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called discrete noise, and continuous variation in phosphodiesterase activity, called contin-
uous noise. These intrinsic noise sources make extracting the signal from the background
more difficult. Another major source of noise in photoreceptors is noise in the light stimulus
that results from the poisson variability in photon arrival rates. Photon noise, called ’’shot
noise” in other systems, is especially evident in dim conditions, so it is particularly relevant
for the rod system. It makes estimating the intensity of the light source more difficult.
It is known that electrical coupling via gap junctions between rod photoreceptors reduces
both intrinsic noise and extrinsic photon noise, at the expense of reduced spatial resolution.
However, the exact nature of this tradeoff are unclear. Using parameters measured from
the salamander retina, we demonstrate that coupling between rods results in an improve-
ment in signal-to-noise ratio for nearly all perceptible stimuli. Investigating this effect in
the salamander rods requires accurate measurements of the rod-rod coupling resistance,
membrane resistance, and membrane capacitance. While estimates of salamander rod-rod
coupling have been made using retinal slices [115], these measurements may overestimate
the coupling resistance because connections between adjacent rods could be disrupted near
the surface of the slice. In this study we estimate the rod-rod coupling resistance in the tiger
salamander retina using both a bar light stimulus and electrical measurements using patch-
clamp in the whole-mount retina. With this data, we demonstrate the functional conse-
quences of rod-rod coupling on photoreceptor noise performance due to both intrinsic and
extrinsic noise, and on image fidelity.