Olfactory function and alternation learning in eating disorders

Edmond and Lily Safra Children's Hospital, Chaim Sheba Medical Center, Tel Hashomer, Israel.
European neuropsychopharmacology: the journal of the European College of Neuropsychopharmacology (Impact Factor: 4.37). 07/2012; 22(9):615-24. DOI: 10.1016/j.euroneuro.2011.12.006
Source: PubMed


Orbitofrontal dysfunction is a prominent feature of obsessive compulsive disorder (OCD). In the present study we assessed orbitofrontal functioning in eating disorders (EDs) which share many features with OCD. For this purpose we studied female adolescent inpatients with anorexia nervosa restricting type (n=40), anorexia nervosa binge/purge type (n=23), a normal weight group including patients with either bulimia nervosa or eating disorder not otherwise specified-purging type (n=33), and 20 non-ED control females. Patients were assessed at admission, and when achieving weight restoration and symptom stabilization at discharge, for depression, non-ED, and ED-related OC symptoms. Orbitofrontal functioning was assessed with an alternation learning task, and with a battery assessing olfactory threshold and discrimination. Control females were assessed once. ED patients of all subtypes performed better on olfactory threshold and discrimination, but not on alternation learning, in comparison to healthy controls. More favorable orbitofrontal functioning was associated with greater ED-related obsessionality. No changes were found in olfactory threshold and discrimination between acutely-ill and symptomatically-stabilized patients. The improvement shown in alternation learning from admission to discharge was suggested to reflect a learning effect rather than being an actual change. Our findings suggest that the better orbitofrontal functioning of ED patients in comparison to healthy controls may represent a core feature of the ED that is independent of malnutrition and deranged eating behaviors, but is associated with ED-related obsessionality.

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    ABSTRACT: Objective: The pathophysiology of anorexia nervosa remains obscure, but structural brain alterations could be functionally important biomarkers. The authors assessed taste pleasantness and reward sensitivity in relation to brain structure, which may be related to food avoidance commonly seen in eating disorders. Method: The authors used structural MR imaging to study gray and white matter volumes in women with current restricting-type anorexia nervosa (N=19), women recovered from restricting-type anorexia nervosa (N=24), women with bulimia nervosa (N=19), and healthy comparison women (N=24). Results: All eating disorder groups exhibited increased gray matter volume of the medial orbitofrontal cortex (gyrus rectus). Manual tracing confirmed larger gyrus rectus volume, and volume predicted taste pleasantness ratings across all groups. Analyses also indicated other morphological differences between diagnostic categories. Antero-ventral insula gray matter volumes were increased on the right side in the anorexia nervosa and recovered anorexia nervosa groups and on the left side in the bulimia nervosa group relative to the healthy comparison group. Dorsal striatum volumes were reduced in the recovered anorexia nervosa and bulimia nervosa groups and predicted sensitivity to reward in all three eating disorder groups. The eating disorder groups also showed reduced white matter in right temporal and parietal areas relative to the healthy comparison group. The results held when a range of covariates, such as age, depression, anxiety, and medications, were controlled for. Conclusion: Brain structure in the medial orbitofrontal cortex, insula, and striatum is altered in eating disorders and suggests altered brain circuitry that has been associated with taste pleasantness and reward value.
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