Figure 1.

The Siamese cat abnormality, as an example of albino abnormalities in mammals. Taken from Kaas (Kaas, 2005) (with permission), the left panel illustrates the normal pattern of partial decussation of visual fibers from the retina to the geniculate, and their normal pattern of projection to visual cortex. The right panel summarizes the abnormal patterns of decussation seen in the Siamese cat, in which fibers from temporal retina that normally project ipsilaterally undergo abnormal crossing at the optic chiasm. This panel also illustrates the two ways in which this abnormal visual input is corrected at the level of the visual cortex, either by a relatively normal pattern of geniculocortical projection (along with relative suppression of the abnormal input) in Midwestern Siamese cats, or reorganization and re-mapping of the abnormal input in the Boston cats.