Thalamocortical augmenting response (Bazhenov et al 1998)

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Accession:37819
In the cortical model, augmenting responses were more powerful in the "input" layer compared with those in the "output" layer. Cortical stimulation of the network model produced augmenting responses in cortical neurons in distant cortical areas through corticothalamocortical loops and low-threshold intrathalamic augmentation. ... The predictions of the model were compared with in vivo recordings from neurons in cortical area 4 and thalamic ventrolateral nucleus of anesthetized cats. The known intrinsic properties of thalamic cells and thalamocortical interconnections can account for the basic properties of cortical augmenting responses. See reference for details. NEURON implementation note: cortical SU cells are getting slightly too little stimulation - reason unknown.
Reference:
1 . Bazhenov M, Timofeev I, Steriade M, Sejnowski TJ (1998) Computational models of thalamocortical augmenting responses. J Neurosci 18:6444-65 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network;
Brain Region(s)/Organism: Thalamus;
Cell Type(s): Thalamus geniculate nucleus (lateral) principal neuron; Thalamus reticular nucleus cell; Neocortex V1 pyramidal corticothalamic L6 cell;
Channel(s): I Na,t; I T low threshold; I A; I K,Ca;
Gap Junctions:
Receptor(s): GabaA; GabaB; AMPA;
Gene(s):
Transmitter(s): Gaba; Glutamate;
Simulation Environment: NEURON;
Model Concept(s): Synchronization; Synaptic Integration;
Implementer(s): Lytton, William [billl at neurosim.downstate.edu];
Search NeuronDB for information about:  Thalamus geniculate nucleus (lateral) principal neuron; Thalamus reticular nucleus cell; Neocortex V1 pyramidal corticothalamic L6 cell; GabaA; GabaB; AMPA; I Na,t; I T low threshold; I A; I K,Ca; Gaba; Glutamate;
: $Id: bg_cvode.inc,v 1.11 2003/01/07 21:00:37 billl Exp $
TITLE Kevin's Cvode modification to Borg Graham Channel Model

COMMENT

Modeling the somatic electrical response of hippocampal pyramidal neurons, 
MS thesis, MIT, May 1987.

Each channel has activation and inactivation particles as in the original
Hodgkin Huxley formulation.  The activation particle mm and inactivation
particle hh go from on to off states according to kinetic variables alpha
and beta which are voltage dependent.  The form of the alpha and beta
functions were dissimilar in the HH study.  The BG formulae are:
	alpha = base_rate * Exp[(v - v_half)*valence*gamma*F/RT]
	beta = base_rate * Exp[(-v + v_half)*valence*(1-gamma)*F/RT]
where,
	baserate : no affect on Inf.  Lowering this increases the maximum
		    value of Tau
	basetau : (in msec) minimum Tau value.
	chanexp : number for exponentiating the state variable; e.g.
		  original HH Na channel use m^3, note that chanexp = 0
		  will turn off this state variable
	erev : reversal potential for the channel
	gamma : (between 0 and 1) does not affect the Inf but makes the
		Tau more asymetric with increasing deviation from 0.5
	celsius : temperature at which experiment was done (Tau will
		      will be adjusted using a q10 of 3.0)
	valence : determines the steepness of the Inf sigmoid.  Higher
		  valence gives steeper sigmoid.
	vhalf : (a voltage) determines the voltage at which the value
		 of the sigmoid function for Inf is 1/2
	vmin, vmax : limits for construction of the table.  Generally,
		     these should be set to the limits over which either
		     of the 2 state variables are varying.
        vrest : (a voltage) voltage shift for vhalf

ENDCOMMENT

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
  RANGE gmax, g, i
  GLOBAL erev, Inf, Tau, vmin, vmax, vrest
} : end NEURON

CONSTANT {
  FARADAY = 96489.0	: Faraday's constant
  R= 8.31441		: Gas constant
} : end CONSTANT

UNITS {
  (mA) = (milliamp)
  (mV) = (millivolt)
  (umho) = (micromho)
} : end UNITS


COMMENT
** Parameter values should come from files specific to particular channels
PARAMETER {
	erev 		= 0    (mV)
	gmax 		= 0    (mho/cm^2)
        vrest           = 0    (mV)

	mvalence 	= 0
	mgamma 		= 0
	mbaserate 	= 0
	mvhalf 		= 0
	mbasetau 	= 0
	mtemp 		= 0
	mq10		= 3
	mexp 		= 0

	hvalence 	= 0
	hgamma		= 0
	hbaserate 	= 0
	hvhalf 		= 0
	hbasetau 	= 0
	htemp 		= 0
	hq10		= 3
	hexp 		= 0

	cao                (mM)
	cai                (mM)

	celsius			   (degC)
	dt 				   (ms)
	v 			       (mV)

	vmax 		= 100  (mV)
	vmin 		= -100 (mV)
} : end PARAMETER
ENDCOMMENT

ASSIGNED {
  i (mA/cm^2)		
  g (mho/cm^2)
  Inf[2]		: 0 = m and 1 = h
  Tau[2]		: 0 = m and 1 = h
  mexp_val
  hexp_val
} : end ASSIGNED 

STATE { m h }

INITIAL { 
  mh(v)
  m = Inf[0] h = Inf[1]
}

BREAKPOINT {
  if (gmax==0.0) { g=0. } else {

  SOLVE states METHOD cnexp

  hexp_val = 1
  mexp_val = 1

  : Determining h's exponent value
  if (hexp > 0) {
    FROM index=1 TO hexp {
      hexp_val = h * hexp_val
    }
  }

  : Determining m's exponent value
  if (mexp > 0) {
    FROM index = 1 TO mexp {
      mexp_val = m * mexp_val
    }
  }

  :			       mexp			    hexp
  : Note that mexp_val is now = m      and hexp_val is now = h 
  g = gmax * mexp_val * hexp_val
  }
  iassign()
} : end BREAKPOINT

: ASSIGNMENT PROCEDURES
: Must be overwritten by user routines in parameters.multi
: PROCEDURE iassign () { i = g*(v-erev) ina=i }
: PROCEDURE iassign () { i = g*ghkca(v) ica=i }

:-------------------------------------------------------------------

DERIVATIVE states {
  mh(v)
  m' = (-m + Inf[0]) / Tau[0] 
  h' = (-h + Inf[1]) / Tau[1]
}
:-------------------------------------------------------------------
: NOTE : 0 = m and 1 = h
PROCEDURE mh (v) {
  LOCAL a, b, j, mqq10, hqq10
  TABLE Inf, Tau DEPEND hbaserate, hbasetau, hexp, hgamma, htemp, hvalence, hvhalf, mbaserate, mbasetau, mexp, mgamma, mtemp, mvalence, mvhalf, celsius, mq10, hq10, vrest, vmin, vmax  FROM vmin TO vmax WITH 200

  mqq10 = mq10^((celsius-mtemp)/10.)	
  hqq10 = hq10^((celsius-htemp)/10.)	

  : Calculater Inf and Tau values for h and m
  FROM j = 0 TO 1 {
    a = alpha (v, j)
    b = beta (v, j)

    Inf[j] = a / (a + b)

    VERBATIM
    switch (_lj) {
      case 0:
      /* Make sure Tau is not less than the base Tau */
if ((Tau[_lj] = 1 / (_la + _lb)) < mbasetau) {
  Tau[_lj] = mbasetau;
}
Tau[_lj] = Tau[_lj] / _lmqq10;
break;
case 1:
if ((Tau[_lj] = 1 / (_la + _lb)) < hbasetau) {
  Tau[_lj] = hbasetau;
}
Tau[_lj] = Tau[_lj] / _lhqq10;
if (hexp==0) {
  Tau[_lj] = 1.; }
  break;
    }

    ENDVERBATIM
  }
} : end PROCEDURE mh (v)
:-------------------------------------------------------------------
FUNCTION alpha(v,j) {
  if (j == 1) {
    if (hexp==0) {
      alpha = 1
    } else {
      alpha = hbaserate * exp((v - (hvhalf+vrest)) * hvalence * hgamma * FRT(htemp)) }
  } else {
    alpha = mbaserate * exp((v - (mvhalf+vrest)) * mvalence * mgamma * FRT(mtemp))
  }
} : end FUNCTION alpha (v,j)

:-------------------------------------------------------------------
FUNCTION beta (v,j) {
  if (j == 1) {
    if (hexp==0) {
      beta = 1
    } else {
      beta = hbaserate * exp((-v + (hvhalf+vrest)) * hvalence * (1 - hgamma) * FRT(htemp)) }
  } else {
    beta = mbaserate * exp((-v + (mvhalf+vrest)) * mvalence * (1 - mgamma) * FRT(mtemp))
  }
} : end FUNCTION beta (v,j)

:-------------------------------------------------------------------
FUNCTION FRT(temperature) {
	FRT = FARADAY * 0.001 / R / (temperature + 273.15)
} : end FUNCTION FRT (temperature)

:-------------------------------------------------------------------
FUNCTION ghkca (v) { : Goldman-Hodgkin-Katz eqn
  LOCAL nu, efun

  nu = v*2*FRT(celsius)
  if(fabs(nu) < 1.e-6) {
    efun = 1.- nu/2.
  } else {
    efun = nu/(exp(nu)-1.) }

    ghkca = -FARADAY*2.e-3*efun*(cao - cai*exp(nu))
} : end FUNCTION ghkca()





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