The nucleus of the optic tract (NOT) in the pretectum in both afoveate and foveate mammals has been considered to be the interface between the retina and premotor nuclei in the pathway conveying signals responsible for horizontal optokinetic nystagmus (OKN). Howevr, the parts of the retina and the kinds of retinal ganglion cells project which their fibers into the NOT are still not completely known.
To clarify this pathway, we injected horseradish peroxidase conjugated with wheatgerm agglutinin into the NOT of the cats. In both retinae, labeled retinal ganglion cells were observed only above the horizontal meridian through the optic disc, and they were situated mainly in the temporal retina lateral to a vertical line through the disc.
In both retinae, the highest concentration of labeled cells was the area centralis and the region adjacent to it. Most of the labeled cells were small cells, i.e., W cells.
However, X-like cells and Y-like cells were also definitely labeled, suggesting that these cells pariticipate in OKN.