Journal of Comparative Physiology A

, Volume 171, Issue 6, pp 735–748

Labile cochlear tuning in the mustached bat

II. Concomitant shifts in neural tuning
  • Russell F. Huffman
  • O. W. HensonJr.
Article

DOI: 10.1007/BF00213070

Cite this article as:
Huffman, R.F. & Henson, O.W. J Comp Physiol A (1993) 171: 735. doi:10.1007/BF00213070

Summary

Acoustic stimuli near 60 kHz elicit pronounced resonance in the cochlea of the mustached bat (Pteronotus parnellii parnellii). The cochlear resonance frequency (CRF) is near the second harmonic, constant frequency (CF2) component of the bat's biosonar signals. Within narrow bands where CF2 and third harmonic (CF3) echoes are maintained, the cochlea has sharp tuning characteristics that are conserved throughout the central auditory system. The purpose of this study was to examine the effects of temperature-related shifts in the CRF on the tuning properties of neurons in the cochlear nucleus and inferior colliculus.

Eighty-two single and multi-unit recordings were characterizedin 6 awake bats with chronically implanted cochlear microphonic electrodes. As the CRF changed with body temperature, the tuning curves of neurons sharply tuned to frequencies near the CF2 and CF3 shifted with the CRF in every case, yielding a change in the unit's best frequency. The results show that cochlear tuning is labile in the mustached bat, and that this lability produces tonotopic shifts in the frequency response of central auditory neurons. Furthermore, results provide evidence of shifts in the frequency-to-place code within the sharply tuned CF2 and CF3 regions of the cochlea. In conjunction with the finding that biosonar emission frequency and the CRF shift concomitantly with temperature and flight, it is concluded that the adjustment of biosonar signals accommodates the shifts in cochlear and neural tuning that occur with active echolocation.

Key words

CochleaCochlear nucleusInferior colliculusTonotopyPteronotus

Abbreviations

BF

best frequency

CF

characteristic frequency

CF2, CF3

second and third harmonic, constant frequency components of the biosonar signal

CM

cochlear microphonic

CN

cochlear nucleus

CRF

cochlear resonance frequency

IC

inferior colliculus

MT

minimum threshold

OAE

otoacoustic emission

Q10dB

BF (or CF) divided by the response bandwidth at 10 dB above MT

Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Russell F. Huffman
    • 1
  • O. W. HensonJr.
    • 2
  1. 1.Curriculum in NeurobiologyThe University of North CarolinaChapel HillUSA
  2. 2.Department of Cell Biology and AnatomyThe University of North CarolinaChapel HillUSA
  3. 3.Department of NeurobiologyDuke University Medical CenterDurhamUSA