Mechanisms of Firing Patterns in Fast-Spiking Cortical Interneurons
Figure 3
Responses of the Model Neuron to Noiseless Current Steps for Large Na+ Window Current (θm = −28 mV)
(A) Phase diagram of the model neuron in the Iapp-gd plane. Solid line: current threshold to action potential firing. Dashed line: to the right of the dashed line, the spike response is almost immediate after the current step onset. Period doubling bifurcations occur on the dotted lines, leading to doublet or complex firing (grey region).
(B) Voltage traces for gd = 0.39 mS/cm2. Top: for Iapp = 1.25 μA/cm2, the neuron displays low frequency delayed tonic firing. Bottom: for Iapp = 1.27 μA/cm2, the neuron fires doublets of action potentials.
(C) The steady-state f-Iapp curve of the neuron; gd is as in (B). The average firing frequency goes to zero at firing threshold. Between the two solid circles, the neuron fires doublets of spikes.