Women with bulimia nervosa (BN) respond more impulsively during psychological testing than do women without eating disorders, according to a recent article in Archives of General Psychiatry.1 Functional MRI showed differences in brain areas responsible for regulating behavior in women with and without BN.
Rachel Marsh, PhD, and colleagues at Columbia University and the New York State Psychiatric Institute compared the results of the Simon Spatial Incompatibility task in 40 women (20 with and 20 without BN) who were undergoing functional MRI. Participants were asked to indicate on a response box the direction an arrow was pointing while wearing nonmagnetic goggles, regardless of where it appeared on the screen. The act of focusing on the arrow and ignoring the rest of the screen requires regulating behavior by fighting the tendency to respond automatically and resolving conflicting messages.
Patients with BN were more impulsive than controls: they responded more quickly and made more errors in the parts of the task that required self-regulatory control. Patients with the most severe symptoms made the most errors. The frontostriatal circuits in the left inferolateral prefrontal cortex, bilateral inferior frontal gyrus, lenticular and caudate nuclei, and anterior cingulate cortex were not activated in patients with BN as they were in the control group. When patients with BN made errors, there was an increase in dorsal anterior cingulate cortex activation. In contrast, when healthy participants responded correctly there was an increase in anterior cingulate cortex activation, and when the healthy controls responded incorrectly there was an increase in striatum activation.
The authors concluded that self-regulation in women with BN is impaired because they cannot appropriately engage frontostriatal circuits. The authors noted several confounders in their study, including menstrual status; lack of inclusion of otherwise healthy but impulsive persons in the control group; and not including adolescents with BN. They called for future, larger studies that would take these factors into account.
1. Marsh R, Steinglass JE, Gerber AJ, et al. Deficient activity in the neural systems that mediate self-regulatory control in bulimia nervosa. Arch Gen Psychiatry. 2009;66:51-63.