Balancing Brains

It takes time for the brain to learn how to interpret the new information, to form a new model, to figure out when to switch from one model to another. And during that transition, when the brain's confused about which model to use, it starts to interpret sensory data in odd ways. You get illusions, for example, that the world around you is moving, when all that's really moving is your head. Headaches and motion sickness are other symptoms of this disorienting transition. "The perceptual illusions that astronauts have are very interesting," he notes.

Paloski, who works with astronauts at the Johnson Space Centre, is trying to find out exactly what cues astronauts to switch models. He's doing this by sending their brains confusing sensory information, which, he believes, will force a shift from one state to another.

About ten years ago, he recalls, during a post-flight neurological test that involved a rotating chair, an astronaut who had already regained the ability to balance somehow lost that ability all over again. Retested, the astronaut kept falling over, "just like on landing day."

"Something happened in that person's brain that caused a switch, we think, from a terrestrial adaptation back to a 0-g adaptation. Probably the brain got confused by the funny signals it was receiving on the chair, and it chose to interpret those signals as saying, I must be back in space. And it flipped back to the model that was congruent with space flight."

Image credit: NASA Using this human-sized centrifuge, Bill Paloski plans to spin astronauts in order to learn more about how our brains manage mental models for balancing.

Now, Paloski is trying to recreate that effect.

"We know that astronauts are just on the verge of readapting to Earth in the 2 to 4 day time frame after short duration space flight. So we thought, why don't we go to day 3, when we think somebody is just about adapted, and see if we can cause the brain to switch states."