[Comp-neuro] (1) Maybe channel biophysics is not the "real" level for analysis of brain function.

[James Schwaber]

A colleague of mine just pointed me to this fascinating thread. It is so 
great to find you unrepentant and unregenerate, Jim! Loving it, as 
always. I have read through some recent posts and would like to add 
three (I hope useful or provocative) thoughts. To keep the length 
compatible with email, I'll send each idea separately, starting below.

_(1) Maybe channel biophysics is not the "real" level for analysis of 
brain function._

I agree with what Harry Erwin said about looking at the brain as an "M" 
system that maintains a model of its environment. Neurons and brains are 
immensely plastic. The plasticity arises from differential receptor 
occupancy linked to biochemical and gene network activity. In this way 
brains continuously learn, modeling and remodeling their experience in 
the environment over time. This supports the rewiring needed not just in 
learning but as the brain is modified by experience, aging, injury etc. 
There is not a fixed, neuronally specific "circuit for function X".

As a result, once you leave purely sensory or motor cells it is the 
normal observation that individual central neurons do not produce 
reliable spike behavior in response to naturalistic stimuli-inputs. Just 
as JB notes about Purkinje cells. Thus we may take a PSTH to "see" what 
the neuron "does", and sometimes get approximate statistical consistency 
this way, sometimes not. This is because the function of the brain is 
held in the biochemical states of its neurons, developed through 
environmental experience, as they behave in complex, dynamically 
shifting networks.

Neurons/brains are at base networked biochemical learning machines.

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