A multiple-channel model for grating detection.

The multiple-channel model that was proposed in 1974 by MacLeod and Rosenfeld to describe the sensitivity of the visual system to complex gratings has been applied to a variety of complex gratings. The model predicts correctly the contrast sensitivity at both high and low spatial frequencies to square-wave gratings, square-wave with missing fundamental, sawtooth-wave, and trapezoid-wave gratings of different ramp widths. It provides a physiologically reasonable explanation of the detection of luminance gradients without requiring special gradient detectors. The model resembles the threshold behavior of the visual system in that it is sensitive to the relative phase of frequency components at low frequencies, but not at high frequencies.