Organization of ascending auditory pathways in the pigeon (Columba livia) as determined by autoradiographic methods

A mixture of tritiated proline and fucose was injected into the labyrinthine endolymphatic space of 5 white king pigeons (Columba livia). Using standard autoradiographic techniques, we observed transsynaptic labeling in ascending auditory pathways to the level of the mesencephalon. Auditory system structures, ipsilateral to the injection site, which labeled heavily were the cochlear nerve, the magnocellular and angular nuclei, and the superior olive. Those ipsilateral structures which were slightly labeled were the lateral lemniscus and the dorsal part of the lateral mesencephalic nucleus. Contralateral structures which labeled were the superior olive, lateral lemniscus, and dorsal part of the lateral mesencephalic nucleus. The results of this study suggest that ascending auditory pathways (to the level of the mesencephalon) in the pigeon are more similar to those described for mammals in general than previously thought.