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### Lambda rule for fast spiking axon

Posted: **Tue Mar 13, 2012 11:30 am**

by **vladimirov**

Hi,

Would the standard d_lambda rule still applicable for a fast spiking axon, when interspike intervals are ~1.5-2 ms? The generic formula suggests

Code: Select all

`nseg = int((L/(0.1*lambda_f(100))+.9)/2)*2 + 1`

is it still good for an axon which conducts trains of high-frequency spikes (>300 Hz)?

Thank you!

### Re: Lambda rule for fast spiking axon

Posted: **Tue Mar 13, 2012 8:39 pm**

by **ted**

Appropriate discretizations for time and space are always empirical issues. The d_lambda rule for spatial discretization generates a very good first guess, and it often produces a satisfactory result. However, it is always a good idea to verify. You might want to do a control run with the discretization produced by the d_lambda rule, then

forall nseg*=3

(which should reduce spatial error by almost an order of magnitude),

then do a test run and compare it against the control result.

This recommendation has nothing to do with whether the model in question has a fast spiking axon--such a test is advisable regardless of what kind of model is being studied.

By the way, I see that hoc code exported from a recent version of the CellBuilder uses a slightly different formula for nseg--

nseg = int((L/(0.1*lambda_f(100))+**.999**)/2)*2 + 1

### Re: Lambda rule for fast spiking axon

Posted: **Wed Mar 14, 2012 10:22 am**

by **vladimirov**

Ok, thanks!