Altered Reward Processing After Recovery from Anorexia Nervosa

Individuals who have recovered from anorexia nervosa (AN) may have difficulty differentiating positive feedback from negative feedback, according to the results of a recent study (Am J Psychiatry 2007; 164:1842). Women with AN are known to be able to sustain self-denial of food as well as most comforts and pleasures in life. Previous studies have shown that patients with AN have changes in striatal dopamine binding.

A team of researchers sought to test the response of the brain’s anterior ventral striatum to reward and loss among patients with AN by giving them a simple monetary reward task, and then measuring the responses on functional magnetic resonance imaging (MRI). When Angela Wagner, MD and her colleagues conducted the study among 13 healthy comparison women and 13 women who had recovered from restricting-type AN, MRI differences appeared between the two groups. To avoid the confounding effects of malnutrition, the women who had recovered from AN had a year of normal weight and regular menstrual cycles, with no binge eating or purging.

The group who had recovered from AN showed greater brain activity on the MRI scans than did the healthy comparison women. Only the recovered women showed a significant positive relationship between trait anxiety and percentage of change in hemodynamic signals in the caudate during either wins or losses. The women in the comparison group could distinguish positive and negative feedback, but the recovered patients had similar responses to either condition.

The exaggerated activation of the caudate, a region of the brain involved in linking action to outcome, may constitute an attempt at “strategic” (instead of hedonic) means of responding to a reward, according to the authors. Dr. Wagner and colleagues hypothesize that individuals with AN have an imbalance in information-processing, and an impaired ability to identify the emotional significance of a stimulus. They do have increased “traffic” in the neurocircuits concerned with planning and consequences.