FIGURE 7.

Models with and without voltage-dependent inactivation can be discriminated. We simulated a spiking neuron having one Na_v channel type with voltage-dependent inactivation rates (cf. Fig. 3 A3) and one n⁴ K_v channel type. The Na_v channel was then replaced by a model with voltage-independent inactivation rates (cf. Fig. 3 A4), and optimal parameters were found with the real-time optimizer. As cost function, we used the shape of one single spike (A) or two consecutive spikes (B), which effectively enforces a match of the spiking frequency. The coupled model could not exactly reproduce the spike simulated with the uncoupled model, especially when fitting two spikes, but differences were small. More obvious was the mismatch between the different sets of steady-state curves (C), and between the time-to-peak plots (D, cf. Fig. 6 C). Similar results were obtained when comparing models with different numbers of activation particles (voltage sensors)—see text.