Additional sensitivity tests were performed on the updated model to determine the dependence of the spike number vs. delay relationship on maximum AMPA input conductances, as well as on the complete set of intrinsic ionic conductances described previously. Sensitivities to changes in the maximum conductances of intrinsic ion channels were similar to those seen for model #1a, although model #1b displayed a trend wherein sensitivity to the combined effects of I-CaHVA and I-KCa decreased at the same time that sensitivity to the combined effects of I-NaP and I-KM increased when compared to model 1a (figures 15a, 15b). The number of spikes produced in the granular cell as a function of input delay maintained a decreasing trend at maximum AMPA conductances between 50% and 105% of the set value for model #1b (figure 16). A constant number of spikes at all delays were seen for maximum AMPA conductances of 150% and above (figure 16).

Contour plots of spike number as a function of maximum I-NaP and I-KM over the full range of input delays revealed a surface similar to that seen for model 1a, although the area of steep spike number gradient was shifted to a slightly decreased ratio of I-KM to I-NaP (figures 17a, 17b). Additionally, the apparent steepness of this gradient was increased relative to model 1a (figures 17a, 17b). These two observations indicate both an increased sensitivity of model 1b to changes in the ratio of these crucial ionic conductances relative to model 1a, and an increased reliance on I-NaP for model 1b in the absence of a prolonged, NMDA-like depolarizing input.

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