Abstract:
A fundamental issue in chromatic induction (CI), the change in perceived
color of a light caused by a nearby inducing stimulus, is whether CI
results from adaptation to surrounding light or, alternatively, is a
consequence of neural coding of contrast at the boundary between the test
and its surround. This article sought to distinguish between these 2
neural hypotheses of CI by introducing an additional stimulus in a region
outside of the surround. Results from 3 observers indicate that CI from
the surround into a central test field is attenuated by a remote
inhomogeneous "checkerboard," composed of squares at 2 different
chromaticities. A uniform remote field, on the other hand, either at the
average or at the most extreme chromaticity of the checkerboard, had a
weaker effect on CI than the inhomogeneous field, implying that chromatic
contrast within the remote region is a critical factor. These results
suggest that CI, mediated by a neural signal for contrast at the edge of
the test, is attenuated by contrast within the remote region. A contrast
gain control set by variation in chromaticity over a broad area can
contribute to the stable color appearance of surfaces embedded within
complex scenes by minimizing CI from locally adjacent regions.
Keywords:
adaptation to surrounding light vs neural coding at border between test &
surround as neural hypotheses of chromatic induction, adult Os
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