Fig. 4.

Modeling the time course of disinhibition of substantia nigra pars compacta dopaminergic neurons. A source of tonically active inhibitory inputs was turned off synchronously (A) or asynchronously (B). This is represented by a step function (A, left) or the complementary cumulative distribution function [f(t) = cCDF (mean μ = 1.0 s, standard deviation σ = 100 ms)] (B, left). Each input is described by the conductance waveform g(t) (middle) with a deactivation time constant (τ) of 6 ms. The time course of disinhibition is determined by their convolution [f*g](t). Thus tonic inhibition decays according to the GABA_A deactivation time constant (A, synchronous) or the complementary cumulative distribution function (B, asynchronous). The time at which an individual GABA_A input in the asynchronous case is removed is taken from a normal distribution.