[Craig] Hi, I'm Craig.  I'm always movin.  And this is Mental Floss Video.

Today I'm gonna answer Craig's big question - what causes motion sickness?

I don't remember asking that.  And I've stopped moving.

Motion sickness is when someone experiences symptoms like nausea or dizziness when their perception of movement differs from their vestibular system's feeling of movement.

Today, I'm gonna talk about why that is.  Let's get vestibular!

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[Craig] There are three different types of motion sickness.  The first one involves things like air sickness, sea sickness, and possibly car sickness, which occur when a person's vestibular system senses motion, but the motion isn't seen.

The vestibular system, by the way, is what senses balance, motion, and equilibrium.  It can be found in the inner ear.  And so can wax.

The second type of motion sickness is when the visual system detects motion but the vestibular system doesn't.  This is like when an IMAX film makes you feel dizzy.

And the final type of motion sickness occurs when both the visual and vestibular sense motion, but they don't feel related.

Experts, as usual, don't know for sure what causes motion sickness in these situations, but there are a few prevailing theories.  The most common one is simply that the conflict between visual and vestibular systems causes dizziness.

There's also the Nystagmus Hypothesis, my nickname in high school, which states that motion sickness is caused by the Vagus Nerve, one of the cranial nerves that brings signals to the brain.  This nerve takes note when the eye muscles have the reflexive traction that accompanies the detection of motion.  

So, the Vagus Nerve triggers the feeling of nausea.  Or nausea [pronounced nawja].

Another theory is that motion sickness is more psychological.  The vestibular system that I mentioned earlier tells the brain that it detects motion, but the eyes don't recognize that same motion, so the brain believes that it has encountered something that's poisonous to the brain.  And this leads to nausea or vomiting - an attempt to get rid of the poison.

In the 70's, psychologist Dr. Michele Trizman claimed that this is an evolutionary response to food poisoning.  There are also new theories being developed, like at the University of Minnesota, kinesiologist Dr. Stoffregen has been studying motion sickness for years.  He believes that it's not connected to the inner ear at all.  Instead he thinks it's the body attempting to maintain posture and then getting dizzy when it's unable to.

The Naval Aerospace Medical Institute has also been studying motion sickness, so they can develop medication to treat it.  They've found that it's related to neurotransmitters like these ones.

Interestingly, medications that treat nausea caused by things like food poisoning and chemotherapy don't tend to effectively treat motion sickness.  So that suggests it's a unique type of nausea.  Or nausea [pronounced nawja].

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Thanks for watching Mental Floss Video, which is made with the help of all these Nystagmus Hypotheses.  If you have a question of your own that you'd like answered, leave it below in the comments.

See you next week.