# Exercise: The effect of gap junctions on synchronization

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.

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