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Sleep is a vital, highly organized process regulated by complex systems of neuronal networks and neurotransmitters. Normal sleep comprises non-rapid eye movement (NREM) and REM periods that alternate through the night. Sleep usually begins in NREM and progresses through deeper NREM stages (2, 3, and 4 stages), but newborns enter REM sleep (active sleep) first before NREM (quiet sleep). A... |
