Auditory scene analysis for perceptually guided behavior in the echolocating bat

Abstract

The echolocating bat actively probes its environment with ultrasonic vocal signals and builds a three-dimensional (3-D) auditory scene from information carried by the returning echoes. The bat’s sonar receiver computes the azimuth and elevation of a sonar target from the intensity, timing, and spectrum of sonar echoes at the two ears. It estimates target distance from the time delay between each sound transmission and returning echo. Rapidly processing spatial-acoustic information, the bat’s perceptual system analyzes the 3-D auditory scene to support spatially guided behaviors in a dynamic environment. Psychophysical data from two-choice phantom target discrimination tasks suggest that the bat integrates and segregates echo streams along the delay axis. These findings, together with the results of laboratory insect capture experiments, show that echo delay information is used to guide and coordinate a complex set of adaptive motor behaviors. Measures of neutral spatial selectivity in the bat superior colliculus (SC) also suggest the importance of echo-delay processing for spatially guided behavior. Spatial tuning of SC neurons may be important to the bat’s acoustic orienting behavior, since changes in its head aim, pinna position, flight behavior, and vocal production patterns are closely coupled to the 3-D location of a target.