LAUSR

World Psychiatry 20:2 June 2021 into understanding the mechanisms underlying clinical features. For example, chronic stress, clinical depression, or a life-threatening traumatic experience that may lead to PTSD could profoundly dampen ventral vagal regulation of the heart and the structures regulated by ventral vagal complex constituting the social engagement system. Disrupting the brainstem locus of social engagement system would functionally impair social communication and co-regulation by reducing vocal prosody and facial affect, and, through the loss of neural tone to the middle ear muscles, influence auditory processing by inducing hypersensitivity to low frequency background sounds and hyposensitivity to voice. In concert with these changes, brainstem communication with higher brain structures would impair cognitive function and affect regulation, while supporting the defense strategies of fight or flight or shutdown (e.g., syncope, dissociation). Monitoring ventral vagal function may provide an objective neurophysiological marker of clinical improvement.