PubMed · 9052774
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P Cavanagh. 1997-03-06. Visual perception. Predicting the present.. https://doi.org/10.1038/386019a0
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The perception of yellow has played a central role in distinguishing two main theories of colour vision. Hering proposed that yellow results from the activation of a distinct retinal-neural mechanism, whereas according to the Young-Helmholtz-Maxwell view, yellow results from the combined activation of red and green cone mechanisms. When red and green images are presented separately to corresponding retinal locations in the two eyes, the resulting sensation is yellow. As the pathways from the two eyes do not converge until the cortex, this suggests that yellow can indeed arise from the central combining of separate red and green channels. I now show that the reverse process can also occur; the visual system can decompose a 'yellow' stimulus into its constituent red and green components. A 'yellow' stimulus was created by optically superimposing a flashed red line onto a moving green bar. If the bar is visible only briefly, the flashed line appears yellow. If the trajectory of the green bar is exposed for sufficient time, however, the line is incorrectly perceived to trail the bar, and appears red. Motion processing occurs in the cortex rather than the retina in primates, and so the ability of motion cues to affect the perception of colour is consistent with the Young-Helmholtz-Maxwell notion of a 'central synthesis' of yellow.
A series of experiments were designed to examine how luminance and color cues influence the occurrence of neon color spreading for the Ehrenstein pattern plus the cross pattern. The proportion of "see" responses for color spreading was obtained for different combinations of the luminance and color of the pattern components. The following were obtained. (1) Increase in the luminance of the inducing pattern and/or the color difference between the cross and the inducing pattern raised the proportion of "see" responses for color spreading. This implies that luminance and color signals additively contribute to the generation of the color spreading, but in different ways. (2) The "iso-spreading contours" for the generation of color spreading were determined on the two-dimensional isoluminant plane composed of the L-M and S-(L+M) axes. The contours were approximately described by rotated quadratic or ellipse functions. The additive interaction within the chromatic systems [the L-M system and the S-(L+M) system] was less significant than that across the luminance and chromatic systems. (3) The pattern of the experimental results could not be explained straightforwardly by existing models.
Robust visual attentional responses are produced by the sudden onset of a visual cue, but the properties of cues that best elicit an attentional response are not fully known. We used the line-motion illusion (Hikosaka et al., 1991) to investigate the optimal cue properties that evoke visual attention. We found that visual attention is driven primarily by the luminance contrast of the cue. Furthermore, by manipulating the spatial, chromatic, and contrast properties of cues, we found that magnocellular (M) stream biased cues always override the response to parvocellular (P) stream biased cues, even when the P stream biased cues are presented first. Our data suggest that cues that preferentially excite the M pathway predominantly capture visual attention.