Which factor does NOT typically cause attenuation of the posterior dominant alpha rhythm in normal adults?

The phenomenon of the posterior dominant alpha rhythm is closely linked to the state of brain activity during relaxed wakefulness. In normal adults, when they are in a relaxed state with their eyes closed, the alpha rhythm is typically prominent and can even become more pronounced. This rhythm is often indicative of a calm and alert mental state.

In contrast, factors like severe anxiety, the transition into sleep, and deep meditation can influence this rhythm significantly. Severe anxiety often leads to a state of heightened arousal, which can suppress the alpha waves. Sleep is associated with a range of different brainwave patterns, including theta and delta rhythms, which replace the alpha rhythm as one transitions into deeper sleep stages. During deep meditation, depending on the style and depth of the meditation, the brain may also shift into different patterns that can diminish or alter the classic alpha activity.

Thus, the relaxed wakefulness with eyes closed is the state where you would most likely expect to observe robust alpha activity, highlighting why this factor does not typically cause attenuation of the posterior dominant alpha rhythm.