For completeness, four-level sensitivity tests were performed on each conductance type. Maximum conductance for each type was set at 50, 90, 110, and 150% of the model value, holding all other maximum conductances fixed. Spike number was then plotted as a function of delay between inputs (figures 9a, 9b). It was possible to separate conductances into groups having different effects on this relationship within this range of variation. For instance, varying the three conductances of I-NaR, I-KA, and I-CaHVA had the effect of tuning the spike number vs. delay relationship within a range that could still conceivably support the desired neural code (figure 9b). On the other hand, variation of the I-KIR, I-NaF, and I-KV conductances within this range produced situations in which the slope of spike number as a function of delay reached zero (figure 9a). The I-NaP and I-KM conductances fell into a third class that nearly abolished this relationship in one direction while producing perfect coincidence detection (full burst at a delay=0ms, no spikes at any other delays) in the other direction (figure 9a-ii,iii). It should be noted that, as expected, increasing the maximum values for depolarizing currents tended to flatten the response at non-zero spike numbers due to I-NaF saturation, while increasing the maximum values for hyperpolarizing currents tended to flatten the response at a spike number of zero.

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