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Robust Cortical Encoding of Slow Temporal Modulations of Speech

  • Nai Ding
  • Jonathan Z. Simon
Conference paper
Part of the Advances in Experimental Medicine and Biology book series (volume 787)

Abstract

This study investigates the neural representation of speech in complex listening environments. Subjects listened to a narrated story, masked by either another speech stream or by stationary noise. Neural recordings were made using magnetoencephalography (MEG), which can measure cortical activity synchronized to the temporal envelope of speech. When two speech streams are presented simultaneously, cortical activity is predominantly synchronized to the speech stream the listener attends to, even if the unattended, competing-speech stream is more intense (up to 8 dB). When speech is presented together with spectrally matched stationary noise, cortical activity remains precisely synchronized to the temporal envelope of speech until the noise is 9 dB more intense. Critically, the precision of the neural synchronization to speech predicts subjectively rated speech intelligibility in noise. Further analysis reveals that it is longer-latency (∼100 ms) neural responses, but not shorter-latency (∼50 ms) neural responses, that show selectivity to the attended speech and invariance to background noise. This indicates a processing transition, from encoding the acoustic scene to encoding the behaviorally important auditory object, in auditory cortex. In sum, it is demonstrated that neural synchronization to the speech envelope is robust to acoustic interference, whether speech or noise, and therefore provides a strong candidate for the neural basis of acoustic-background invariant speech recognition.

Notes

Acknowledgments

We thank NIH grant R01 DC 008342 for support.

References

  1. Brungart DS (2001) Informational and energetic masking effects in the perception of two simultaneous talkers. J Acoust Soc Am 109:1101–1109PubMedCrossRefGoogle Scholar
  2. Ding N, Simon JZ (2012) The emergence of neural encoding of auditory objects while listening to competing speakers. Proc Natl Acad Sci USA 109(29):11854–11859PubMedCrossRefGoogle Scholar
  3. Ding N, Simon JZ (2013) Adaptive temporal encoding leads to a background insensitive cortical representation of speech. J Neurosci 33:5728–5735Google Scholar
  4. Robinson BL, McAlpine D (2009) Gain control mechanisms in the auditory pathway. Curr Opin Neurobiol 19:402–407PubMedCrossRefGoogle Scholar
  5. Stone MA, Fullgrabe C, Mackinnon RC, Moore BCJ (2011) The importance for speech intelligibility of random fluctuations in “steady” background noise. J Acoust Soc Am 130:2874–2881PubMedCrossRefGoogle Scholar
  6. Woodfield A, Akeroyd MA (2010) The role of segmentation difficulties in speech-in-speech understanding in older and hearing-impaired adults. J Acoust Soc Am 128:EL26–EL31PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Department of Electrical and Computer EngineeringUniversity of MarylandCollege ParkUSA
  2. 2.Department of BiologyUniversity of MarylandCollege ParkUSA

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