Figure 12.

Optimal coder threshold parameter and reconstruction error. (A) Threshold parameter c (ordinate) as a function of normalized amplitude ε = s/A (abscissa) showing the wide range of ε over which the asymptotic value of the threshold (c = 0.5) holds. As ε approaches 1, c decreases rapidly. When the signal is small, such that ε <1/$\sqrt{12}$ = 0.289 (c ≤ 0.21), the optimum policy is to suppress firing because the reconstruction error upon firing a spike will be larger than the error from not spiking. (B) Reconstruction error (ordinate, in dBV) as a function of threshold parameter c (abscissa) parameterized by the amplitude ratio ε. The locus of optimum values c^* for which error is a minimum is shown by dashed line. The large signal asymptote (c = 0.5) is shown as dotted line. The shaded region indicates the values of ε between the 10th and 90th percentile for the noise stimulus shown in Figures 8, 10. In this range the optimum c^* lies between 0.464 ≤ c ≤ 0.478.