Figure 2
From: The photocurrent response of human cones is fast and monophasic
Comparison of human photocurrent estimated from the ERG and predicted by the model, in response to flashes of different strength. The symbols are taken from the figure numbered 9 in [2], and represent the normalized cone current obtained in paired-flash ERG measurements from the human eye. The measurements have been rescaled slightly (~ 5%) from [2], to compensate for what we presume to have been a small offset in the zero level of current. Thus the resting level (unity) has been retained unaltered, and a linear transformation has been applied so that a level of -0.05 in the above-mentioned figure of [2] has been converted to zero current here. The symbols employ the same colours as in the original figure, and represent the responses to brief flashes of the following intensities: 4 td s (gray open circles), 11 td s (purple diamonds), 22 td s (yellow asterisks), 37 td s (blue squares), 68 td s (green filled circles), 140 td s (red triangles), and 330 td s (black filled circles). The continuous curves of corresponding colour show the predictions of the model for the normalized current J(t)/J(0), using the parameter values listed in Table 1. The background intensity was set to 60 td, as measured for the blue rod-saturating background used in the ERG experiments. For comparison, the inset shows the curves predicted by the original model of [3] with the generic values for all parameters except the gain factor kβ, which was reduced from 1.6·10-4 (ms)-1 td-1 to 10-4 (ms)-1 td-1. In the present formulation, these curves correspond to setting τm = 0, and represent Ios in the notation of [3].