EEG Normal EEG Waveforms 5

Question 1

Which normal EEG feature is defined as a 12–14 Hz waxing-and-waning burst lasting 0.5–3 seconds, maximal over central-parietal regions?

Accepted Answer

Sleep spindle

Answer

Sleep spindles are 12–14 Hz (sigma band) bursts with a characteristic spindle shape appearing in stage N2 sleep.

Question 2

Gamma oscillations (>30 Hz) in the normal EEG are most associated with which cognitive state?

Accepted Answer

High-level cognitive processing and sensory binding

Answer

Gamma oscillations are linked to higher cognitive functions such as attention, working memory, and cross-modal sensory binding.

Question 3

A normal adult EEG background shows a well-organized 10 Hz posterior dominant rhythm. This rhythm is categorized as which frequency band?

Accepted Answer

Alpha

Answer

10 Hz falls squarely within the alpha band (8–13 Hz), the normal posterior dominant rhythm of a relaxed, eyes-closed adult.

Question 4

Positive occipital sharp transients of sleep (POSTS) are a normal variant that appear during which sleep stage?

Accepted Answer

Stage N2, N3, and sometimes REM

Answer

POSTS are surface-positive sharp transients over the occipital regions seen in stage N2, N3, and sometimes REM sleep.

Question 5

What is the minimum percentage of an epoch that must consist of delta waves for that epoch to be scored as stage N3 sleep?

Accepted Answer

20%

Answer

By AASM scoring rules, stage N3 requires that delta waves (0.5–2 Hz, >75 µV) occupy at least 20% of a 30-second epoch.

EEG - Electroencephalography Practice Test