Curent clamp

[stelescu]

I’ve have recently started to use NEURON. I’ve been using AlphaSynapses as voltage clamp. Is it possible to use current clamp in the same manner that the voltage clamp (like AlphaSynapse?)

[Raj]

The AlphaSynapse itself is not a clamp mechanism, but a time dependent conductance. You can study it using the built in VClamp, IClamp, SEClamp clamping mechanisms.

If, assuming you use a single compartment/section, you combine AlphaSynapse with voltage clamp (VClamp) you will be able to see that VClamp injects a constant current plus a current component that follows the time course of the AlphaSynapse conductance.
Just plot the 'i' member variable of your VClamp object. (You can plot voltage, current and state variables using the Graph menu.)

You can instead use IClamp object to inject a fixed amount of current and then look at the voltage response of your cell, e.g soma.v(0.5). This response will now be more complicated and not simply follow the AlphaSynapse time course. This is because the injected current is accumulating on the membrane, leaking away through the same membrane and due to changes in membrane potential also the voltage dependent currents in your cell will change.

[ted]

99 times out of 100, SEClamp is the correct choice. SEClamp is a perfect voltage
source in series with a resistor.

Code: Select all

vc ---'\/\/`--- cell
        rs

(read about it in the Programmer's Reference
http://www.neuron.yale.edu/neuron/stati ... ml#SEClamp
). Use SEClamp if your primary interest is to discover what happens to voltage-
gated conductances during a voltage clamp experiment.

VClamp is a model of a two-electrode voltage clamp, with this equivalent circuit

Code: Select all

                 tau2
                 gain
                +-|\____rstim____>to cell
-amp --'\/`-------|/
                |
                |----||---
                |___    __|-----/|___from cell
                    '\/'        \|
                    tau1

(read about it in the Programmer's Reference
http://www.neuron.yale.edu/neuron/stati ... tml#VClamp
). Only rarely is all this complexity necessary--specifically, when your primary goal
is to examine the artifacts that can occur if you are using a two electrode voltage
clamp that has limited gan and/or bandwidth.