Final answer:
During NREM sleep, oxygen consumption in the brain is reduced compared to wakefulness, reflecting the lower metabolic activity and slower brainwave activity of this sleep stage.
Step-by-step explanation:
Oxygen consumption in the brain is indeed reduced during non-rapid eye movement (NREM) sleep compared to wakefulness. As we begin to fall asleep and enter the various stages of NREM sleep, the brain undergoes significant changes in brainwave activity with a gradual decrease in frequency and an increase in amplitude. Specifically, stage 1 of NREM sleep is marked by a reduced rate of respiration and a slower heartbeat, indicating that the body is entering a state of reduced metabolic activity and, thus, reduced oxygen consumption. As one progresses into deeper stages of NREM sleep, such as slow-wave sleep which is characterized by delta waves, brain activity continues to slow down, further indicating a reduction in metabolic demand and oxygen consumption. The sleep cycle then alternates between NREM and REM sleep, with REM sleep showing brainwave patterns similar to wakefulness and an increased metabolic rate compared to NREM sleep.