Haptic perception in Anorexia nervosa

Martin Grunwald


In the mid 1990s we, at the Institute for Neurophysiology at the Friedrich Schiller University in Jena, Germany, conducted psycho-physiological trials into brain electrical changes during haptic examination [1, 2]. The experimental task consisted of having subjects haptically explore sunken reliefs with closed eyes and then reproduce the image presented upon them afterwards with their eyes open. The aim was to analyse the stimuli-dependant changes in the subjects EEG. The more than 30 probands in this trial had, as expected, no major problems meeting this demand. However, much to our surprise, one test subject was completely unable to perform the task. Her exploratory times were much longer than the average. Despite this, the drawn reproductions that she produced showed that her perception of the stimuli’s entire structure was completely false and distorted. The subject, an intelligent, female university student in her third semester, had a good school record and was, in no way, neurologically conspicuous. She was, however, extremely thin and her skin’s texture was abnormal. We wanted to explain these unexpected individual findings and followed a series of theoretical considerations and experimental studies which led us to the field of clinical-experimental psychology and an extreme mental disorder – anorexia nervosa.
Anorexia nervosa (AN) is one of the most severe mental disorders. For the most part, this illness affects young girls and 10–15% dies as a result of the physical effects over the course of time. The illness is characterised by extremely low body weight and with an obsessive fear of gaining weight. Anorexia nervosa patients often control body weight by voluntary starvation, vomiting, purging, excessive exercise, sports or other weight control measures [3–5]. The illness often begins in puberty and the affected do not, as a rule, believe that they are sick despite their being extremely underweight. In various experimental studies it has been repeatedly observed that patients with anorexia tend to over-estimate the size or fatness of their own bodies [6–8]. Disturbances of body image are among the most important predictors for clinical severity of AN. However, current therapeutic approaches are relatively inefficient to this parameter [9, 10].
The reasons for the development of anorexia nervosa are still not fully explained. It is unanimously agreed that multifactorial conditions are responsible. Alongside psychological and social factors, genetic and patho-physiological processes are being discussed. Because body image and body schema distortion represent a critical factor in anorexia nervosa (and because the reasons for the disorder are still not completely understood as well as the fact that there is still no truly effective therapy for the disease) these aspects of the illness should be granted special attention. Especially body schema represents an absolutely central and basal aspect of one’s mental bodily representation.