Virtual reality isn't just helping scientists understand and treat fellow humans -- it's helping them make sense of their four-legged friends, too. Researchers have built a virtual maze that convinces mice they're running through hallways when they're really running on a ball. The invention makes it possible to keep the rodent's head still and study how its brain works while it's navigating. That's important when you can usually collect only limited data while a critter is on the move. Unlike earlier prototypes, this doesn't require training the mice before they can give the experience a try.