Figure 2.

Procedure for measuring signal and noise. A, Four current responses of a mouse on α ganglion cell to a flash producing on average 0.02 Rh*/rod delivered at time 0 with no background. Template (thick trace) is the average of 28 responses. Holding potential was −60 mV. Filtered at 100 Hz. B, Four responses to a flash producing on average 0.06 Rh*/rod with a background of 0.6 Rh*/rod/s. Template (thick trace) is the average of 28 responses. C, Distribution of correlations between the template and responses to a flash producing on average 1 Rh*/rod in darkness (N = 39). Thick trace is a Gaussian fit (mean ± SD, 1.09 ± 0.52). D, Noise trials in darkness. E, Noise trials on the same background in B. F, Distribution of the correlations between the noise trials with no background (N = 39) and the template. Thick trace is a Gaussian fit (SD of 0.0089). The SD of the noise distribution defines the flash-independent noise.