RPSGT RPSGT Sleep Staging & Scoring 2 — Questions and Answers
Question 1: What distinguishes Stage N1 from Stage Wake in a subject who generates occipital alpha rhythm?
- Presence of K-complexes
- Alpha activity present for <50% of the epoch (Correct answer)
- Presence of sleep spindles
- Absence of chin EMG activity
Correct answer: Alpha activity present for <50% of the epoch
N1 is scored when alpha activity occupies <50% of the epoch, replaced by low-amplitude mixed-frequency activity.
Question 2: Sawtooth waves during polysomnography are most commonly associated with which sleep stage?
- N1
- N2
- N3
- REM (Correct answer)
Correct answer: REM
Sawtooth waves (2–6 Hz, notched waveforms) are a characteristic feature of REM sleep, often preceding bursts of rapid eye movements.
Question 3: An EEG frequency shift qualifies as an arousal in AASM scoring if it lasts a minimum of how many seconds?
- 1 second
- 3 seconds (Correct answer)
- 5 seconds
- 10 seconds
Correct answer: 3 seconds
AASM defines an arousal as an abrupt EEG frequency shift lasting ≥3 seconds, preceded by ≥10 seconds of stable sleep.
Question 4: Which of the following correctly states the amplitude criterion for slow wave activity in N3 scoring?
- Peak-to-peak >50 µV in occipital leads
- Peak-to-peak >75 µV in frontal leads (Correct answer)
- Peak-to-peak >100 µV in central leads
- Peak-to-peak >150 µV in temporal leads
Correct answer: Peak-to-peak >75 µV in frontal leads
AASM requires slow waves to have peak-to-peak amplitude >75 µV measured over the frontal derivations.
Question 5: What frequency range defines the theta activity that predominates in Stage N1 sleep?
- 0.5–2 Hz
- 4–7 Hz (Correct answer)
- 8–12 Hz
- 13–30 Hz
Correct answer: 4–7 Hz
Theta activity (4–7 Hz) is the predominant EEG frequency in Stage N1, replacing the alpha rhythm seen during wakefulness.
Question 6: In subjects who do not generate occipital alpha activity, which criterion is used to distinguish Stage Wake from Stage N1?
- Presence of sleep spindles
- Eye blink rate exceeding 3 per minute
- Presence of irregular conjugate eye movements and/or eye blinks (Correct answer)
- Chin EMG amplitude exceeding a set threshold
Correct answer: Presence of irregular conjugate eye movements and/or eye blinks
In non-alpha generators, Stage W is scored by the presence of eye blinks, reading eye movements, or irregular conjugate eye movements with normal or high-amplitude mixed-frequency EEG.
Question 7: How is a sleep cycle most accurately defined in standard PSG scoring?
- One NREM period followed by one REM period (Correct answer)
- 90 minutes of consecutive sleep
- A period from sleep onset to the first arousal
- A period from N1 onset to the next Stage Wake
Correct answer: One NREM period followed by one REM period
A sleep cycle consists of one NREM period (N1–N2–N3) followed by a REM period, typically repeating every 90–110 minutes.
RPSGT RPSGT Sleep Staging & Scoring 2
What distinguishes Stage N1 from Stage Wake in a subject who generates occipital alpha rhythm?