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Our discussion this past week of the communication between corollary discharge signals and sensory neurons was interesting and allowed me to understand a bit about motion sickness (something about which I’ve always been curious). The idea that discomfort as a passenger of a vehicle is, in part, due to a difference in what the nervous system expects (I’m sitting still and my NS, or corollary discharge signals, expect signals from sensory neurons to agree with this) and the actual signals received (unexpected input signals of motion from sensory neurons) makes sense to me.

I don’t generally get carsick, unless the traffic is stop and go, and I’m reading. Looking out a window in a moving vehicle doesn’t bother me, and perhaps now this can be explained as my nervous system adapting to this kind of input. Or, is my nervous system innately better able to adjust to these discrepancies between expected inputs and actual inputs? For example, my father never seems to get carsick and can go on any manner of theme park ride without physical consequences. This could be explained by the fact that his NS learned to deal with these inputs over time but for the fact that my mother’s NS has never “learned” to adjust to those motion signals. While she perhaps is not as prone to carsickness as she was as a child, she is still more likely to be affected by these differenced between expectation of input and actual input. How much of our ability to adjust to these differences is inborn, and how much is learned through experience? What causes one person to become more ill than another given similar sensory input?

I do get motion sickness when I distract my NS by reading in a car in traffic. The words in front of me bounce up and down, the car jerks suddenly (it’s movements are unpredictable to me and I am not in control of the braking), and I lose my place on the page. I get dizzy, nauseas, and develop a headache. Maybe this can be explained by my NS not being able to anticipate such choppy movement and adjust in its processing of words when they are not still. In fact, anytime an image in front of me changes or moves when I, or my NS, do not expect it (I have trouble watching movies in cars as well), I feel ill. Perhaps when I am looking out of the window of the car, my NS is able to use visual sensory inputs to better adjust to the unexpected movement. When I read, my vision is focused on something else, and without the help of these visual sensory neurons, it is possible that my NS is more unable to adjust. Finally, perhaps, when I’m reading, but the car is moving smoothly, my NS is less dependent upon visual cues and can better adjust (as I do not feel sick in these situations)?