[Reading Science] Binge Eating After Dieting Caused by Brain Circuit Abnormalities

Research Team at Stanford University School of Medicine Observes Changes in Brain Areas Related to Habit Formation

A study has found that eating disorders such as bulimia, which women commonly suffer from as a post-dieting aftereffect, are related to the brain's habit formation areas.

A research team from Stanford University School of Medicine published this study in the international journal Science Translational Medicine on the 29th of last month. According to the international journal Nature, human habitual behaviors are usually triggered by external factors, much like reaching for a seatbelt immediately after getting into a car. Scientists have confirmed through previous studies observing the brains of rats that a specific brain region called the striatum is involved in such habitual behaviors. However, it had not yet been clarified whether a similar structure exists in the human brain.

Binge eating disorder. Stock photo. Not related to the article.

The research team focused on the area connected to the striatum in the rat brain. They then used high-resolution magnetic resonance imaging (MRI) data from 178 participants in the Human Connectome Project, a program aimed at mapping the human brain, to conduct their study. The goal was to identify whether the human brain has structures that play a similar role to the rat's striatum. Through this, the team identified the sensorimotor putamen and associative caudate as candidate regions. Subsequently, they investigated whether these two areas were activated when eating disorders occurred in 34 female subjects.

The results revealed that the brains of individuals with eating disorders such as bulimia showed changes in these two regions compared to those without such disorders. The structure of the gray matter was altered, and changes in dopamine signaling were detected in the sensorimotor putamen. Additionally, the connectivity between the sensorimotor putamen, which reinforces habits, and parts of the cerebral cortex was much stronger than normal. Conversely, connectivity with the anterior cingulate cortex (ACC), part of the frontal cortex, was weakened, while the connection between the orbitofrontal cortex and motor cortex increased. Laura Berner, a professor of neuropsychiatry at Icahn School of Medicine at Mount Sinai in New York, USA, evaluated, "This study adds evidence suggesting that brain circuits related to the sensorimotor putamen are linked to binge-eating behavior."

The research team speculates that these brain behavior changes are related to dopamine, a neurotransmitter secreted in response to rewards. They hypothesize that the brains of people with eating disorders such as bulimia have undergone changes due to repeated exposure to rewards. In fact, the sensorimotor putamen in their brains had fewer dopamine receptors compared to healthy individuals. The team suggests that decreased dopamine secretion may have dulled the sensitivity of dopamine receptors and reduced their numbers.

Although the team cannot definitively state that the sensorimotor putamen and associative caudate found in the human brain are involved in habit formation exactly like the striatum in rats, they believe that at least a new pathway for researching this has been opened. This is particularly seen as providing clues for new treatments for people suffering from eating disorders and binge eating.

Allen Wang, a researcher at Stanford University School of Medicine who led the study, said, "This research result could open the way for new treatments targeting specific brain regions for diseases like eating disorders using technologies such as deep brain stimulation or transcranial magnetic stimulation. I believe that in the future, many neuropsychiatric treatment techniques will directly target brain circuits."