Search found 19 matches

by calu
Thu Sep 01, 2016 2:54 pm
Forum: Getting started
Topic: Membrane current scaling
Replies: 2
Views: 5009

Re: Membrane current scaling

Right, I went in the wrong direction in the end. Thanks
by calu
Thu Sep 01, 2016 6:28 am
Forum: Getting started
Topic: Membrane current scaling
Replies: 2
Views: 5009

Membrane current scaling

Dear all, this question has already been answered, but I did not understand the answer. Maybe I am too bad at adding single digit numbers. (Sorry Ted, you answered here already https://www.neuron.yale.edu/phpBB/viewtopic.php?f=15&t=2931&p=11969&hilit=membrane+current+area#p11969 .) Following this ta...
by calu
Mon Jun 13, 2016 1:02 pm
Forum: Other questions
Topic: Extracellular stimulation: Why dV/dx and not V as input
Replies: 7
Views: 2535

Re: Extracellular stimulation: Why dV/dx and not V as input

Hi, this helpful, thanks. So, I'll just go through your questions. Which leg of the Pi is depolarized (has a positive shift of membrane potential)--the one that is attached to the positive terminal of the battery, or the one that is grounded? The grounded one is depolarized. It's v.m = v.int - v.ext...
by calu
Wed Jun 08, 2016 9:47 am
Forum: Other questions
Topic: Extracellular stimulation: Why dV/dx and not V as input
Replies: 7
Views: 2535

Re: Extracellular stimulation: Why dV/dx and not V as input

Thank you very much for this answer. Suggest you instead perform this simple gedankenexperiment. Consider a circuit that consists of three resistors connected in series, but laid out like the upper case greek Pi. That is, two of the resistors are the vertical legs of the Pi, and the third resistor r...
by calu
Tue Jun 07, 2016 9:02 am
Forum: Other questions
Topic: Extracellular stimulation: Why dV/dx and not V as input
Replies: 7
Views: 2535

Re: Extracellular stimulation: Why dV/dx and not V as input

Oh... right. It is the voltage. Sorry, got that wrong. I am still unclear about dV/dx vs V in extracellular stimulation. I do not understand (much like already discussed here https://www.neuron.yale.edu/phpBB/viewtopic.php?f=15&t=1609) why a gradient will stimulate the cell, an arbitrary increase in...
by calu
Mon Jun 06, 2016 12:57 pm
Forum: Other questions
Topic: Extracellular stimulation: Why dV/dx and not V as input
Replies: 7
Views: 2535

Extracellular stimulation: Why dV/dx and not V as input

Hello, extracellular stimulation seems to have produced many questions in this forum and maybe this is an unneccessary one. But I can't make sense of the basic approach. I understand that the parameter set by segment._ref_e_extracellular is the field strength abs(E) = abs(dV/dx) (if the gradient is ...
by calu
Sun May 15, 2016 3:39 pm
Forum: Modeling networks
Topic: Thin myelinated fibers
Replies: 9
Views: 6873

Re: Thin myelinated fibers

Hi, I tried both your proposed method of changing g[...]bar and mine of inserting a fast potassium channel in the FLUT segments. By increasing gkbar_axnode by 50%, I could eliminate the multiple action potentials. With my method, only very high (unrealistic, more than 10 times higher than observed) ...
by calu
Thu May 12, 2016 5:59 pm
Forum: Modeling networks
Topic: Thin myelinated fibers
Replies: 9
Views: 6873

Re: Thin myelinated fibers

Here are three other measures that would not add new differential equations to the model but should reduce its propensity to fire repeatedly after a single stimulus. 1. Decrease gnapbar_axnode. I suspect this will be most effective. 2. Increase gkbar_axnode. 3. Decrease gnabar_axnode. Yes, this sho...
by calu
Thu May 12, 2016 4:40 pm
Forum: Modeling networks
Topic: Thin myelinated fibers
Replies: 9
Views: 6873

Re: Thin myelinated fibers

Hi, Two questions. 1. Why would that be more of a problem for small diameter than large diameter? Because the node length does not scale with diameter, but the distance between nodes does. So the relation of (membrane area of node)/(membrane area of internodal compartments) ~ (inward current during ...
by calu
Thu May 12, 2016 12:03 pm
Forum: Modeling networks
Topic: Thin myelinated fibers
Replies: 9
Views: 6873

Re: Thin myelinated fibers

Thanks Ted and sorry for the late reply. I tried out your suggestions and still have mutliple APs, with just over threshold stimuli. I now assume that the effect arises from a simplification the McIntyre model applies. There are no fast K+-channels in the internodal compartments that are observed in...
by calu
Thu Apr 28, 2016 1:26 pm
Forum: Modeling networks
Topic: Thin myelinated fibers
Replies: 9
Views: 6873

Thin myelinated fibers

Dear all, I need to simulate thin (0.2 - 3µm) myelinated fibers of the autonomic nervous system. For larger (motor) ones (>5.7µm), the McIntyre model seems to be today's standard. However when simply extrapolating the parameters to smaller diameters, strange effects like muliple action potentials fo...
by calu
Tue Mar 15, 2016 2:29 pm
Forum: NEURON + Python
Topic: Python package needs NEURON extensions - where to save
Replies: 1
Views: 4670

Python package needs NEURON extensions - where to save

Hello! I am building a Python package that relies on NEURON and that needs some extensions (e.g. AXNODE.mod). In order to load these extensions, I normally just compile them in my project folder via nrnivmodl and NEURON finds the x86_64 folder (or i386 etc.) when I call "import neuron" in a script i...
by calu
Tue Mar 01, 2016 12:21 pm
Forum: Modeling networks
Topic: Stimulate multiple axons with IClamp
Replies: 6
Views: 6918

Re: Stimulate multiple axons with IClamp

Ok, I will look into these examples, they seem pretty informative and indeed I did not find them over a general google enquiry. An extensive documentation for Python would be extermely useful to many NEURON users, I guess.

So thank you again very much for the detailed explanation and the hints!
by calu
Tue Mar 01, 2016 8:07 am
Forum: Modeling networks
Topic: Stimulate multiple axons with IClamp
Replies: 6
Views: 6918

Re: Stimulate multiple axons with IClamp

Aaaah, thanks Ted! I missed the sec= in the call of h.IClamp(0, sec= <axonname>). So sec is an optional parameter for the IClamp constructor? How is h.IClamp(0, <axonname>) without sec= interpreted by NEURON? Where can I get an overview of the functions in the neuron.h model and their input paramete...
by calu
Fri Feb 26, 2016 2:33 pm
Forum: Modeling networks
Topic: Stimulate multiple axons with IClamp
Replies: 6
Views: 6918

Re: Stimulate multiple axons with IClamp

Thanks for the reply, maybe I was not clear enough. When I do any of the following - connect IClamp to first axon - connect IClamp to second axon - connect IClamp to both axons I always get the same result: Only the first axon I instantiate is stimulated. Meaning adding the following code changes no...