Which EEG rhythm is observed during relaxed wakefulness with eyes closed?

Which EEG rhythm is observed during relaxed wakefulness with eyes closed?

• A. Delta
• B. Alpha
• C. Theta
• D. Beta

Answer: (B)

In EEG, different rhythms reflect different states of arousal. When someone is relaxed and awake with eyes closed, the dominant pattern appears most clearly over the back of the brain—the posterior alpha rhythm. This rhythm typically runs about 8–12 Hz and is strongest in the occipital cortex. It serves as a marker of a calm, resting visual state and tends to fade (alpha blocking) when eyes are opened or mental activity increases. Delta waves are slow (less than 4 Hz) and show up mainly during deep sleep or certain pathological conditions. Theta waves (4–7 Hz) occur in drowsiness or light sleep and in some developmental or cognitive contexts. Beta waves are faster (above 13 Hz) and are associated with active thinking and alertness. Since the scenario describes relaxed wakefulness with eyes closed, alpha is the best fit.

In EEG, different rhythms reflect different states of arousal. When someone is relaxed and awake with eyes closed, the dominant pattern appears most clearly over the back of the brain—the posterior alpha rhythm. This rhythm typically runs about 8–12 Hz and is strongest in the occipital cortex. It serves as a marker of a calm, resting visual state and tends to fade (alpha blocking) when eyes are opened or mental activity increases.

Delta waves are slow (less than 4 Hz) and show up mainly during deep sleep or certain pathological conditions. Theta waves (4–7 Hz) occur in drowsiness or light sleep and in some developmental or cognitive contexts. Beta waves are faster (above 13 Hz) and are associated with active thinking and alertness. Since the scenario describes relaxed wakefulness with eyes closed, alpha is the best fit.