DETECTION OF GLOBAL STRUCTURE IN GLASS PATTERNS - IMPLICATIONS FOR FORM VISION

Glass (Nature 1969,223:578-580) patterns are random dot stimuli that g enerate a percept of global structure. To study the mechanisms underly ing this global form perception, concentric, radial, hyperbolic, and p arallel Glass patterns were constructed. Thresholds for detecting each type of pattern were measured by degrading the patterns through the a ddition of noise. Concentric patterns yielded the lowest thresholds fo r all subjects, while radial and hyperbolic patterns produced somewhat higher thresholds. For all subjects the parallel patterns produced th e highest thresholds. Threshold measurements as a function of the area containing pattern structure provided evidence for global pooling of orientation information in the detection of radial and concentric Glas s patterns but only local pooling in the detection of parallel pattern s. Monte-Carlo simulations demonstrate that plausible neural models ca n accurately predict the data. These models indicate that the visual s ystem contains networks that pool orientation information within regio ns 3.5-4.5 degrees in diameter in central vision. This pooling is orga nized to extract cross-shaped, X-shaped, and quasi-circular forms from the retinal image. The results are in good agreement with recent sing le unit physiology of primate al ea V4, an intermediate level of the f orm vision pathway. (C) 1998 Elsevier Science Ltd. All rights reserved .