Abstract
AU The:ability Pleaseconfirmthatallheadinglevelsarerepresentedcorrectly to navigate “cocktail party” situations by focusing:on sounds of interest over irrelevant, background sounds is often considered in terms of cortical mechanisms. However, subcortical circuits such as the pathway underlying the medial olivocochlear (MOC) reflex modulate the activity of the inner ear itself, supporting the extraction of salient features from auditory scene prior to any cortical processing. To understand the contribution of auditory subcortical nuclei and the cochlea in complex listening tasks, we made physiological recordings along the auditory pathway while listeners engaged in detecting non(sense) words in lists of words. Both naturally spoken and intrinsically noisy, vocoded speech—filtering that mimics processing by a cochlear implant (CI)—significantly activated the MOC reflex, but this was not the case for speech in background noise, which more engaged midbrain and cortical resources. A model of the initial stages of auditory processing reproduced specific effects of each form of speech degradation, providing a rationale for goal-directed gating of the MOC reflex based on enhancing the representation of the energy envelope of the acoustic waveform. Our data reveal the coexistence of 2 strategies in the auditory system that may facilitate speech understanding in situations where the signal is either intrinsically degraded or masked by extrinsic acoustic energy. Whereas intrinsically degraded streams recruit the MOC reflex to improve representation of speech cues peripherally, extrinsically masked streams rely more on higher auditory centres to denoise signals.
Original language | English (US) |
---|---|
Article number | e3001439 |
Journal | PLoS biology |
Volume | 19 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2021 |
Funding
H.H.P. was supported in this study by an International Macquarie University Excellence Scholarship (https://www.mq.edu.au/research/ phd-and-research-degrees/scholarships/ scholarship-search/data/international-hdr-mainscholarship-round) and the The HEARing Cooperative Research Centre (https://www. hearingcrc.org/) J.M.H. was supported in this study by an Australian Research Council Laureate Fellowship (FL 160100108) awarded to D.M (https://www.arc.gov.au/grants/discoveryprogram/australian-laureate-fellowships).The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors thank Prof. David Poeppel for his contributions during experimental design. We thank Prof. David Ryugo for his comments on the manuscript. In addition, we thank Ronny Ibrahim, Jaime Undurraga, Lindsey Van Yper, and Greg Stewart for their technical support and EEG analysis and Nicholas Clark for his assistance with MAP_BS. The authors thank Ray Meddis for bringing the MAP_BS model to our attention.
ASJC Scopus subject areas
- General Agricultural and Biological Sciences
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology
- General Neuroscience