| Impulsivity presents as a common symptom or characteristic of many mental illnesses. Although the neuropathology underlying most of these illnesses remains uncertain, the common feature of poor impulse control suggests that these patient populations may suffer from a compromise in structure or function of specific cortical networks. In search of a common affected brain circuit or region, this dissertation aims to explore cortical thickness and function in three impulse control disorder populations. The research presented in this dissertation involves the use of structural and functional magnetic resonance imaging (sMRI and (MRI, respectively) to investigate the neural substrates of impulsivity by (a) studying differences in cortical thickness of patients with deficits in impulse control where study groups include (1) violent individuals diagnosed with antisocial personality disorder (APD) or schizophrenia (SZ) and (2) obsessive-compulsive disorder (OCD) patients and demographically similar healthy comparison subjects, and by (b) investigating differences in brain activation associated with a response inhibition task and a risky decision-making task between an impulse control disorder population of pathological gamblers and controls.;The first study revealed that violent behavior was associated with cortical thinning in the right inferior mesial cortices in individuals with APD. This suggests that this region is important for decision making and impulse control which may underlie these subjects' violent behaviors. The second study showed that individuals with OCD had cortical thickening in the right inferior frontal cortex (rIFC), suggesting a site of pathology associated with their repetitive thoughts and behavior. Finally, compared to non gamblers, PGs showed less impulse control related activation in the rIFC when inhibiting a response on the Stop Signal Task and more mesial prefrontal cortical and accumbens activation when expecting a reward on the Balloon Analog Risk Task. These results suggest a possible network of pathology related to their impulsivity and addiction to gambling. Overall our findings suggest a general area of common pathology seated in the right frontal cortices that may contribute to impulse control problems in our three impulse control disorder groups. This fits well in the literature, as the rIFC has been shown to be very important for impulse control and response inhibition in the normal population. |
