Steady state frequency distributions for different values of dopamine releasability, <i>W</i>₃₄.

These distributions are obtained by simulating Eqs (7a)–(7d). With increasing W34, the curves exhibit a gradual transition of relative sample distributions from lower to higher stable state. Additive noise strengths used here are σ1 = 0.05, σ2 = 0.01, σ3 = 0.001, σ4 = 0.05, estimated in accordance with the scales of magnitude acquired by the different variables in the circuit dynamics.