Which feature is characteristic of Stage N2 sleep?

Which feature is characteristic of Stage N2 sleep?

• A. Presence of sleep spindles and K-complexes
• B. Delta waves large
• C. REM begins
• D. Absence of EEG activity

Answer: (C)

Stage N2 sleep is defined by two distinctive EEG features: sleep spindles and K-complexes. Sleep spindles are brief bursts of activity in the 12–14 Hz range that last about half a second to a couple of seconds, while K-complexes are large, alone or paired, high-amplitude waves that often occur in response to stimuli. These patterns signal a deeper level of non-REM sleep than Stage N1 and help protect sleep by buffering the brain from minor arousals. In contrast, large delta waves characterize Stage N3 (deep sleep), and the onset of REM sleep marks a transition into REM with a different EEG pattern and eye movements. Absence of EEG activity isn’t seen in normal sleep stages, as there is ongoing brain activity throughout sleep. So the feature that truly characterizes Stage N2 is the presence of sleep spindles and K-complexes.

Stage N2 sleep is defined by two distinctive EEG features: sleep spindles and K-complexes. Sleep spindles are brief bursts of activity in the 12–14 Hz range that last about half a second to a couple of seconds, while K-complexes are large, alone or paired, high-amplitude waves that often occur in response to stimuli. These patterns signal a deeper level of non-REM sleep than Stage N1 and help protect sleep by buffering the brain from minor arousals. In contrast, large delta waves characterize Stage N3 (deep sleep), and the onset of REM sleep marks a transition into REM with a different EEG pattern and eye movements. Absence of EEG activity isn’t seen in normal sleep stages, as there is ongoing brain activity throughout sleep. So the feature that truly characterizes Stage N2 is the presence of sleep spindles and K-complexes.