Target Images in the Sonar of Bats
Abstract
Echolocating bats (Eptesicus fuscus) perceive complex sonar targets as consisting of individual reflecting elements separated by short distances. The target's nearest element, which returns the earliest component of the echo is represented by the timing of neural discharges encoding echo delay. In simultaneous discrimination tests, the range of this part of the target relative to that of a comparison target varies with the amplitude of comparison echoes because echo amplitude influences neural response latency. The bat uses echo spectral properties to estimate the equivalent underlying delay separations. In sequential discrimination test, which require the bat to judge targets from remembered acoustic images, the apparent ranges of all the target's elements shift together as echo amplitude changes, so that they maintain their correct positions with respect to the nearest element. These results indicate that the bat initially develops a mixed time/frequency representation of echoes but ultimately expresses the acoustic images of targets exclusively in the time domain, which corresponds directly to the natural spatial dimension along which the target is distributed. Keywords: Biosonar, Target ranging, Acoustic images, Echo delay, Echo spectrum, Target classification.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1988
- Accession Number
- ADA205679
Entities
People
- Cynthia F. Moss
- James A Simmons
- Michael Ferragamo
Organizations
- Brown University