Functional structure of mitral cell dendritic tuft (Djurisic et al. 2008)

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The computational modeling component of Djurisic et al. 2008 addressed two primary questions: whether amplification by active currents is necessary to explain the relatively mild attenuation suffered by tuft EPSPs spreading along the primary dendrite to the soma; what accounts for the relatively uniform peak EPSP amplitude throughout the tuft. These simulations show that passive spread from tuft to soma is sufficient to yield the low attenuation of tuft EPSPs, and that random distribution of a biologically plausible number of excitatory synapses throughout the tuft can produce the experimentally observed uniformity of depolarization.
1 . Djurisic M, Popovic M, Carnevale N, Zecevic D (2008) Functional structure of the mitral cell dendritic tuft in the rat olfactory bulb. J Neurosci 28:4057-68 [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: Olfactory bulb;
Cell Type(s): Olfactory bulb main mitral GLU cell;
Channel(s): I K; I Sodium;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Dendritic Action Potentials; Active Dendrites; Synaptic Integration; Olfaction;
Implementer(s): Carnevale, Ted [Ted.Carnevale at];
Search NeuronDB for information about:  Olfactory bulb main mitral GLU cell; I K; I Sodium;
// $Id: analyze_active.hoc,v 1.1 2007/04/19 17:01:11 ted Exp ted $

// based on analyze_spiketuft.hoc
// analyses results

// monx can't detect v at 0 or 1 end
// so we must use Vector record() to determine peak at origin of tuft
objref vorigin
vorigin = new Vector()  // this is used by procs plotresults() and plotvmaxrvp()
apic[2] vorigin.record(&v(0))

objref areavec, normareavec, vpeakvec, resultvec
totalarea = 0

proc preanalysis() {
  areavec = new Vector()
  forsec tuft for (x,0) {
//  areavec.printf()
  totalarea = areavec.sum()
  normareavec = new Vector()
  normareavec = areavec.c.div(totalarea)

// calculate totalarea and contents of areavec and normareavec just once, before doing any simulations

// for diagnosis and development

Modified from implementation in processpeakdata.hoc
$o1 is vpvec
In implementation from processpeakdata.hoc, $o3 is temprvec which returns results

objref si, normareacusum, svpvec, snormareavec

wmedian = -1  // three nonsense values
wpctlo = -1
wpcthi = -1

// proc percentiles() { local ii, wmedian, wpctlo, wpcthi
proc percentiles() { local ii
  si = new Vector(normareavec.size())
  $o1.sortindex(si)  // the elements of si sort $o1 (which is vpvec) in numerical order
  normareacusum = new Vector(normareavec.size())
  // set up snormareavec here--we'll use it later for the distribution graph
  snormareavec = new Vector()
  snormareavec.index(normareavec, si)

  normareacusum = snormareavec.c
  // snormareavec and normareacusum hold the normalized areas
  //   in order of increasing peak v
  for ii=1,normareavec.size()-1 normareacusum.x[ii] += normareacusum.x[ii-1]
//  normareacusum.printf()
  // now normareacusum holds the cusum of the normalized areas

  svpvec = $o1.c.sort()  // we're going to use the sorted vpvec repeatedly
                         // so might as well sort it once and for all
  // find the index of the first element of normareacusum 
  //   whose value is > 0.5
  ii = normareacusum.indwhere(">", 0.5)

  wmedian = svpvec.x[ii-1]  // we want the immediately preceding value
  ii = normareacusum.indwhere(">", $2/100)
  wpctlo = svpvec.x[ii-1]
  ii = normareacusum.indwhere(">", (100-$2)/100)
  wpcthi = svpvec.x[ii-1]
  $o3.x[MEDIAN] = wmedian
  $o3.x[PCTLO] = wpctlo
  $o3.x[PCTHI] = wpcthi
  print "wmedian ", wmedian, " wpctlo ", wpctlo, " wpcthi ", wpcthi


proc analyze() { local ii, num, wmean, wvar, wstdev  localobj tmpvec
  vpeakvec = new Vector()
  forsec tuft for (x,0) {
  vpeakvec.sub(v_init)  // so amplitude is relative to resting potential

  // weighted mean
  tmpvec = vpeakvec.c()
  wmean = tmpvec.sum()/totalarea
  // weighted variance
  tmpvec = vpeakvec.c()
  for ii=0,tmpvec.size()-1 tmpvec.x[ii]*=tmpvec.x[ii]
  num = tmpvec.size()
  wvar = (tmpvec.sum()/totalarea)*(num/(num-1))
  // weighted stdev
  wstdev = sqrt(wvar)

  printf("Mean %4.3f  Min %4.3f  Max %4.3f  Var %5.4f  StDev %5.4f\n", \
         wmean, vpeakvec.min(), vpeakvec.max(), wvar, wstdev)

  resultvec = new Vector()

  percentiles(vpeakvec, LOWPCTTHRESH)

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