Bulimia linked to brain circuit abnormalities

Jan 6 2009

Scientists in the U.S. are suggesting that women who suffer from bulimia nervosa may have an abnormality in the brain circuit.

The researchers from Columbia University and the New York State Psychiatric Institute, say brain scans of those with eating disorders show differences in the areas responsible for regulating behaviour during psychological testing.

Bulimia nervosa mainly affects females and often starts in adolescence or early adulthood and is characterized by recurrent episodes of binge eating followed by self-induced vomiting or another compensatory behaviour to avoid weight gain.

Experts believe these episodes of binge eating are associated with a severe sense of loss of control.

Dr. Rachel Marsh and her colleagues compared the performance of 20 women with bulimia nervosa with that of 20 healthy women in a psychological test on a computer while undergoing functional magnetic resonance imaging (fMRI).

The test checked pathways between nerve cells known as frontostriatal circuits which help individuals control their own voluntary behaviours. The test, the 'Simon Spatial Incompatibility task', requires that participants indicate the direction an arrow is pointing regardless of where it appears on a screen.

The task is easier when the arrow direction matches the side of the screen, but more difficult when, for instance, an arrow that points leftward appears on the right side of the screen.

Ignoring the side of the screen to focus on the arrow direction requires regulating behaviour by fighting the tendency to respond automatically and resolving conflicting messages.

The researchers say patients with bulimia nervosa were far more impulsive than the others and responded faster and made more errors on conflict trials that required self-regulatory control to respond correctly.

The researchers say the differences in performance and patterns of brain activity suggest that individuals with bulimia nervosa do not activate frontostriatal circuits appropriately and this inability contributes to their inability to regulate binge-type eating and other impulsive behaviours.

They say research in future should try to test this hypothesis by including impulsive individuals who have healthy weights and eating behaviours.

The research is published in the current issue of the Archives of General Psychiatry.