New model of human luminance pattern vision mechanisms: analysis of the effects of pattern orientation spatial phase and temporal frequency

摘要

Models of human pattern vision mechanisms are examined in light of new results in psychophysics and single-cell recording. Four experiments on simultaneous masking of Gabor patterns by sinewave gratings are described. In these experiments target contrast thresholds are measured as functions of masker contrast, orientation, spatial phase, and temporal frequency. The results are used to test the theory of simultaneous masking proposed by Legge and Foley that is based on mechanisms that sum excitation linearly over a receptive field and produce a response that is an s-shaped transform of this sum. The theory is shown to be inadequate. Recent single-cell-recording results from simple cells in the cat show that these cells receive a broadband divisive input as well as an input that is summed linearly over their receptive fields. A new theory of simultaneous masking based on mechanisms with similar properties is shown to describe the psychophysical results well. Target threshold vs masker contrast (TvC) functions for a set of target-masker pairs are used to estimate the parameters of the theory including the excitatory and inhibitory sensitivities of the mechanisms along the various pattern dimensions. The human luminance pattern vision mechanisms, unlike most of the cells, do not saturate at high contrast.