RPSGT RPSGT Electroencephalography & Signal Interpretation — Questions and Answers
Question 1: Which EEG frequency band is most prominently associated with active cognitive processing and problem-solving?
- Delta (0.5–4 Hz)
- Theta (4–8 Hz)
- Alpha (8–13 Hz)
- Beta (13–30 Hz) (Correct answer)
Correct answer: Beta (13–30 Hz)
Beta activity predominates during active mental engagement, concentration, and problem-solving tasks.
Question 2: A 60-Hz artifact appearing on EEG channels is most likely caused by:
- Patient movement
- Electrode impedance mismatch
- AC electrical interference (Correct answer)
- Muscle artifact from the frontalis
Correct answer: AC electrical interference
60-Hz artifact results from alternating current (AC) electrical interference from nearby equipment or poor grounding.
Question 3: During N3 sleep, the EEG is characterized by:
- Sleep spindles and K-complexes
- Low-voltage mixed-frequency activity
- High-amplitude slow waves occupying ≥20% of the epoch (Correct answer)
- Sawtooth waves and REMs
Correct answer: High-amplitude slow waves occupying ≥20% of the epoch
N3 is defined by slow-wave activity (0.5–2 Hz, ≥75 µV) comprising at least 20% of the 30-second epoch.
Question 4: Vertex sharp waves (V waves) in a sleep study are most characteristic of which sleep stage?
- REM sleep
- N1 sleep (Correct answer)
- N2 sleep
- N3 sleep
Correct answer: N1 sleep
Vertex sharp waves are electropositive transients maximal at the vertex and are a hallmark of N1 sleep.
Question 5: A HEOG (horizontal electro-oculogram) montage detects eye movements by placing electrodes:
- Above and below each eye
- At the outer canthi of each eye (Correct answer)
- At the inner canthi of each eye
- At the supraorbital ridge bilaterally
Correct answer: At the outer canthi of each eye
HEOG electrodes are placed at the outer canthi (lateral edges) of each eye to detect lateral eye movements.
Question 6: Which artifact is characterized by rhythmic, high-frequency bursts on EEG channels that correlate with the pulse rate?
- Sweat artifact
- ECG artifact
- Electrode pop artifact
- Pulse artifact (Correct answer)
Correct answer: Pulse artifact
Pulse artifact appears as rhythmic slow waves or spikes on EEG caused by an electrode placed over a pulsating blood vessel.
Question 7: In referential (monopolar) EEG recording, the reference electrode should ideally be placed at a site that is:
- Maximally active electrically
- Electrically neutral or minimally active (Correct answer)
- Directly over the frontal lobe
- On the same side as the active electrode
Correct answer: Electrically neutral or minimally active
A reference electrode should be electrically neutral to accurately reflect the potential of the active electrode without introducing its own signal.
Question 8: POSTS (positive occipital sharp transients of sleep) are normal EEG variants seen during which stage?
- N3 sleep
- REM sleep
- N1 and N2 sleep (Correct answer)
- Wakefulness only
Correct answer: N1 and N2 sleep
POSTS are normal, benign waveforms seen in N1 and N2 sleep, maximal over occipital regions, and should not be mistaken for pathology.
Question 9: The international 10-20 electrode placement system derives its name from the fact that electrodes are placed at intervals of:
- 10 mm and 20 mm apart
- 10% and 20% of skull circumference distances (Correct answer)
- 10 and 20 microvolts apart
- 10 Hz and 20 Hz frequency bands
Correct answer: 10% and 20% of skull circumference distances
The 10-20 system spaces electrodes at 10% and 20% intervals of the total skull circumference measured in each plane.
Question 10: A patient's EEG shows continuous, diffuse high-amplitude delta activity throughout an entire overnight study. This pattern is most consistent with:
- Normal Stage N3 sleep throughout
- Severe encephalopathy or deep coma (Correct answer)
- REM behavior disorder
- Idiopathic hypersomnia
Correct answer: Severe encephalopathy or deep coma
Continuous diffuse delta without normal sleep architecture cycling suggests severe cerebral dysfunction such as encephalopathy or coma.
Question 11: Which filter setting in PSG is specifically used to reduce slow-moving artifacts such as sweat and movement?
- High-frequency filter (HFF)
- Low-frequency filter (LFF) / High-pass filter (Correct answer)
- Notch filter at 60 Hz
- Band-stop filter at 0.5 Hz
Correct answer: Low-frequency filter (LFF) / High-pass filter
The low-frequency filter (high-pass filter) attenuates very slow frequencies, reducing sweat and movement artifacts that appear as slow undulations.
Question 12: K-complexes on EEG must have a total duration of at least:
- 0.25 seconds
- 0.5 seconds (Correct answer)
- 1.0 second
- 2.0 seconds
Correct answer: 0.5 seconds
By AASM definition, a K-complex is a well-delineated negative sharp wave followed by a positive component with total duration ≥0.5 seconds.
Question 13: In a bipolar EEG derivation, if the potential at electrode A is +50 µV and at electrode B is +20 µV, the recorded deflection will be:
- +70 µV upward deflection
- +30 µV deflection reflecting A minus B (Correct answer)
- +30 µV deflection reflecting B minus A
- No deflection because both are positive
Correct answer: +30 µV deflection reflecting A minus B
Bipolar recording subtracts the second electrode from the first (A − B), yielding +30 µV; the polarity convention determines deflection direction.
Question 14: Sleep spindles are generated primarily by thalamo-cortical circuits and are typically recorded at maximum amplitude over which scalp region?
- Occipital (O1, O2)
- Frontal (Fp1, Fp2)
- Central (C3, C4) (Correct answer)
- Temporal (T3, T4)
Correct answer: Central (C3, C4)
Sleep spindles are maximal over central scalp regions because of their thalamocortical origin projecting to sensorimotor cortex.
