ORCID Profile
0000-0002-4496-6355
Current Organisation
Northwestern University
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Publisher: Elsevier BV
Date: 09-2005
DOI: 10.1016/J.HEARES.2005.04.005
Abstract: Otoacoustic emissions provide unambiguous evidence that the cochlea supports energy propagation both towards, and away from, the stapes. The standard wave model for energy transport and cochlear mechanical lification provides for compressional and inertial waves to transport this energy, the compressional wave through the fluids and the inertial wave along the basilar membrane via fluid coupling. It is generally accepted that energy propagation away from the stapes is dominated by a traveling wave mechanism along the basilar membrane. The mechanism by which energy is predominantly transported back to the stapes remains controversial. Here, we compared signal onset delay measurements and rise/steady-state/fall times for SFOAEs and 2f1-f2 OAEs (f2/f1=1.2) obtained using a pulsed-tone paradigm in guinea pig. Comparison of 2f1-f2 OAE signal onset delay for the OAE arising from the f2 region with SFOAE signal onset delay (matched to the f2 stimulus frequency) based on signal onset occurring at 10% of the peak signal litude was suggestive of a bi-directional traveling wave mechanism. However, significant variability in signal onset delay and signal rise, steady-state duration, and fall times for both the 2f1-f2 OAE and SFOAE was found, qualifying this interpretation. Such variability requires explanation, awaiting further studies.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2018
Publisher: Public Library of Science (PLoS)
Date: 20-10-2021
DOI: 10.1371/JOURNAL.PBIO.3001439
Abstract: The ability 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.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2003
Publisher: Cold Spring Harbor Laboratory
Date: 06-2020
DOI: 10.1101/2020.05.31.115444
Abstract: Navigating “cocktail party” situations by enhancing foreground sounds over irrelevant background information is typically considered from a cortico-centric perspective. However, subcortical circuits, such as the medial olivocochlear (MOC) reflex that modulates inner ear activity itself, have le opportunity to extract salient features from the auditory scene prior to any cortical processing. To understand the contribution of auditory subcortical nuclei and the cochlea, physiological recordings were made along the auditory pathway while listeners differentiated non(sense)-words and words. Both naturally-spoken and intrinsically-noisy, vocoded speech — filtering that mimics processing by a cochlear implant—significantly activated the MOC reflex, whereas listening to speech-in-background noise revealed instead engagement of midbrain and cortical resources. An auditory periphery model reproduced these speech degradation-specific effects, providing a rationale for goal-directed gating of the MOC reflex to enhance representation of speech features in the auditory nerve. Our data reveals the co-existence of two strategies in the auditory system that may facilitate speech understanding in situations where the speech signal is either intrinsically degraded or masked by extrinsic auditory information.
Publisher: Frontiers Media SA
Date: 10-12-2015
Publisher: Author(s)
Date: 2018
DOI: 10.1063/1.5038496
No related grants have been discovered for Sumitrajit Dhar.