Correcting space clamp in dendrites (Schaefer et al. 2003 and 2007)

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In voltage-clamp experiments, incomplete space clamp distorts the recorded currents, rendering accurate analysis impossible. Here, we present a simple numerical algorithm that corrects such distortions. The method enabled accurate retrieval of the local densities, kinetics, and density gradients of somatic and dendritic channels. The correction method was applied to two-electrode voltage-clamp recordings of K currents from the apical dendrite of layer 5 neocortical pyramidal neurons. The generality and robustness of the algorithm make it a useful tool for voltage-clamp analysis of voltage-gated currents in structures of any morphology that is amenable to the voltage-clamp technique.
1 . Schaefer AT, Helmstaedter M, Sakmann B, Korngreen A (2003) Correction of conductance measurements in non-space-clamped structures: 1. Voltage-gated K+ channels. Biophys J 84:3508-28 [PubMed]
2 . Schaefer AT, Helmstaedter M, Schmitt AC, Bar-Yehuda D, Almog M, Ben-Porat H, Sakmann B, Korngreen A (2007) Dendritic voltage-gated K+ conductance gradient in pyramidal neurones of neocortical layer 5B from rats. J Physiol 579:737-52 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Neocortex M1 L5B pyramidal pyramidal tract GLU cell;
Channel(s): I K; I K,leak; I M; I Potassium;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Parameter Fitting; Influence of Dendritic Geometry; Detailed Neuronal Models;
Implementer(s): Schaefer, Andreas T [andreas.schaefer at];
Search NeuronDB for information about:  Neocortex M1 L5B pyramidal pyramidal tract GLU cell; I K; I K,leak; I M; I Potassium;

begintemplate TwoElectrodeIdealVClamp

public xmeasure, xinject, set_vc, vc, ic, valid

// usage:
// e = TwoElectrodeIdealVClamp()
// section e.xmeasure(x) // measurement electrode location
// section e.xinject(x) // current injection electrode location
// e.set_vc(control_potential) // sets the value of b.x[2]
// // returns the value of b.x[2]
// e.ic() // returns the value of y.x[2]
// e.valid() returns true if the clamp is part of the simulation

public b, y // if you want to use the addresses instead of the
        // functions for plotting. They are necessary for
        // recording the current into a Vector, or playing a Vector into
        // the control potential.

objref c, g, y, b, model, nil
objref sec[2], x, sl

proc init() {
print "init"
        c = new Matrix(5,5,2) //sparse
        g = new Matrix(5,5)
        y = new Vector(5)
        b = new Vector(5)
        g.x[1][3] = 1
        g.x[2][4] = 1
	g.x[3][0] = -1e+06
	g.x[3][1] = 1
	g.x[3][2] = 1e+06
	g.x[4][2] = 1
        x = new Vector(2)
print "init return"

proc install() {
        if (sec[0] != nil && sec[1] != nil) {
                sl = new SectionList()
                sec[0].sec sl.append()
                sec[1].sec sl.append()
                model = new LinearMechanism(c, g, y, b, sl, x)
		print "attached TEVC to cell"

proc xmeasure() { 
        x.x[0] = $1
        sec[0] = new SectionRef()

proc xinject() { local a
        x.x[1] = $1
        sec[1] = new SectionRef()
	a = area(x.x[1])
	print "area at current injection electorde ", a
	print "g"

proc set_vc() { b.x[4] = $1 }
func vc() { return b.x[4] }
func ic() { return y.x[3] }

func valid() {
        if (model != nil) {
                return model.valid
        return 0

endtemplate TwoElectrodeIdealVClamp