The motor symphony and the central pattern generation are vital for understanding behavior. Central pattern generation can be seen as a way of explaining instinct. This is opposed to a motor symphony which is a coordinated movement in a specified pattern. The most important aspect of a motor symphony is that it is being updated in parallel with its action. The distinction between the two modes, is the importance of sensory input and how it affects output. Is it that there is some sensory input which then generates the output, and thus there is a reafferent loop, or that we create new outputs in response to some input ? Do we affect our reality or does it affect us ? Our behaviour is tailored to allow us to survive in our world, and to be able to deal with all the changes that come about. Some behaviours are instinctual, and others must be tailored to suit the situation.

Some central patterns seem to be inherited between generations, such as the sucking reaction. These are behaviours vital for our survival and they are programmed into us before we are even born. In this way central patterns do seem to have a function in our daily lives. There are some variations on the basic central pattern because adaptation is the only way we can survive, we must have some change. The variation of "scores" present is like the recombination of genes in the processes of creating a new human being. There must be a way of passing on instinctual behaviours which are necessary for preserving our species.

A motor symphony on the other hand must be adaptable, we must somehow adapt to ourselves to the outer reality, and create something within. A motor symphony must be adaptable because conditions are constantly changing, and it order to survive we must accommodate these changes. This adaptability is a way of surviving in our ever changing reality. A motor symphony can be seen as coming from the cerebral cortex, where the higher functions are thought of, whereas a central pattern generation seems to emerge from the spinal cord. A specified pattern is a product of sensory neurons talking to motor neurons in the spinal cord, and in most of us the conversation being relayed to the cerebral cortex, where a plan of action in approved. This is what is so important about a motor symphony, it is the product of higher thinking.

The two forms are vital for our survival because we must both be able to> adjust our movements through sensory perception, or we must be able to make instinctual movements to survive.

General points important, but don't link them too tightly too a "motor symphony"/CPG dichotomy. As I use the phrase, motor symphony is simply a descriptor of the complex motor neuron discharge underlying movement, any movement. And a CPG is one possible way of accounting for that motor neuron discharge. Your broader concerns are, on the other hand, intriguing and important. One must, in general, have both stabilty and variability in biological systems. And the latter is present at several different levels based on several different mechanisms. PG