EEG Normal EEG Waveforms 4

Question 1

Which EEG frequency band is most prominent during deep NREM sleep (stage N3)?

Accepted Answer

Delta (0.5–4 Hz)

Answer

Stage N3 (slow-wave sleep) is defined by high-amplitude delta waves occupying at least 20% of the epoch.

Question 2

What is the typical voltage (amplitude) range of normal alpha waves recorded from the scalp?

Accepted Answer

20–200 µV

Answer

Alpha waves normally range from about 20 to 200 µV in amplitude when recorded from scalp electrodes.

Question 3

The 'mu rhythm' seen over the central scalp in a relaxed, awake subject has a frequency overlapping with which other rhythm?

Accepted Answer

Alpha

Answer

The mu rhythm (8–13 Hz) overlaps the alpha frequency band but is maximal over central (C3/C4) rather than occipital electrodes.

Question 4

During hyperventilation in a normal adult, what EEG change is expected?

Accepted Answer

Increased high-amplitude slow activity

Answer

Hyperventilation causes cerebral vasoconstriction and hypocapnia, producing diffuse high-amplitude slow (delta/theta) activity in normal subjects.

Question 5

Which waveform is considered a normal variant and is characteristically seen at the vertex during stage N1 sleep?

Accepted Answer

Vertex sharp wave

Answer

Vertex sharp waves (V-waves) are normal, high-amplitude transients maximal at Cz that appear during drowsiness and stage N1 sleep.

EEG - Electroencephalography Practice Test