| Separate processing of color and form is controversial. Cells selectively tuned to both chromaticity and orientation are found in early visual cortex, suggesting that color and form are processed in a combined manner. If this were the case, a distinct neural binding process for color and form would not be necessary. The neural representation of color and form during binocular rivalry was investigated to investigate this question.; In Experiment 1, the chromatic-surround influence on binocular color rivalry was measured. The results showed the chromatic-surround influence on binocular color rivalry was not significantly affected by spatial structure within the surround, such as the spatial frequency or orientation of a surrounding grating. This supports separate processing of color and form.; In Experiment 2, interocular grouping based on congruency of color between the two eyes was investigated. Interocular grouping based on chromatic congruity was observed irrespective of the spatial structure of the stimuli. This also supports separate processing of color and form.; In Experiment 3, perceptual misbinding during binocular rivalry was investigated. When a red/gray isoluminant grating was presented to the left eye and a blue/gray isoluminant grating to the right eye, perceptual alternation between two colored regions was perceived initially. After less than 30 seconds of viewing, however, these rivalrous stimuli resulted in the percept of a red/blue grating. A series of experiments showed that the percept of two-color grating resulted from perceptual misbinding of color and form, not from chromatic contrast or optical misalignment. Errors in binding of color and form revealed the necessity of a distinct neural binding process for color and form.; In Experiment 4, perceptual alternation was observed for two physically identical chromaticities that appeared different in hue due to only chromatic induction. This showed the neural binding process occurs after neural encoding of appearance changes due to chromatic induction.; In sum, results from four experiments clearly supported separate neural processing of color and form, indicating the necessity of a distinct neural binding process for the unified percept of a colored object. |
