A 400% increase in the maximum conductance for the channels described by the I-KCa current was the only significant change in the ionic conductances between this model and its extrinsically controlled counterpart, model 1a (figure 3b). This increased hyperpolarizing conductance allowed the slow K⁺ conductance (I-KM) to overtake the noninactivating depolarizing effects of I-NaP and eventually end the burst without the influence of any hyperpolarizing currents of external origin. In this fashion the number of spikes produced by the granular cell as a function of delay was controlled by the translation of differing initial summated levels of depolarization into a range of latencies the initial spike in the burst. This burst onset latency ultimately controlled the number of spikes in the response, since larger latencies correspond to higher I-KM conductance levels at burst onset (figure 11).

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