Abstract
As retinal illuminance increases, contrast sensitivity passes from a linear range (i.e., proportional to luminance) to a de Vries-Rose range (i.e., proportional to the square root of the background luminance) to a Weber range (i.e., independent of luminance). It is generally admitted that contrast sensitivity is limited by quantal noise (i.e., absorption probability) in the de Vries-Rose range, by spontaneous activity at the retina level (i.e., dark light) in the linear range and by neural noise occurring after contrast normalization in the Weber range. The target of the current study was to measure the spatiotemporal maps of these three internal noises in order to differentiate the spatiotemporal and luminance range of these three internal noise sources and better characterize the internal factors limiting contrast sensitivity. Contrast thresholds to flickering gratings were measured with and without external noise over a wide range of spatiotemporal frequencies and retinal illuminance. For each spatiotemporal frequency, contrast thresholds as a function of retinal illuminance enabled us to estimate the levels of the three internal noises (quantal, dark light and late neural), which were then used to build the three corresponding spatiotemporal maps. These maps led us to elaborate a model characterizing the factors limiting contrast sensitivity as a function of spatial and temporal frequencies.
Meeting abstract presented at VSS 2017