on delay-discounting tasks. This model corresponds to impulsive choices made during delay-discounting tasks, defined by choosing smaller-sooner reinforcers over larger-later reinforcers. A comparative factor analysis has demonstrated that each task assesses variance unique to that particular task (Dougherty et al. 2003a, p. 1153). In addition to these theoretical distinctions, there are also unique neuroanatomical processes that further support a distinction between tasks. When performing CPT tasks, brain activation occurs in the inferior and medial prefrontal cortex, and the inferior parietal cortex (Garavan et al. 1999). When performing stop tasks, brain activation occurs in the right medial, mesial, and inferior frontal cortex, and the left caudate nucleus (Aron et al. 2003; Casey et al. 2002; Rubia et al. 2001). For delay-discounting tasks, Bechara (2005) has proposed that a dynamic interaction exists between the amygdala and the ventral medial prefrontal cortex (including Brodmann’s areas in the medial orbitofrontal cortex). This interaction is supported by imaging studies, which have shown that brain activation during the performance of this task occurs in the orbitofrontal cortex, along with activation of the striatum (Rogers et al. 2004).
