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Evidence for “Pitch Neurons” in the Auditory Midbrain of Chinchillas

  • U. W. Biebel
  • G. Langner

Abstract

An important feature of our auditory system is its ability to detect voiced signals even under extremly noisy conditions (“cocktail party effect”). By spectral filtering, the cochlea improves signal-to-noise relations. However, this gives rise to the problem that information about a broadband signal gets scattered over various frequency channels in the auditory system. Psychophysic experiments show that for voiced or harmonic sounds the auditory system seems to make use of periodicity information to recombine this distributed information (Assman and Summerfield, 1990). In the auditory periphery, the envelope of complex tones is coded by phase locking (Shofner et al., 1996; Zhao & Liang, 1995; Ruggero, 1991). In the auditory midbrain this kind of temporal information is degraded and periodicity information is transformed into a rate-place code. In the inferior colliculus (ICC) best modulation frequencies (BMF = maximum of a modulation transfer function) of neurons are represented topographically, roughly orthogonal to the tonotopic organization (Langner, 1992). Modulation frequencies relevant for communication sounds (especially human speech) are in general below 1000 Hz. Therefore neurons in the inferior colliculus, that are tuned to low frequencies (characteristic frequency = CF < 1000 Hz) are likely candidates for spectral integrators of distributed activity representing a broadband signal. The aim of the present investigation was to look for such neurons with low CFs that may integrate particular periodicity information over a broad frequency range.

Keywords

Modulation Frequency Auditory System Pure Tone Inferior Colliculus Dorsal Cochlear Nucleus 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Assmann, P.F. and Summerfield, Q. (1990) Modeling the perception of concurrent vowels — vowels with different fundamental frequencies. J.Acoust.Soc.Am. 88:680–697.PubMedCrossRefGoogle Scholar
  2. Langner, G. (1992) Periodicity coding in the auditory system. Hear. Res. 60, 115–142.PubMedCrossRefGoogle Scholar
  3. Malmierca. M.S., Rees. A., Le Beau, F.E.N.. & Bjaalie, J.G. (1995) Laminar organization of frequency-defined local axons within and between the inferior colliculi of the guinea pig. J. Comp. Neurol. 357, 124–144.PubMedCrossRefGoogle Scholar
  4. McFadden, D. (1988) Failure of a missing-fundamental complex to interact with masked and unmasked pure-tones at its fundamental-frequency. Hear. Res. 32, 23–40.PubMedCrossRefGoogle Scholar
  5. Oliver, D.L., Kuwada, S., Yin, T.C.T., Haberly, L.B., & Henkel, C.K. (1990) Dendritic and axonal morphology of HRP-Injected neurons in the inferior colliculus of the cat. J. Comp. Neurol. 303, 75–100.CrossRefGoogle Scholar
  6. Ritsma, R.J. (1962) Existence region of the tonal residue I. J. Acoust. Soc. Am. 34, 1224–1229.CrossRefGoogle Scholar
  7. Ruggero, M.A. (1991) Physiology and Coding of Sound in the Auditory Nerve. In A.N. Popper & R.R. Fay (Eds.), The Mammalian Auditory Pathway: Neurophysiology, Springer, New York, Berlin, pp. 34–93.Google Scholar
  8. Schreiner, C.E. and Langner, G. (1988) Periodicity coding in the inferior colliculus of the cat. II. Topographical organization. J.Neurophysiol. 60, 1823–1840.PubMedGoogle Scholar
  9. Shofner, W.P., Sheft, S., & Guzman, S.J. (1996) Responses of ventral cochlear nucleus units in the chinchilla to amplitude modulation by low-frequency, two-tone complexes. J. Acoust. Soc. Am. 99, 3592–3605.PubMedCrossRefGoogle Scholar
  10. Zhao, H.-B., & Liang, Z.-A. (1995) Processing of modulation frequency in the dorsal cochlear nucleus of the guinea pig: Amplitude modulated tones. Hear. Res. 82, 244–256.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • U. W. Biebel
    • 1
  • G. Langner
    • 1
  1. 1.Institute of ZoologyTHDDarmstadtGermany

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