The role of chromatic information in 3-D shape perception is
controversial. We resolve this controversy by showing that chromatic
orientation flows are sufficient for accurate perception of 3-D shape.
Chromatic flows required less cone contrast to convey shape than did
achromatic flows, thus ruling out luminance artifacts as a problem.
Luminance artifacts were also ruled out by a protanope's inability to
see 3-D shape from chromatic flows. Since chromatic orientation flows can
only be extracted from retinal images by neurons that are responsive to
color modulations and selective for orientation, the psychophysical
results also resolve the controversy over the existence of such neurons.
In addition, we show that identification of 3-D shapes from chromatic
flows can be masked by luminance modulations, indicating that it is
subserved by orientation-tuned neurons sensitive to both chromatic and
luminance modulations.
Decoding depth order and three-dimensional shape perception from human cortical activity of dorsal and ventral areas