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 pa ttern of interhemispheric connections through the corpus callosum in o ccipital cortex of pigmented and albino rats. Callosal connections wer e revealed in tangential sections through the flattened cortex followi ng multiple injections of horseradish peroxidase into the opposite hem isphere. In pigmented rats, we found that monocular enucleation induce s the development of an anomalous band-like accumulation of callosal c onnections in middle portions of striate cortex in the hemisphere ipsi lateral to the remaining eye, as reported previously. In one-eyed albi no rats, we also found callosal connections anomalously placed in midd le 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 d ifference between rat strains was statistically significant. The incre ased patchiness in the callosal pattern of one-eyed albino rats may re flect differences in the ipsilateral retinal projections in albino ver sus pigmented rats.