Aberrant somatosensory perception in Anorexia Nervosa

ArticleinPsychiatry Research 200(2-3) · May 2012with26 Reads
DOI: 10.1016/j.psychres.2012.05.001 · Source: PubMed
Anorexia Nervosa (AN) patients have a disturbed experience of body size and shape. Previously it has been shown that these body representation disturbances extend to enlarged perception of tactile distances. Here we investigated whether misperception of tactile size could be related to inaccurate elementary somatosensory perception. Tactile size perception was measured with the Tactile Estimation Task (TET) (see Keizer et al., 2011). Elementary somatosensory perception was assessed with a pressure detection task and two point discrimination (TPD). Compared to controls (n=28), AN patients (n=25) overestimated tactile size, this effect was strongest for the abdomen. Elementary tactile perception deviated in AN as well: Patients had a lower threshold for detecting pressure on their abdomen, and a higher threshold for TPD on both the arm and abdomen. Regression results implied that group membership predicted tactile size estimation on the arm. Both group membership and TPD predicted tactile size estimation on the abdomen. Our results show that AN patients have a disturbance in the metric properties of the mental representation of their body as they overestimate the size of tactile stimuli compared to controls. Interestingly, AN patients and controls differ in elementary somatosensory perception as well. However, this could not solely explain misperception of tactile distances, suggesting that both bottom-up and top-down processes are involved.
    • "This index expresses the percentage of similarity with respect to physical body, so that values close to 100 represent an estimated body similar to the physical one. In the tactilebased estimation task (Keizer et al., 2011Keizer et al., , 2012 Scarpina et al., 2014), patient was blindfolded for the duration of the task and the experimenter simultaneously lightly pressed the two points of a caliper on the patient's abdomen. The patient was asked to estimate the distance between the two tactile stimuli (i.e., 50, 60, and 70 mm) by varying the separation between the thumb and the index finger of the left hand on a table. "
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: The available clinical guidelines for super-super obese patients (i.e., with body mass index (BMI) > 60 kg/m²) that are not suitable for bariatric surgery mandate a palliative multidisciplinary treatment (i.e., production and maintenance of weight loss) provided in a center of excellence. However, the modality and the impact of this approach are still controversial. Moreover, it is not able to address the high level of body dissatisfaction and body distortions that are common among these patients. Clinical Presentation: We report the case of a non-operable super–super obesity – a 37 year old woman with a BMI of 62 kg/m² – receiving a specialized treatment for her obstructive sleep apnea. She entered a multidisciplinary program that promoted healthy behaviors, including physical activities and psychological intervention. To improve body dissatisfaction, which was linked to a significant multisensory impairment of body perception, she also entered a virtual reality (VR) body-swapping illusion protocol. At the end of the current investigation, the patient continued her multidisciplinary program, reporting an increase in the motivation for undertaking healthy behavior and a decrease in the anxiety feelings associated with her clinical condition. Conclusion: This case provides preliminary evidence that both body dissatisfaction and body-size distortions of non-operable super-super obesity patients could be addressed by a VR body-swapping protocol, which is important because the palliative multidisciplinary treatment recommended for these patients is not able to address them. Interestingly, the use of a VR body-swapping illusion protocol seems to be able to improve not only the experience of the body in these patients but their motivation for change, too.
    Full-text · Article · Jun 2016
    • "Ben-Tovim et al., 1990). Further, and more directly related to somatosensation, recent results have found that individuals with anorexia show impaired tactile processing, overestimating the size of tactile stimuli (Keizer et al., 2011; Keizer, Smeets, Dijkerman, van Elburg, & Postma, 2012). Intriguingly, this bias, though apparent on the arm as well, was strongest on the abdomen, and predicted the severity of body dissatisfaction. "
    [Show abstract] [Hide abstract] ABSTRACT: Several forms of perception require that sensory information be referenced to representations of the size and shape of the body. This requirement is especially acute in somatosensation in which the main receptor surface (i.e., the skin) is itself coextensive with the body. This paper reviews recent research investigating the body representations underlying somatosensory information processing, including abilities such as tactile localization, tactile size perception, and position sense. These representations show remarkably large and stereotyped distortions of represented body size and shape. Intriguingly, these distortions appear to mirror distortions characteristic of somatosensory maps, though in attenuated form. In contrast, when asked to make overt judgments about perceived body form, participants are generally quite accurate. This pattern of results suggests that higher-level somatosensory processing relies on a class of implicit body representation, distinct from the conscious body image. I discuss the implications of these results for understanding the nature of body representation and the factors that influence it.
    Full-text · Article · Dec 2015
    • "A last limit of the study concerns the size of the clinical sample. It is worth nothing that although in line with previous studies on body representation in eating disorders (Nico et al. 2010; Keizer et al. 2011 Keizer 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. "
    [Show abstract] [Hide abstract] ABSTRACT: A core symptom of Anorexia Nervosa (AN) is a severe alteration of body representations. Evidence from somatoperception studies point to a generic disturbances of somatosensory components of body representations. Here we have investigated whether AN patients (N=18) and controls differed in the perception of tactile stimuli differently oriented along the body axes. We tested the hypothesis that patients perceive and represent their body selectively larger in only one dimension. To this aim we used elementary tactile measures for tactile acuity (Von Frey's test and two-point discrimination thresholds - 2PD) and tactile discrimination measures. The rationale is based on the assumption that AN patients have a wider body representation, and that tactile body representation tasks (Tactile Distance task) oriented across the bodies (horizontally) are influenced by distorted body representations compared with tactile stimuli oriented along the bodies (vertically) which should not be influenced by body representations. Results showed that patients judged horizontal tactile stimuli significantly wider than the same stimuli oriented vertically.These results suggest that human brain perceives things differently based on body representations and that the beliefs concerning body size influence the specific somatosensory process of tactile experience.
    Full-text · Article · Aug 2015
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