Towards an advancement of multisensory integration deficits in anorexia nervosa: Exploring temporal discrimination processing of visuo-auditory stimuli

Anorexia nervosa (AN) is a severe eating disorder affecting mostly young females and involving significant weight loss, a high fear of gaining weight and a distorted body image. Anorectic patients incur overestimations of their own body, thus suggesting that a distorted experience of body may play a crucial role in this disease. Specifically, a recent model (Riva et al., 2014) posits that a distorted body image could be due to difficulties in integrating the perception of signals from different parts of the body. Many studies evidenced that patients affected by Eating Disorders (EDs) have impairments at the visual, interoceptive, proprioceptive, and tactile level. However, it is still unexplored whether anorectic patients struggle to integrate auditory-visual signals together. In this study, we tested whether temporal discrimination processing of visuo-auditory stimuli is impaired in patients with AN using the Sound-Induced Flash Illusion (SIFI). The more we experience this illusion, the more impaired is our temporal discrimination processing. We hypothesized that ANs showed less correct responses at the task compared to healthy participants. We exposed healthy women and ANs selected from the Centro Pilota Regionale per i disturbi del comportamento alimentare (Regional Pilot Center for Eating behavioral disorders) (SR CDCA) Spedali Civili of Brescia (Spedali Civili of Brescia), to this illusion to assess the degree of impairment of visuo-auditory integration and we compared their performances in terms of accuracy. Result showed that ANs gave less correct responses than controls especially for longer Stimulus-onset asynchronies (SOAs). This study can have crucial implications for designing new treatments of EDs since it can elucidate processes underlying multisensory integration impairments, which can be specific for this population.