Fig. 4.
Single spike dynamics. A: noninjected pyramidal neuron. The first spike at 15 pA shows a long latency and a slowly developing afterhyperpolarization. B: same neuron as in A after the injection of a 1-μS slow K channel. The first spike occurs at 48 pA and exhibits a short latency and a pronounced afterhyperpolarization. Spikelets at subthreshold stimulus currents suggest the existence of an equilibrium point of the dynamics with complex eigenvalues, which makes a transition from stable (attracting) to unstable (repelling) as the threshold is exceeded. C: computational model reproducing the behavior in A. The first spike is at 40 pA. D: computational model reproducing the behavior in B after the addition of 1.5 μS. The first spike is at 82 pA. Higher levels of stimulation current and Kv conductance were needed in the model than in the experimental recording (most likely because this cell had a higher input resistance than average).