Retinogeniculostriate projections in guinea pigs: Albino and pigmented strains compared

A relatively consistent pattern of input to the contralateral striate cortex was observed in the pigmented guinea pigs, while several patterns were seen in the albinos.

Abstract

The retinogeniculate fibers and geniculocortical projections of pigmented and albino guinea pigs were studied by anatomical degeneration methods and by electrophysiological techniques. In one experiment, an eye was enucleated from each of six pigmented and six albino animals. Six to δ days later the animals were killed and the crossed and uncrossed retinal projections to the dorsal lateral geniculate nuclei studied in serial sections prepared by the Nauta silver method. An organized uncrossed retinogeniculate projection was invariably present in the pigmented guinea pig but was not seen in the albino. There was a consistency in the pattern of the crossed retinogeniculate projections among the pigmented guinea pigs but not among the albino animals. Between ocular enucleation and histological analyses, visually evoked responses at the cerebral cortex were recorded. Indications of an input to the striate cortex via noncrossing fibers were found only in the pigmented strain. A relatively consistent pattern of input to the contralateral striate cortex was observed in the pigmented guinea pigs, while several patterns were seen in the albinos.