The phenomenon of corollary discharge has some interesting ramifications on the model of the neural system which we have been building in class. It means that the behavior of central pattern generators is controlled by other central pattern generators in addition to self-firing neurons and external input. Since behavior is regarded as a complicated subject it makes sense that one would required a complex system for modeling behavior (i.e. the nervous system).

The presence of corollary discharge also makes the nervous system more difficult to study in an experimental setting. Generally an experimenter is forced to work within a limited and somewhat simple set of parameters. The complexity of the nervous system in which central pattern generators can be affected by each other, external information, or self-firing neurons makes the identification of cause and effect relationships within the nervous system much more difficult; narrowing the number of variables down such that one still can obtain significant data becomes the most important task. An effect with multiple causes is much more difficult to explain. Are all variables of equal importance? If not, which variables are more important and why?

In class we have discussed the problem of motion sickness and it's causes. An individual suffering from motion sickness is receiving contradictory information from the external sensory system and from corollary discharge signals. The external sensory system is telling the nervous system that the person is moving whereas the corollary discharge signals are telling the nervous system that the person is not moving. The nervous system becomes "confused" resulting in dizziness, headaches, and even nausea

Here, it's shown that the corollary discharge signals and the external sensory signals both contribute to a person's sense of motion. However, there still remains the issue of those who do not get motion sickness. Do they have faulty sensory signals or are they receiving fewer corollary discharge signals? If they are receiving fewer or discarding the information transmitted via corollary discharge, how and why? It seems likely that a person who does not suffer from sea-sickness receives the same amount of corollary discharge signals, but that the central nervous system does not process these signals in the same manner that the sea-sick individual does. Eventually, those who suffer from sea-sickness will recover from it if left at sea for a lengthy period of time. Therefore it stands to reason that the individual is processing the corollary discharge information that was confusing her/his nervous system in a different way. It seems likely that the corollary discharge information resulting in the motion sickness are being discarded in a manner not unlike olfactory desensitization.

Yes, its probably true that the nervous system is more complex in its causal relations than most experimenters are entirely comfortable with. So, simplify to get reliable results? Or try and develop ways to characterize its complexity? Nice problem. So too the differences in susceptability to motion sickness. Seems to me worth noting that there ARE at least two possibilities: people less prone to seasickness MIGHT, as you say, have less potent CD signals. OR the same signals might have less effect. Which would suggest different possible forms of therapy. How might one distinguish among these (and other) possibilities in terms of additional observations? PG