Although anorexia nervosa is categorized as an eating disorder, it is not known whether there are alterations of the portions of the brain that regulates appetite.
Now, a new study finds that women with anorexia have distinct differences in the insulta -- the specific part of the brain that is important for recognizing taste -- according to a new study by University of Pittsburgh and University of California, San Diego researchers currently on line in advance of publication in the journal Neuropsychopharmacology.
The study also implies that there may be differences in the processing of information related to self-awareness in recovering anorexics compared to those without the illness -- findings that may lead to a better understanding of the cause of this serious and sometimes fatal mental disorder.
In the study led by Angela Wagner, M.D., University of Pittsburgh School of Medicine, and Walter H. Kaye, M.D., of the University of Pittsburgh and the University of California, San Diego (UCSD) Schools of Medicine, the brain activity of 32 women was measured using functional magnetic resonance imaging (fMRI.) The research team looked at images of the brains of 16 women who had recovered from anorexia nervosa -- some of whom had been treated at the Center for Overcoming Problem Eating at Western Psychiatric Institute and Clinic of the University of Pittsburgh Medical Center --and 16 control subjects. They measured their brains' reactions to pleasant taste (sucrose) and neutral taste (distilled water.) The results of the fMRI study are the first evidence that individuals with anorexia process taste in a different way than those without the eating disorder.
In response to both the sucrose and water, imaging results showed that women who had recovered from anorexia had significantly reduced response in the insula and related brain regions when compared to the control group. These areas of the brain recognize taste and judge how rewarding that taste is to the person. In addition, while the controls showed a strong relationship between how they judged the pleasantness of the taste and the activity of the insula, this relationship was not seen in those who had recovered from anorexia.
According to Kaye, it is possible that individuals with anorexia have difficulty recognizing taste, or responding to the pleasure associated with food. Because this region of the brain also contributes to emotional regulation, it may be that food is aversive, rather than rewarding. This could shed light on why individuals with anorexia avoid normally "pleasurable" foods, fail to appropriately respond to hunger and are able to lose so much weight.
"We know that the insula and the connected regions are thought to play an important role in interoceptive information, which determines how the individual senses the physiological condition of the entire body," said Kaye. "Interoception has long been thought to be critical for self-awareness because it provides the link between thinking and mood, and the current body state."
This lack of interoceptive awareness may contribute to other symptoms of anorexia nervosa such as distorted body image, lack of recognition of the symptoms of malnutrition and diminished motivation to change, according to Kaye.
Anorexia nervosa is a serious and potentially lethal illness, which may result in death in ten percent of cases. It is characterized by the relentless pursuit of thinness, emaciation and the obsessive fear of gaining weight. Anorexia commonly begins during adolescence, but strikes throughout the lifespan, and is nine times more common in females than in males. These characteristics support the possibility that biological processes contribute to developing this disorder.
Many individual with anorexia nervosa have difficulty obtaining treatment because it is not considered a biological illness.
The research was funded through grants from the National Institute of Mental Health and the Price Foundation.
Co-authors of the study include Howard Aizenstein, Laura Mazurkewicz and Lorie Fischer of the University of Pittsburgh School of Medicine; Julie Fudge of the University of Rochester Medical Center; Guido K. Frank of the University of Pittsburgh School of Medicine and University of California, San Diego; Karen Putnam of the University of Cincinnati; and Ursula F. Bailer of the University of Pittsburgh School of Medicine and Medical University of Vienna.
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