In stage N1 sleep, which pattern is typically observed?

In stage N1 sleep, which pattern is typically observed?

• A. K-complexes
• B. Sleep spindles
• C. Theta with vertex sharp waves
• D. Delta waves

Answer: (C)

Stage N1 sleep is the transition from wakefulness to sleep, and its EEG signature is a shift from awake alpha to low‑amplitude theta activity in the 4–7 Hz range. A key feature that identifies this stage is the appearance of vertex sharp waves—brief, sharp negative deflections often seen at the vertex leads that may be followed by a positive deflection. This pattern — theta activity with vertex sharp waves — marks N1. Sleep spindles and K-complexes belong to stage N2, while delta waves indicate deeper sleep, stage N3.

Stage N1 sleep is the transition from wakefulness to sleep, and its EEG signature is a shift from awake alpha to low‑amplitude theta activity in the 4–7 Hz range. A key feature that identifies this stage is the appearance of vertex sharp waves—brief, sharp negative deflections often seen at the vertex leads that may be followed by a positive deflection. This pattern — theta activity with vertex sharp waves — marks N1.

Sleep spindles and K-complexes belong to stage N2, while delta waves indicate deeper sleep, stage N3.