Dataset Information

Effect of instantaneous frequency glides on interaural time difference processing by auditory coincidence detectors.

ABSTRACT: Detecting interaural time difference (ITD) is crucial for sound localization. The temporal accuracy required to detect ITD, and how ITD is initially encoded, continue to puzzle scientists. A fundamental question is whether the monaural inputs to the binaural ITD detectors differ only in their timing, when temporal and spectral tunings are largely inseparable in the auditory pathway. Here, we investigate the spectrotemporal selectivity of the monaural inputs to ITD detector neurons of the owl. We found that these inputs are selective for instantaneous frequency glides. Modeling shows that ITD tuning depends strongly on whether the monaural inputs are spectrotemporally matched, an effect that may generalize to mammals. We compare the spectrotemporal selectivity of monaural inputs of ITD detector neurons in vivo, demonstrating that their selectivity matches. Finally, we show that this refinement can develop through spike timing-dependent plasticity. Our findings raise the unexplored issue of time-dependent frequency tuning in auditory coincidence detectors and offer a unifying perspective.

SUBMITTER: Fischer BJ

PROVIDER: S-EPMC3207647 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Effect of instantaneous frequency glides on interaural time difference processing by auditory coincidence detectors.

Fischer Brian J BJ Steinberg Louisa J LJ Fontaine Bertrand B Brette Romain R Peña Jose L JL

Proceedings of the National Academy of Sciences of the United States of America 20111017 44

Detecting interaural time difference (ITD) is crucial for sound localization. The temporal accuracy required to detect ITD, and how ITD is initially encoded, continue to puzzle scientists. A fundamental question is whether the monaural inputs to the binaural ITD detectors differ only in their timing, when temporal and spectral tunings are largely inseparable in the auditory pathway. Here, we investigate the spectrotemporal selectivity of the monaural inputs to ITD detector neurons of the owl. We ...[more]

PMID: 22006305

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Project description:For amplitude-modulated sound, the envelope interaural time difference (ITDENV) is a potential cue for sound-source location. ITDENV is encoded in the lateral superior olive (LSO) of the auditory brainstem, by excitatory-inhibitory (EI) neurons receiving ipsilateral excitation and contralateral inhibition. Between human listeners, sensitivity to ITDENV varies considerably, but ultimately decreases with increasing stimulus carrier frequency, and decreases more strongly with increasing modulation rate. Mechanisms underlying the variation in behavioral sensitivity remain unclear. Here, with increasing carrier frequency (4-10 kHz), as we phenomenologically model the associated decrease in ITDENV sensitivity using arbitrarily fewer neurons consistent across populations, we computationally model the variable sensitivity across human listeners and modulation rates (32-800 Hz) as the decreasing range of membrane frequency responses in LSO neurons. Transposed tones stimulate a bilateral auditory-periphery model, driving model EI neurons where electrical membrane impedance filters the frequency content of inputs driven by amplitude-modulated sound, evoking modulation filtering. Calculated from Fisher information in spike-rate functions of ITDENV, for model EI neuronal populations distinctly reflecting the LSO range in membrane frequency responses, just-noticeable differences in ITDENV collectively reproduce the largest variation in ITDENV sensitivity across human listeners. These slow to fast model populations each generally match the best human ITDENV sensitivity at a progressively higher modulation rate, by membrane-filtering and spike-generation properties producing realistically less than Poisson variance. Non-resonant model EI neurons are also sensitive to interaural intensity differences. With peripheral filters centered between carrier frequency and modulation sideband, fast resonant model EI neurons extend ITDENV sensitivity above 500-Hz modulation.

Dataset Information

Effect of instantaneous frequency glides on interaural time difference processing by auditory coincidence detectors.

Publications

Effect of instantaneous frequency glides on interaural time difference processing by auditory coincidence detectors.

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