This directory contains a hippocampal granule cell model implemented by Erik
De Schutter. This was used in his model of Ca diffusion in the hippocampus
granule cell, which was described in:
E. De Schutter and J.M. Bower: Sensitivity of synaptic plasticity to the
Ca2+-permeability of NMDA-channels: a model of long term potentiation in
hippocampal neurons. Neural Computation 5: 681-694 (1993).
ABSTRACT
We have examined a model by Holmes and Levy (1990) of the induction of
associative long term potentiation (LTP) by a rise in the free Ca2+
concentra- tion ([Ca2+]) after synaptic activation of dendritic spines. The
previously reported amplification of the change in [Ca2+] caused by
coactivation of several synapses was found to be quite sensitive to changes
in the perme-ability of the N-methyl-D-aspartate (NMDA) receptor channels to
Ca2+. Varying this parameter indi-cates that maximum amplification is
obtained at values that are close to Ca2+ permeabilities reported in the
literature. However, amplification fails if per-meability is reduced by
more than 50%. We also found that the maximum free [Ca2+] reached in an
individual spine during synaptic coactivation of several spines, depended on
the location of that spine on the dendritic tree. Distal spines attained a
higher [Ca2+] than proximal ones, with differences of up to 80%. The
implications of this result for the uniformity of induction of associative
LTP in spines in differ-ent regions of the dendrite are discussed.
IMPLEMENTATION
The script AUTO_CA_fract.g outputs [Ca2+] concentration in the head of 7
spines in the file 'fname'. The variable CA_FRACT controls the relative
Ca2+permeability of the NMDA channel (1 corresponds to permeability as in
Mayer and Westbrook (1987)). After loading the script, ampli96 will
co-activate 96 spines at 200Hz, ampli1 will activate 1 spine at 200Hz.
The two files are:
granule.p: a sketchy representation of the cell
AUTO_CA_fract.g: a complete script controlling the simulation. Is
reasonably well documented inside. Produces only file output.
To run the simulation, include this (it loads the cell) and
type do_ampli1 (activates 1 spine) or do_ampli96 (activates 96
spines).