(Peter Heil, Heinrich Neubauer)

A prerequisite for any analysis and recognition of auditory patterns by the brain´s auditory system is the detection of sounds, and a thorough understanding of the system´s operation requires knowledge of how detection thresholds are mediated. The project aims to better understand the processes mediating detection thresholds, in both normal-hearing and hearing-impaired ears. For this purpose we utilize responses of single auditory neurons and auditory-nerve fibers and we measure with great precision detection thresholds of human listeners to a large variety of sounds.

Figure:
In human and animals with sensorineural hearing losses the rate of temporal integration (i.e., the decrease in threshold amplitude with increasing stimulus duration) can be substantially modified compared with normal-hearing listeners. We have developed a simple and physiologically plausible model (Neubauer & Heil, JARO 2004; Heil & Neubauer, Z. Audiol. 2004) which explains this and other phenomena observed in such hearing-impaired listeners. The model assumes that sound pressure below some elevated but still relatively small value remains ineffective in driving the auditory system. In normal-hearing listeners that value is zero or very close to zero.

Collaborations:

Prof. Dexter R.F. Irvine, Monash University, Melbourne, Australia
Prof. George M. Gerken, University of Texas at Dallas, USA

Key publications:

1. Neubauer, H. and Heil, P. (2005) Towards a unifying basis of auditory thresholds: the effects of hearing loss on temporal integration reconsidered. Journal of the Association for Research in Otolaryngology 5: 436-458.
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2. Heil, P. and Neubauer, H. (2004) Neue Erkenntnisse zu Ruhehörschwellen in gesunden und geschädigten Ohren. Zeitschrift für Audiologie (Audiological Acoustics) 43:188-195.
3. Heil, P. (2004) First-spike latency of auditory neurons revisited.
   Current Opinion in Neurobiology 14: 461-467.
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4. Heil, P. and Neubauer, H. (2003) A unifying basis of auditory thresholds based on temporal summation. Proceedings of the National Academy of Sciences USA 100: 6151-6156.
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5. Heil, P. and Neubauer, H. (2001) Temporal integration of sound pressure determines thresholds of auditory-nerve fibers. Journal of Neuroscience 21:7404-7415
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6. Heil, P. and Neubauer, H. (2004) Towards a unifying basis of auditory thresholds.
   In: The Auditory Cortex – A Synthesis of Human and Animal Research. (Eds. R. König, P. Heil, E. Budinger, H. Scheich) Lawrence Erlbaum Assoc. Oxford, pp. 207-224
7. Heil, P. and Neubauer, H. (2004) Detection thresholds for tones in quiet re-examined.
   In: Proc. 18th International Congress on Acoustics, Kyoto, IV, pp. 2643-2646
8. Heil, P. and Neubauer, H. (2005) Auditory thresholds re-visited.
   In: Auditory Signal Processing: Physiology, Psychoacoustics, and Models (Eds. D. Pressnitzer, A. de Cheveigne, S. McAdams and L. Collet), Springer, New York, pp. 454-470.
9. Heil, P., Neubauer, H., Tiefenau, A., and von Specht, H. (2006) Comparison of absolute thresholds derived from an adaptive forced-choice procedure and from reaction probabilities and reaction times in a simple reaction time paradigm. Journal of the Association for Research in Otolaryngology 7: 279-298
10. Heil, P., Neubauer, H., Irvine, D.R.F. and Brown, M. (2007) Spontaneous activity of auditory-nerve fibers: insights into stochastic processes at ribbon synapses.
    Journal of Neuroscience 27 (31): 8457-8474 (see also Editorial: From Ribbon Synapses to Spike Trains.)
11. Neubauer, H. and Heil, P. (2007) A physiological model for the stimulus-dependence of first-spike latency of auditory-nerve fibers.
    Brain Research (Sep 14; [Epub ahead of print])
12. Heil, P., Neubauer, H., Brown, M. and Irvine, D.R.F. (2008) Towards a unifying basis of auditory thresholds: distributions of the first-spike latencies of auditory-nerve fibers.
    Hearing Research 238: 25-38