Exercise: The effect of gap junctions on synchronization
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Dendrodendritic connections between interneurons via gap junctions
("electical synapses") are believed to facilitate synchronized firing in
networks.  (For example, see the 2009 Hjorth et al striatal interneuron
network model on the genesis-sim web site.) In GENESIS, a gap junction
between compartments in two different cells can be implemented by passing
an RAXIAL message directly from each compartment to the other, with the Ra
field replaced by a number representing the resistance of the gap junction.
The BoG gives an example of this in Section 19.6.

To see this effect, create two neurons that receive independent
random excitation, and then experiment with different values of
gap junction coupling beteeen the dendrites.  The simple-network
exercise provides a good starting point for this, with a graphics
script to plot the results and the files needed to create the
simple two-compartment cells.  Instead of applying current injection
to the soma, set the frequency field of the excitatory synchan to
about 200 Hz, in order to provide Poisson-distributed activation
at the specified average frequency.  After plotting the firing
of the two cells, add the gap junction beteeen the dendrite
compartments of the two cells, and note the result for different
values of the gap resistance.
