joyful air to the proceedings, as though the subject had set herself awhirl—the tipsy stenographer at the office Christmas party. At the experimenter’s command, the subjects, eyes closed, tilt their heads left and then right while spinning. I took a brief turn in the rotating chair that resides in the lab of space motion sickness researcher Pat Cowings, at NASA Ames. At the first head tilt, something lurched inside. “I can make a rock sick,” said Cowings, and I believe her.
What has aeromedical science learned from the combined tortures of motion sickness research? For starters, we now know what causes it: sensory conflict. Your eyes and your vestibular system can’t get their stories straight. Say you are a passenger belowdecks on a heaving ship. Since you are moving along with the walls and floor, your eyes report to your brain that you are sitting still in the room. But your inner ear tells a conflicting story. As the ship moves you up and down and around, your otoliths—tiny calcium pebbles that rest atop hairs that line the vestibule of the inner ear—register these movements. If the ship dips down into a trough, for instance, the otoliths rise; when the ship crests, they press down. Because the room is moving with you, your eyes detect neither. The brain gets confused and, for reasons not well understood, responds by nauseating you. Soon you are heaving too. (This is why it helps to stay up on deck, where your eyes can register the boat’s motion relative to the horizon.)
Zero gravity presents a uniquely perplexing sensory conflict. On Earth, when you’re upright, gravity brings your otoliths to rest on the hair cells along the bottom of the inner ear. When you lie down on your side, they come to rest on the hairs on that side. During weightlessness, the otoliths, in both situations, just float around in the middle. Now if you suddenly turn your head, they are free to ricochet back and forth off the walls. “So your inner ear says you just laid down and stood up and laid down and stood up,” says Cowings. Until your brain learns to reinterpret the signals, the contradiction can be sick-making.
Given the culpability of the human otolith, it is not surprising to learn that sudden head movements are extremely, to use the lingo of motion sickness experts, “provocative.” If you look at back issues of Aerospace Medicine, you can find pictures of grim-looking World War II troops with their heads wedged between padded vertical slats on the walls of troop transport planes: someone’s attempt to stem the vomitous tide. (The smell of other people’s emissions in close quarters is also highly “provocative.” Cowings likes the term “inspirational.”) Airsickness and seasickness were serious enough problems during the war that the government, in 1944, convened an entire United States Subcommittee on Motion Sickness. (Then again, it has also convened a U.S. Subcommittee on Poultry Nutrition and one on sedimentation.) Charles Oman, resident motion sickness expert at the National Space Biomedical Research Institute, confirmed the perils of wanton head-swiveling by mounting accelerometers on the backs of astronauts’ headwear. The ones who, just by nature, tend to jerk their heads around a lot are the ones most likely to suffer from motion sickness during a mission. What’s true in space is true in a car on a winding road: No matter how much the driver behind looks like the GEICO caveman, don’t whip your head around to look. According to work done by prolific 1960s motion sickness researcher Ashton Graybiel, even one head movement in highly susceptible people produces a measurable increase in their sweat level—an indication that nausea is just around the bend.*
“We actually proposed making a beeping beanie,” Oman said. If astronauts moved their head too fast or too much, they’d hear a beep letting them know. Oman did not record the astronauts’ responses to the beeping beanie proposal, but I’m
What has aeromedical science learned from the combined tortures of motion sickness research? For starters, we now know what causes it: sensory conflict. Your eyes and your vestibular system can’t get their stories straight. Say you are a passenger belowdecks on a heaving ship. Since you are moving along with the walls and floor, your eyes report to your brain that you are sitting still in the room. But your inner ear tells a conflicting story. As the ship moves you up and down and around, your otoliths—tiny calcium pebbles that rest atop hairs that line the vestibule of the inner ear—register these movements. If the ship dips down into a trough, for instance, the otoliths rise; when the ship crests, they press down. Because the room is moving with you, your eyes detect neither. The brain gets confused and, for reasons not well understood, responds by nauseating you. Soon you are heaving too. (This is why it helps to stay up on deck, where your eyes can register the boat’s motion relative to the horizon.)
Zero gravity presents a uniquely perplexing sensory conflict. On Earth, when you’re upright, gravity brings your otoliths to rest on the hair cells along the bottom of the inner ear. When you lie down on your side, they come to rest on the hairs on that side. During weightlessness, the otoliths, in both situations, just float around in the middle. Now if you suddenly turn your head, they are free to ricochet back and forth off the walls. “So your inner ear says you just laid down and stood up and laid down and stood up,” says Cowings. Until your brain learns to reinterpret the signals, the contradiction can be sick-making.
Given the culpability of the human otolith, it is not surprising to learn that sudden head movements are extremely, to use the lingo of motion sickness experts, “provocative.” If you look at back issues of Aerospace Medicine, you can find pictures of grim-looking World War II troops with their heads wedged between padded vertical slats on the walls of troop transport planes: someone’s attempt to stem the vomitous tide. (The smell of other people’s emissions in close quarters is also highly “provocative.” Cowings likes the term “inspirational.”) Airsickness and seasickness were serious enough problems during the war that the government, in 1944, convened an entire United States Subcommittee on Motion Sickness. (Then again, it has also convened a U.S. Subcommittee on Poultry Nutrition and one on sedimentation.) Charles Oman, resident motion sickness expert at the National Space Biomedical Research Institute, confirmed the perils of wanton head-swiveling by mounting accelerometers on the backs of astronauts’ headwear. The ones who, just by nature, tend to jerk their heads around a lot are the ones most likely to suffer from motion sickness during a mission. What’s true in space is true in a car on a winding road: No matter how much the driver behind looks like the GEICO caveman, don’t whip your head around to look. According to work done by prolific 1960s motion sickness researcher Ashton Graybiel, even one head movement in highly susceptible people produces a measurable increase in their sweat level—an indication that nausea is just around the bend.*
“We actually proposed making a beeping beanie,” Oman said. If astronauts moved their head too fast or too much, they’d hear a beep letting them know. Oman did not record the astronauts’ responses to the beeping beanie proposal, but I’m
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