RETINAL GANGLION-CELLS RELATED TO OPTOKINETIC NYSTAGMUS IN THE RAT

The nucleus of the optic tract (NOT) in the pretectum is the visuo-motor relay between the retina and preoculomotor structure in the pathway conveying signals responsible for optokinetic nystagmus (OKN) in both afoveate and foveate animals. Unilateral lesions of the NOT abolish OKN toward the side ipsilateral to the lesion. However, what parts of the retina and what kinds of retinal ganglion cells project their fibers into the NOT are still unknown. To examine this, horseradish peroxidase conjugated with wheatgerm agglutinin was injected into the NOT of the rat. Labeled retinal ganglion cells were diffusely documented in the contralateral side, whereas those situated only in the lower temporal crescent, were found in the ipsilateral side. Ganglion cells dominated in the range of small cells, i.e., W cells. Therefore, ganglion cells responsible for OKN are believed to be related to W cells. However, medium-sized and large cells were definitely labeled in the rat, suggesting possible participation of these cells in OKN.