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Anorexia nervosa is characterized by anxiety-driven behaviors, such as food avoidance and distressing persistent thoughts about weight gain and body image. The present study used a classical fear conditioning procedure to test the processes of fear acquisition and generalization, extinction, and renewal in patients with anorexia nervosa and healthy controls. An app-based fear conditioning procedure was administered remotely to 64 patients and 60 healthy controls, over two sessions. A human female scream served as the unconditioned stimulus (US) and two neutral shapes were used as either the paired conditioned stimulus (danger cue; CSþ) or the unpaired conditioned stimulus (safe cue; CSÀ). Patients with anorexia nervosa reported greater threat expectancy in response to the danger cue during the extinction and renewal phases and overall higher levels of negative affect throughout the task, compared with controls. Future research is warranted to replicate these findings and highlight the role that anxiety plays in explaining fear conditioning responses in patients with anorexia nervosa. General Scientific SummaryThis preliminary study investigated fear conditioning in anorexia nervosa. Patients with anorexia nervosa had greater threat expectancy in response to stimuli previously associated with a loud scream, even when the stimuli were no longer presented with the scream. If replicated, these results might contribute to explaining patients' difficulties to extinguish fear in relation to eating and its consequences.
Purpose of Review In recent years, the food addiction hypothesis of loss-of-control eating has gained traction in the field of eating disorders. In particular, the neural process of food addiction plays a dominant role in the recently formulated "addictive appetite" model of bulimia nervosa and binge eating disorder. Nonetheless, several components of the food addiction hypothesis, including the presence of withdrawal and tolerance effects, as well as the proposition that some foods possess "addicting" properties, remain highly controversial. In response, the current review synthesises existing evidence for withdrawal and tolerance effects in people with bulimia nervosa. Recent Findings The recent development of a validated tool to measure withdrawal from highly processed foods will aid in measuring withdrawal symptoms and testing hypotheses related to withdrawal in the context of food addiction. We subsequently describe preclinical and human evidence for a central insulin-and dopamine-mediated pathway by which recurrent loss-ofcontrol binge eating is maintained in bulimia nervosa. Summary Evidence in populations with bulimia nervosa and loss-of-control eating provides preliminary support for the role of food addiction in the maintenance of bulimia nervosa. Future longitudinal research is needed to develop a clearer profile of illness progression and to clarify the extent to which dysregulation in glucose metabolism contributes to food craving and symptom maintenance in bulimia nervosa.
Background There is extensive evidence for volumetric reductions in the hippocampus in patients with anorexia nervosa (AN), however the impact on function is unclear. Pattern separation and recognition are hippocampus-dependent forms of learning thought to underlie stimulus discrimination. Methods The present study used the Mnemonic Similarity Task to investigate pattern separation and recognition for the first time in patients with AN (N = 46) and healthy controls (N = 56). An Analysis of Covariance examined between-group differences, controlling for age, antidepressant use and method of task delivery (remote vs. in person). Results When controlling for covariates, pattern recognition memory scores were lower in the AN group with a medium effect size (d = 0.51). In contrast, there was a small effect whereby patients with AN had a greater pattern separation score than controls (d = 0.34), albeit this difference was not significant at the p = 0.05 threshold (p = 0.133). Furthermore, pattern separation and recognition memory abilities were not related to age, body mass index, eating disorder psychopathology or trait anxiety levels. Conclusions This preliminary study provides initial evidence for an imbalance in pattern separation and recognition abilities in AN, a hippocampus-dependent cognitive ability. Further studies should endeavour to investigate pattern separation and recognition performance further in AN, as well as investigate other hippocampus-dependent functions.
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