(A) Configuration for recording. The flash intensity was adjusted to produce occasional responses, as shown in the example trace. Determination of quantal analysis parameters: a template (the average response) was scaled to match the rising phase of the flash-aligned response. The amplitude distribution was fit with a quantal response model, where:
is the probability of activating n rhodopsin molecules, and:
is the probability that n active rhodopsin molecules produce a response with amplitude a, with parameters: mean Rh*/flash (λ), failure noise (σD), mean SPR amplitude (A), and SPR dispersion (σA) (Baylor et al., 1979). The full distribution is given as:
(B) Thresholds for classifying responses θ1, θ2 were calculated such that:
Plotted are the cell selection criteria, θ1/σDark for each cell, included or rejected, for each mouse strain. On the right are example amplitude distributions for a cell that fails the criterion (θ1/σDark < 2.33) (left plot) and one that passes (right plot).