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 AG Basic mechanisms of auditory pattern recognition

 Mechanisms of phase-locking of auditory-nerve fibers

Figures: Pictographs (presumably 500 to 600 years old) in Blair Valley in the Anza-Borrego State Park in Southern California suggest that the Kumeyaay Indians knew about DNA, hair cells, and spikes in response to sinusoidal stimuli, but not about phase-locking (Photographs by Alan R. Palmer).

Project description:

A hallmark of the extraordinary temporal precision of the auditory system and its processing speed is phase-locking of neuronal discharges (spikes) of auditory-nerve fibers (ANFs; the primary afferents), and some more central neurons, to the fine-structure of acoustic stimuli. Phase-locking manifests itself as a non-uniform distribution of spikes over a stimulus cycle, even if as short as 200 µs or less (the limit depending on species), and the temporal dispersion of spikes can be as low as 30 µs. Phase-locked spikes constitute the primary input to neural circuits specialized to extract interaural time differences down to a few microseconds for sound localisation and may be crucial also for the perception of pitch, a salient feature of many vocalisations and music. Phase-locking by ANFs has also been used as a tool to infer basilar membrane mechanics. It is commonly quantified by a synchronisation index and a mean phase. However, the period histograms, generally used to display phase-locking, show intriguing features which vary with stimulus frequency and level, that are not sufficiently captured by standard measures and whose origin is poorly understood. In this project, we aim to develop a parsimonious physiological model that accounts for the detailed features of ANF period histograms. We intend to apply the model to mammalian data and attempt to relate it to other ANF response characteristics, such as the precision of first-spike timing and the rate-level function. Our work will help identify the key players underlying this remarkable property of ANFs.

The project is part of the Priority Program 1608 of the Deutsche Forschungsgemeinschaft: Ultrafast and temporally precise information processing: normal and dysfunctional hearing

Collaborator:

Adam J. Peterson (Department Auditory Learning & Speech)

Funding:

Deutsche Forschungsgemeinschaft He1721/11-1 (2012-2015) to Heil P: Mechanisms of phase-locking of auditory-nerve fibers: a modelling approach

Some key publications:

Heil P, Neubauer H, Irvine DRF (2011) An improved model for the rate-level functions of auditory-nerve fibers. Journal of Neuroscience 31:15424-15347

Heil P, Neubauer H (2010) Summing across different active zones can explain the quasi-linear Ca2+-dependencies of exocytosis by receptor cells. Frontiers in Synaptic Neuroscience 2: 148. doi: 10.3389/fnsyn.2010.00148. (featured in Faculty1000 by PA Fuchs)

Neubauer H, Heil P (2008) A physiological model for the stimulus-dependence of first-spike latency of auditory-nerve fibers. Brain Research 1220: 208-223

Heil P, Neubauer H, Brown M, Irvine DRF (2008) Towards a unifying basis of auditory thresholds: distributions of the first-spike latencies of auditory-nerve fibers. Hearing Research 238: 25-38

Heil P, Neubauer H, Irvine DRF, Brown M (2007) Spontaneous activity of auditory-nerve fibers: insights into stochastic processes at ribbon synapses. Journal of Neuroscience 27: 8457-8474 (see also Editorial: From Ribbon Synapses to Spike Trains)

Peterson AJ (2012) A viscoelastic mechanical model of adaptation behavior in cat auditory-nerve fibers. M.Sc. Thesis, Otto-von-Guericke University Magdeburg

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