Mechanisms of Firing Patterns in Fast-Spiking Cortical Interneurons
Figure 2
Responses of the Model Neuron to Noiseless Current Steps for Small Na+ Window Current (θm = −24 mV)
(A) The phase diagram of the model neuron in the Iapp-gd plane. The solid line represents the current threshold, Ith, as a function of gd. To the left of this line, the neuron is quiescent. To the right of the dashed line, the spike response is almost immediate after the current step onset. Stuttering emerges on the dotted line via a torus bifurcation.
(B) Top panel: the membrane potential V in response to a step of current for gd = 0.1 mS/cm2 and Iapp = 3.35 μA/cm2. The neuron exhibits non-delayed, high-frequency tonic firing. Bottom panel: the f-Iapp curve for gd = 0.1 mS/cm2 is discontinuous at the current threshold. The minimal frequency is 27.4 Hz.
(C) For gd = 0.39 mS/cm2, Iapp = 3.35 μA/cm2, the neuron exhibits delayed, high-frequency tonic firing.
(D) For gd = 1.8 mS/cm2 and Iapp = 4.2 μA/cm2, the neuron exhibits delayed stuttering.