Visual Neuroscience

Research Article

S-cone discrimination for stimuli with spatial and temporal chromatic contrast


a1 Visual Science Laboratories, Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois

a2 School of Optometry and the Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia


In the natural environment, color discriminations are made within a rich context of spatial and temporal variation. In classical laboratory methods for studying chromatic discrimination, there is typically a border between the test and adapting fields that introduces a spatial chromatic contrast signal. Typically, the roles of spatial and temporal contrast on chromatic discrimination are not assessed in the laboratory approach. In this study, S-cone discrimination was measured using stimulus paradigms that controlled the level of spatio-temporal S-cone contrast between the tests and adapting fields. The results indicate that S-cone discrimination of chromaticity differences between a pedestal and adapting surround is equivalent for stimuli containing spatial, temporal or spatial-and-temporal chromatic contrast between the test field and the surround. For a stimulus condition that did not contain spatial or temporal contrast, the visual system adapted to the pedestal instead of the surround. The data are interpreted in terms of a model consistent with primate koniocellular pathway physiology. The paradigms provide an approach for studying the effects of spatial and temporal contrast on discrimination in natural scenes.

(Received August 31 2007)

(Accepted January 15 2008)


c1 Address correspondence and reprint requests to: Joel Pokorny, Visual Science Laboratories, The University of Chicago, 940 East 57th Street, Chicago, IL 60637. E-mail: