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Anorexia nervosa, diet restriction model, activity-based anorexia model, mesolimbic reward circuitry, habit-centered model.
Anorexia nervosa is an eating disorder characterized by persistent, restricted food intake which leads to drastic weight loss, and has the potential of leading to death. It disproportionately affects young females and has a peak onset age between 14 and 18 years old. The significance of studying this disorder is highlighted by the fact that young women with anorexia nervosa have the highest mortality rate in their age group, and of those suffering other psychiatric disorders. Anorexia nervosa, however, presents an enigma for researchers. It has many clinical symptoms, an unknown complex etiology and the added lack of a comprehensive animal model that can be used for therapeutic research. This minireview presents two animal models that are currently used by researchers, the diet restriction model and the activity-based anorexia model. The diet restriction and the activity-based anorexia models recapitulate characteristics of anorexia nervosa as the physiological and cognitive effects of reduced food intake, and hyperactivity and self-induced starvation, respectively. There are two neurobiological models of anorexia nervosa, the reward-centered model and the habit-centered model. The reward-centered model is based on evidence from neuroimaging studies that show increased activity in the mesolimbic reward circuitry in anorexia nervosa patients associated with reduced food intake. The habit-centered model of anorexia nervosa developed from evidence of functional connectivity between the dorsal striatum and the dorsolateral prefrontal cortex. The frontostriatal circuitry is associated with habit formation and led to understanding of reduced food intake as a learned behaviour.