mats_trash at hotmail.com
Mon Jan 14 15:13:42 EST 2002
"Edmund M?ler" <edmund.mueller at freenet.de> wrote in message news:<a1ufmv$t8j0k$1 at ID-9504.news.dfncis.de>...
> Hi NG,
> in some computer simulation we use the HH model as described in
> Hodgkin, A. L. and A.F. Huxley. 1952d. A quantitive description of membrane
> current and its application to conduction and excitation in nerve. J.
> Physiol. (Lond.) 117: 500-544.
> Well, this is half a century old. I wonder it in the mean time other models
> were tried and published or the model was modified and improved.
> They themselves mentioned for example, that the "curve fitting" might have
> been improved by using higher exponents of n They used n^4 to reduce the
> computational effort, quite understandable at those times, I think. Nowadays
> computational power is manyfold. So maybe somebody has tried the suggestion?
> What about the knowledge of the assumption of "valves" (probabilitiy of
> being open: n, m, h in HH) in channnel proteins today. Is it still valid,
> e.g. potassium channels having four particles of which all must be in a
> certain position to open it (n^4), and 3 similar and one different for
> natrium channels? Or are the numbers different? And is it the same in rat
> hippocampal neurons?
> Sorry for the lots of question, but I'm actually a foreigner to
> neurophysiology who touched the topic from a technical side.
> Interdisciplinary work can sometimes be hard ...
It depends a lot on how detailed you want to get I think. Though the
hodgkin-huxley model is still used as the paradigmatic model of action
potentials, the picture is not as clear as it suggests. We now know
about numerous other ion channels (a plethora of subtypes of Na and K
channels, but also Ca and Cl and more), each with different kinetics
with various types of neurones expressing differeing patterns of
these channels. Some are voltage operated, some are opened by
intracelluar signals etc. There is a vast volume of literature on
these different channels and their function, but I don't know of a
model that integrates them all mainly because its so daunting. Not
only are there the channels to consider but the morphology of
neurones, the integration of synaptic potentials and more.
Consequently, as far as I know, neuron models are still described at a
higher level, approximating certain aspects. Christof Koch at Caltech
is an expert in modelling neurones, and he has a couple of good books
on different types of neuronal modelling (stochastics, modelling at
network level etc.) one is published by MIT press "Methods in
Neuronal Modelling" and the other by OUP "Biophysics of Computation"
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