NASA Uses Fish to Fight Space Sickness

By | March 5, 2010 love doing zero-G stunts on the International Space Station, but only after the urge to vomit from space sickness has faded. Now fish, snails and other animals could help understand whether living in space can create long-term or even permanent damage in the inner ear.

Scientists found that the inner ears of toadfish have high sensitivity to even the slightest movements, and that the toadfish brain can both boost and reduce signals from the sensitive inner ear. Because humans have very similar ear structures to these and other animals, toadfish could provide clues about how astronauts’ inner ears adapt to spaceflight.

“You can drop a fish’s inner ear right into a human and it fits right in there,” said Richard Boyle, a biologist at the NASA Ames Research Center in Moffett Field, Calif.

Humans do eventually adjust to living in a weightless environment. But their inner ears have to go through a second round of readjustment to full Earth gravity once they return — and scientists still don’t know how easily the inner ear can make that switch after longer space missions.

Boyle’s work is detailed in a study published in the February issue of the journal Proceedings of the National Academy of Science. His co-researchers included lead author Stephen Highstein, a marine biologist at the Marine Biological Laboratory in Woods Hole, Mass., and Richard Rabbitt, a bioengineer at the University of Utah in Salt Lake City.

Getting your space bearings

Living beings evolved inner ears with hair cell sensory organs that can detect sounds as well as movements of the head. The balance sensory organs include tiny ear stones made of calcium carbonate that act as small weights because of gravity.

When the head moves, the inertial lag of such stones creates force on the hair cells — not unlike how car passengers will feel the press of inertial lag when their vehicle jerks forward from a standstill. That signal gets amplified so that the brain automatically registers even the smallest head movements. The inner ear similarly detects bigger events such as the sudden drop when a person steps off a curb.

The system works beautifully on Earth, but quickly leads to disorientation and nausea for spaceflyers who first experience weightlessness in space.

“When you’re up in space, you still have mass but no weight,” Boyle told “So you can’t detect gravity, and the structures sensitive to inertial acceleration and orientation with respect to gravity lose their properties.”

Inner ears go haywire for a few days before the brain takes charge to regain a sense of balance. The nervous system also begins boosting the signal strength from the inner ear, so that the human or animal becomes hypersensitive to movement.

via NASA Uses Fish to Fight Space Sickness – Yahoo! News.

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