Sleep spindles are:

Sleep spindles are:

• A. Associated with stage 3 sleep
• B. 12-14 Hz
• C. Have specific amplitude requirements
• D. Associated with stage 1 sleep

Answer: (B)

Sleep spindles are bursts of brain activity in the sigma range, about 12–14 Hz, lasting roughly 0.5 to 2 seconds. This frequency is the defining feature that makes them identifiable, which is why the best answer pins them to 12–14 Hz. They are most characteristic of stage N2 sleep, often appearing alongside K-complexes. They aren’t a feature of stage 3 sleep, which is dominated by slow, high-amplitude delta waves, nor of stage 1 sleep, which shows lighter, mixed-frequency activity without spindles. Amplitude isn’t a fixed criterion for spindles; the key identifying trait is the specific frequency and duration in the sigma range.

Sleep spindles are bursts of brain activity in the sigma range, about 12–14 Hz, lasting roughly 0.5 to 2 seconds. This frequency is the defining feature that makes them identifiable, which is why the best answer pins them to 12–14 Hz. They are most characteristic of stage N2 sleep, often appearing alongside K-complexes. They aren’t a feature of stage 3 sleep, which is dominated by slow, high-amplitude delta waves, nor of stage 1 sleep, which shows lighter, mixed-frequency activity without spindles. Amplitude isn’t a fixed criterion for spindles; the key identifying trait is the specific frequency and duration in the sigma range.