addiction. Moreover, there are similarities in behavior between addicted individuals and patients with PFC damage. For example, damage to the human OFC (Berlin et al., 2004), but not the ventromedial frontal lobe (Fellows and Farah, 2005), increases the tendency to choose immediate rewards over larger, delayed rewards. Similar results are seen in rats with lesions of the OFC (Mobini et al., 2002; Rudebeck et al., 2006). Such bias towards immediate rewards may be viewed as a form of impulsivity (Evenden, 1999), and a phenotype important for the neural bases of addiction (Reynolds, 2006). After injury to the prefrontal cortex, patients recover normal intelligence, memory and other cognitive functions, but emotional, affect and social behavior change (Bechara, 2005). Furthermore, damage to the OFC impairs the ability to refrain from responding to formerly rewarding cues that are no longer reinforced (Dias et al., 1996; McAlonan and Brown, 2003; Mishkin, 1964; Ostlund and Balleine, 2007; Rahman et al., 1999; Rolls et al., 1994; Schoenbaum and Roesch, 2005; Schoenbaum et al., 2007; Tait and Brown, 2007). Rule shifting is an executive function that can be tested using reversal learning models in animals. The ability to change responding to a previously rewarded activity relates to
