Abstract
Body image disorders in anorexia nervosa (AN) patients and recovered AN (RAN) patients have been suggested to stem from aberrant integration of sensory information. Previous research by Case et al. (2012) used the size-weight illusion (SWI) to study multisensory integration in AN. Their results showed a diminished SWI in AN patients, which they interpreted as evidence of decreased integration of visual and proprioceptive information. However, their method did not distinguish between visual and haptic size information, which was presented concurrently while making weight judgements. Therefore, the reported effect might be attributed to integrating visual, haptic size cues, or a combination of both processes with proprioceptive input. Here, we use the SWI to investigate the integration of visual and haptic object-related sensory information in a sample of AN patients (n = 30), RAN patients (n = 29) and healthy controls (HC) (n = 29). We aimed to distinguish the contribution of visual and haptic object size by including separate visual and haptic SWI conditions. In addition to explicit measures, we included grip force measurements to assess implicit expectations about object weight. We further analysed the correlation between the SWI and a visual body size estimation (VSE) task. In contrast to Case et al. (2012), we found no evidence of differential SWI experience between groups. All participants reported a stronger visual SWI compared to haptic SWI. Grip force rate (but not peak) showed evidence of motor adaptation for the larger object in the visual condition. Furthermore, there was no correlation between the VSE and SWI, indicating no relation between perceived object weight and body size estimation. These results do not support the hypothesised impairment of visual-haptic object related integration in AN.
Highlights
Anorexia nervosa (AN) is an eating disorder where patients have an intense fear of gaining weight, despite being underweight
Misperception of object weight in anorexia nervosa image that is limited to distorted thoughts about the body and involves disturbances in body perception [1,2,3,4]. These body image disturbances (BID) are strongly associated with the development and maintenance of eating disorders (ED), and relapse is known to be predicted by the severity of the disorder [5,6,7]
The results showed a diminished size-weight illusion (SWI) in AN compared to healthy controls (HC); i.e. unlike HC, AN patients were less likely to perceive the smaller disk as heavier when the actual weight of the large and small disks was similar, despite normal weight discrimination abilities [21]
Summary
Anorexia nervosa (AN) is an eating disorder where patients have an intense fear of gaining weight, despite being (severely) underweight. Misperception of object weight in anorexia nervosa image that is limited to distorted thoughts about the body and involves disturbances in body perception [1,2,3,4]. These body image disturbances (BID) are strongly associated with the development and maintenance of eating disorders (ED), and relapse is known to be predicted by the severity of the disorder [5,6,7].
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