Sj. Ault et al., ABNORMAL IPSILATERAL VISUAL-FIELD REPRESENTATION IN AREA-17 AND AREA-18 OF HYPOPIGMENTED CATS, Journal of comparative neurology, 354(2), 1995, pp. 181-192
We compared the central projections of retinal ganglion cells in tempo
ral retina and the cortical representation of visual fields in areas 1
7 and 18 in cats with various hypopigmentation phenotypes (albino, het
erozygous albino, Siamese, and heterozygous Siamese). In all cats stud
ied, we found that the extent of abnormal ipsilateral visual field rep
resentation varied widely, and more of the ipsilateral visual field wa
s represented in area 18 than in area 17. The greatest degree of ipsil
ateral visual field representation was found in albino cats, followed
by Siamese, heterozygous albino and heterozygote Siamese cats, respect
ively. Additionally, in the different groups there was wide variation
in the numbers of contralaterally projecting alpha and beta ganglion c
ells in temporal retina. In all cases, however, contralaterally projec
ting alpha cells were found to extend further into temporal retina tha
n beta cells. We found that in each cat studied, the maximum extent of
the abnormal ipsilateral visual field representation in areas 18 and
17 corresponded to the location of the 50% decussation line (i.e., the
point where 50% of the ganglion cells in temporal retina project to t
he contralateral hemisphere) for alpha and beta cells, respectively, f
or that cat. Our results suggest that the extent of the abnormal visua
l field representations in visual cortex of hypopigmented cats reflect
s the extent of contralaterally projecting retinal ganglion cells in t
emporal retina. (C) 1995 Wiley-Liss, Inc.