Alcohol effects on associative and sensorimotor cortico-thalamo-basal ganglia circuits alter decision making and alcohol intake

Much of the behavioral repertoire of humans and other vertebrates is learned and controlled through the function of brain circuits involving the cortex, thalamus and Basal Ganglia (for simplicity we will refer to this as the Cortico-Thalamo-Basal Ganglia, or CTBG, circuitry). As the name implies, these circuits include the different regions of cortex and thalamus, as well as BG subregions including the striatum, globus pallidus (GP), substantia nigra (SN)/ventral tegmental area (VTA), and the subthalamic nucleus (STN). This circuitry has developed evolutionarily to provide overarching control of actions following discrete environmental events as well as self-initiated actions. Several parallel CTBG circuits have been identified and linked to different aspects of action control under different circumstances. Research in experimental psychology and Neuroscience has established how different CTBG circuits contribute to control of actions based on environmental circumstances and past learning history. There is also a large and growing body of evidence that misused substances, including alcohol, act on cells within these circuits. These actions promote acute intoxication and drug seeking and contribute to changes in behavior induced by chronic alcohol exposure, withdrawal and relapse. Alcohol exposure also influences which of the different CTBG circuits has the strongest influence on behavior. This review will cover the relevant circuitry and describe the current state of knowledge as to how alcohol alters CTBG circuit function and control of behavior. Studies in rodents, non-human primates and humans will be discussed. Finally, ideas for future research directions in this area will be considered.