Aberrant somatosensory perception in Anorexia Nervosa

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

“…It is worth nothing that although in line with previous studies on body representation in eating disorders (Nico et al 2010;Keizer et al 2011Keizer et al , 2012, the sample size of the present study is relatively low due to practical difficulties in recruiting well-diagnosed cases of AN and involving patients is such kind of tasks. Future investigations will hopefully confirm the present findings.…”

“…Keizer et al (2012) found that AN patients overestimated distances between tactile stimuli on both the arm and abdomen suggesting a generalized trend of AN patients to perceive the whole body as bigger. Our study refines this conclusion, since we show that AN patients overestimate only the stimuli oriented along the altered dimension of the body which support the hypothesis of a selective abnormal body representation only in the horizontal direction.…”

“…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.…”

Altered body schema processing in frontotemporal dementia with C9ORF72 mutations

“…Body schema alterations in our C9ORF72-FTD group also extended to the more elementary processing required to encode somatic spatial relations or postural change, in the two-point discrimination and proprioceptive localisation tasks. Deficits of tactile discrimination have been identified in paradigmatic disorders of body schema, including schizotypy (liability to schizophrenia33) and anorexia nervosa,28 and are likely to index a fundamental abnormality of low-level somatic coding. The conjunction of impaired tactile spatial acuity and normal baseline proprioceptive acuity in C9ORF72-FTD would be consistent with the existence of multiple neural representations for these functions within the multimodal body matrix 15 21…”