Morphological alterations of the visual system in white zebra finches.

Visual system anomalies in albino mammals are generally caused by a lack of retinal pigment and misrouting of retinofugal optic fibres. This study shows that the visual system of white zebra finches differs morphologically from that of normally coloured (wild type) birds, although eye pigmentation and retinofugal projection are normal. In white zebra finches, the recrossing tectorotundal projection is enhanced and a new (reciprocal) connection is established between the n. rotundi of both hemispheres. The morphological alterations found in this study may contribute to the previously described enhanced processing of ipsilateral stimuli in white zebra finches.