Imaging Study on Women with Anorexia Nervosa

"Sense of Taste Different
in Women with Anorexia Nervosa" 
Imaging Study Finds Brain Changes Associated with the Regulation of Appetite .
September 25, 2007
By Debra Kain

Although anorexia nervosa is categorized as an eating disorder, it is not known whether there are alterations of the portions of the brain that regulate appetite. Now, a new study finds that women with anorexia have distinct differences in the insula – 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. 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.


Why does this study hold significance?

Anorexia Nervosa is a disorder of unknown etiology. The stigma that has lastingly attached itself to the disease supports that psychological reasons are responsible for the birth of the disorder. Despite this, it is being questioned whether individuals afflicted with anorexia, have a primary disturbance of pathways that modulate feeding, or if disturbed appetite is secondary to psychological elements of the disease such as anxiety, and an obsession with weight gain. Through this case study, we are able to see that the controlled women acknowledged a pleasant relationship with the ingestion of sucrose and their signal activity supported that as well. Conversely, the recovered anorexics of this study possessed no relationship between the pleasantness of sugar’s taste and any brain region. Both groups showed no anxiety or pleasantness of the taste of water in relation to any brain region. These results support the hypothesis that recovered anorexics have disturbances in their taste processing via the central nervous system. We see that the insula can assert the value of taste stimuli and consequently influence how that stimuli affect’s the state of the human body. If an anorexic cannot distinguish her feelings towards particular foods—if she experiences no neurological reward or taste value—it is easier for her to fall into disordered eating habits, especially if she has psychological instabilities that would only strengthen her resistance to food. Essentially, this study was the first of its kind in showing that there is a disturbance in the insula and other primary taste regions of the brain in anorexics, which in turn can help professionals potentially treat Anorexia Nervosa in a more inclusive way.

http://www.nytimes.com/2007/02/06/health/psychology/06brain.html

The link above has a more specified article on the insula, and an interesting diagram to match, if anyone wants more background information on the insula.

Other Sources:

www.neuropyschopharmacology.org
"The Mind Has a Body of its Own," by Sandra and Matthew Blakeslee.