It is now generally accepted that addiction is a type of learning, i.e., learned associations between the rewarding effects of drugs and environmental cues that predict drug availability, which significantly contributes to compulsive drug use and the propensity to relapse even after long periods of abstinence. As subjects make the transition from initiation to habitual drug use, neuro-adaptations in areas such as the hippocampus and amygdala are thought to underlie drug-associated learning and memories. A single episode of drug use itself can influence synaptic transmission and repeated or prolonged drug use can cause long-lasting alterations in synaptic strengths—defined as synaptic plasticity, reflected through molecular changes as well as persistent modification of neurotransmitter release. These drug-induced changes in the brain are a critical component in the development of dependence and are thought to drive compulsive intake and relapse. There are many factors that play into addictive processes and understanding the neurobiological underpinnings of these events will enlighten possible therapeutic targets.
