Rapid eye movement sleep resemblance to waking life), and incorporation of instinctual themes. Sometimes they include elements of the dreamer's recent experience taken directly from episodic memory. By one estimate, 80% of dreams occur during REM. Hobson and McCarley proposed that the PGO waves characteristic of “phasic” REM might supply the visual cortex and forebrain with electrical excitement which amplifies the hallucinatory aspects of dreaming. However, people woken up during sleep do not report significantly more bizarre dreams during phasic REMS, compared to tonic REMS. Another possible relationship between the two phenomena could be that the higher threshold for sensory interruption during REM sleep
REM rebound of normal human sleep, experimenters started depriving test subjects of only REM sleep, to test its unique importance. Every time a subject's electroencephalogram and eye movements indicated the beginning of REM sleep, the experimenter would thoroughly wake them for several minutes. As this “dream deprivation” continued, tendency to initiate REM increased, and the subjects were woken up more and more times each night. The subjects became irritable, anxious, and hungry, and several left the study early. After five nights, the remaining subjects were allowed to sleep undisturbed, and showed a significant increase in percentage of sleep devoted to REM: from