I am quite new to NEURON and I have a (hopefully) very simple problem since I could reduce the core of it to its simple basis:

I have just one cylinder with simple passive properties and I inject a positive current for some time.

Actually, I should be able to measure tau from the voltage decay when current injection is over, either by:

1) Checking at which time V has decayed to 1/e

2) Get the slope of the (natural) logarithmic voltage plot. tau is 1/slope

The first solution works, even with more complex morphologies, at least the "experimental" tau is in the range of the theoretical tau = cm*Rm

However, I've read that the assumption with the 1/e decay is only true for a isopotential sphere. In cylinders it decays faster. Also, noise would be a problem.

Hence, I tried to use solution 2). However when I do the logarithmic plot, t

**here is no linear slope part**after current injection is gone! Not with complex morphologies and not with the simple cylinder.

What am I doing wrong?

I attached an image of the simple cylinder experiment. On the left, the voltage over time can be seen, on the right the (negative, but that does not matter) voltage is plotted logarithmically.

You can see the properties of the cylinder in the console as well as the IClamp parameters.

I should admit, that of course you might define some part of the logarithmic plot as linear, however the tau I would get from it, is not in the range of the theoretical tau.

By the way: When I do the slope thing with

**real data**, i.e. averaged voltage traces, it actually works, you see a clearly linear part.

Hopefully, someone can help me. Thank you in advance!