Hippocampus temporo-septal engram shift model (Lytton 1999)

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Accession:7400
Temporo-septal engram shift model of hippocampal memory. The model posits that memories gradually move along the hippocampus from a temporal encoding site to ever more septal sites from which they are recalled. We propose that the sense of time is encoded by the location of the engram along the temporo-septal axis.
Reference:
1 . Lytton WW, Lipton P (1999) Can the hippocampus tell time? The temporo-septal engram shift model. Neuroreport 10:2301-6 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network;
Brain Region(s)/Organism: Hippocampus;
Cell Type(s):
Channel(s): I Na,t; I K;
Gap Junctions:
Receptor(s): GabaA; AMPA;
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Pattern Recognition; Temporal Pattern Generation; Spatio-temporal Activity Patterns; Simplified Models;
Implementer(s): Lytton, William [billl at neurosim.downstate.edu];
Search NeuronDB for information about:  GabaA; AMPA; I Na,t; I K;
/
lytton99
README
AMPA.mod
GABAA.mod
kdr.mod
matrix.mod *
naf.mod *
passiv.mod *
pulse.mod *
sinstim.mod *
vecst.mod
vecst.mod.orig
bg.inc *
bg_cvode.inc
boxes.hoc *
declist.hoc *
decvec.hoc *
default.hoc *
directory
fig1.gif
grvec.hoc
init.hoc
ivl.vecs
labels.hoc
loadr.hoc *
local.hoc
mosinit.hoc
net.hoc
netcon.inc
nrnoc.hoc
ovl.vecs
params.hoc *
params.hoc.SAV *
proc.hoc
run.hoc
simctrl.hoc *
spkts.hoc
syncode.hoc
tmpl.hoc
                            
: $Id: netcon.inc,v 1.7 1999/08/03 18:23:18 billl Exp $

COMMENT
USAGE: for most receptors
*****************************************************************************
    NEURON {
      POINT_PROCESS NAME
    }

    PARAMETER {
      Cdur	= 1.08	(ms)		: transmitter duration (rising phase)
      Alpha	= 1	(/ms mM)	: forward (binding) rate
      Beta	= 0.02	(/ms)		: backward (unbinding) rate
      Erev	= -80	(mV)		: reversal potential
    }
    
    INCLUDE "netsyn.inc"
*****************************************************************************

USAGE: for NMDA receptor
*****************************************************************************
    NEURON{ POINT_PROCESS NMDA
      RANGE B 
    }

    PARAMETER {
      mg        = 1.    (mM)     : external magnesium concentration
      Cdur	= 1.	(ms)	 : transmitter duration (rising phase)
      Alpha	= 4.	(/ms mM) : forward (binding) rate
      Beta	= 0.0067 (/ms)	 : backward (unbinding) rate 1/150
      Erev	= 0.	(mV)	 : reversal potential
    }

    ASSIGNED { B }

    INCLUDE "netcon.inc"
    : EXTRA BREAKPOINT MUST BE BELOW THE INCLUDE
    BREAKPOINT {
      rates(v)
      g = g * B : but don't really need to readjust conductance
      i = i * B : i = g*(v - Erev)
    }

    PROCEDURE rates(v(mV)) {
      TABLE B
      DEPEND mg
      FROM -100 TO 80 WITH 180
      B = 1 / (1 + Exp1(0.062 (/mV) * -v) * (mg / 3.57 (mM)))
    }
*****************************************************************************
ENDCOMMENT

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

NEURON {
  RANGE g
  NONSPECIFIC_CURRENT i
  GLOBAL Cdur, Alpha, Beta, Erev, Rinf, Rtau
}

UNITS {
  (nA) = (nanoamp)
  (mV) = (millivolt)
  (umho) = (micromho)
  (mM) = (milli/liter)
}

ASSIGNED {
  v		(mV)		: postsynaptic voltage
  i 		(nA)		: current = g*(v - Erev)
  g 		(umho)		: conductance
  Rinf				: steady state channels open
  Rtau		(ms)		: time constant of channel binding
  R				: fraction of open channels
  synon
}

STATE {Ron Roff}

INITIAL {
  R = 0
  Rinf = Alpha / (Alpha + Beta)
  Rtau = 1 / (Alpha + Beta)
  synon = 0
}

BREAKPOINT {
  SOLVE release METHOD cnexp
  g = (Ron + Roff)*1(umho)
  i = g*(v - Erev)
}

DERIVATIVE release {
  Ron' = (synon*Rinf - Ron)/Rtau
  Roff' = -Beta*Roff
}

: following supports both saturation from single input and
: summation from multiple inputs
: if spike occurs during CDur then new off time is t + CDur
: ie. transmitter concatenates but does not summate
: Note: automatic initialization of all reference args to 0 except first

NET_RECEIVE(weight, on, nspike, r0, t0 (ms)) {
  : flag is an implicit argument of NET_RECEIVE and  normally 0
  if (t>0) { : bug fix so that init doesn't send a false event
    if (flag == 0) { : a spike, so turn on if not already in a Cdur pulse
      nspike = nspike + 1
      if (!on) {
        r0 = r0*Exp1(-Beta*(t - t0))
        t0 = t
        on = 1
        synon = synon + weight
        state_discontinuity(Ron, Ron + r0)
        state_discontinuity(Roff, Roff - r0)
      }
      : come again in Cdur with flag = current value of nspike
      net_send(Cdur, nspike)
    }
    if (flag == nspike) { : if this associated with last spike then turn off
      r0 = weight*Rinf + (r0 - weight*Rinf)*Exp1(-(t - t0)/Rtau)
      t0 = t
      synon = synon - weight
      state_discontinuity(Ron, Ron - r0)
      state_discontinuity(Roff, Roff + r0)
      on = 0
    }
  }
}

FUNCTION Exp1(x) {   
  if (x < -100) {
    Exp1  = 0
  } else if (x > 100) {
    Exp1 = exp(100)
  } else{
    Exp1 = exp(x)
  }
}

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