Journal of comparative physiology

, Volume 132, Issue 1, pp 47–54

Disproportionate frequency representation in the inferior colliculus of doppler-compensating Greater Horseshoe bats: Evidence for an acoustic fovea

  • Gerd Schuller
  • George Pollak
Article

Summary

  1. 1.

    The inferior colliculus of 8 Greater Horseshoe bats (Rhinolophus ferrumequinun) was systematically sampled with electrode penetrations covering the entire volume of the nucleus. The best frequencies and intensity thresholds for pure tones (Fig. 2) were determined for 591 neurons. The locations of the electrode penetrations within the inferior colliculus were histologically verified.

     
  2. 2.

    About 50% of all neurons encountered had best frequencies (BF) in the frequency range between 78 and 88 kHz (Table 1, Fig. 1A). Within this frequency range the BFs between 83.0 and 84.5 kHz were overrepresented with 16.3% of the total population of neurons (Fig. 1B). The frequencies of the constant frequency components of the echoes fall into this frequency range.

     
  3. 3.

    The representation of BFs expressed as number of neurons per octave shows a striking correspondence to the nonuniform innervation density in the afferent innervation of the basilar membrane (Bruns and Schmieszek, in press). The high innervation density of the basilar membrane in the frequency band between 83 and 84.5 kHz coincides with the maximum of the distribution of number of neurons per octave across frequency in the inferior colliculus (Fig. 1 C).

     
  4. 4.

    The disproportionate representation of frequencies in the auditory system of the greater horseshoe bat is described as an acoustical fovea functioning in analogy to the fovea in the visual system. The functional importance of the Doppler-shift compensation for such a foveal mechanism in the auditory system of horseshoe bats is related to that of tracking eye movements in the visual system.

     

Abbreviations

BF

best frequency

CF

constant frequency

DSC

Doppler-shift compensation

FM

frequency modulated

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Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • Gerd Schuller
    • 1
  • George Pollak
    • 2
  1. 1.Arbeitskreis Neuro- und Rezeptorphysiologie, Fachbereich BiologieUniversität FrankfurtFrankfurtFederal Republic of Germany
  2. 2.Department of ZoologyThe University of TexasAustinUSA

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