Neurobiology of social behavior in individuals with selective mutism

Selective mutism (SM) is a psychiatric disorder characterized by compromised social engagement behaviors and heightened states of anxiety. No research has been published on the neurophysiological mechanisms that may mediate the psychological and behavioral features of SM. The research is based on the Polyvagal Theory, which provides a theoretical framework in which to examine the relationship between neurophysiology and social behavior. The theory proposes that social behavior emerges from a combination of regulation of the Social Engagement System (SES) and a neural detection of safety in the environment. The compromised social engagement behaviors in individuals with SM during novel social situations may emerge as a result of either a dysregulation of the SES or a "false alarm" (i.e., nervous system detection of danger in the environment when there is no real risk), which may shift neurophysiological state to promote mobilization behaviors.;The current study investigated physiological responses to social and physical challenges as a potential portal into the mechanisms that mediate the atypical behaviors that characterize SM. Heart period, RSA, motor activity, respiratory rate and tidal volume were recorded in 3-17 year old children with selective mutism (n=14) and typically developing children (n=43). The study yielded 5 important findings: (1) individuals with SM have similar baseline autonomic state as typically-developing individuals; (2) individuals with SM are more mobilized in anticipation of a new event; (3) individuals with SM have a longer physiological recovery period following an event; (4) individuals with SM have similar coupling of autonomic measures as typically-developing individuals; (5) individuals with SM demonstrated dampened autonomic reactivity during physical exercise.;The study provides new information on autonomic reactivity in individuals with SM. These findings are interpreted within the framework of the Polyvagal Theory and demonstrate that individuals with deficits in social behavior have dampened autonomic reactivity and context-specific dysregulation of the SES.