Corollary discharge signals help explain many of the previously unexplainable and incomprehensible components of behavior in the "brain is behavior" model. One of the overwhelmingly apparent aspects of behavior is that the nervous system often produces different outputs for the same set of inputs, and such a system is more easily justifiable with the presence of corollary discharge signals. Since such signals reach many more neurons than the average action potential, it is possible for differnt outputs and motor symphonies to be produced because a greater number of neurons may be activated at differnt times. Corollary discharge signals therefore expand on the concept of the "boxes" of the nervous system. Although one still recognizes that there are distinct "boxes" of various sizes that comprise the nervous system, the links between them are multiplied with the existence of corollary discharge signals.
Another function of corollary discharge signals is that they are continuous monitors of sensory input in that they provide a set of expectations for what the sensory should be and compare in relation to what it is. Such a function helps explain multiple examples of behavioral phenomenon, most specifically the discomfort felt by amputees in their amputated limbs and various cases of motion sickness.
The most fundamental function of corollary discharge signals is to provide a basis for central pattern generaters to work together without relying on control from any other source. Some of the specifics of how this system works have been previously explained and it is evident that corollary discharge signals account for much of the unaccounted for in a more simplistic "box" model of the nervous system, such as the presence of outputs without inputs, coordinated outputs and other behavioral patterns. In viewing the brain (or nervous system) as behavior, the function of CD signals becomes essential because they justify that much of the source of behavior is purely biological and they show the vast connections of all the parts of the nervous system.
Nice description of both some specifics and generalities. Can imagine any additional things CDs might help explain? PG