Non-rapid eye movement sleep activation occurs during NREM that is comparable to the type that occurs during REM. It is this sub-cortical activation that results in dreaming during the NREM stage during the morning hours. During non-REM sleep, the tonic drive to most respiratory muscles of the upper airway is inhibited. This has two consequences: However, because the diaphragm is largely driven by the autonomous system, it is relatively spared of non-REM inhibition. As such, the suction pressures it generates stay the same. This narrows the upper airway during sleep, increasing resistance and making airflow through the upper airway turbulent and noisy. For example,
Rapid eye movement sleep humor, the liquid between cornea and iris, was stagnant if not stirred. Among the supportive evidences, he calculated that if aqueous humor was stagnant, oxygen from iris had to reach cornea by diffusion through aqueous humor, which was not sufficient. According to the theory, when the animal is awake, eye movement (or cool environmental temperature) enables the aqueous humor to circulate. When the animal is sleeping, REM provides the much-needed stir to aqueous humor. This theory is consistent with the observation that fetuses, as well as eye-sealed newborn animals, spend much time in REM sleep, and that during a normal