Noise and the absolute thresholds of cone and rod vision

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Vision Research. 1992. 32: 853-866

Title: Noise and the absolute thresholds of cone and rod vision
Author: Donner, K.
Contributor organization: Department of Biological and Environmental Sciences
Bio- ja ympäristötieteiden laitos
Bio- och miljövetenskaper, Institutionen för
Publisher: Elsevier
Date: 1992
Language: eng
ISSN: 0042-6989
Abstract: Literature data on light detection by cone and rod vision at absolute threshold are analysed in order (1) to decide whether the threshold performance of dark-adapted cone vision can, like that of rod vision, be consistently explained as limited by noise from a “dark light”; (2) to obtain comparable estimates of the dark noise and dark light of (foveal) cones and (peripheral) rods. The dark noise was estimated by a maximum-likelihood procedure from frequency-of-seeing data and compared with the dark light derived from increment-threshold functions. In both cone and rod vision, the estimated dark noise coincides with Poisson fluctuations of the estimated dark light if 17% (best estimate) of λmax-quanta incident at the cornea produce excitations. At that fraction of quanta exciting, dark lights are equivalent to 112 isomerisations per sec in each foveal cone and 0.011 isomerisations per sec in each rod. It is concluded that (1) the threshold performance of dark-adapted cone as well as rod vision can be consistently described as noise-limited, but not by postulating a multi-quantum coincidence requirement for single receptors; (2) die underlying intrinsic activity in both the cone and the rod system is light-like as regards correspondence between noise effect and background adaptation effect. One possibility is that this activity is largely composed of events identical to the single-photon response, originating in the visual pigment, in cones as well as in rods.
Subject: Retinal noise
Visual sensitivity
Sensory thresholds
Purkinje shift

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