CA1 pyramidal neuron: as a 2-layer NN and subthreshold synaptic summation (Poirazi et al 2003)

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We developed a CA1 pyramidal cell model calibrated with a broad spectrum of in vitro data. Using simultaneous dendritic and somatic recordings, and combining results for two different response measures (peak vs. mean EPSP), two different stimulus formats (single shock vs. 50 Hz trains), and two different spatial integration conditions (within vs. between-branch summation), we found the cell's subthreshold responses to paired inputs are best described as a sum of nonlinear subunit responses, where the subunits correspond to different dendritic branches. In addition to suggesting a new type of experiment and providing testable predictions, our model shows how conclusions regarding synaptic arithmetic can be influenced by an array of seemingly innocuous experimental design choices.
1 . Poirazi P, Brannon T, Mel BW (2003a) Arithmetic of subthreshold synaptic summation in a model CA1 pyramidal cell. Neuron 37:977-987 [PubMed]
2 . Poirazi P, Brannon T, Mel BW (2003b) Pyramidal Neuron as Two-Layer Neural Network. Neuron 37:989-999 [PubMed]
3 . Poirazi P, Brannon T, Mel BW (2003ab-sup) Online Supplement: About the Model Neuron 37 Online:1-20
4 . Polsky A, Mel BW, Schiller J (2004) Computational subunits in thin dendrites of pyramidal cells. Nat Neurosci 7:621-7 [PubMed]
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): Hippocampus CA1 pyramidal cell;
Channel(s): I Na,p; I Na,t; I L high threshold; I T low threshold; I A; I K; I M; I h; I K,Ca; I Calcium;
Gap Junctions:
Receptor(s): GabaA; GabaB; NMDA; Glutamate;
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Activity Patterns; Dendritic Action Potentials; Active Dendrites; Influence of Dendritic Geometry; Detailed Neuronal Models; Action Potentials; Depression; Delay;
Implementer(s): Poirazi, Panayiota [poirazi at];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal cell; GabaA; GabaB; NMDA; Glutamate; I Na,p; I Na,t; I L high threshold; I T low threshold; I A; I K; I M; I h; I K,Ca; I Calcium;
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TITLE L-type calcium channel with low threshold for activation
: used in somatic and proximal dendritic regions 
: it calculates I_Ca using channel permeability instead of conductance

	(mA) = (milliamp)
	(mV) = (millivolt)
	FARADAY = 96520 (coul)
	R = 8.3134 (joule/degK)
	KTOMV = .0853 (mV/degC)


PARAMETER {		:parameters that can be entered when function is called in cell-setup 
        dt              (ms)
	v               (mV)
	celsius = 34	(degC)
	gcalbar = 0     (mho/cm2) : initialized conductance
	ki  = 0.001     (mM)  
	cai = 5.e-5     (mM)      : initial internal Ca++ concentration
	cao = 2         (mM)      : initial external Ca++ concentration
        tfa = 5                   : time constant scaling factor
        eca = 140                 : Ca++ reversal potential

	USEION ca READ cai,cao WRITE ica
        RANGE gcalbar, minf,taum

STATE {	m }                      : unknown parameter to be solved in the DEs 

ASSIGNED {                       : parameters needed to solve DE
	ica (mA/cm2)
        gcal  (mho/cm2) 

INITIAL {                        : initialize the following parameter using rates()
        m = minf
	gcal = gcalbar*m*h2(cai)

	SOLVE states
	gcal = gcalbar*m*h2(cai) : maximum channel permeability
	ica = gcal*ghk(v,cai,cao): calcium current induced by this channel

FUNCTION h2(cai(mM)) {
	h2 = ki/(ki+cai)

FUNCTION ghk(v(mV), ci(mM), co(mM)) (mV) {
        LOCAL nu,f
        f = KTF(celsius)/2
        nu = v/f
        ghk=-f*(1. - (ci/co)*exp(nu))*efun(nu)

FUNCTION KTF(celsius (degC)) (mV) { : temperature-dependent adjustment factor
        KTF = ((25./293.15)*(celsius + 273.15))

FUNCTION efun(z) {
	if (fabs(z) < 1e-4) {
		efun = 1 - z/2
		efun = z/(exp(z) - 1)

FUNCTION alpm(v(mV)) {
	TABLE FROM -150 TO 150 WITH 200
	alpm = 0.055*(-27.01 - v)/(exp((-27.01-v)/3.8) - 1)

FUNCTION betm(v(mV)) {
        TABLE FROM -150 TO 150 WITH 200
        betm =0.94*exp((-63.01-v)/17)

LOCAL facm
:if state_cagk is called from hoc, garbage or segmentation violation will
:result because range variables won't have correct pointer.  This is because
:only BREAKPOINT sets up the correct pointers to range variables.
PROCEDURE states() {     : exact when v held constant; integrates over dt step
        m = m + facm*(minf - m)
        return 0;

PROCEDURE rates(v (mV)) { :callable from hoc
        LOCAL a
        a = alpm(v)
        taum = 1/(tfa*(a+betm(v))) : estimation of activation tau
        minf = a/(a+betm(v))       : estimation of activation steady state value
        facm = (1 - exp(-dt/taum))

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