Similarities and differences between behavioral control by drug-produced stimuli and by sensory stimuli

Drug-induced state-dependent learning and drug discriminations may be based on sensory stimuli induced by drug actions, or at least on events in the brain that have properties analogous to those of sensory stimuli. A variety of comparisons between behavioral control by drug-induced stimuli and by classically defined interoceptive and exteroceptive stimuli are possible. These allow inferences to be made about the nature of drug stimuli, the properties of behavioral paradigms that we use to investigate them, and the mechanisms by which drugs achieve behavioral control in drug discrimination and state-dependent learning paradigms. Each of these topics is selectively reviewed in this paper.