Energy model for contrast detection: spatial-frequency and orientation selectivity in grating summation

Models of spatial vision usually assume a 'front-end' of spatial-frequency and orientation selective channels. Subthreshold-summation studies have pro vided some of the strongest support for this notion. We applied a single-ch annel energy model and a multiple-channels probability-summation model to e xplore subthreshold-summation phenomena. We measured the contrast threshold s for detection of two superimposed Gabor patches as a function of the spat ial-frequency and orientation difference between the components. The stimul i were centred 7.5 deg above the fixation point and were windowed by a Gaus sian function with one of two different spatial spreads. We have shown that the spatial-frequency and orientation selectivity in subthreshold summatio n of Gabor patches is determined by the similarity (cross-correlation) betw een the stimulus components. A single-channel energy model as well as a mul tiple-channels probability-summation model could explain the summation data . (C) 2001 Elsevier Science Ltd. All rights reserved.