A Case of Extreme Simultaneous Color-Contrast in a Patient with Hypoxic Encephalopathy

Abstract

We conducted a series of tests on color vision for a patient with simultaneous agnosia after cortical damage from cerebral anoxia (hypoxic encephalopathy). He suffered from shape perception in the wide range of visual area; he could perceive only a small part of an object at a time. He showed regular performance in color vision tests, such as panel D-15 test, or color naming tests under D₆₅ simulating fluorescent lamp with and without colored glasses (color-constancy test). However, he showed extremely strong colorcontrast effect. We conducted a precise psychophysical experiment to investigate the characteristics of his color-contrast effect. He made achromatic adjustments so that the center color patch had almost the same chromaticity as its surround. These results suggest that his regular performance in the color-constancy test could have been realized by the use of local chromatic-contrast signal between the edge of target and its surround, with higher priority than normal observers.