Question

Normal EEG frequency range is

• A. \( \text{50-500 Hz} \)
• B. \( \text{0.5-50 Hz} \)
• C. \( \text{0.05-5 Hz} \)
• D. \( \text{1-200 Hz} \)

Hint:

Remembering the approximate frequency ranges for different EEG rhythms (Delta, Theta, Alpha, Beta, Gamma) is crucial for interpreting EEG recordings. These bands correlate with different states of consciousness and brain activity, making EEG a valuable tool in neurology and sleep studies.

Answer 1

The Correct Option is B

The Electroencephalogram (EEG) measures the electrical activity of the brain. The frequencies of these electrical signals vary depending on the brain state (e.g., wakefulness, sleep, cognitive activity). The standard frequency bands for EEG are:

• Delta waves: (0.5-4 Hz) - Associated with deep sleep, infancy, and some brain disorders.
• Theta waves: (4-8 Hz) - Associated with drowsiness, light sleep, and some meditative states.
• Alpha waves: (8-13 Hz) - Prominent in relaxed wakefulness with eyes closed.
• Beta waves: (13-30 Hz) - Associated with alert wakefulness, active thinking, and problem-solving.
• Gamma waves: (30-100+ Hz) - Involved in higher cognitive functions and perception, though the upper limit can vary.

Considering these ranges, a general normal EEG frequency range spans from very low frequencies (around 0.5 Hz) up to approximately 50 Hz, encompassing delta, theta, alpha, and beta waves. While gamma waves can go higher, the primary and most commonly observed range for routine EEG interpretation typically falls within 0.5-50 Hz. Options (A) and (D) are too broad or too high, and option (C) is too narrow, missing the higher frequency bands.