The interpolated contrast discrimination functions gave the threshold buy TSA HDAC contrast, Δc, for any contrast, c, for a behavioral sensitivity of d′ = 1 (see above, Psychophysical Contrast-Discrimination Functions), thus: equation(6) R(c+Δc)=R(c)+σ.R(c+Δc)=R(c)+σ.

To compute the next point on the contrast-response function, we thus applied Equation 6, for c = 0 and Δc as estimated from the interpolated contrast discrimination function, i.e., R(Δc) = b + σ. Subsequent values of R were computed by repeated application of Equation 6 in which each new c was set to c+Δc from the previous iteration and Δc for that new contrast c, was retrieved from the interpolated contrast discrimination function (see Supplemental Experimental Procedures, for more details on the fitting procedure). σ and b were adjusted to produce the best fit of the contrast-response functions in the least-squares sense. The contrast-discrimination functions were fit (nonlinear least-squares) by the selection model, using (1) and (3). To perform Decitabine ic50 the fit, the contrast discrimination performance of the selection model (percent [%] correct) was computed by simulating synthetic trials based on

responses computed from the measured contrast-response functions. Contrast-response functions were interpolated with a simplified version of Equation 3 (a Naka-Rushton type equation), which lacked the exponent s. The exact form of the interpolation function was not essential (see Supplemental Experimental Procedures).

For any fixed value of k ( Equation 1) and value of the sensory noise (σ), the selection model performance (percent [%] correct) was computed as follows. For each pedestal contrast, Gaussian response distributions were computed for each stimulus location and each ever interval of the task ( Figure 7A). The mean of each response distribution was determined according to the interpolated contrast-response functions. The standard deviations of the Gaussian response distributions were set to the σ parameter. Responses were then combined into “readout” distributions using the max-pooling rule ( Equation 1) and the parameter k ( Figure 7B). On each of 10,000 simulated trials, a response was taken from the readout distribution for each interval. If the larger of these two responses was in the same interval as the increment in contrast, the trial was marked as correct. The Δc that produced 76% correct values using this procedure was taken as the discrimination threshold. Values of k and σ were adjusted to produce the best fit of the contrast discrimination functions in the least-squares sense. We also computed two variations of the aforementioned model (see Figure 8). One variation included two σ values (σf and σd), one for the focal cue and one for the distributed cue trials.