Fig. 1.

Empirical S/R suite of rod responses. (A) Ref flash responses from larval tiger salamander rods (whole-cell, voltage-clamped recordings in the perforated patch mode; data provided by J.I. Korenbrot, UCSF). Stimuli were 20-ms flashes at 520 nm: 13, 27, 54, 148, 310, 620 to 3541 R^*/flash. (B) Time-to-peak (T_pk) versus log (R^*/flash). T_pk for the Ref flash responses are shown as filled circles with solid lines, along with T_pk data from four other cells recorded under the same conditions. The T_pk of the Ref data decreases by ∼380 ms/log unit from 1400 ms to 760 ms, over the 3-log-unit range of I. All five rods undergo comparable changes in T_pk with intensity (C) Peak response amplitude (R_pk) vs log (R^*) for the same 5 rods (Ref data, filled circles). Note that the I_1/2 of the Ref rod (95 R^*/flash) is representative of the 5 rods shown, and is close to the values reported in Miller and Korenbrot (1994) and Korenbrot (1995). (D) Step responses from newt rods (Forti et al., 1989; Torre et al., 1990).^*,^† Note the “nose” at step onset that recovers to a steady-state (LA) level, and a multiphasic response at step offset exhibiting a fast recovery phase followed by a slow phase, with some damped resonant behavior in between. (E) Highly saturated, DA responses to 100-ms flashes along with corresponding T_sat functions taken at four recovery criteria (lowest T_sat function corresponds to a 10% recovery criterion, as indicated by the horizontal dashed line through the photocurrent data). Data are from Pepperberg et al. (1992). Flashes ranged from 8 R^*/flash to more than 2.9 ×10⁷ R^*/flash (>6.5 log₁₀ units). Note that the T_sat functions have a slope of ∼2 s/ln unit, and that the T_sat data accelerate at the highest intensities. (F) LA flash sensitivity versus log (I_b). Flash sensitivity is defined as the peak amplitude of a flash response in the presence of a background, divided by the DA peak flash response amplitude (R/R_DA). The data are from six newt rods studied by Torre et al. (1990). Note the data obey the Weber-Fechner relation over ∼4 log units of I_b, and have an I_1/2 of 100 R^*/s.