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Normal EEG Waveforms Flashcards

7 cards from real EEG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  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?

    Answer: Sleep spindle

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

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

    Answer: High-level cognitive processing and sensory binding

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

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

    Answer: Alpha

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

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

    Answer: Stage N2, N3, and sometimes REM

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

  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?

    Answer: 20%

    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.

  6. The K-complex is a normal EEG feature of stage N2 sleep. What is its characteristic morphology?

    Answer: A negative sharp wave followed by a positive slow component, often superimposed by a spindle

    A K-complex is a well-delineated negative sharp component followed by a positive slow wave, lasting ≥0.5 s, often with a superimposed sleep spindle.

  7. In normal neonatal EEGs, which activity pattern is considered developmentally appropriate but would be abnormal in a healthy adult?

    Answer: Trace alternant (burst-suppression-like) pattern during quiet sleep

    Trace alternant, characterized by alternating bursts and interburst intervals during quiet sleep, is a normal pattern in full-term neonates up to about 44 weeks conceptional age.