Reversed discriminatory responses of heart rate during human REM sleep

This study investigated the transfer of conditioned responses (CR) from wakefulness ro sleep in humans, particularly focusing on an inverse relationship between wakefulness and rapid eye movement (REM) sleep. Eight subjects underwent classical differential conditioning during wakefulness using heart rate (HR) as a measure. After the conditioning, an extinction series was presented during stage 2 or REM sleep. Results showed: 1) that the direction of the evoked-HR response depended on the behavioral state (deceleration during wakefulness and acceleration during sleep), 2) a significant discrimination to the conditioned stimuli (CS) was observed during REM sleep but not during stage 2 sleep, and 3) the discriminatory CR was reversed during REM sleep. These facts suggest a difference in information processing during wakefulness and sleep, in particular REM sleep.