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Neuroimaging of eating disorders

In this video from the Università di Torino we will briefly discuss some neuroimaging studies of eating disorders.
There are many reasons that led neuroscientists to investigate eating disorders. Some researchers are interested in high-level functions such as consciousness, self-image and reward systems, while others focus on the areas of the brain linked to life memories and emotion processing. The variety of interests and of possible tools led to the adoption of many approaches, but many studies use imaging techniques, tools that allow us to measure brain volume or metabolic brain activity through indirect measures. There are some questions that neuroimaging
seeks to answer: is there a decrease in the brain volume in eating disorders, is it linked to a single disorder such as anorexia and, if there is a decrease, is it focused on specific areas or we can imagine it as a global “shrinking” of the brain? There is a substantial agreement between neuroimaging studies on the fact that patients with anorexia nervosa show a decrease of their global brain
volume: the gray matter, where the neuron bodies are more densely packed and the white matter, composed of axons bundles connecting different areas, are affected. In contrast, patients with bulimia nervosa or binge eating disorder do not show the same decrease in brain volume. This change could, therefore, be linked to prolonged periods of calorie restriction and failure to maintain a healthy weight, but can it be reversed in patients that recovered from the illness? Luckily, it seems that adults that fully recover from anorexia nervosa also recover their brain volumes.
These results are very interesting: they show us that the brain is affected by anorexia, but the changes are likely not due to the death of neurons. We can reach this conclusion because, in the brain, neurons that die aren’t replaced. The changes in gray matter volume must then depend on other factors, such as the loss of the connections between neurons, or to an imbalance in salts dissolved in bodily fluids. When an adequate caloric intake is restored connections can be formed again, the synthesis of neurotransmitters fully resumes and the chemical environment of the brain returns to normality.
Shifting our focus to local variations allows us to identify brain areas that could have a role in causing eating disorders or that are particularly affected by them. One example is the insula, whose activity is linked to emotions such as fear and disgust, to the sensing of one’s own body, to the perception of tastes and to the reward system. The brain reward system is of great interest in relation to eating disorders and it was studied intensively using neuroimaging techniques. For instance, a study found that repeated administration of a sweet liquid caused a decreased response in the striatum of anorexic patients, but a higher response in the one of bulimic patients.
This is of particular interest to neuroscientists, as studies using different techniques already revealed an altered functioning of the dopamine system in anorexia and in bulimia, and evidence coming from front approaches could lead to a complete picture and to new therapeutic approaches. For instance, if there is an alteration of the dopaminergic system in eating disorders we could hope that restoring them to normality could lead to a quicker recovery.
However, the picture is still not clear: on one hand studies show that medications, such as olanzapine, that block the dopamine receptors in the brain can increase the bodily weight of the patients and reduce pathological thoughts related to eating. On the other hand, many antipsychotics and antidepressants, including olanzapine, induce an increase in body weight both in anorexic and non-anorexic patients. Unfortunately, we are still far from the discovery of the perfect therapy for anorexia nervosa and eating disorders in general. Luckily, thousands of scientists coming from very different backgrounds are at work day in and day out to understand the mechanisms that cause these serious disorders and to find new pharmacological and psychotherapeutic therapies.

How do eating disorders affect our brain?

In the last decade, neuroscientists started investigating the effects of anorexia nervosa and bulimia nervosa on the brain, trying to find the answer to a few key questions. For instance, they were (and still are) interested in the possible loss of brain volume in patients with anorexia nervosa and in its recovery once the eating disorder is treated.

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