Persistent brain abnormalities in women with anorexia, even in those recovered (maintaining a healthy weight for a period of a year) may play a vital role in the high relapse rate for this disorder. According to a study at the University of Pittsburg and published in the American Journal of Psychiatry, anorexics show a decreased ability to differentiate between winning and losing, not fully experiencing immediate pleasure and so possibly not appreciating the positive feelings associated with food.
The study consisted of 13 women who had recovered from anorexia, had maintained healthy weight, and had regular menstrual cycles for at least a year, and 13 healthy women. Comparing fMRI (Functional Magnetic Resonance Imaging) results of non Anorexics with recovered Anorexics during a guessing game showed reduced function in the anterior ventral striatum and excessive firing of circuits in the caudate.
“The high activity in the caudate probably reflects a heightened attempt to control the test situation. Unlike the normal controls, the anorexic women still thought they could find a way to control the outcome of the psychological challenge, even though this was impossible," said Dr. Angela Wagner.The game: Guess if a number higher or lower than 5 was represnted by a flashing question mark on a computer screen. Correct answer; win $2. Incorrect answer; forfeit $1
Formerly anorexic women showed much more activity in the caudate regions during the game then the control group, leading Dr. Wagner to suspect that those with a history of anorexia nervosa focused excessively on the consequences of their choices, noting that anorexics are overly anxious and obsess about doing things the right way.
According to another fMRI study at the University of Pittsburg, anorexics' sense of taste differes from non-anorexics. Responses to sucrose (pleasant taste) and water (neutral taste) were measured. Imaging showed the response to both sucrose and water were significantly reduced in the insula and other related brain regions when compared the non-anorexic control group, making it possible that those with anorexia may have difficulty recognizing taste or experiencing the pleasure associated with it. This same region of the brain contributes to the regulation of emotions which may explain why some anorexics don't respond to hunger and avoid what is normally considered pleasurable foods."The investigators believe that the results of this study indicate that healthy women respond to wins and losses by “living in the moment” and moving on to the next task. However, the women with a history of anorexia were unable to do this."
“Our study shows a biological background to the disease of anorexia nervosa,” commented Dr. Wagner. “It is not just a result of environmental influences. In the past, our approach as clinicians was to focus on behavior and on getting patients to eat. The functional studies suggest that perhaps we should also focus on mindset, on finding ways to train these patients to accept change and to experience pleasure. A logical next step also would be to study neurotransmitters, especially dopamine, and try to understand the differences we identified in brain circuits. This might, in turn, point the way to a new approach to pharmacologic therapy for anorexia nervosa.”
One question is whether these brain changes predate and predispose patients to anorexia nervosa or whether the changes are a “scar” in the brain resulting from past malnutrition and weight loss. The researchers are now using fMRI to study brain function in similar challenge situations in women with current anorexia nervosa.
"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.
sources:http://www.neuropsychiatryreviews.com/08jan/brainfunction.html
andhttp://www.psychologyandwellbeing.org/pn/modules.php?name=News&file=article&sid=150 picturesource:http://math.lbl.gov/~deschamp/png/myBrain.png
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