Figure 5.
Mutual information with sigmoidal response functions and Poisson output noise. A, The sigmoidal response model (see Materials and Methods) is illustrated for an ON cell showing the maximum expected spike count Nmax, the gain (red dashed), and the threshold (green dashed) of the cell. The schematic shows the effect of varying the gain for a fixed threshold. B, The ratio of mutual information transmitted by the optimal ON–OFF versus ON–ON systems about a stimulus drawn from a Laplace distribution. The total mean spike count of each system, Nmean, was constrained. C, The optimal thresholds of the sigmoidal response functions for the ON–ON system when constraining the total mean spike count. Below a critical value of the gain, the two thresholds are identical. D, The optimal thresholds of the sigmoidal response functions for the ON–OFF system when constraining the total mean spike count. The two thresholds are different except in the limit of small gain and large mean spike count.