While electrical synapses have been positively identified between presynaptic primary afferent terminals and the somata of medial ELL granular cells in Gnathonemus petersii (Meek and Bell, 1999), there has been no evidence that such synapses exist between the EOCD-carrying juxtalobar afferent and these granular cells. The model addresses the possible presence of electrical synapses by incorporating a relatively simple mechanism to simulate the effects of both known and possible direct electrical coupling between these cells.

An electrical synapse is characterized by direct opening between two cells. Since the fluid in this juction is relatively homogenous with the cytoplasms of both the pre- and postsynaptic cells, the only electrical transformations that accompany the transfer of current from the input cell to the output cell are due to the increased resistivity of the junction (decreased diameter with respect to the presynaptic terminal) and the differential regenerative ion conductances present on either side of the electrical synapse. For these reasons, electrical input to the model granular cell was simulated by direct current injection (I_clamp point process in NEURON simulator) at the soma. The duration of the current injection was set at 3ms to reflect the width of the incoming presynaptic action potential, and the amplitude of the current in nA was set in a range thought to reflect a reasonable attenuation of the presynaptic current due to the increased resistivity of the electrical synapse. Since the exact degree of attenuation between these cells has not been experimentally quantified, the current amplitude parameter was allowed to vary in accordance with experimentally defined limitations on the relative sizes of the juxtalobar and primary afferent PSPs, as well as with the experimentally suggested and hypothesized voltage outputs of the granular cell itself.

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