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Zusammenfassung:
Obesity is associated with approaching rather than avoiding problematic stimuli, such as unhealthy food. This behavior is driven by automatic processing of food cues, making it difficult to inhibit unwanted responses. Obesity therapies mainly focus on explicit knowledge instead of implicit behaviors. In contrast, cognitive bias modification (CBM) aims to alter automatic behaviors by turning problematic approach tendencies into beneficial routines. Underlying mechanisms targeted by CBM in obesity are yet unclear. Candidate mechanisms are (a) altering reward values of food stimuli or (b) strengthening inhibitory abilities. 34 obese individuals completed either a CBM or a sham training during fMRI scanning. The CBM condition consisted of an implicit training to approach healthy and avoid unhealthy food. At baseline, all subjects showed an approach bias towards food. Activity in the right angular gyrus (rAG) was higher when avoiding versus approaching food. This relates to resolving stimulus response conflict and behavioral control. CBM training diminished the behavioral approach bias towards unhealthy food, decreased activation in the rAG, and increased activation in the anterior cingulate cortex. Relatedly, functional connectivity between rAG and the right superior frontal gyrus increased. Further, resting-state fMRI functional connectivity increased between brain regions important for inhibitory control, such as the left middle frontal gyrus, anterior insula and right middle frontal gyrus, but also between the left inferior frontal gyrus and left nucleus accumbens. CBM seems to strengthen behavioral inhibition when faced with unhealthy foods by targeting mostly inhibitory brain regions, thus indicating the efficacy of implicit interventions in obesity.
