Spatial contrast sensitivity in dynamic and static additive luminance noise

Abstract

The purpose of this study was to define the quantitative relationship between the temporal characteristics of additive luminance noise and the properties of the spatial contrast sensitivity function (CSF). CSFs were obtained from two observers using Gabor patch targets of short duration that were added to white luminance noise with a range of root-mean-square contrasts ( c rms ). The noise was either dynamic or static and was either of the same duration as the test target (synchronous) or of longer duration (asynchronous). For targets presented in asynchronous dynamic, synchronous dynamic, and synchronous static noise, the CSFs became increasingly band-pass with increasing c rms , whereas the CSFs were low-pass at all levels of c rms for targets presented in asynchronous static noise. For all noise types, the properties of the CSFs were well-predicted by the linear amplifier model (LAM), in which the signal energy at threshold ( E t ) is related linearly to noise spectral density ( N). The fundamentally different characteristics of CSFs obtained in asynchronous static noise can be accounted for by a previous proposal that this noise type biases contrast sensitivity toward transient (inferred magnocellular) mechanisms. The other three modes of noise presentation appear to emphasize detection by sustained (inferred parvocellular) mechanisms.