Tactile body image disturbance in anorexia nervosa

Abstract

Body image disturbances are central to anorexia nervosa (AN). Previous studies have focused mainly on attitudinal and visual aspects. Studies on somatosensory aspects thus far have been scarce. We therefore investigated whether AN patients and controls differed in tactile perception, and how this tactile body image related to visual body image and body dissatisfaction. The Tactile Estimation Task (TET) measured tactile body image: Two tactile stimuli were applied to forearm and abdomen, and, while blindfolded, participants estimated the distance between the two tactile stimuli between their thumb and index finger. The Distance Comparison Task (DCT) measured visual body image. Compared to controls (n=25), AN patients (n=20) not only visualized their body less accurately, but also overestimated distances between tactile stimuli on both the arm and abdomen, which might reflect a disturbance in both visual and tactile body image. High levels of body dissatisfaction were related to more severe inaccuracies in the visual mental image of the body, and overestimation of tactile distances. Our results imply that body image disturbances in AN are more widespread than previously assumed as they not only affect visual mental imagery, but also extend to disturbances in somatosensory aspects of body image.

The two dimensions of the body representation in women suffering from Anorexia Nervosa

“…Our results on pure tactile detection are not fully in line with those by Keizer et al (2011), who described unusual somatosensory performance in eating disorders participants. The authors found that as compared to controls, AN patients need a lower pressure to detect a simple stimulus on the abdomen, whereas they have a worse discrimination threshold when asked to discriminate between one or two touches on the abdomen or on the arm.…”

“…In line with this view, we and other authors have suggested that primary tactile processing responsible for detecting an object in contact with the skin, can be anatomically and functionally dissociated from a secondary higher-order tactile processing, such as the discrimination of the sizes of objects touching different body parts (Serino et al, 2008;Gallace and Spence, 2009;Spitoni et al, 2010Spitoni et al, , 2013 We have proposed that, in order to extract metric information from the skin surface, the brain has to link information related to the single locations on the skin where touch is applied with a representation of the stimulated body part, and therefore, a "tactile size estimation task" can be used as an implicit proxy of the body representations. (Keizer et al, 2011(Keizer et al, , 2012) used a tactile size estimation task to study tactile performance in patients suffering from AN and they found that relative to controls, AN patients overestimated the distance between two tactile stimuli for the stimulated body parts. According to the authors, this evidence result from top-down influences of body dissatisfaction on the body representations.…”

“…In the present study we applied this approach to a group of female anorexic patients. Differently from Keizer et al (2011Keizer et al ( , 2012 however, we believe that in order to measure the perceived size of a body part, tactile stimuli need to be presented as oriented at least along the two main proximo-distal and medio-laterally axes, so to provide a measure of 2D perception of specific body parts. In particular, we hypothesize that AN patients represent their bodies wider and fatter that they really are, so we expected that tactile perception of the stimuli oriented across their bodies (mediolaterally/horizontal) should be profoundly disturbed by representational distortions.…”

A testképtől a testképzavarig

“…Az egyik irányzat képviselői a test percepciójának multiszenzoros károsodásaként [56] vagy általános szomatoszenzoros zavar részeként [57,58] értelmezik a testkép-zavart, beleértve a taktilis, az interoceptív és a testi percepció, illetve ezek integrálásának érintettségét. Taktilis anhedoniaként [58] emlegetik azt a jelenséget, hogy a gyengéd érintést az anorexiás páciensek kevésbé érzé-kelik, illetve kevesebb kellemességérzést csatolnak hozzá.…”

“…Taktilis anhedoniaként [58] emlegetik azt a jelenséget, hogy a gyengéd érintést az anorexiás páciensek kevésbé érzé-kelik, illetve kevesebb kellemességérzést csatolnak hozzá. Az interoceptív deficit befolyásolhatja a test teljes reprezentációját, a testtudatosság alakulását [59].…”