Neural Processing of Disorder-Related Stimuli in Patients with Anorexia Nervosa: A Narrative Review of Brain Imaging Studies

Abstract

Abnormalities and alterations in brain function are commonly associated with the etiology and maintenance of anorexia nervosa (AN). Different symptom categories of AN have been correlated with distinct neurobiological patterns in previous studies. The aim of this literature review is to provide a narrative overview of the investigations into neural correlates of disorder-specific stimuli in patients with AN. Although findings vary across studies, a summary of neuroimaging results according to stimulus category allows us to account for methodological differences in experimental paradigms. Based on the available evidence, the following conclusions can be made: (a) the neural processing of visual food cues is characterized by increased top-down control, which enables restrictive eating, (b) increased emotional and reward processing during gustatory stimulation triggers disorder-specific thought patterns, (c) hunger ceases to motivate food foraging but instead reinforces disorder-related behaviors, (d) body image processing is related to increased emotional and hedonic reactions, (e) emotional stimuli provoke increased saliency associated with decreased top-down control and (f) neural hypersensitivity during interoceptive processing reinforces avoidance behavior. Taken together, studies that investigated symptom-specific neural processing have contributed to a better understanding of the underlying mechanisms of AN.

Strengthened Default Mode Network Activation During Delay Discounting in Adolescents with Anorexia Nervosa After Partial Weight Restoration: A Longitudinal fMRI Study

“…Further, it remains unclear how treatment-related changes in DMN activation during DD might be related to the observed clinical improvements as no correlations were found. As previously implied by Decker et al [16], however, the lack of correlation between the measures of DD and the clinical variables might be partially attributable to the monetary rewards used in our paradigm and future research, including disorder-relevant stimuli [64], which might be more informative in this respect [12]. Last but not the least, differentiating between state and trait effects is one of the challenges in AN research.…”

“…Importantly, however, the fMRI analysis targeting brain regions involved in executive decision-making (regessor 1) revealed less deactivation in the core nodes of the "task-negative" DMN at follow-up relative to baseline (TP2 > TP1). This finding is relevant not only to the literature on reward-based decision-making (including DD) in AN [7,60,61], but also to the greater functional neuroimaging literature in the disorder [10,[62][63][64], for at least three reasons. First, the "task-negative" DMN regions in which longitudinal changes were observed (medial prefrontal cortex, posterior cingulate/precuneus, inferior parietal lobule) highly overlapped those in which we previously found abnormally decreased activation (i.e., greater deactivation) in acAN-T1, in comparison to HC, using the same analysis [40].…”

Evaluation of spontaneous regional brain activity in weight-recovered anorexia nervosa

“…The inferior temporal gyrus as part of the ventral visual stream is involved in higher-order object processing 55 . Multiple fMRI studies have revelaed alterations in this pathway both at rest and during visual presentation of face, food or body stimuli in adult AN and individuals with body dysmorphic disorder 34,[56][57][58][59][60][61][62] . Interestingly, the infertior temporal gyrus also shows similar alteration in fALFF values in individuals with autism spectrum disorder 63 , who share deficits in social cognition 64,65 .…”

A Neglected Topic in Neuroscience: Replicability of fMRI Results With Specific Reference to ANOREXIA NERVOSA

“…However, the design and the results differed between the included studies. Three further reviews confirmed these inconsistencies ( 6 – 8 ) and therefore conclusions remain questionable. None of the studies were confirmed by replication, so the reported findings should not yet be regarded as established scientific knowledge.…”