This study investigated chromatic induction from inhomogeneous
background patterns. Previous work showed that a background pattern
detected by only S cones induced strong color shifts in a nearby test area
(Monnier & Shevell, 2003). In that work, the
S-cone patterns were composed with constant L- and M-cone stimulation over
the entire background; in terms of L and M cones, therefore, the
background was uniform. S-cone stimulation was varied over space to
produce S-cone-isolated background patterns. These S-cone patterns,
however, established spatial structure (the pattern) at both the
receptoral level (S-cone stimulation) and the postreceptoral level
(S/(L+M)). Here, these two levels of pattern representation were
unconfounded to determine whether color shifts induced by S-cone patterns
were due to spatial structure within an S-cone-specific neural pathway
versus a pathway that combines responses from S cones and other cone types
(e.g. S/(L+M)). The results showed that the induced color shifts were
mediated by signals within a pathway that combines responses from multiple
cone types. These results are consistent with a
+s/−s spatially antagonistic neural receptive
field, which is found in some neurons in V1 and V2.