Abstract
Catching a ball or passing through an aperture without damage depends on vision and on a motor prediction that takes into account the physical dimensions of the body parts involved in the action; for instance, the shoulder width in order to pass through an aperture. A distortion of the representation of their own body is always found in patients suffering from anorexia nervosa: they believe that their body is fatter than actually is. This body image distorsion would increase their obsessive will of weight-loss. However, the precise nature of this cognitive bias and its all consequences are still unknown. Is it a mere ‘state of mind’, a false believe about one's self restricted to the aesthetic representation of body image? Does this cognitive distortion rather reflect an abnormal neural processing of the embodied self? Using a motorically driven perceptual decision task, we tested this latter hypothesis. Twenty-five patients and 25 control participants had to visually judge if an aperture could allow the passage without rotating the shoulders. The results showed that the critical ratio (critical aperture /shoulder width) was significantly higher in the patients. In this group, the critical ratio was also correlated with the degree of body concerns (Body Shape Questionnaire, Eating Disorder Inventory-2) and with the duration of disease. This finding suggests that the false believe about their body image, systematically reported by patients with anorexia nervosa, is an embodied misperception. It may take its source in a lived abnormal conscious experience of bodily forms and might be caused by abnormal processing in fronto-parietal networks.