Fig. 3.

Simulations of order selectivity.A, The panel on the left shows the disynaptic circuit and the synaptic weights. The voltage of the Ex unit (top traces) and Inh unit (bottom traces) in response to a 100 msec interval. Depending on the strength of two synapses, Input → Ex and GABA_B → Ex, the Ex unit responds selectively to the first (green) or second pulse (red). B, Parametric analysis of synapse space. Each plot varies the strength of the Input → Ex (x-axis), and GABA_B → Ex (y-axis). The strength of the GABA_A→ Ex was also varied as shown across the two subplots. Simulations were performed in the presence of noise in both units. The color scale represents the probability of firing to the first pulse and second pulse. Intense green means that given those synaptic strengths, the probability of firing to the first pulse and not to the second was 1.0. Red represents conditions in which the Ex unit responds selectively to the second pulse. Yellowrepresents nonselective responses to both pulses. Note that in each panel there is a transition along the diagonal that represents the point in which a unit changes its selectivity from the second to first pulse and that this transition points shifts to the leftacross plots.