Retinal ganglion cells projecting to the nucleus of the optic tract and the dorsal terminal nucleus of the
accessory optic system in macaque monkeys
I. Telkes, C. Distler & K.-P. Hoffmann
European Journal of Neuroscience, 12:2367-2375, 2000
- Using classical neuroanatomical retrograde tracing methods we investigated retinal ganglion cells of origin
of the projection to the nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system (NOT-DTN)
in macaque monkeys. Our main question was to quantify the strength of the projection from the ipsilateral retina
to the NOT-DTN. We therefore examined the number, distribution, and soma size of retinal ganglion cells involved
in this projection. Electrophysiologically controlled small injections into the NOT-DTN revealed a clearly bilateral
retinal projection mainly originating from the central retina but also involving peripheral retinal regions. Labelled
cells were found nasally in the contralateral retina and temporally in the ipsilateral retina with some overlap
in the fovea. The projection from the ipsilateral retina was 36%-43% of that from the contralateral retina. On
average, only 1-6% of the local population of ganglion cells projected to the NOT-DTN. Small soma size and large
dendritic fields imply that in monkey rarely encountered, "specialized" ganglion cells provide the direct
retinal input to the accessory optic system. These results are discussed with respect to the symmetry of monocular
horizontal optokinetic nystagmus in primates.
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