The role of cochlear place coding in the perception of frequency modulation
Abstract
Natural sounds convey information via frequency and amplitude modulations (FM and AM). Humans are acutely sensitive to the slow rates of FM that are crucial for speech and music. This sensitivity has long been thought to rely on precise stimulus-driven auditory-nerve spike timing (time code), whereas a coarser code, based on variations in the cochlear place of stimulation (place code), represents faster FM rates. We tested this theory in listeners with normal and impaired hearing, spanning a wide range of place-coding fidelity. Contrary to predictions, sensitivity to both slow and fast FM correlated with place-coding fidelity. We also used incoherent AM on two carriers to simulate place coding of FM and observed poorer sensitivity at high carrier frequencies and fast rates, two properties of FM detection previously ascribed to the limits of time coding. The results suggest a unitary place-based neural code for FM across all rates and carrier frequencies.
Data availability
Source data files have been provided for Figures 2-6 and all figure supplements.
Article and author information
Author details
Funding
National Institutes of Health (R01 DC005216)
- Andrew J Oxenham
University of Minnesota (Eva O. Miller Fellowship)
- Kelly L Whiteford
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Human subjects: Informed consent, and consent to publish, was obtained from all participants. All protocols were approved by the Institutional Review Board of the University of Minnesota (0605S85872).
Copyright
© 2020, Whiteford et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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