modeling giant fiber

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demar
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modeling giant fiber

Post by demar » Tue Apr 12, 2011 5:59 am

Hi

I would like a point of view about this model:

http://senselab.med.yale.edu/modeldb/Sh ... Ccable.hoc

It describes uniform myelinated fiber.

Is it accurate for bigger fiber, with diameter around 100 um and so internode distance around 1 cm?

demar
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Joined: Tue Apr 12, 2011 5:46 am

Re: modeling giant fiber

Post by demar » Tue Apr 12, 2011 11:12 am

Some precisions:
I'm trying to modelise the earthworm axons, while my colleague performs experiment on real worms. My problem is that on the model, the threshold is highter for the smaller fiber (30 um) than for the bigger (80 um). The experiment gives the opposite result.
I'm trying to add diameter dependencies on the axon properties (cm, Ra and g_pas), but no succesfull result.

Any suggestions?

ted
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Re: modeling giant fiber

Post by ted » Wed Apr 13, 2011 10:37 am

demar wrote:I would like a point of view about this model:
. . .
It describes uniform myelinated fiber.

Is it accurate for bigger fiber, with diameter around 100 um and so internode distance around 1 cm?
The code in ModelDB entry 9851 was written by Michael Hines to reproduce the results presented in the paper Moore et. al 1978. That model was developed for the purpose of examining the effects of axon geometry on spike propagation. It should not be interpreted as being a model of a particular axon from a particular organism. The model's anatomical and biophysical properties are suitable for studies of excitation and conduction from the theoretical perspective taken by Moore et al., but axons from other organisms will have properties that are at least quantitatively different, and in the case of ion channnels may also have important qualitative differences.

With regard to the properties assigned in the file cable.hoc, please note that at least some of these are likely to be overridden by statements in other hoc files. For example, fig2.hoc contains statements that change diameter, and fig3.hoc contains statements that alter sodium and potassium conductance densities.

If you are interested in a particular kind of axon from a particular organism, it would be best to use hoc statements that assign properties appropriate for that organism.

ted
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Re: modeling giant fiber

Post by ted » Wed Apr 13, 2011 10:41 am

demar wrote:on the model, the threshold is highter for the smaller fiber (30 um) than for the bigger (80 um).
By "the model" you mean something that your hoc code creates? What is your hoc code that specifies the anatomical and biophysical properties of your model?
I'm trying to add diameter dependencies on the axon properties (cm, Ra and g_pas)
Not sure what this means.

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