Anatomical study of neural projections to the superior colliculus of the big brown bat, Eptesicus fuscus.

Auditory inputs to the intermediate and deep layers of the superior colliculus of the bat, Eptesicus fuscus, were studied by iontophoretic injection of horseradish peroxidase (HRP) into the superior colliculus. HRP was injected into the recording sites of superior collicular neurons that responded to acoustic stimuli (4 ms duration, 0.5 ms rise-decay times). The results showed that the superior colliculus received its auditory projections mainly from the inferior colliculus bilaterally, but with ipsilateral projections prevailing. A few projections came from the dorsal nucleus of the lateral lemniscus. HRP-labeled neurons were also found in 11 other brain structures.