Skip to 0 minutes and 7 secondsThere are many reasons that led neuroscientists to investigate eating disorders. For instance, cognitive neuroscientists are interested in high-level functions, such as consciousness, self-image and reward systems, while dysfunctional emotion processing, and its substrates in the brain, Are of interest to clinical psychologists and psychiatrists. The variety of interests and of possible tools led to different approaches in research, but many studies use neuroimaging techniques – tools that allow us to measure brain volume,or metabolic brain activity, through indirect measures.
Skip to 0 minutes and 53 secondsThere 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 substantial agreement between neuroimaging studies on the fact patients with anorexia nervosa show a decrease of their global brain volume. Both the gray matter – where the neuron body 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 global volume decrease.
Skip to 1 minute and 48 secondsGlobal changes In brain volumes therefore seem to be linked to prolonged periods of calorie restriction and failure to maintain a healthy weight. Is the volume decrease reversed in recovered patients? Is there any difference in the effects that anorexia can have on a developing brain, like the one of an adolescent, and on an adult brain? Luckily, it seems that adults that fully recover from anorexia nervosa also increase their brain volumes, to the point that there aren’t differences between a group of patients who recovered from their eating disorders and healthy control subjects. However, this might not be the case for adolescents, as a study found that after six months recovering subjects still showed decreased gray matter volumes.
Skip to 2 minutes and 47 secondsThese 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 grey 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 fluid. 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. While only anorexia nervosa is linked to global changes in brain volumes, both anorexia and bulimia are linked with changes in specific areas.
Skip to 3 minutes and 45 secondsShifting 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 in eating disorders has been investigated with neuroimaging techniques. While there is a large variability in the studies, it seems that patients with anorexia nervosa and bulimia nervosa have “symmetric” alterations of it.
Skip to 4 minutes and 33 secondsFor instance, a study found lower response to repeated subministration of a sweet taste in the striatum of anorexic patients, but a higher response in the case of bulimic patients. Neuroimaging of the reward system could then provide a clearer picture of the roles played by it and by dopamine pathways in eating disorders. This is of particular interest to neuroscientists, as studies using different techniques already revealed an altered functioning of the dopaminergic system in anorexia and in bulimia, And evidence coming from different approaches could lead to a complete picture and to new therapeutic approaches.
Skip to 5 minutes and 20 secondsFor 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 Unfortunately the picture is not clear – on one hand, studies show that medications, such as olanzapine, that blocks 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 other antipsychotics and antidepressants, including olanzapine, induce an increase in body weight both in anorexic and non anorexic patients.
Skip to 6 minutes and 4 secondsIn fact, increased weight is often included in the side effects of this class of drugs.unfortunately, we are still far from the discovery of the perfect therapy for anorexia nervosa and eating disorders in general. Luckily, thousand of scientists coming from very different backgrounds are at work, day in and day out, to understand the mechanisms that cause these serious disorders.
Neuroimaging of eating disorders
How do eating disorders affect our brain?
In the last decades, 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.
In this video, we will discuss some neuroimaging studies of eating disorders, before moving to the last steps of this activity: a poll and a discussion about the role of society in causing eating disorders.