Disorders of Consciousness (DoCs). However, evidence regarding its effectiveness remains limited. In this context, although the Mismatch Negativity (MMN) is a well-established neurophysiological index associated with recovery in DoCs, its modulation by AVNT has not yet been investigated. This study aimed to evaluate the effect of AVNT on MMN in DoCs. Methods: Forty-four participants with DoCs were evenly assigned to either an experimental or a control group, alongside twenty-two healthy participants used to establish normative data in neurotypical conditions. The latency, peak and peak-to-peak MMN amplitude were assessed as a complement to the Coma Recovery Scale Revised (CRS-R). Subsequently, only the experimental group received AVNT, followed by a second assessment across all groups. Results: The control group showed extensive changes across sessions in both peak and peak-to-peak amplitudes. In contrast, the experimental group exhibited a significant change only in peak amplitude for the fronto-central region, with no changes in peak-to-peak amplitude. Between-session changes in peak and peak-to-peak amplitudes differed between the control and healthy groups in the parieto-occipital region. After adjustment for the inter-session interval, the ANCOVA showed an overall group effect on peak-to-peak amplitude changes in the parieto-occipital and right regions. No differences were detected between the control and experimental groups or between the experimental and healthy groups. Finally, no significant effects were found for MMN latency. Conclusions: These findings could be compatible with a possible effect of AVNT, although the evidence remained insufficient to demonstrate a direct effect of the intervention.