The retinal projection to the ventral part of the lateral geniculate nucleus. An experimental study with silver-impregnation methods and axoplasmic protein tracing.

The retinal projection to the ventral part of the lateral geniculate nucleus (LGNv) was studied in 25 adult cats. In 12 cats one or both eyes were enucleated and the terminal degeneration in the LGNv was studied with silver impregnation methods. In 12 cats one or both eyes were injected with 3H-leucine and the terminal labelling in the LGNv was studied with autoradiography. In one animal one eye was enucleated and the other injected. In this case alternate sections were silver impregnated and processed for autoradiography. The series were cut in parasagittal, transverse or horizontal planes. The results revealed by degeneration were in very good agreement with those revealed by axoplasmic protein tracing. Two fields of retinal projection were found in the LGNn. The larger, dorsal one was restricted to subnucleus k (Jordan and Holländer, 1972) and comprised an ipsilateral and a contralateral component which did not overlap each other. The smaller, ventral field of projection was contralateral and extended from subnucleus b into c, e and a. The afferent optic tract fibres to both terminal fields were of small calibers.