Dopaminergic modulation of integration of pallidal inputs. (A) Illustration of dopaminergic neuromodulation. GP inputs are labeled red or blue for neurons increasing or decreasing their firing rate. Dopaminergic input from the SNc is labeled in magenta. Black traces illustrate the effect of dopamine on GABAergic conductance of GP-EP synapses. (i), basal dopamine levels, parameters are consistent with the simulations so far. (ii), increased dopamine concentration, simulated by a decrease in the amplitude and depression of GP-EP synapses. (iii), decreased dopamine concentration, simulated by an increase in amplitude and depression of GP-EP synapses. (B) Raster plot of the activity of 10 simulated GP neurons that change their firing rate for 200 ms. Half of the neurons increased their firing rate and half of the neurons decreased their firing rate. The baseline firing rate of all neurons was 20 Hz. (C) Predicted membrane potential of an EP neuron that receives input from 10 GP neurons in B. Dashed red line indicates two SD from the mean membrane potential. (D) Predicted change in membrane potential as a function of the multiplication factor and the baseline firing rate. (E) Duration of the inhibitory phase induced by the change in presynaptic activity. The duration was defined as the time during which the postsynaptic membrane potential was significantly hyperpolarized (more negative than 2 SD below the mean membrane potential).