Female patients with bulimia nervosa seem to respond more impulsively in psychological tests in comparison to patients without eating disorders, according to a report released on January 5, 2008 in Archives of General Psychiatry, one of the JAMA/Archives journals. Additionally, functional magnetic resonance imaging brain scans of these patients show different activities in the areas responsible for regulating behavior.
Bulimia nervosa is an eating disorder “characterized by recurrent episodes of binge eating followed by self-induced vomiting or another compensatory behavior to avoid weight gain,” the authors write. It often occurs in females and begins in the adolescent or young adult years. The authors continue: “These episodes of binge eating are associated with a severe sense of loss of control.”
Frontostriatal circuits are pathways between nerve cells in the brain that allow individuals to control voluntary behaviors. These can be tested in the Simon Spatial Incompatibility task, in which a subject indicates the direction of an arrow regardless of its location on a screen. If the arrow points in the direction corresponding with its location on the screen, this is simple, but when there is dissonance between the directions, the subject must voluntarily ignore the extraneous information to resolve the conflict.
To investigate the behavior of these circuits in patients with bulimia, Rachel Marsh, Ph.D., and colleagues at Columbia University and the New York State Psychiatric Institute, New York, examined 20 women with bulimia and 20 healthy control females under functional magnetic resonance imaging (fMRI) while performing the Simon Spatial Incompatibility task.
The authors summarized the results as follows: “Patients with bulimia nervosa exhibited greater impulsivity than did control participants, responding faster and making more errors on conflict trials [where the arrow direction and location did not match] that required self-regulatory control to respond correctly,” they write. “They responded faster on congruent trials following incorrect conflict trials, suggesting impulsive responding even immediately after having committed an error.” Patients with bulimia generally, when responding correctly in a mismatched arrow, had less activation in their frontostriatal circuits than women in the control group.
The authors conclude that these differences in frontostriatal circuit activity could be significant. “These group differences in performance and patterns of brain activity suggest that individuals with bulimia nervosa do not activate frontostriatal circuits appropriately, perhaps contributing to impulsive responses to conflict stimuli that normally require both frontostriatal activation and the exercise of self-regulatory control to generate a correct response,” they write. “We speculate that this inability to engage frontostriatal systems also contributes to their inability to regulate binge-type eating and other impulsive behaviors.”
They further note that future investigations should include other populations, including impulsive individuals with healthy weights and eating behaviors, adolescents near the age of average bulimia nervosa development, and patients with varying symptom severity.
Deficient Activity in the Neural Systems That Mediate Self-regulatory Control in Bulimia Nervosa
Rachel Marsh, PhD; Joanna E. Steinglass, MD; Andrew J. Gerber, MD; Kara Graziano O’Leary, MA; Zhishun Wang, PhD; David Murphy, MSci; B. Timothy Walsh, MD; Bradley S. Peterson, MD
Arch Gen Psychiatry. 2009;66(1):51-63.
Written by Anna Sophia McKenney