Question

Which of the following are EEG signal bands ?
A. Alpha ($\alpha$)
B. Beta ($\beta$)
C. Lambda ($\lambda$)
D. Theta ($\theta$)
E. Delta ($\delta$)
Choose the correct answer from the options given below :

• A. A, B, C, D Only
• B. B, C, D, E Only
• C. A, B, D, E Only
• D. C, B, D, E Only

Hint:

Learn the bands in order of increasing frequency: Delta (slowest, deep sleep) $\rightarrow$ Theta (drowsy) $\rightarrow$ Alpha (relaxed, eyes closed) $\rightarrow$ Beta (awake, thinking) $\rightarrow$ Gamma (fastest, intense focus).

Answer 1

The Correct Option is C

Step 1: Concept:
This question tests clinical neurophysiology, specifically asking the student to identify the standard frequency bands (rhythms) used to classify brainwaves recorded by an Electroencephalogram (EEG).

Step 2: Step-by-step Explanation:

• The electrical activity of the brain is highly rhythmic. Clinically, these rhythms are categorized into specific "bands" based strictly on their frequency (measured in Hertz, Hz). The major physiological bands are:
1. Delta ($\delta$) (E): 0.5 - 4 Hz. Deep, slow-wave sleep.
2. Theta ($\theta$) (D): 4 - 8 Hz. Drowsiness or light sleep.
3. Alpha ($\alpha$) (A): 8 - 13 Hz. Awake, relaxed state with eyes closed.
4. Beta ($\beta$) (B): 14 - 30 Hz. Awake, alert, active concentration.
5. Gamma ($\gamma$): $>30$ Hz. High-level cognitive processing (not listed in options).

• What about Lambda ($\lambda$) (C)? While "lambda waves" do exist in clinical EEG terminology, they are sharp, transient waveform events seen over the occipital lobe when scanning visual patterns. They are not a continuous frequency "band" like the others.

• Therefore, the classic frequency bands listed are Alpha, Beta, Theta, and Delta.

Step 3: Final Answer:
The correct options are A, B, D, and E Only.