Bodily self recognition and autonomic correlates during social interaction: implications for Restrictive Anorexia

It is widely known that among others, the most pervasive symptoms characterizing Anorexia nervosa (AN) concern their body-image overestimation, a wide range of autonomic system disturbances, and the difficulty to discriminate their emotional states and visceral sensations. Since these pervasive symptoms largely contribute to the onset and maintenance of Eating Disorders, we investigated the nature of the body image distortion in AN (restrictive subtype), and its possible relation with Interoceptive Sensitivity (IS, the sensitivity to stimuli originating inside the body). Furthermore, since previous studies found that IS seems to contribute to the autonomic regulation of social behavior, as measured by Respiratory Sinus Arrhythmia (RSA), here we aimed at assessing the possible relation between IS and autonomic regulation both in resting state and during social interactions in AN patients, whose ability to perceive their bodily signal is impaired. For these purposes, we recorded reaction times of both healthy controls (HC) and AN patients during two tasks requiring an implicit or explicit recognition of self/other hands stimuli, in which the perceived size of the stimuli was manipulated. To assess IS, we used a widely used Heartbeat perception task. Finally, we measured participantsࢠautonomic reactivity, recording their RSA responses during both the resting state and a social task (Physiological proxemics task). Our results showed not only that the perceived size of hands stimuli could modulate the implicit self-recognition in HC, but also the body image distortion of AN patients, beside stemming from a disturbed body image (i.e. explicit perceptual, semantic, aesthetic and emotional representation of the body) reflects ࢠat least partly ࢠabnormal neural processing of the implicit and pre-reflective motor experience of the bodily self. Furthermore, we found that IS predicts the ability to execute a hand mental rotation (Implicit task: higher IS, faster RTs) but not the ability to perform a task (explicit task) in which more cognitive and/or perceptually-based mechanisms are likely involved. More importantly this relationship was lacking in AN patients, whose IS, was also significantly lower than HC. In addition, we found that IS, might be strictly related to social disposition (as measured by RSA responses at rest) since the higher was IS, the higher were RSA responses at rest. This relation was lack in AN patients, who showed significantly lower RSA at rest, and a flattened autonomic regulation during the social task compared to HC. In the light of our results, we conclude AN patientsࢠblunted IS might play a pivotal role in the lack of the implicit, pre-reflective sense of self as power for action leading to a less efficient self/other distinction. The lack of contact with the inner body might also account for the affected social disposition of AN patients and their autonomic regulation in social contexts.