Brain Imaging Studies
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The cause of eating disorders is thought to be complex and influenced by psychological, cultural, and biological factors. However, the exact nature of these interactive processes remains unclear. The search for biological factors which may contribute to vulnerability for developing anorexia and bulimia nervosa is the focus of our research. Better understanding of the biological contribution to eating disorders might inform and improve both prevention and treatment efforts.
Studies of Brain Neurotransmitter Activity
The nerve cells in the brain use neurotransmitters, which are chemicals, to send messages to each other. Studies of these chemicals may help us learn more about disturbances of appetite, weight, and behavior. Many people who have eating disorders have problems with depression, anxiety, and obsessions, in addition to alterations in eating patterns. One way of looking at this association between depression, anxiety, and abnormal eating patterns is to see if these problems represent some change in the activity of certain chemicals in the brain. Chemicals that may be of particular importance are the neurotransmitters serotonin and dopamine. These neurotransmitters have been linked to the control of hunger as well as depression, anxiety and obsessions, physical activity, and reward. Moreover, other studies have suggested that serotonin and dopamine may play a role in anorexia and bulimia nervosa.
Positron Emission Tomography (PET) Studies Investigating Serotonin and Dopamine Function in Anorexia Nervosa and Bulimia Nervosa
One problem in trying to determine if alterations in brain mechanisms are related to eating disorders is that studying chemicals in peoples' brains has been very difficult until recently. Now, the technology of Positron Emission Tomography (PET) allows us to more clearly assess the activity of serotonin and dopamine in the brain. PET scanning produces images that show changes in brain chemistry which may be associated with eating disorders.
More specifically, we are looking at the receptors for the serotonin system. Serotonin and dopamine molecules are secreted by neurons in the brain and work by stimulating specific receptors on other neurons. In this way, the neurons in the brain can communicate with each other. The receptors that we are investigating are called serotonin1A, serotonin2A, and dopamineD2. In addition, we are investigating the serotonin transporter, which is a component of the serotonin system that increases the amount of serotonin in neurons.
Our research studies use PET images to examine if there are differences in serotonin and dopamine pathways in women who have suffered from eating disorders and those who have never had an eating disorder. By studying these differences, we hope to better understand the neurobiology of anorexia nervosa and bulimia nervosa.
Functional Magnetic Resonance Imaging (fMRI) of Anorexia or Bulimia Nervosa
Another new technology for understanding the brain is called functional magnetic resonace imaging (fMRI). fMRI is different from PET. While PET imaging can potentially show overall differences in neurotransmitter function, fMRI imaging permits investigations of how brain regions respond to various stimuli, e.g., food. In fact, certain parts of the brain are very important in modulating hunger and fullness. fMRI uses powerful magnetic fields, which magnetize chemicals in the brain. This allows a scanner and computer to take a very detailed picture of the structure and activity of the brain. By utilizing this technology, scientists are able to see changes in blood flow and oxygen use of the brain during eating.