(credit: Thomas Hartung, Johns Hopkins Bloomberg School of Public Health) Tiny, rolling balls of brain cells knocking around in a lab may one day help keep you from losing your marbles—among other things. The small cellular balls act like mini-brains, mimicking aspects of the real thing, including forming noggin-like structures and pulsing with electrical signals like a thinking mind, researchers reported Friday at the annual meeting of the American Association for the Advancement of Science in Washington.