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Joel Pokorny, Vivianne C. Smith; Sensitivity regulation in the visual system. Journal of Vision 2005;5(12):1. doi: 10.1167/5.12.1.
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© ARVO (1962-2015); The Authors (2016-present)
For over a century, a pervasive theme in vision science has been the characterization of the changes in visual performance associated with variation in light level. Our approach to describing the mechanisms responsible for light level dependent changes in sensitivity is to measure temporal contrast sensitivity functions at different light levels; intracellularly in primate H1 horizontal cells (data collected in Dennis Dacey's lab), extracellularly in primate Parvocellular and Magnocellular retinal ganglion cells (data collected in Barry Lee's lab) and psychophysically in humans. We start with a quasi-linear model of sensitivity regulation in the primate H1 horizontal cell, one synapse removed from the cone photoreceptors. The model incorporates an early time-dependent stage of sensitivity regulation by the cones. The H1 model was then applied to responsivity data of Parvocellular and Magnocellular retinal ganglion cells. The ganglion cell model incorporates center-surround subtraction. The H1 based model can predict the Parvocellular data. The Magnocellular data require an additional time-dependent stage of sensitivity regulation that results in Weber's Law. Psychophysical data reflect the sensitivity regulation of the retinal ganglion cell pathways but show a decline in high-frequency temporal sensitivity that is most pronounced for the Parvocellular post-retinal signals.
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