Projections from the striate cortex to the diencephalon in the squirrel monkey (Saimiri sciureus). A light microscopic radioautographic study following intracortical injection of H3 leucine.

Abstract

AbstractTritiated leucine was injected into three different regions of the striate cortex in nine squirrel monkeys and the axoplasmic transport of labelled protein in the neurons was used to identify terminal fields of projection in the thalamus. The regions of injection corresponded to those representing about 3°, 10°, and 30° eccentricity in the contralateral visual field. The periods of post‐injection survival were 9–19 hours, 8 days, and 23 days. The exposure was about three weeks in all cases. In the thalamus terminal fields of projection were identified in the lateral geniculate nucleus, the posterior nucleus of the thalamus, the inferior and lateral pulvinar nucleus, the reticular nucleus of the thalamus and the pregeniculate nucleus. In most of the projections the location of the terminal fields varied systematically with the location of the injection site indicating a retinotopic organization. In eight of the nine experiments all of the thalamic projections were observed. In the cases with postinjection survival times of 8 and 23 days pronounced axonal labelling was seen, and the corticothalamic pathway could be traced from the site of injection to the thalamus. In one experiment in which only the superficial layers of the cortex were labelled by the injection no thalamic projection was found.