Conditioned salivation and associated dreams from REM sleep

Although research has investigated the feasibility of establishing classica lly conditioned physiological responses during sleep, very few experimental studies have considered whether classically conditioned cognitive associat ions are possible. Since dreams have previously been described as a state o f "hyper-association," an experiment involving classical conditioning of th e human salivary response and associated dream content was conducted. Durin g wakefulness, repeated pairings of a conditioned stimulus (CS; a red light ) with an unconditioned stimulus (UCS; citrus juice) yielded a conditio aut onomic response (CR; salivation) on presentation of the CS alone. After exp osure to the CS during REM sleep, salivary excretion rates measured upon aw akening were significantly higher than measures taken from baseline REM awa kenings. However, no CR-related dreams were reported by the participants. T his result could be interpreted as evidence that participants in this exper iment did not experience higher-order memory associations to the external s timuli presented during REM. Alternatively, the lack of CR-related dreams c ould be explained by previous findings that the autonomic nervous system of ten works independently of higher-order cognitive activity. Therefore, if a n autonomic association is formed, this does not necessarily imply a cognit ive one.