Which pattern is a high-amplitude brain wave associated with non-REM sleep, particularly stage 2?

Which pattern is a high-amplitude brain wave associated with non-REM sleep, particularly stage 2?

• A. Delta waves
• B. Sleep spindles
• C. K complexes
• D. Alpha waves

Answer: (C)

In non-REM sleep, especially stage 2, two hallmark EEG features appear, and the standout high-amplitude pattern is the K complex. A K complex is a single, large biphasic wave—a sharp negative deflection followed by a positive component—that can occur spontaneously or in response to a stimulus, and its big size helps dampen external arousal to protect sleep. Sleep spindles also occur in stage 2, but they are brief bursts of 12–16 Hz activity and aren’t defined by high amplitude like a K complex. Delta waves reflect deep, slow-wave sleep (stage 3), while alpha waves are linked to wakeful rest with eyes closed and fade as sleep deepens.

In non-REM sleep, especially stage 2, two hallmark EEG features appear, and the standout high-amplitude pattern is the K complex. A K complex is a single, large biphasic wave—a sharp negative deflection followed by a positive component—that can occur spontaneously or in response to a stimulus, and its big size helps dampen external arousal to protect sleep. Sleep spindles also occur in stage 2, but they are brief bursts of 12–16 Hz activity and aren’t defined by high amplitude like a K complex. Delta waves reflect deep, slow-wave sleep (stage 3), while alpha waves are linked to wakeful rest with eyes closed and fade as sleep deepens.