Topography of retinal representation in the rabbit cortex: an experimental study using transneuronal and retrograde tracing techniques.

The cortical representation of the retina in rabbits was studied autoradiographically using transneuronal transport of tritiated proline and tritiated fucose. Injection of one eye produced cortical labelling on both sides. There was no indication of ocular dominance columns. On the contralateral side, the labelling was found in cortical layers II-IV, and partly also in layer VI of area striata and the caudal part of area peristriata, and in layer IV of most of area occipitalis. In addition, there was a patch of labelling in layers II-IV of the temporal cortex. On the ipsilateral side, the labelling was restricted to layer IV in a strip of cortex comprising area striata and area occipitalis along their common border. The cortical labelling in area striata and occipitalis was interpreted as evidence for a direct geniculo-cortical projection. This was confirmed by demonstration of retrogrately labelled nerve cells in the lateral geniculate nucleus produced by small injections of horseradish peroxidase into area occipitalis and area striata. In experiments with intraocular injections of tritiated adenosine, transneuronal cortical labelling was much weaker and more diffuse. In addition to the neuropil, nerve cell bodies and glial cells were also labelled.