Reply to comment

So, I was especially intrigued last week when we were discussing how the neuromuscular (and other systems) may in fact run as feedback loops that seem to have a 'purpose' by virtue of their set point that seems to drive the function towards some kind of end. In addition, what intrigued me was the change in set points: how that happens, why, and at what rates.  With that notion of recursion in mind, I have a few issues that I'd like to discuss.

1. What about the existence of a foundational (and universal?) set point?

Is there some default set point, such that a system can revert to that value?  The analogy I'm thinking of is with evolutionary systems (i.e. Steve Jay Gould's notion of evolution of complexity/ 'drunk-man's stumble'), where Gould argues that complexity arises through short bursts of complexity that are NOT directed towards some goal (e.g. complex morphotype), but instead arise through the overcrowding of a very simple niche.  This notion goes against a directed notion of evolution (e.g. natural selection) and instead implies that evolution of complexity can occur through too many simpler forms.  The important thing about this analogy is that the simple/basic is seen as the foundation and goal, NOT the teliological quest for complexity/ progress that we would probably assume would be the goal of evolution.  If this notion applied to the nervous system, it would seem that our perspective is all wrong about the set point being the purpose, when in fact the purpose might be something else.

2.  The definition of 'purpose' raises a lot of interesting issues. 

a.First of all, why are we defining the 'purpose' of the nervous system as some implicit teliological goal?  Couldn't the purpose be the rate of change of the set points, not just the set point itself?  I guess my closest analogy is with particular morphogens during development of embryos.  The morphogen's method of action is NOT just the concentration but the rate at which the morphogen's concentration changes.  If the change is drastic enough, then a resulting change occurs in the phenotype, but if that rate of change threshold is not achieved, then no change results.

3. Could the set point be a strong enough factor in the nervous system such that the loop changes directions entirely based on the set point change?  For instance, we were assuming with examples such as anorexia that the negative feedback loop keeps getting more negative with a change in set point.  But, could the set point be independent enough/strong enough driver of the system that it could switch the whole system in another direction (e.g. positive feedback loop) instead?