Mechanisms of Firing Patterns in Fast-Spiking Cortical Interneurons
Figure 10
Noise-Induced Stuttering Activity for Small Na+ Window Current (θm = −24 mV)
(A,B) Voltage traces in response to a step current of amplitude Iapp = 3 μA/cm2.
(A) In the absence of noise in the input (D = 0), the membrane potential depolarizes during the current step but the neuron does not fire action potentials.
(B) Noise of variance D = 0.1 μA2 × ms/cm4 induces irregular bursts of action potentials (irregular stuttering).
(C,D) Voltage traces in response to a step current of amplitude Iapp = 3.2 μA/cm2.
(C) For D = 0, the neuron exhibits delayed tonic firing.
(D) For D = 0.1 μA2 × ms/cm4, the neuron stutters irregularly. For all panels, gd = 0.5 mS/cm2. Projection of the phase portraits on the V-h plane for constant values of b (0.046 in (A) and 0.22 in (C)) are shown below the traces in (A,C). These values of b are either the fixed-point value (in (A)) or the average value on the limit cycle (in (C)). Solid circles denote stable fixed points, solid lines denote stable limit cycles, and dotted lines denote unstable limit cycles.