The retino-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 aH-proline, 3H-leucine or aH-fueose. 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, DLAme 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 pa thway ~da D L L v and an ipsilatera] retino-teleneephalic pa thway 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 eontralateral retino-thalamo-hyperstriatal pa thway in a combined series of experiments, where the autoradiographic and the retrograde degeneration techniques were applied in the same animal.