Since There's no Up or Down in Space, How do our Brains Deal With This?

Astronauts and cosmonauts in space have reported spatial disorientation problems, where they find it hard to get a sense of direction, or distinguish between what might be considered "up" or "down."  This is called "Visual Reorientation Illusions" (VRIs) where the spacecraft floors, walls and ceiling surfaces can suddenly exchange subjective identities. An extreme example of …