Journal of Comparative Physiology A

, Volume 197, Issue 5, pp 541–559

Auditory fovea and Doppler shift compensation: adaptations for flutter detection in echolocating bats using CF-FM signals

Authors

    • Animal PhysiologyInstitute of Neurobiology, University of Tuebingen
  • Annette Denzinger
    • Animal PhysiologyInstitute of Neurobiology, University of Tuebingen
Review

DOI: 10.1007/s00359-010-0569-6

Cite this article as:
Schnitzler, H. & Denzinger, A. J Comp Physiol A (2011) 197: 541. doi:10.1007/s00359-010-0569-6

Abstract

Rhythmical modulations in insect echoes caused by the moving wings of fluttering insects are behaviourally relevant information for bats emitting CF-FM signals with a high duty cycle. Transmitter and receiver of the echolocation system in flutter detecting foragers are especially adapted for the processing of flutter information. The adaptations of the transmitter are indicated by a flutter induced increase in duty cycle, and by Doppler shift compensation (DSC) that keeps the carrier frequency of the insect echoes near a reference frequency. An adaptation of the receiver is the auditory fovea on the basilar membrane, a highly expanded frequency representation centred to the reference frequency. The afferent projections from the fovea lead to foveal areas with an overrepresentation of sharply tuned neurons with best frequencies near the reference frequency throughout the entire auditory pathway. These foveal neurons are very sensitive to stimuli with natural and simulated flutter information. The frequency range of the foveal areas with their flutter processing neurons overlaps exactly with the frequency range where DS compensating bats most likely receive echoes from fluttering insects. This tight match indicates that auditory fovea and DSC are adaptations for the detection and evaluation of insects flying in clutter.

Keywords

Echolocation Bats Auditory fovea Doppler shift compensation Flutter detection

Abbreviations

BM

Basilar membrane

CF

Constant frequency

CM

Cochlear microphonics

DS

Doppler shift

DSC

Doppler shift compensation

FM

Frequency modulated

HRP

Horseradish peroxidase

IC

Inferior colliculus

N1

Evoked potentials from auditory nerve

N4

Evoked potentials from IC

Copyright information

© Springer-Verlag 2010