Giz Explains: What Causes Motion Sickness?

Giz Explains: What Causes Motion Sickness?

If the motion of the ocean leaves you queasy, the open road makes you dry heave, or the floating feeling at taking off makes your head spin, you’re not alone. Motion sickness is a common occurrence among travellers — and one not easily remedied. That’s why you have to stop motion sickness before it starts.

What Is Motion Sickness?

Motion sickness is a disturbance of the inner ear caused by repetitive motion, such as boats bobbing on ocean swells or planes passing through turbulence, that affects a person’s sense of equilibrium, spacial orientation, and balance.

And it’s not just physical motion. Driving and flying simulators, VR headsets like the Oculus Rift, or just looking through a microscope can bring on a case of motion sickness for some sufferers. Oddly, rates of motion sickness vary throughout the population, affecting kids (age 5-12), women and the elderly more often and more severely.

Why Is the Room Spinning?

The physiological root of motion sickness stems from the way that the brain perceives motion. See, the brain gets information regarding the body’s spatial orientation — whether you’re sitting, lying down, standing on your feet, standing on your head — from three separate sources. First, there’s the fluid-filled inner ear that monitors motion, acceleration, and gravity. Second, your eyes play a vital role in determining your orientation, acting as a check against which the signals from the inner ear can be measured. Third, deep tissues of the body surface, known as proprioceptors, help generate a sense of limb orientation by measuring and reporting the joint angle, muscle tension, and muscle length of your arms and legs. These systems each release varying levels of histamine, acetylcholine, and norepinephrine.

For example: You get dizzy from spinning in a circle because the fluid in your inner ear is still sloshing around after you’ve stopped physically spinning. This sloshing is still telling your brain, “such spin, so twirly” while your eyes are providing contradictory information, “none spin, twirls gone, so sad” and your proprioceptors are going, “screw all the spinning, are we even still standing?,” and all that information is getting blasted into your brain at the same time and it’s all, “Da fuq?”

It’s the same with motion sickness. The repetitive motion of the ocean gets the fluids in your inner ear sloshing, which send a signal to your brain from that’s contradictory to the one being reported by the other two systems.

“In motion sickness the fluids of the inner ear are moving along with you in the moving vehicle. The brain is interpreting that movement, [and] instead of saying ‘yes you are in a moving car,’ it’s interpreting it as an incorrect stimulus,” Sujana Chandrasekhar, director of New York Otology and ENT surgeon at the New York Head and Neck Institute, told Popular Science.

What’s really nuts is what causes the nausea associated with motion sickness. When your brain gets these contradicting signals, it automatically assumes that one of the three sensory systems is stoned. Seriously — the brain treats the contradicting incoming signal as evidence of a hallucination brought about by poisoning, and reflexively instigates a purge of your stomach contents.

Forget the Science, Just Make It Stop

Sorry, but unless you wanna go ahead and remove your inner ears, there’s no effective way of stopping motion sickness once it’s started, short of halting the vehicle’s motion altogether. You’ll have to just wait it out, though finding the least moving section of the vehicle — ie, a seat just over the plane’s wing, or at the very lowest center point of the boat — will help significantly lessen the effects. Just looking at the horizon can help steady your legs by giving your brain a static point of reference from which to work.

A variety of both prescription and over-the-counter medications that interact with the relative levels of histamine, acetylcholine, and norepinephrine are also available, and certainly work better than the $US40 acupressure bracelets you find in Sky Mall. [MedicineWebMDWikiPopular ScienceUniversity of Washington]