Audiomotor integration for active sensing in the echolocating bat, Eptesicus fuscus

Abstract

Echolocation depends upon the dynamic interplay between auditory information processing and adaptive motor control. We are conducting experiments aimed at understanding the neural mechanisms supporting audiomotor integration for echolocation in the big brown bat, Eptesicus fuscus. In this work we focus on the superior colliculus (SC), a midbrain structure implicated in species-specific orienting behaviors. We have characterized the spatial response profiles of auditory neurons in the bat SC, and have discovered a population of cells that show echo-delay tuning, a response property believed to encode target distance in the bats sonar receiver. These data reveal a 3-D spatial coordinate system that may be used to guide appropriate orienting responses. Our studies also demonstrate that the bat SC plays a functional role in the execution of motor commands used for acoustic orientation by sonar. In particular, SC microstimulation elicits head and pinna movements, along with the production of sonar vocalizations. Multi-unit recordings from the SC of tethered, vocalizing bats reveal bursts of neural activity preceding the production of each sonar cry. Collectively, these results suggest that the bat SC plays a functional role in both auditory information processing and orienting behaviors that operate together in echolocation. [Work supported by the NSF, the NIMH, and the Whitehall Foundation.]