Conditioned salivation and associated dreams from REM sleep.

Abstract

Although research has investigated the feasibility of establishing classically conditioned physiological responses during sleep, very few experimental studies have considered whether classically conditioned cognitive associations are possible. Since dreams have previously been described as a state of “hyper-association,” an experiment involving classical conditioning of the human salivary response and associated dream content was conducted. During wakefulness, repeated pairings of a conditioned stimulus (CS; a red light) with an unconditioned stimulus (UCS; citrus juice) yielded a conditioned autonomic response (CR; salivation) on presentation of the CS alone. After exposure to the CS during REM sleep, salivary excretion rates measured upon awakening were significantly higher than measures taken from baseline REM awakenings. However, no CR-related dreams were reported by the participants. This result could be interpreted as evidence that participants in this experiment did not experience higher-order memory associations to the external stimuli presented during REM. Alternatively, the lack of CR-related dreams could be explained by previous findings that the autonomic nervous system often works independently of higher-order cognitive activity. Therefore, if an autonomic association is formed, this does not necessarily imply a cognitive one.