Trying to read while in a car provokes dizziness and nausea. Here’s how the wiring works.
When your head moves, the vestibular organs inside both ears has little tentacles that detect the movement, and sends a message to your brainstem. That is the input. That wire stimulates another wire called the output which responds automatically. The easiest way to experience is to look in the mirror and turn your head left and right and notice that if you relax notice your eyes stay still even though your head turns. When you turn your head to the left the vestibular system detects the movement, inputs that to the brainstem, and stimulates the eyes to move in the opposite direction. This is called the vestibular ocular reflex (VOR). It is not the only reflex involving the vestibular system, but we will emphasize it here because it is so clearly involved in the problems associated with dizziness and nausea provoked by reading while riding in a car.
Reflexes are great because they act so quickly and precisely but there are times when you have to deal with much more difficult situations. In order to play sports you have to control more than the eyes. When you have large volumes of input flooding the brainstem, all that information has to go somewhere.
If you slowly turned your head left and right, your eyes would respond proportionally, and you would not experience nausea or dizziness. If you were to turn your head faster, you might. What happens when you move faster is that the volume of information going into your brainstem is much higher. At some point the actual amount of information is more that what can be absorbed by the output. There is an overflow road that moves up towards the brain. It is at the point that the brain receives too much information that you feel unsettled.
The first exercise to practice is simply to practice turning your head slowly while relaxing the eyes. What you are dong is increasing the capacity of the normal system so that you can tolerate a lot more movement before information has to be diverted to the overflow. Here is a video on how to do the basic vestibular drill.
So it should make sense why faster spinning or roller coaster rides would make someone feel nauseous or dizzy. But why are things dramatically so worse while driving in a car? We are built with two main systems, one of which is designed for easy repetitive tasks and one that is designed for more deliberate difficult tasks. Now, suppose you have to focus on small words or some icon on your computer. You don’t think about it, but your eyes have to aim very precisely to converge on the target. What happens is that you actually block the output portion of the VOR. As we mentioned here, (link to be added later), there are five states of mind that exist in the brain, and one of those states we call focus). When focusing on something specific, we have to be still, and this VOR gives some
insight into the mechanism of focusing.
What happens in this situation is as follows. The eye muscles are under both deliberate and automatic control. However, in order to precisely control the eyes as required for reading, the input from the vestibular system to the eyes is automatically blocked. This is not a problem normally because you are sitting still while reading. However, when in a car, all that information cannot flow out into the eye muscles but instead flows exclusively into the brain. The nauseation is simply an experience of sensory overload.