Model 2b, Summary
Ionic conductances remained relatively unchanged in this model with respect to model 2a (figure 3b). The presence of slow NMDA conductances alleviated the need to increase I-NaP and I-NaR conductances, as had been the case in the development of model 1b. Furthermore, spike number response and burst onset/offset latencies for model 2b were relatively unchanged from model 2a (figures 11, 23). Sensitivity tests for model 2b, shown in figures 24a, 24b, and 25, indicate fairly stringent restrictions on the degree to which maximum ionic conductances and maximum input currents can be varied while maintaining the desired graded spike number response in the granular cell across different input delays.
Despite this increased sensitivity to perturbations in input and ionic conductance parameters, model 2b was successful in eliminating the necessity of an EOCD-delivered electrical synaptic input that was shown for model 2a. Since model 2b also used a plausible combination of glutamatergic synaptic currents and eliminated the necessity of uncharacterized LMI burst offset control, it was the most parsimonious model tested overall in terms of experimentally given constraints. However, the large discrepancy between burst offset latencies for model 2b and experimental results (figure 11), along with the abovementioned sensitivity to relatively small changes in maximum ionic conductance parameters, argues for the necessity of LMI controlled burst offset latency (model 1b).
