Thalamic organization of the retmo-thalamo-hyperstriatal pathway in the pigeon (Columba Livia)

1. The distribution of labeled macromolecules was studied within the dorsolateral thalamic nuclei of the pigeon after unilateral intraocular injection of either 3H-proline, 3H-leucine or 3H-fucose. The highest densities of grains were found in nucleus dorsolateralis anterior, pars lateralis at its dorsolateral aspect (DLLd) and in nucleus lateralis anterior (LA) whereas moderate labeling was observed in the ventral aspect of DLL (DLLv) and in nucleus dorsolateralis anterior, pars magnocellularis (DLAmc). No significant label was found on the ipsilateral side. 2. After circumscribed unilateral ablation of the visual wulst, the cells in DLLv were most severely affected by retrograde degeneration, whereas DLLd, DLAmc and LA remained intact. Bilateral ablation of the wulst or combination of wulst damage with section of the supraoptic decussation gave rise to additional degeneration in DLLd, thus suggesting a contralateral retinotelencephalic pathway via DLLv and an ipsilateral retino-telencephalic pathway via DLLd and recrossing via DSO. LA and DLAmc represent relays in retinothalamo-telencephalic pathways of unknown destination. 3. DLLv was confirmed as relay in the contralateral retino-thalamo-hyperstriatal pathway in a combined series of experiments, where the autoradiographic and the retrograde degeneration techniques were applied in the same animal.