Morphological correlates of visual field transformation in the corpus callosum.

Horseradish peroxidase (HRP) injections at the boundary of areas 17 and 18 in cat visual cortex resulted in retrograde labelling of neurones located in contralateral areas 17 and 18. The HRP-positive neurones were spread over a region located around the representation of the vertical meridian; they were most numerous in the locus for area centralis. Layer III pyramidal cells and stellate cells in upper layer IV were identified as the principal neurones of origin of the visual callosal pathway.