Which of the following does NOT attenuate alpha rhythm?

When considering what does not attenuate alpha rhythm, it's important to understand the nature of alpha waves and the factors that influence their presence.

Alpha rhythm, typically ranging from 8 to 12 Hz, is associated with a relaxed, awake state, particularly when the eyes are closed and the individual is in a resting state. Eye closing is a common method to enhance or maintain alpha activity, as it reduces visual stimuli, allowing the brain to relax into a rhythm characteristic of a calm state.

Conversely, activities like eye opening, exposure to external auditory stimuli, and increased mental activity are known to diminish or attenuate alpha rhythm. Eye opening invites visual processing and alertness, both of which disrupt the stability of alpha waves. External auditory stimuli can serve as distractions that provoke attentiveness, while increased mental activity typically shifts the brain's focus to beta waves, reflecting higher levels of cognitive engagement and alertness.

Therefore, eye closing is the correct answer, as it does not diminish alpha rhythm but rather promotes its stability and prominence.