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 method. The Gabor gratings, which were either complete or sharply truncated to a square shape, were presented either in the presence or absence of static noise. Contrast thresholds were determined for different truncation areas and different widths of the two-dimensional Gaussian weighting function. Contrast detection performance was found to depend only on the effective spatial spread of the stimuli. The spatial spread is a physical description of signal area, which takes into account the spatial inhomogeneity of the signal. The highest detection efficiencies were obtained when the spatial spread was small independently of whether the stimuli were sharply truncated or complete smooth Gabor gratings. The results show that the contrast detection mechanism takes into account the shape of the signal window and does not collect information outside the area of the signal.
Syväjärvi
A
A
Department of Optometry and Vision Sciences, University of Wales, College of Cardiff, UK.
Näsänen
R
R
Rovamo
J
J
D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008960:Models, Psychological; D010775:Photic Stimulation / Q000379:methods*; D012684:Sensory Thresholds; D013028:Space Perception