Title of Dissertation: A ROLE FOR THE SUPERIOR COLLICULUS IN THE CONTROL OF SONAR VOCAL PRODUCTION IN THE ECHOLOCATING

Microchiroptera have evolved a biological sonar system that enables aerial foraging in total darkness. These echolocating bat species emit sequences of ultrasonic vocalizations and use the returning echoes to create acoustic images of the environment. Bats orient their gaze in space by adjusting their sonar vocalizations, flight dynamics, and head aim in a coordinated manner when approaching targets. Insectivorous species of echolocating bats have been shown to actively modulate the features of sonar vocalizations with changing target distance. Therefore, variations in the time–frequency structure and temporal patterning of sonar calls produced by foraging bats reflect adaptive goal directed behaviors. The bat's heavy reliance on sound production and processing is reflected in neural specializations of auditory and motor structures. The experiments described in this dissertation probe the midbrain superior colliculus (SC), a vertebrate sensorimotor nucleus mediating orienting behaviors, and they specifically explore adaptations in the SC of the insectivorous bat, Eptesicus fuscus, for acoustic orienting. The anatomical experiments conducted demonstrate that the bat SC ha