Three-dimensional auditory localization in the echolocating bat

Echolocating bats exhibit accurate three-dimensional (3D) auditory localization to avoid obstacles and intercept prey. The bat achieves high spatial resolution through a biological sonar system. Key features of the bat's sonar system are (1) high frequency, directional echolocation signals; (2) high frequency hearing; (3) mobile ears; and (4) measurement of distance from the time delay between sonar emission and echo reception. The bat's sonar receiver is a standard mammalian auditory system that computes azimuth from inter-aural differences and elevation from spectral filtering by the ear [1–3]. Target range is computed from echo arrival time [4, 5], and the bat auditory system contains neurons that show echo delay-tuned responses to pulse-echo pairs [6]. Ultimately, information about sound source azimuth, elevation and range converge to create a unified representation of 3D space.