Hi! Dear Friends,
i wrote a simple code that includes a soma with inserted mechanism like HH, pas,...
I like to test some behavior of my single compartment model,I would like to inject current to soma when membrane potential (of soma) is holded at a special membrane potential level , e.g; -95 , -85 , -75, -65 ,...
could you tell me what should i do?
Thank's in advance!
karlo
inject current at some special level of membrane potential
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thats_karlo
inject current at some special level of membrane potential
Last edited by thats_karlo on Wed Oct 12, 2005 4:11 pm, edited 1 time in total.
inject current at some special level of membrane potential
Some quick and brief answers:
VClamp or SEClamp objects give you the opportunity to clamp the membrane potential. Making a 'for'-loop in which you set the amplitude variable to a new value on each iteration and executing run from this loop will show you simulations which will use the parameter values you specified to SEClamp or VClamp in the 'for'-loop. It can be nice to add some code to save your results to the loop aswell.
If you want to compare your simulation to actual voltage clamp data you might instead want to read up on using the MultipleRunFitter.
VClamp or SEClamp objects give you the opportunity to clamp the membrane potential. Making a 'for'-loop in which you set the amplitude variable to a new value on each iteration and executing run from this loop will show you simulations which will use the parameter values you specified to SEClamp or VClamp in the 'for'-loop. It can be nice to add some code to save your results to the loop aswell.
If you want to compare your simulation to actual voltage clamp data you might instead want to read up on using the MultipleRunFitter.
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ted
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Re: inject current at some special level of membrane potenti
The question is ambiguous. My best guess is that you want to do a current clampthats_karlo wrote:I would like to inject current to soma when membrane potential (of soma) is holded at a special membrane potential level , e.g; -95 , -85 , -75, -65 ,...
experiment, in which you inject a steady current (a "polarizing" or "holding" current)
in order to drive membrane potential to a new resting level. Then, after the model settles
at this new resting level. you want to inject a current pulse (a "stimulus" or "test" current).
You can do this exactly the same in NEURON as you would in an experiment on a real
cell. Use two IClamps, one to inject the holding current, and the other to apply the test
current.
But you need to let the model cell have enough time to settle to the new resting
potential before you apply the test pulse. That works, but it can be a nuisance,
especially if your model has very slow dynamics (which can occur if your model
has slow biophysical mechanisms, or significant electrotonic extent). Also, you're
specifying the amplitude of the polarizing current, not the resting potential.
There are ways to work around both of these limitations, but
--they would lead us into more complexity than is appropriate for one of the
"Getting started" discussion threads
--this answer is already pretty long, especially since I'm only guessing at what
you really want to know
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thats_karlo
clear question
Dear freinds
Thanks' for your answer. and forgive me for my english.
Actually i would like to test behavior of neuron in different membrane potential.
for example i like to inject a positive current to neuron when the membrane potential is at V_m , V_m+10, V_m-10 level.
what's is the best way to do that?
karlo
Thanks' for your answer. and forgive me for my english.
Actually i would like to test behavior of neuron in different membrane potential.
for example i like to inject a positive current to neuron when the membrane potential is at V_m , V_m+10, V_m-10 level.
what's is the best way to do that?
karlo
inject current at some special level of membrane potential
Karlo,
If you inject current while applying a voltage clamp you might find that little happens because the voltage clamp mechanism will compensate for the positive (or negative) current you inject into the same compartment (You mentioned working on a single compartment model). All you would be able to see is a change in the current needed for clamping.
If what Ted was speculating is true, that is you don't want to voltage clamp the cell, but instead want to change its "resting potential" by injecting a current after which you inject additional current to test the now changed response to a current injection change, then there are two ways to go:
1. you read about optimization and make the optimizer find appropriate injection currents for you
2. Much easier to implement, you make a plot of resting potential as a function of the injected current, then by interpolation you should be able to find the approximate values at which the current reaches the desired membrane potentials. If you put the table in a function you can even make a function do the interpolation for you.
As you might read from my answer it is not completely clear to me what your aim is.
Regards,
Ronald
If you inject current while applying a voltage clamp you might find that little happens because the voltage clamp mechanism will compensate for the positive (or negative) current you inject into the same compartment (You mentioned working on a single compartment model). All you would be able to see is a change in the current needed for clamping.
If what Ted was speculating is true, that is you don't want to voltage clamp the cell, but instead want to change its "resting potential" by injecting a current after which you inject additional current to test the now changed response to a current injection change, then there are two ways to go:
1. you read about optimization and make the optimizer find appropriate injection currents for you
2. Much easier to implement, you make a plot of resting potential as a function of the injected current, then by interpolation you should be able to find the approximate values at which the current reaches the desired membrane potentials. If you put the table in a function you can even make a function do the interpolation for you.
As you might read from my answer it is not completely clear to me what your aim is.
Regards,
Ronald
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thats_karlo
hi!
Actually i would like to test respone of thamalus with different membrane potential to a positive inject current.
because, as you know, the firing pattern for thamalus will be changed by membrane potential for ex. at -65 we have tonic firing, -75 passive response and -85 burst firing for a positive, say 0.2 nA injected current.
I have a singel compartment model with Na+/K+ fast current and IT current.
should i use voltage clump or two current clamp?
thank's
Actually i would like to test respone of thamalus with different membrane potential to a positive inject current.
because, as you know, the firing pattern for thamalus will be changed by membrane potential for ex. at -65 we have tonic firing, -75 passive response and -85 burst firing for a positive, say 0.2 nA injected current.
I have a singel compartment model with Na+/K+ fast current and IT current.
should i use voltage clump or two current clamp?
thank's
Aha!
That is a full fledged research question.
It is time to start asking yourself questions and to be prepared to spend quite some time on finding the answers. Several mechanisms can change the resting potential and you have to develop an idea which process brings these changes about in the thalamus. (Unfortunately I know little about the thalamus.)
If you would know (which is a totally fictive example) that during the low resting potential there is a lot of inhibitory input from an other brain area then you have to somehow mimick this. Options are among others:
- stimulate inhibitory synapses which you put on your cell
- simply inject the current using a currentclamp (IClamp Mechanisms), which seems a crude method but it might answer your question.
Similar considerations hold for the high resting potential phase.
Anyway there are many, many options and you'll have to turn to literature, other modelers or experimenters to learn what is reasonable. From the currents included inyour model it seems to me that you already had a look at the neuron models for the thalamus you can find on ModelDB (I just gave it glance one minute ago). Having a look at the associated papers might give you new clues aswell.
A first question you might consider is if the activation and inactivation properties can explain the behavior. For that you can start with simply using current clamp (IClamp mechanism) to lower the membrane potential. You would still have to make the graph (which I suggested before) to estimate the right clamp current. Then for doing your experiment the simplest option is to add an extra IClamp to inject the extra depolarizing 0.2 nA current. For this to be likely to work your burst should be a transient burst, i.e after bursting the cell settles down in a new resting potential, otherwise I would expect that you have to dive deeper into biophysics of the whole system.
It is time to start asking yourself questions and to be prepared to spend quite some time on finding the answers. Several mechanisms can change the resting potential and you have to develop an idea which process brings these changes about in the thalamus. (Unfortunately I know little about the thalamus.)
If you would know (which is a totally fictive example) that during the low resting potential there is a lot of inhibitory input from an other brain area then you have to somehow mimick this. Options are among others:
- stimulate inhibitory synapses which you put on your cell
- simply inject the current using a currentclamp (IClamp Mechanisms), which seems a crude method but it might answer your question.
Similar considerations hold for the high resting potential phase.
Anyway there are many, many options and you'll have to turn to literature, other modelers or experimenters to learn what is reasonable. From the currents included inyour model it seems to me that you already had a look at the neuron models for the thalamus you can find on ModelDB (I just gave it glance one minute ago). Having a look at the associated papers might give you new clues aswell.
A first question you might consider is if the activation and inactivation properties can explain the behavior. For that you can start with simply using current clamp (IClamp mechanism) to lower the membrane potential. You would still have to make the graph (which I suggested before) to estimate the right clamp current. Then for doing your experiment the simplest option is to add an extra IClamp to inject the extra depolarizing 0.2 nA current. For this to be likely to work your burst should be a transient burst, i.e after bursting the cell settles down in a new resting potential, otherwise I would expect that you have to dive deeper into biophysics of the whole system.