From: Brad Wyble <[EMAIL PROTECTED]> >> Nonlinear dendritic integration can be accurately captured by the >> comparmental model which divides dendrites into small sections >> with ion channels and other internal reaction mechanisms. This >> is the most accurate level of modeling. It may be possible to >> simplify this model with machine learning techniques and without >> significant loss in accuracy. > >I am well aware of compartmental modelling and have done it myself. But >this type of model only accounts for the physical size/character of a >dendrite, ignoring, in principle, a whole raft of complex molecular >dynamics of what might be occuring inside it. Such molecular dynamics >will sure contribute to the nonlinear aspects of a dendrite.
Each compartment can have internal models of ligand- and voltage- -gated channels, thier de-/phosphorylation and other forms of neuromodulation, etc. So that's one more level of organization, but no more than that. This can be incorporated in the compartmental framework. >> >Just as an example, a new type of neuron has recently been discovered that >> >can hold a steady state of firing in isolation, apply current, rate >> >increases and remains stable at a new threshold. It's dynamically >> >settable, which blows away all standard Integrate & Fire models. >> >> I don't know the exact mechanisms that give rise to that type >> of neurons, but the comparmental model should be able to cover >> this. What is needed is a large-scale database of neuronal >> characteristics (automation). > >Yes, one can create a model of a neuron that does this, it's already been >done. It's far from a standard model though. The problem here is that we do not have enough *data* about that neuronal cell-type in question. The basic formulation of the model is OK. We just need to plug in the database; which requires large scale automated bioassays. >My point, however, was that there is an entire world of complexity within >the cell that will be relevant to its role in a neural network (as opposed >to simply metabolic) that we are just beginning to understanding. Unless you're talking about complex intracellular information processing, which I already explained there is no evidence of such so far. I'm currently looking into simple organisms to try to get more decisive clues to this issue. I'm optimistic. In the end, there is only one difference: the difference between 'do' and 'talk'. And once you've decided to do it, there is only one direction to go. I'm willing to work on it even though I'm not certain of success. It's an emotional thing I guess =) YKY ____________________________________________________________ Find what you are looking for with the Lycos Yellow Pages http://r.lycos.com/r/yp_emailfooter/http://yellowpages.lycos.com/default.asp?SRC=lycos10 ------- To unsubscribe, change your address, or temporarily deactivate your subscription, please go to http://v2.listbox.com/member/[EMAIL PROTECTED]
