Model 1a, Input Properties
Input properties were set to initially maximize the dynamic range of the relationship between spike number in the granular cell and the delay between EOCD and primary afferent inputs. Corollary discharge PSPs were delivered by an NMDA-like synapse with a reversal potential of 0mV, decay time of 40ms, and a maximum depolarizing conductance of 0.000015nS (figure 7). An Iclamp current injection, with a duration of 3ms and amplitude of 0.023nA, was paired with this EPSP (figure 7) to contribute to the temporal precision of this response, although a corresponding electrical synapse between the juxtalobar fiber and the ELL granular cell has yet to be identified in vivo. The duration of the current input was set to approximate the width of an action potential in the presynaptic cell.
Primary afferent inputs were set to be roughly equivalent to their EOCD counterparts, since experimental results show a relatively symmetric granular cell voltage response with respect to whether the primary afferent input arrives before or after the EOCD input (figure 2b, Bell and Grant, 1992). An NMDA-like synapse with t decay=40ms, reversal potential of 0mV, and maximum conductance of 0.00014nS was complemented with an electrical synaptic input simulated by an Iclamp current injection of 0.012nA over 3ms (figure 7). An electrical synapse from the primary afferent fiber onto the soma of the ELL granular cell has been shown in vivo (Bell and Grant, 1992).
