The kinetics, gain, and reliability of light responses of rod and cone photoreceptors are important determinants of overall Visual sensitivity. In voltage recordings from photoreceptors in an intact primate retina, rods were found to be functionally isolated from each other, unlike the tightly coupled rods of cold-blooded vertebrates. Cones were observed to receive excitatory input from rods, which indicates that the cone pathway also processes rod signals, This input might be expected to degrade the spatial resolution of mesopic vision.