Which sleep stage is the lightest stage of non-REM sleep?

Which sleep stage is the lightest stage of non-REM sleep?

• A. N2
• B. N1
• C. N3
• D. REM

Answer: (B)

The main idea here is how deep each sleep stage is within non-REM sleep. The lightest non-REM stage is the initial N1 stage. It’s basically the transition from wakefulness into sleep, so you’re just drifting off and can be easily awakened. On an EEG it shows slower, low-amplitude theta activity as you slip from awake alpha rhythms. You may have slow eye movements and only a slight drop in muscle tone, and some people experience brief hypnic jerks as you settle in. Because you’re still close to wakefulness, this stage is the easiest to wake from, which is why it’s considered the lightest non-REM sleep. By contrast, the next non-REM stage (N2) is deeper and features sleep spindles and K-complexes, and N3 is the deepest, with slow delta waves. REM sleep, while active and dream-filled, is a different category altogether with its own distinctive brain activity and muscle atonia.

The main idea here is how deep each sleep stage is within non-REM sleep. The lightest non-REM stage is the initial N1 stage. It’s basically the transition from wakefulness into sleep, so you’re just drifting off and can be easily awakened. On an EEG it shows slower, low-amplitude theta activity as you slip from awake alpha rhythms. You may have slow eye movements and only a slight drop in muscle tone, and some people experience brief hypnic jerks as you settle in. Because you’re still close to wakefulness, this stage is the easiest to wake from, which is why it’s considered the lightest non-REM sleep. By contrast, the next non-REM stage (N2) is deeper and features sleep spindles and K-complexes, and N3 is the deepest, with slow delta waves. REM sleep, while active and dream-filled, is a different category altogether with its own distinctive brain activity and muscle atonia.