Children love to play pretend, holding imaginary tea parties, educating classrooms of teddies or running their own grocery stores.

WEDNESDAY, Jan. 21, 2026 (HealthDay News) -- Ever notice how hard it is to stay sharp after a rough night of sleep. A recent study published in the journal Nature Neuroscience points to a surprising reason why: The brain may briefly shift into a sleep-like cleaning mode, even while you're awake.