Spatial integration of signal information in Gabor stimuli

We studied spatial integration of Gaussian weighted cosine gratings (Gabor gratings) in contrast detection by using a two-alternative forced-choice me thod. The Gabor gratings, which were either complete or sharply truncated t o a square shape, were presented either in the presence or absence of stati c noise. Contrast thresholds were determined for different truncation areas and different widths of the two-dimensional Gaussian weighting function. C ontrast detection performance was found to depend only on the effective spa tial spread of the stimuli. The spatial spread is a physical description of signal area, which takes into account the spatial inhomogeneity of the sig nal. The highest detection efficiencies were obtained when the spatial spre ad was small independently of whether the stimuli were sharply truncated or complete smooth Gabor gratings. The results show that the contrast detecti on mechanism takes into account the shape of the signal window and does not collect information outside the area of the signal, (C) 1999 The College o f Optometrists. Published by Elsevier Science Ltd. All rights reserved.