Biology Reference
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hues. Also, they found the rod effect to be most marked with small
test fields.
To explain their results, they suggested that rods might
contribute to both the R-G and Y-B opponent channels, and that
there was a reciprocal antagonistic interaction between the rod and
cone receptor signals. The reduced influence of the rods with size
of the test field, for example, was explained by the assumption that
the cones became progressively more effective in suppressing the rod
signals as the size of the test field increased, in a similar way to their
suppression when test intensity increased above cone threshold. They
also attempted to explain the change in the spectrum loci of unique
blue and green towards shorter wavelengths with rod intrusion on
the assumption that rod signals tended to inhibit the short-wave cone
input to the R-G and Y-B opponent channels (Nerger et al ., 1995 ).
In summary, the study of chromatic rod vision made it clear
that the two basic assumptions of the orthodox duplicity theory,
that rods and cones function independently of each other and that
rods mediate achromatic vision only, were wrong. Yet, it must be
admitted that our understanding of the underlying mechanisms of
chromatic rod vision is still in a rudimentary state.
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