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 the developing brain by providing the neural stimulation that newborns need to form mature neural connections. Sleep deprivation have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, and decreased brain mass, and can result in an abnormal amount of neuronal cell death. The strongest evidence for the ontogenetic hypothesis comes from experiments on REM deprivation and the development of the visual system in the lateral geniculate nucleus and primary visual cortex. Ioannis Tsoukalas of Stockholm University has hypothesized that REM sleep is an evolutionary transformation of a well-known defensive mechanism, the tonic immobility reflex.