Multiplexing in the brain is apparently achieved by maintaining a high and low (theta) peak frequency -- when at a ratio of the golden mean, each separate period of high activity doesn't interfere with the other. Makes sense, when you think about brainwave bands being harmonics (frequency doublings), as that is what permits frequency coupling-- whereas irrational ratios prevent coupling.

Pletzer, B., Kerschbaum, H., & Klimesch, W. (2010). When frequencies never synchronize: the golden mean and the resting EEG. Brain research, 1335, 91-102.