Abstract

The association between orbital frontal cortex (OFC) volume and aggression and impulsivity was investigated among a heterogeneous group of non-psychotic psychiatric clients. Fifteen non-psychotic subjects from two different psychiatric clinics (New England Medical Center and Lemuel Shattuck Hospital) with a variety of diagnoses were sequentially referred for magnetic resonance imaging (MRI) for clinical purposes. This convenience sample, clinically stable at the time of evaluation, received a standardized psychiatric diagnostic interview, aggression and impulsivity psychometrics (Barratt Impulsivity, Lifetime History of Aggression, and Buss-Perry Aggression scales), and an MRI protocol with image analysis. OFC gray matter volume, total as well as left and right, was significantly and positively associated with motor impulsivity. OFC asymmetry was associated with aggression, though total, left, and right OFC volume measurements were not. For subjects without affective disorder, there was a strong and positive association of the OFC to motor and no-planning subscales of the Barratt Impulsivity Scale. For subjects with affective disorder, there was a strong association of OFC asymmetry to both of the aggression psychometrics. Consistent with expectation, results are suggestive of OFC involvement in the neural circuitry of impulsivity and aggression. The findings suggest a dissociation of the role of the OFC in relation to aggression and impulsivity, such that the OFC may play a part in the regulation of aggressive behavior and a generative role in impulsive behavior.