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
Rapid eye movement sleep tomography, and reports of dreamers upon waking, have all been used to study this phase of sleep. REM sleep is "paradoxical" because of its similarities to wakefulness. Although the body is paralyzed, the brain acts somewhat awake, with cerebral neurons firing with the same overall intensity as in wakefulness. Electroencephalography during REM deep sleep reveal fast, low amplitude, desynchronized neural oscillation (brainwaves) that resemble the pattern seen during wakefulness which differ from the slow δ (delta) waves pattern of NREM deep sleep. An important element of this contrast is the θ (theta) rhythm in the hippocampus that show 40–60 Hz