Memory Systems and the Addicted Brain

Abstract

The view that anatomically distinct memory systems differentially contribute to the development of drug addiction and relapse has received extensive support. The present brief review revisits this hypothesis as it was originally proposed 20 years ago (1) and highlights several recent developments. Extensive research employing a variety of animal learning paradigms indicates that dissociable neural systems mediate distinct types of learning and memory. Each memory system potentially contributes unique components to the learned behavior supporting drug addiction and relapse. In particular, the shift from recreational drug use to compulsive drug abuse may reflect a neuroanatomical shift from cognitive control of behavior mediated by the hippocampus/dorsomedial striatum toward habitual control of behavior mediated by the dorsolateral striatum (DLS). In addition, stress/anxiety may constitute a cofactor that facilitates DLS-dependent memory, and this may serve as a neurobehavioral mechanism underlying the increased drug use and relapse in humans following stressful life events. Evidence supporting the multiple systems view of drug addiction comes predominantly from studies of learning and memory that have employed as reinforcers addictive substances often considered within the context of drug addiction research, including cocaine, alcohol, and amphetamines. In addition, recent evidence suggests that the memory systems approach may also be helpful for understanding topical sources of addiction that reflect emerging health concerns, including marijuana use, high-fat diet, and video game playing.

Keywords: amygdala; anxiety; drug addiction; hippocampus; memory; stress; striatum.

Figure 1

White’s (1) multiple memory systems view of drug addiction. Like natural reinforcers, addictive drugs possess several “reinforcer actions,” including the ability to invoke positive/negative affect, approach, and modulation of memory systems. The amygdala, caudate–putamen (i.e., dorsal striatum), and hippocampus mediate dissociable memory systems, and each memory system presumably encodes unique components of drug-related memories. Given their memory modulatory properties, addictive drugs can potentially enhance their own self-administration by enhancing the function of these systems. (Reprinted from White with permission from John Wiley & Sons.)