Several brain circuits are relevant in the neurobiology of addiction and result in an enhanced motivational value of the drug (secondary to learned associations through conditioning and habits) at the expense of other reinforcers (secondary to decreased sensitivity of the reward circuit) and an impaired ability to inhibit the intentional actions associated with the strong desires to take the drug (secondary to impaired executive function) that result in compulsive drug taking in addiction (67). In addition, disrupted executive function contributes to impaired insight in addiction, which interferes with the recognition of disease and the need for treatment. Because these neuronal systems also play fundamental roles in social behaviors (88), understanding their disruption in addiction is providing insight into why drugs can be so disruptive to social relationships and why the typical positive reinforcers used to promote positive behaviors (e.g., pay increases, promotion) or the typical negative reinforcers used to deter negative behaviors (e.g., incarceration, fines) are by themselves ineffective in stopping drug use in addicted subjects (89). This model suggests a multipronged therapeutic approach to addiction designed to strengthen the neuronal systems that become disrupted in addiction.
