Augmentative effects of tDCS on a body-related attentional retraining in women with bulimia nervosa

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Overvaluation of shape and weight on self-esteem and corresponding body dissatisfaction are a core diagnostic feature of both bulimia nervosa (BN) and subthreshold BN (Other Specified Feeding or Eating Disorder [OSFED]). Cognitive models of eating disorders suggest that salient stimuli such as the exposure with the self-body or the comparison with another body activate selective memory, interpretation and attentional processes, assumed to substantially contribute to behavior typically associated with eating disorders such as body checking, body avoidance and pathological eating behavior. In accordance, eye movement studies showed that women with a (sub)clinical eating disorder preferentially process body parts typically associated with weight change or body parts which they subjectively dislike (compared to like). Of note, experimental evidence suggests a causal link between the selective attentional bias for body parts and body dissatisfaction, in that a retraining of attention towards self-defined unattractive body parts reduces, while a retraining of attention towards attractive body parts increases body satisfaction in body dissatisfied women. However the latter was shown to be more difficult, needing a more extensive retraining.Recent evidence suggests that the cortical stimulation of the dorsolateral prefrontal cortex (dlPFC) by transcranial direct current stimulation (tDCS) can ameliorate attentional biases and increase the effects of attentional retraining. Therefore, the aim of the present project is to investigate whether a positive body-related attentional retraining reduces selective attention for unattractive body parts and increases body satisfaction in a group of women with BN, as well as subthreshold BN (OSFED), and whether these effects can be enhanced by tDCS.To this end we will recruit a total of 80 women with BN or BN-OSFED according to DSM-5 criteria and will compare them to a group of 40 weight and age matched women without lifetime eating disorders with regard to attention allocation towards three self-defined most (un)attractive self-body parts and its neurophysiological signatures by means of a combined eye tracking and electroencephalogram (EEG) paradigm as well as a combined near-infrared spectroscopy (NIRS) and eye tracking paradigm. Subsequently, only patients with BN/BN-OSFED will be administered active tDCS or sham tDCS during a repeated body-related attentional retraining (AR) which aims to increase the selective processing of self-defined attractive body parts, or a respective attentional retraining control condition (AR-CC) in a double-blind between-subject comparison. After the last training session, attention allocation towards the three self-defined most (un)attractive self-body parts will be assessed once more by the experimental paradigms. Body dissatisfaction will be assessed by questionnaires at the experimental sessions, prior to and after the training and at four-week and three months follow-up.