Why does motion sickness happen?

 I'm sure all of you would be familiar with motion sickness. If you are not a victim of one, you would've had a mom who has it or dad, or uncle, aunt or a distant relative, or at least a friend who cribs about it all the time. It is a common condition that occurs to some people when they travel in a car, train, plane, boat, roller coaster or similar amusement park rides. It starts as a feeling of uneasiness or sweating and progresses to maybe dizziness or nausea and vomiting. Have you ever wondered why this happens?

At least I'd never wondered all these years as to why something as simple as moving in a car should disturb your entire system and send you throwing up all over the place. Apparently, our brain receives signals from the ocular ( the eyes) and vestibular ( the ears ) systems for inputs on our movements. (if you are wondering how the ear is involved in detecting movement, please hold on to that question for another minute. For now just assume it has that added responsibility too apart from the usual hearing responsibility.)

What if the ear and the eyes give contradictory inputs to the brain? What happens then? Let's say the eyes are telling the brain that the person is not moving while the ear is telling the brain that the person is moving? The brain gets confused and assumes the worst, that we are hallucinating. And goes on to assume that we've been poisoned. So , it very dutifully sends signal to the gut asking it to empty its contents. Hence the never ending puke!!

If you would've noticed, the effects are accentuated when we are reading a book, or looking at a person and talking, or have our eyes fixed on our phones. Because in all these cases the eyes seem to think that we are not moving.  And if you've had your share of wise old grandparents, they would've suggested you to look out of the window to minimise the effects. Well, they were just helping your eyes understand that we were indeed in a state of motion!

Now the ear and it's extra power. The ear is more complex that we think. It can do more than just

hear. It has three semi circular canals which can detect rotations, namely, a twirl( we stand in one place and rotate our body till we get dizzy and drop off ), a cartwheel( gymnastic movement which looks like a sideways somersault ) and the nodding of the head movement. And it has two other small structures that can detect linear movement, head tilt and can detect how fast we accelerate. It sure looks complicated. I'm going to break it down to crude facts that give us the logic, logic enough to proceed with this post. Basically these semi circular canals or the two other small structures, they contain teeny hair particles, that detect the movement of a fluid present in them and transmit the information thus gathered to the concerned nerve endings, who so dutifully carry them along alerting the brain and the concerned parts of the body.

In fact motion sickness is one other common sickness like common cold, that is so less understood. Over the decades, everyone seems to have their own theory. We've heard the first theory so far. The brain gets confusing inputs from the two sensory organs and decides we are infected with toxins and helps us eliminate the toxins by throwing up. Before we move on to theory two, let me give some more information right about here.

According to theory number one, motion sickness happens in three ways. One, when the ears sense motion and the eye doesn't, as is the case with car sickness, air sickness, sea sickness,dizziness due to spinning. Two, when the ears don't sense any motion but the eyes do, as is the case with 3d movie viewing, virtual reality experience, for some, video game playing. Three, is when both sense motion, but they do not correspond, as is the case with moving on a bumpy rode at a slow speed. The eye thinks we are moving terribly slow, wherein the jerks make the ear feel that the movement is vigorous. Do look at the lovely video present in this page when you find time.

That being understood, lets move on to the theory number two. This theory is called negative reinforcement. For those of you who have toddlers or have children who have just passed the toddler phase, you know that an effective way of parenting is positive reinforcement. That is, when your child exhibits good behaviour, throw all the attention and love on him, thus reinforcing the fact that good behaviour gets rewards, thereby encouraging him to be a goody goody boy. Negative enforcement is just the opposite. When he does something bad, give him attention by punishing him reprimanding him, taking away screen time and so on. While this is not recommended to be a good parenting technique, it comes handy to understand what our body is telling us. When we spin in our favourite merry go round or one of those fancy rides in an amusement park, just for the kicks of it, our body doesn't like it. And would like to warn us never to do that again. So what does our body do? Gives us a series of unpleasant feelings to scare us away from doing it again.

One other theory is regarding the occular vestibular system. Just a fancy way of saying eye-ear system. Have you noticed, when you turn your head to the right, your eyes 'automatically' turn to the left. Why does this happen? When you turn your head to the right, the images on your retina get disturbed. So your eye moves in the opposite direction to compensate to make sure the images are intact. How does this happen? The ear, vestibular system, (like mentioned way above) can sense a head turn or a tilt. When it does that , it sends signals to the eye muscles asking them to move in the opposite direction. In our i'm-reading-a-book-in-the-car scenario, there are two type of eye movements. Voluntary (as in, when you read from left to right) and involuntary when your head moves because of the jerks on the road. Now when both these kind of movement excite the occular muscles, sometimes it so happens that they contradict each other and thereby end up exciting a nerve called the vagus nerve. Who is connected to the vomiting centre of the brain ( Yes, we do have something called the vomiting centre in our brains!!) And that sends us hurling unpleasant stuff from our gut all over the car! This vagus nerve also sends automatic reflexes like reducing the heart beat, the pressure and there by could get you to faint!

There could be more reasons but I think for a fair understanding three would do. Now, how do we treat this motion sickness? Some say, look out of the window, whiff of fresh air (car sickness), close your eyes, sleep. Some people tend to take some over the counter medication. What does this medication do? Prevents the nerves from getting excited, thereby preventing them from sending signals to the brain. These kind of medications, may induce blurriness of the vision because the inhibit the occular-vestibular co-operation. Other type of medications soothe the vomiting centre, thereby preventing a nasty throw up. The ones that soothe the vomiting centre also have some side effects that induce drowsiness, which in this case, adds on to our advantage.

There is no one solution yet that would cure motion sickness and free everyone from this inconvenience. And not everyone is affected the same way. This post is just a fair understanding of the subject. Let's look over or beyond or above or even under the horizon and hope for a break through to get us understand this bewildering behaviour of our very own human body. Doesn't it make you feel humble and doesn't it keep you grounded to know how much there is to learn yet, despite the immense developments and highly invested researches, despite the wondorous scientific advancement in the last decade. Amazing isn't it, the amount of mysteries waiting to be unlocked. For now, let's stay humbled and just say three very small aaaha's and be content!