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 addiction, because addiction is an inability to change, i.e. loss of control, when alcohol or other drugs cause negative consequences. Reversal learning, which is impaired in cocaine addicts and animals that have chronically self-administered cocaine (Schoenbaum and Shaham, 2008) or alcohol (Obernier et al., 2002b) provides an experimental approach to investigating drug induced changes in cognition. A circuit including orbitofrontal cortex, basolateral amygdala and striatum subserves reversal learning, specifically orbitofrontal cortex loses the ability to signal expected outcomes, and basolateral amygdala becomes fixed emotional memories of reward. Executive cognitive flexibility must bring attention and working memory to inhibit learned responses that are currently wrong. The lack of rule shifting is consistent with the loss of control that is characteristic of addiction. Thus, the hallmark of addiction, i.e. continued drug taking with negative consequences, represents increased impulsivity and an inability to reverse previously learned rewarding activities.
