Figure 1. Empirical Response Suite I

A: Sub-saturated flash responses obtained from toad rods obtained by Rieke & Baylor [16]. Each model was simultaneously optimized to a subset of these data and to the Murnick & Lamb saturated data (shown in Figure 3). The sub-saturating responses used for optimization were the responses to the lowest four intensities: 0.10, 0.35, 1.29, and 4.35 photons/m²/10 ms flash, or 2.26, 7.91, 29.15, and 98.3 R*/10 ms flash assuming an effective collecting area of 22.6 m².

B: Step responses obtained from newt rods by Forti et al. [17]. These data have two qualitative, signature features that have been observed in step responses from rods of other species (e.g., salamander [22]; primate [18]). (1) A "nose" on the leading edge of the response that recovers slowly to a steady-state level. (2) A pronounced, multi-phasic response at step-offset, exhibiting a fast recovery phase followed by a slow phase, with some damped resonant behavior in between.

C: A summary of the intensity-dependence of saturation period (T_sat) observed by Murnick & Lamb. The signature feature is the slope of the T_sat versus ln(I) function. The thick red dashed line has a slope of 2.8 s/ln unit, the slope for the cell presented in Figure 3 of Murnick & Lamb. The cell presented in their Figure 3 (whose data are analyzed in this paper) only provided two data points on the T_sat function (filled red squares). However, the T_sat slope for this cell closely matches data from another rod presented in their Figure 1 (filled red circles), and is close to the average of the T_sat slopes of seven cells presented in their Table 1 (2.7 s/ln unit).

D: The decrease in flash sensitivity as a function of background light intensity (LA flash sensitivity). The data (filled red circles) are from 6 newt rods studied by Torre et al. [23]. The dashed red curve is the Weber-Fechner relation fit to the Torre et al. data: i.e., R/R_dark = (1 + I/I_1/2)^-1. The intensity that caused the incremental flash sensitivity to decrease by a factor of 2 (I_1/2) was 100R*s^-1. The signature feature of note is the relatively large dynamic range over which flash sensitivity obeys the Weber-Fechner relation. In this case, the Torre et al. [23] data obeys the Weber-Fechner relation over a ~4 log unit intensity range.