The callosal pattern in striate cortex is more patchy in monocularly enucleated albino than pigmented rats.

We investigated the effect of neonatal monocular enucleation on the pattern of interhemispheric connections through the corpus callosum in occipital cortex of pigmented and albino rats. Callosal connections were revealed in tangential sections through the flattened cortex following multiple injections of horseradish peroxidase into the opposite hemisphere. In pigmented rats, we found that monocular enucleation induces the development of an anomalous band-like accumulation of callosal connections in middle portions of striate cortex in the hemisphere ipsilateral to the remaining eye, as reported previously. In one-eyed albino rats, we also found callosal connections anomalously placed in middle portions of striate cortex, but they tended to form several patches of labeling rather than a single continuous band as in pigmented rats. Densitometric analysis of the callosal patterns revealed that this difference between rat strains was statistically significant. The increased patchiness in the callosal pattern of one-eyed albino rats may reflect differences in the ipsilateral retinal projections in albino versus pigmented rats.