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.
"These patients misperceive tactile distances (Keizer et al., 2011) and have increased two point discrimination thresholds (Keizer et al., 2012) consistent with our thesis that such elementary tactile abilities depend on perceived body size. However, Anorexia Nervosa patients show lowered (more sensitive) tactile detection thresholds (Keizer et al., 2012) unlike the effects reported here that showed consistent increases. This reflects a difference between short-term and long-term distortions of perceived body size. "
[Show abstract][Hide abstract] ABSTRACT: To accurately interpret tactile information, the brain needs to have an accurate representation of the body to which to refer the sensations. Despite this, body representation has only recently been incorporated into the study of tactile perception. Here, we investigate whether distortions of body representation affect tactile sensations. We perceptually altered the length of the arm and the width of the waist using a tendon vibration illusion and measured spatial acuity and sensitivity. Surprisingly, we found reduction in both tactile acuity and sensitivity thresholds when the arm or waist was perceptually altered, which indicates a general disruption of low-level tactile processing. We postulate that the disruptive changes correspond to the preliminary stage as the body representation starts to change and may give new insights into sensory processing in people with long-term or sudden abnormal body representation such as are found in eating disorders or following amputation. (PsycINFO Database Record (c) 2014 APA, all rights reserved).
Journal of Experimental Psychology Human Perception & Performance 12/2014; 41(1). DOI:10.1037/a0038514 · 3.36 Impact Factor
"On one side, the tendency of our perception to be affected by our recurring thoughts produces an attentional bias on body related stimuli. For example, the Stroop effects found for body/shape stimuli in AN patients (Dobson and Dozois, 2004), and the lower pressure detection threshold AN patients have on their abdomen (Keizer et al., 2012), apparently support this interpretation: anorectic individuals selectively attend to body stimuli because they represent their greater psychological threat (Dobson and Dozois, 2004). On the other side, it draws the subject's attention to the contents of the stored body image. "
[Show abstract][Hide abstract] ABSTRACT: Clinical psychology is starting to explain eating disorders (ED) as the outcome of the interaction among cognitive, socio-emotional and interpersonal elements. In particular two influential models-the revised cognitive-interpersonal maintenance model and the transdiagnostic cognitive behavioral theory-identified possible key predisposing and maintaining factors. These models, even if very influential and able to provide clear suggestions for therapy, still are not able to provide answers to several critical questions: why do not all the individuals with obsessive compulsive features, anxious avoidance or with a dysfunctional scheme for self-evaluation develop an ED? What is the role of the body experience in the etiology of these disorders? In this paper we suggest that the path to a meaningful answer requires the integration of these models with the recent outcomes of cognitive neuroscience. First, our bodily representations are not just a way to map an external space but the main tool we use to generate meaning, organize our experience, and shape our social identity. In particular, we will argue that our bodily experience evolves over time by integrating six different representations of the body characterized by specific pathologies-body schema (phantom limb), spatial body (unilateral hemi-neglect), active body (alien hand syndrome), personal body (autoscopic phenomena), objectified body (xenomelia) and body image (body dysmorphia). Second, these representations include either schematic (allocentric) or perceptual (egocentric) contents that interact within the working memory of the individual through the alignment between the retrieved contents from long-term memory and the ongoing egocentric contents from perception. In this view EDs may be the outcome of an impairment in the ability of updating a negative body representation stored in autobiographical memory (allocentric) with real-time sensorimotor and proprioceptive data (egocentric).
Frontiers in Human Neuroscience 05/2014; 8:236. DOI:10.3389/fnhum.2014.00236 · 2.99 Impact Factor
"To ensure optimal treatment, we believe it is crucial to gain insight into all facets of body representation disturbances in AN. For example, recently it was found that AN patients’ tactile perception is altered as well: Patients perceived tactile stimuli on their skin as further apart than they actually were , . However, no studies have yet directly addressed body representation disturbances in AN beyond perceptual processing, and focused on the possibility that body representation disturbances could extend to more unconscious, action-related, aspects of body representation. "
[Show abstract][Hide abstract] ABSTRACT: To date, research on the disturbed experience of body size in Anorexia Nervosa (AN) mainly focused on the conscious perceptual level (i.e. body image). Here we investigated whether these disturbances extend to body schema: an unconscious, action-related representation of the body. AN patients (n = 19) and healthy controls (HC; n = 20) were compared on body-scaled action. Participants walked through door-like openings varying in width while performing a diversion task. AN patients and HC differed in the largest opening width for which they started rotating their shoulders to fit through. AN patients started rotating for openings 40% wider than their own shoulders, while HC started rotating for apertures only 25% wider than their shoulders. The results imply abnormalities in AN even at the level of the unconscious, action oriented body schema. Body representation disturbances in AN are thus more pervasive than previously assumed: They do not only affect (conscious) cognition and perception, but (unconscious) actions as well.
PLoS ONE 05/2013; 8(5):e64602. DOI:10.1371/journal.pone.0064602 · 3.23 Impact Factor
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