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Jedrzejczak WW, Pilka E, Pastucha M, Skarzynski H, Kochanek K. Magnitude of medial olivocochlear reflex assayed by tone-burst-evoked otoacoustic emissions: reliability and comparison with click-evoked emissions. Int J Audiol 2024; 63:293-299. [PMID: 37129585 DOI: 10.1080/14992027.2023.2207116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 04/20/2023] [Indexed: 05/03/2023]
Abstract
OBJECTIVE The purpose of this pilot study was to evaluate the magnitude of the medial olivocochlear reflex (MOCR) estimated by the reduction in tone-burst evoked otoacoustic emissions (TBOAEs) measured at three levels and at three frequencies in response to fixed contralateral white noise. Results were compared with commonly used click-evoked otoacoustic emissions (CEOAEs). DESIGN TBOAEs and CEOAEs, with and without contralateral 60 dB SPL white noise, were measured in response to stimulation at 55, 65, and 75 dB peSPL. In each subject, the set of measurements was performed twice. Of particular interest were the MOCR and its repeatability. STUDY SAMPLE 15 normally hearing persons (13 women, average age 32.3 years, SD = 8.1). RESULTS For both CEOAE and TBOAEs, the reliability of the MOCR was much better for broadband measurements than for half-octave-band filtered estimates. At the same time, the reliability of MOCR in half-octave bands was higher for TBOAEs than for CEOAEs, especially at 2 and 4 kHz. CONCLUSIONS For general applications where broadband MOCR is of interest, the highest magnitude and reliability is provided by CEOAEs. However, TBOAEs may be better if a particular frequency band is of interest.
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Affiliation(s)
- W Wiktor Jedrzejczak
- Institute of Physiology and Pathology of Hearing, Warsaw, Poland
- World Hearing Center, Kajetany, Nadarzyn, Poland
| | - Edyta Pilka
- Institute of Physiology and Pathology of Hearing, Warsaw, Poland
- World Hearing Center, Kajetany, Nadarzyn, Poland
| | - Malgorzata Pastucha
- Institute of Physiology and Pathology of Hearing, Warsaw, Poland
- World Hearing Center, Kajetany, Nadarzyn, Poland
| | - Henryk Skarzynski
- Institute of Physiology and Pathology of Hearing, Warsaw, Poland
- World Hearing Center, Kajetany, Nadarzyn, Poland
| | - Krzysztof Kochanek
- Institute of Physiology and Pathology of Hearing, Warsaw, Poland
- World Hearing Center, Kajetany, Nadarzyn, Poland
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2
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Boothalingam S, Peterson A, Powell L, Easwar V. Auditory brainstem mechanisms likely compensate for self-imposed peripheral inhibition. Sci Rep 2023; 13:12693. [PMID: 37542191 PMCID: PMC10403563 DOI: 10.1038/s41598-023-39850-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 08/01/2023] [Indexed: 08/06/2023] Open
Abstract
Feedback networks in the brain regulate downstream auditory function as peripheral as the cochlea. However, the upstream neural consequences of this peripheral regulation are less understood. For instance, the medial olivocochlear reflex (MOCR) in the brainstem causes putative attenuation of responses generated in the cochlea and cortex, but those generated in the brainstem are perplexingly unaffected. Based on known neural circuitry, we hypothesized that the inhibition of peripheral input is compensated for by positive feedback in the brainstem over time. We predicted that the inhibition could be captured at the brainstem with shorter (1.5 s) than previously employed long duration (240 s) stimuli where this inhibition is likely compensated for. Results from 16 normal-hearing human listeners support our hypothesis in that when the MOCR is activated, there is a robust reduction of responses generated at the periphery, brainstem, and cortex for short-duration stimuli. Such inhibition at the brainstem, however, diminishes for long-duration stimuli suggesting some compensatory mechanisms at play. Our findings provide a novel non-invasive window into potential gain compensation mechanisms in the brainstem that may have implications for auditory disorders such as tinnitus. Our methodology will be useful in the evaluation of efferent function in individuals with hearing loss.
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Affiliation(s)
- Sriram Boothalingam
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA.
- Macquarie University, Sydney, NSW, 2109, Australia.
- National Acoustic Laboratories, Sydney, NSW, 2109, Australia.
| | - Abigayle Peterson
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Macquarie University, Sydney, NSW, 2109, Australia
| | - Lindsey Powell
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Vijayalakshmi Easwar
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Macquarie University, Sydney, NSW, 2109, Australia
- National Acoustic Laboratories, Sydney, NSW, 2109, Australia
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3
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Lee D, Lewis JD. Inter-Subject Variability in the Dependence of Medial-Olivocochlear Reflex Strength on Noise Bandwidth. Ear Hear 2023; 44:544-557. [PMID: 36477401 DOI: 10.1097/aud.0000000000001302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Abstract
OBJECTIVES The objective of the study was to quantify inter-subject variability in the dependence of the medial-olivocochlear reflex (MOCR) on noise bandwidth. Of specific interest was whether inter-subject variability in MOCR dependence on bandwidth explained variability in the MOCR response elicited by wideband noise. DESIGN Thirty-two young adults with normal hearing participated in the study. Click-evoked otoacoustic emissions were measured in the ipsilateral ear with and without noise presented in the contralateral ear. Presentation of contralateral noise served to activate the MOCR. The MOCR was activated using five different noise stimuli with bandwidths ranging from 1- to 5-octaves wide (center frequency of 2 kHz; bandwidth incremented in 1-octave steps). Noise spectral levels (19.6 dB SPL/Hz) were held constant across all bandwidths. MOCR metrics included the normalized-percent change in the otoacoustic emission (OAE), the MOCR-induced OAE magnitude shift, and the MOCR-induced OAE phase shift. Linear mixed-effect models were fit to model the dependence of MOCR-induced OAE magnitude and phase changes on noise bandwidth. The use of a mixed-effect modeling approach allowed for the estimation of subject-specific model parameters that capture on- and off-frequency contributions to the MOCR effects. Regression analysis was performed to evaluate the predictive capacity of subject-specific model parameters on the MOCR response elicited by wideband noise. RESULTS All OAE-based MOCR metrics increased as the noise bandwidth increased from 1- to 5-octaves wide. The dependence of MOCR-induced OAE magnitude and phase shifts on activator bandwidth was well approximated using a linear model with intercept and slope terms. On average, MOCR-induced magnitude and phase shifts increased at a rate of 0.3 dB/octave and 0.01 cycles/octave, respectively, as bandwidth extended beyond the predicted region of OAE generation. A statistically significant random effect of subject was found for both the intercept and slope parameter of each model. Subject-specific slope estimates were statistically significant predictors of a repeated measure of the wideband MOCR response. A higher slope was predictive of larger wideband MOCR effects. CONCLUSIONS MOCR-induced changes to the OAE are greatest when the MOCR is elicited using wideband noise. Variability in the process of spectral integration within the MOCR pathway appears to explain, in part, inter-subject variability in OAE-based estimates of the MOCR response elicited by wideband noise.
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Affiliation(s)
- Donguk Lee
- Department of Audiology and Speech Pathology, University of Tennessee Health Science Center, Knoxville, Tennessee, USA
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4
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Acuña F, Jeria R, Pavez E, Aguilar-Vidal E. Efferent Control in Musicians: A Review. Audiol Res 2023; 13:76-85. [PMID: 36648928 PMCID: PMC9844302 DOI: 10.3390/audiolres13010007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/30/2022] [Accepted: 01/03/2023] [Indexed: 01/11/2023] Open
Abstract
It is widely established that musicians possess a higher level in certain auditory perceptual abilities when compared to non-musicians. This improvement may be mediated, at least in part, by changes in the cochlear response induced by reflex activation of the olivocochlear efferent system. In this review, we describe and analyze the scientific evidence regarding possible differences in the efferent response in musicians and non-musicians. The main evidence observed is that musicians present a greater robustness of the efferent olivocochlear reflex when measured by suppression of otoacoustic emissions and compared to non-musicians. Analyzing the articles presented in this review, it is possible to point out that the differential role of the efferent effect in musicians is not yet established. There is not enough evidence to support the idea that the olivocochlear system favors comparative changes in the properties of musicians' auditory filters. New studies with psychoacoustic techniques, among others, are needed to measure the effect of the olivocochlear reflex on tuning, gain, compression, or temporal resolution in musicians and non-musicians.
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Affiliation(s)
- Francisca Acuña
- Escuela de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago 8380453, Chile
| | - Rodrigo Jeria
- Escuela de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago 8380453, Chile
| | - Elisabeth Pavez
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago 8380453, Chile
| | - Enzo Aguilar-Vidal
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago 8380453, Chile
- Correspondence:
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5
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Sensitivity of Vowel-Evoked Envelope Following Responses to Spectra and Level of Preceding Phoneme Context. Ear Hear 2022; 43:1327-1335. [DOI: 10.1097/aud.0000000000001190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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6
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Shirakura M, Kawase T, Kanno A, Ohta J, Nakasato N, Kawashima R, Katori Y. Different contra-sound effects between noise and music stimuli seen in N1m and psychophysical responses. PLoS One 2021; 16:e0261637. [PMID: 34928999 PMCID: PMC8687558 DOI: 10.1371/journal.pone.0261637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 12/06/2021] [Indexed: 11/26/2022] Open
Abstract
Auditory-evoked responses can be affected by the sound presented to the contralateral ear. The different contra-sound effects between noise and music stimuli on N1m responses of auditory-evoked fields and those on psychophysical response were examined in 12 and 15 subjects, respectively. In the magnetoencephalographic study, the stimulus to elicit the N1m response was a tone burst of 500 ms duration at a frequency of 250 Hz, presented at a level of 70 dB, and white noise filtered with high-pass filter at 2000 Hz and music stimuli filtered with high-pass filter at 2000 Hz were used as contralateral noise. The contralateral stimuli (noise or music) were presented in 10 dB steps from 80 dB to 30 dB. Subjects were instructed to focus their attention to the left ear and to press the response button each time they heard burst stimuli presented to the left ear. In the psychophysical study, the effects of contralateral sound presentation on the response time for detection of the probe sound of a 250 Hz tone burst presented at a level of 70 dB were examined for the same contra-noise and contra-music used in the magnetoencephalographic study. The amplitude reduction and latency delay of N1m caused by contra-music stimuli were significantly larger than those by contra-noise stimuli in bilateral hemisphere, even for low level of contra-music near the psychophysical threshold. Moreover, this larger suppressive effect induced by contra-music effects was also observed psychophysically; i.e., the change in response time for detection of the probe sound was significantly longer by adding contralateral music stimuli than by adding contra-noise stimuli. Regarding differences in effect between contra-music and contra-noise, differences in the degree of saliency may be responsible for their different abilities to disturb auditory attention to the probe sound, but further investigation is required to confirm this hypothesis.
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Affiliation(s)
- Masayuki Shirakura
- Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Tetsuaki Kawase
- Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
- Laboratory of Rehabilitative Auditory Science, Tohoku University Graduate School of Biomedical Engineering, Sendai, Miyagi, Japan
- Department of Audiology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
- * E-mail:
| | - Akitake Kanno
- Department of Electromagnetic Neurophysiology, Tohoku University School of Medicine, Sendai, Miyagi, Japan
- Department of Epileptology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Jun Ohta
- Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Nobukazu Nakasato
- Department of Electromagnetic Neurophysiology, Tohoku University School of Medicine, Sendai, Miyagi, Japan
- Department of Epileptology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Ryuta Kawashima
- Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi, Japan
| | - Yukio Katori
- Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
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7
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Boothalingam S, Goodman SS, MacCrae H, Dhar S. A Time-Course-Based Estimation of the Human Medial Olivocochlear Reflex Function Using Clicks. Front Neurosci 2021; 15:746821. [PMID: 34776849 PMCID: PMC8581223 DOI: 10.3389/fnins.2021.746821] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 09/28/2021] [Indexed: 11/22/2022] Open
Abstract
The auditory efferent system, especially the medial olivocochlear reflex (MOCR), is implicated in both typical auditory processing and in auditory disorders in animal models. Despite the significant strides in both basic and translational research on the MOCR, its clinical applicability remains under-utilized in humans due to the lack of a recommended clinical method. Conventional tests employ broadband noise in one ear while monitoring change in otoacoustic emissions (OAEs) in the other ear to index efferent activity. These methods, (1) can only assay the contralateral MOCR pathway and (2) are unable to extract the kinetics of the reflexes. We have developed a method that re-purposes the same OAE-evoking click-train to also concurrently elicit bilateral MOCR activity. Data from click-train presentations at 80 dB peSPL at 62.5 Hz in 13 young normal-hearing adults demonstrate the feasibility of our method. Mean MOCR magnitude (1.7 dB) and activation time-constant (0.2 s) are consistent with prior MOCR reports. The data also suggest several advantages of this method including, (1) the ability to monitor MEMR, (2) obtain both magnitude and kinetics (time constants) of the MOCR, (3) visual and statistical confirmation of MOCR activation.
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Affiliation(s)
- Sriram Boothalingam
- Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, United States.,Waisman Center, University of Wisconsin-Madison, Madison, WI, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - Hilary MacCrae
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States
| | - Sumitrajit Dhar
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States.,Knowles Center, Northwestern University, Evanston, IL, United States
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8
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DeRoy Milvae K, Strickland EA. Behavioral Measures of Cochlear Gain Reduction Depend on Precursor Frequency, Bandwidth, and Level. Front Neurosci 2021; 15:716689. [PMID: 34671236 PMCID: PMC8520990 DOI: 10.3389/fnins.2021.716689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 09/06/2021] [Indexed: 11/25/2022] Open
Abstract
Sensory systems adjust to the environment to maintain sensitivity to change. In the auditory system, the medial olivocochlear reflex (MOCR) is a known physiological mechanism capable of such adjustment. The MOCR provides efferent feedback between the brainstem and cochlea, reducing cochlear gain in response to sound. The perceptual effects of the MOCR are not well understood, such as how gain reduction depends on elicitor characteristics in human listeners. Physiological and behavioral data suggest that ipsilateral MOCR tuning is only slightly broader than it is for afferent fibers, and that the fibers feed back to the frequency region of the cochlea that stimulated them. However, some otoacoustic emission (OAE) data suggest that noise is a more effective elicitor than would be consistent with sharp tuning, and that a broad region of the cochlea may be involved in elicitation. If the elicitor is processed in a cochlear channel centered at the signal frequency, the growth of gain reduction with elicitor level would be expected to depend on the frequency content of the elicitor. In the current study, the effects of the frequency content and level of a preceding sound (called a precursor) on signal threshold was examined. The results show that signal threshold increased with increasing precursor level at a shallower slope for a tonal precursor at the signal frequency than for a tonal precursor nearly an octave below the signal frequency. A broadband noise was only slightly more effective than a tone at the signal frequency, with a relatively shallow slope similar to that of the tonal precursor at the signal frequency. Overall, these results suggest that the excitation at the signal cochlear place, regardless of elicitor frequency, determines the magnitude of ipsilateral cochlear gain reduction, and that it increases with elicitor level.
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Affiliation(s)
- Kristina DeRoy Milvae
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN, United States
| | - Elizabeth A Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN, United States
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9
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Salloom WB, Strickland EA. The effect of broadband elicitor laterality on psychoacoustic gain reduction across signal frequency. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:2817. [PMID: 34717476 PMCID: PMC8520488 DOI: 10.1121/10.0006662] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 09/17/2021] [Accepted: 09/21/2021] [Indexed: 05/19/2023]
Abstract
There are psychoacoustic methods thought to measure gain reduction, which may be from the medial olivocochlear reflex (MOCR), a bilateral feedback loop that adjusts cochlear gain. Although studies have used ipsilateral and contralateral elicitors and have examined strength at different signal frequencies, these factors have not been examined within a single study. Therefore, basic questions about gain reduction, such as the relative strength of ipsilateral vs contralateral elicitation and the relative strength across signal frequency, are not known. In the current study, gain reduction from ipsilateral, contralateral, and bilateral elicitors was measured at 1-, 2-, and 4-kHz signal frequencies using forward masking paradigms at a range of elicitor levels in a repeated measures design. Ipsilateral and bilateral strengths were similar and significantly larger than contralateral strength across signal frequencies. Growth of gain reduction with precursor level tended to differ with signal frequency, although not significantly. Data from previous studies are considered in light of the results of this study. Behavioral results are also considered relative to anatomical and physiological data on the MOCR. These results indicate that, in humans, cochlear gain reduction is broad across frequencies and is robust for ipsilateral and bilateral elicitation but small for contralateral elicitation.
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Affiliation(s)
- William B Salloom
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, Indiana 47907, USA
| | - Elizabeth A Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, Indiana 47907, USA
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10
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Otoacoustic Emissions Evoked by the Time-Varying Harmonic Structure of Speech. eNeuro 2021; 8:ENEURO.0428-20.2021. [PMID: 33632811 PMCID: PMC8046024 DOI: 10.1523/eneuro.0428-20.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 02/11/2021] [Accepted: 02/15/2021] [Indexed: 11/23/2022] Open
Abstract
The human auditory system is exceptional at comprehending an individual speaker even in complex acoustic environments. Because the inner ear, or cochlea, possesses an active mechanism that can be controlled by subsequent neural processing centers through descending nerve fibers, it may already contribute to speech processing. The cochlear activity can be assessed by recording otoacoustic emissions (OAEs), but employing these emissions to assess speech processing in the cochlea is obstructed by the complexity of natural speech. Here, we develop a novel methodology to measure OAEs that are related to the time-varying harmonic structure of speech [speech-distortion-product OAEs (DPOAEs)]. We then employ the method to investigate the effect of selective attention on the speech-DPOAEs. We provide tentative evidence that the speech-DPOAEs are larger when the corresponding speech signal is attended than when it is ignored. Our development of speech-DPOAEs opens up a path to further investigations of the contribution of the cochlea to the processing of complex real-world signals.
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11
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Abstract
OBJECTIVE The medial olivocochlear (MOC) reflex provides efferent feedback from the brainstem to cochlear outer hair cells. Physiologic studies have demonstrated that the MOC reflex is involved in "unmasking" of signals-in-noise at the level of the auditory nerve; however, its functional importance in human hearing remains unclear. DESIGN This study examined relationships between pre-neural measurements of MOC reflex strength (click-evoked otoacoustic emission inhibition; CEOAE) and neural measurements of speech-in-noise encoding (speech frequency following response; sFFR) in four conditions (Quiet, Contralateral Noise, Ipsilateral Noise, and Ipsilateral + Contralateral Noise). Three measures of CEOAE inhibition (amplitude reduction, effective attenuation, and input-output slope inhibition) were used to quantify pre-neural MOC reflex strength. Correlations between pre-neural MOC reflex strength and sFFR "unmasking" (i.e. response recovery from masking effects with activation of the MOC reflex in time and frequency domains) were assessed. STUDY SAMPLE 18 young adults with normal hearing. RESULTS sFFR unmasking effects were insignificant, and there were no correlations between pre-neural MOC reflex strength and sFFR unmasking in the time or frequency domain. CONCLUSION Our results do not support the hypothesis that the MOC reflex is involved in speech-in-noise neural encoding, at least for features that are represented in the sFFR at the SNR tested.
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Affiliation(s)
- S B Smith
- Department of Communication Sciences and Disorders, University of Texas at Austin, Austin, TX, USA
| | - B Cone
- Department of Speech, Language, and Hearing Sciences, University of Arizona, Tucson, AZ, USA
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12
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Mesik J, Wojtczak M. Effects of noise precursors on the detection of amplitude and frequency modulation for tones in noise. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 148:3581. [PMID: 33379905 PMCID: PMC8097715 DOI: 10.1121/10.0002879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 11/05/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Recent studies on amplitude modulation (AM) detection for tones in noise reported that AM-detection thresholds improve when the AM stimulus is preceded by a noise precursor. The physiological mechanisms underlying this AM unmasking are unknown. One possibility is that adaptation to the level of the noise precursor facilitates AM encoding by causing a shift in neural rate-level functions to optimize level encoding around the precursor level. The aims of this study were to investigate whether such a dynamic-range adaptation is a plausible mechanism for the AM unmasking and whether frequency modulation (FM), thought to be encoded via AM, also exhibits the unmasking effect. Detection thresholds for AM and FM of tones in noise were measured with and without a fixed-level precursor. Listeners showing the unmasking effect were then tested with the precursor level roved over a wide range to modulate the effect of adaptation to the precursor level on the detection of the subsequent AM. It was found that FM detection benefits from a precursor and the magnitude of FM unmasking correlates with that of AM unmasking. Moreover, consistent with dynamic-range adaptation, the unmasking magnitude weakens as the level difference between the precursor and simultaneous masker of the tone increases.
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Affiliation(s)
- Juraj Mesik
- Department of Psychology, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Magdalena Wojtczak
- Department of Psychology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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13
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Boothalingam S, Allan C, Allen P, Purcell DW. The Medial Olivocochlear Reflex Is Unlikely to Play a Role in Listening Difficulties in Children. Trends Hear 2020; 23:2331216519870942. [PMID: 31558110 PMCID: PMC6767729 DOI: 10.1177/2331216519870942] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The medial olivocochlear reflex (MOCR) has been implicated in several auditory processes. The putative role of the MOCR in improving speech perception in noise is particularly relevant for children who complain of listening difficulties (LiD). The hypothesis that the MOCR may be impaired in individuals with LiD or auditory processing disorder has led to several investigations but without consensus. In two related studies, we compared the MOCR functioning of children with LiD and typically developing (TD) children in the same age range (7-17 years). In Study 1, we investigated ipsilateral, contralateral, and bilateral MOCR using forward-masked click-evoked otoacoustic emissions (CEOAEs; n = 17 TD, 17 LiD). In Study 2, we employed three OAE types: CEOAEs (n = 16 TD, 21 LiD), stimulus frequency OAEs (n = 21 TD, 30 LiD), and distortion product OAEs (n = 17 TD, 22 LiD) in a contralateral noise paradigm. Results from both studies suggest that the MOCR functioning is not significantly different between the two groups. Some likely reasons for differences in findings among published studies could stem from the lack of strict data quality measures (e.g., high signal-to-noise ratio, control for the middle ear muscle reflex) that were enforced in the present study. The inherent variability of the MOCR, the subpar reliability of current MOCR methods, and the heterogeneity in auditory processing deficits that underlie auditory processing disorder make detecting clinically relevant differences in MOCR function impractical using current methods.
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Affiliation(s)
- Sriram Boothalingam
- Department of Communication Sciences and Disorders, University of Wisconsin, Madison, WI, USA.,Waisman Center, University of Wisconsin, Madison, WI, USA
| | - Chris Allan
- School of Communication Sciences and Disorders, Western University, London, ON, Canada.,National Centre for Audiology, Western University, London, ON, Canada
| | - Prudence Allen
- School of Communication Sciences and Disorders, Western University, London, ON, Canada.,National Centre for Audiology, Western University, London, ON, Canada
| | - David W Purcell
- School of Communication Sciences and Disorders, Western University, London, ON, Canada.,National Centre for Audiology, Western University, London, ON, Canada
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14
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Cochlear Efferent Innervation Is Sparse in Humans and Decreases with Age. J Neurosci 2019; 39:9560-9569. [PMID: 31628179 DOI: 10.1523/jneurosci.3004-18.2019] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 09/27/2019] [Accepted: 10/05/2019] [Indexed: 12/26/2022] Open
Abstract
The mammalian cochlea is innervated by two cholinergic feedback systems called the medial olivocochlear (MOC) and lateral olivocochlear (LOC) pathways, which send control signals from the brainstem back to the outer hair cells and auditory-nerve fibers, respectively. Despite countless studies of the cochlear projections of these efferent fibers in animal models, comparable data for humans are almost completely lacking. Here, we immunostained the cochlear sensory epithelium from 23 normal-aging humans (14 males and 9 females), 0-86 years of age, with cholinergic markers to quantify the normal density of MOC and LOC projections, and the degree of age-related degeneration. In younger ears, the MOC density peaks in mid-cochlear regions and falls off both apically and basally, whereas the LOC innervation peaks near the apex. In older ears, MOC density decreases dramatically, whereas the LOC density does not. The loss of MOC feedback may contribute to the age-related decrease in word recognition in noise; however, even at its peak, the MOC density is lower than in other mammals, suggesting the MOC pathway is less important for human hearing.SIGNIFICANCE STATEMENT The cochlear epithelium and its sensory innervation are modulated by the olivocochlear (OC) efferent pathway. Although the medial OC (MOC) reflex has been extensively studied in humans, via contralateral sound suppression, the cochlear projections of these cholinergic neurons have not been described in humans. Here, we use immunostaining to quantify the MOC projections to outer hair cells and lateral OC (LOC) projections to the inner hair cell area in humans 0-89 years of age. We show age-related loss of MOC, but not LOC, innervation, which likely contributes to hearing impairments, and a relative paucity of MOC terminals at all ages, which may account for the relative weakness of the human MOC reflex and the difficulty in demonstrating a robust functional role in human experiments.
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Beim JA, Oxenham AJ, Wojtczak M. No effects of attention or visual perceptual load on cochlear function, as measured with stimulus-frequency otoacoustic emissions. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:1475. [PMID: 31472524 PMCID: PMC6715442 DOI: 10.1121/1.5123391] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 08/02/2019] [Accepted: 08/05/2019] [Indexed: 06/10/2023]
Abstract
The effects of selectively attending to a target stimulus in a background containing distractors can be observed in cortical representations of sound as an attenuation of the representation of distractor stimuli. The locus in the auditory system at which attentional modulations first arise is unknown, but anatomical evidence suggests that cortically driven modulation of neural activity could extend as peripherally as the cochlea itself. Previous studies of selective attention have used otoacoustic emissions to probe cochlear function under varying conditions of attention with mixed results. In the current study, two experiments combined visual and auditory tasks to maximize sustained attention, perceptual load, and cochlear dynamic range in an attempt to improve the likelihood of observing selective attention effects on cochlear responses. Across a total of 45 listeners in the two experiments, no systematic effects of attention or perceptual load were observed on stimulus-frequency otoacoustic emissions. The results revealed significant between-subject variability in the otoacoustic-emission measure of cochlear function that does not depend on listener performance in the behavioral tasks and is not related to movement-generated noise. The findings suggest that attentional modulation of auditory information in humans arises at stages of processing beyond the cochlea.
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Affiliation(s)
- Jordan A Beim
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, Minnesota 55455, USA
| | - Andrew J Oxenham
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, Minnesota 55455, USA
| | - Magdalena Wojtczak
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, Minnesota 55455, USA
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16
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Bulut E, Öztürk G, Taş M, Türkmen MT, Gülmez ZD, Öztürk L. Medial olivocochlear suppression in musicians versus non-musicians. Physiol Int 2019; 106:151-157. [PMID: 31262207 DOI: 10.1556/2060.106.2019.11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The medial olivocochlear efferent (MOCE) branch synapses with outer hair cells (OHCs), and the efferent pathway can be activated via a contralateral acoustic stimulus (CAS). The activation of MOCE can change OHC motile responses and convert signals that are capable of controlling the sensitivity of the peripheral hearing system in a frequency-specific manner. The aim of this study was to examine the MOCE system activity in professional musicians using transient evoked otoacoustic emission test and CAS. Musician group showed stronger suppression in all frequency bands in the presence of CAS.
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Affiliation(s)
- E Bulut
- 1 Department of Audiology, Faculty of Health Sciences, Trakya University , Edirne, Turkey.,5 Department of Physiology, Faculty of Medicine, Trakya University , Edirne, Turkey
| | - G Öztürk
- 2 Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Trakya University , Edirne, Turkey.,5 Department of Physiology, Faculty of Medicine, Trakya University , Edirne, Turkey
| | - M Taş
- 1 Department of Audiology, Faculty of Health Sciences, Trakya University , Edirne, Turkey
| | - M T Türkmen
- 3 Department of Otorhinolaryngology, Faculty of Medicine, Trakya University , Edirne, Turkey
| | - Z D Gülmez
- 4 Department of Audiology, Faculty of Health Sciences, Istanbul University , Istanbul, Turkey
| | - L Öztürk
- 5 Department of Physiology, Faculty of Medicine, Trakya University , Edirne, Turkey
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17
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Exploring the Role of Medial Olivocochlear Efferents on the Detection of Amplitude Modulation for Tones Presented in Noise. J Assoc Res Otolaryngol 2019; 20:395-413. [PMID: 31140010 PMCID: PMC6646499 DOI: 10.1007/s10162-019-00722-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 04/15/2019] [Indexed: 10/26/2022] Open
Abstract
The medial olivocochlear reflex has been hypothesized to improve the detection and discrimination of dynamic signals in noisy backgrounds. This hypothesis was tested here by comparing behavioral outcomes with otoacoustic emissions. The effects of a precursor on amplitude-modulation (AM) detection were measured for a 1- and 6-kHz carrier at levels of 40, 60, and 80 dB SPL in a two-octave-wide noise masker with a level designed to produce poor, but above-chance, performance. Three types of precursor were used: a two-octave noise band, an inharmonic complex tone, and a pure tone. Precursors had the same overall level as the simultaneous noise masker that immediately followed the precursor. The noise precursor produced a large improvement in AM detection for both carrier frequencies and at all three levels. The complex tone produced a similarly large improvement in AM detection at the highest level but had a smaller effect for the two lower carrier levels. The tonal precursor did not significantly affect AM detection in noise. Comparisons of behavioral thresholds and medial olivocochlear efferent effects on stimulus frequency otoacoustic emissions measured with similar stimuli did not support the hypothesis that efferent-based reduction of cochlear responses contributes to the precursor effects on AM detection.
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18
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Hegland EL, Strickland EA. The effects of preceding sound and stimulus duration on measures of suppression in younger and older adults. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 144:3548. [PMID: 30599663 PMCID: PMC6308016 DOI: 10.1121/1.5083824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 11/04/2018] [Accepted: 11/26/2018] [Indexed: 05/19/2023]
Abstract
Despite clinically normal audiometric thresholds, some older adults may experience difficulty in tasks such as understanding speech in a noisy environment. One potential reason may be reduced cochlear nonlinearity. A sensitive measure of cochlear nonlinearity is two-tone suppression, which is a reduction in the auditory system's response to one tone in the presence of a second tone. Previous research has been mixed on whether suppression decreases with age in humans. Studies of efferent cochlear gain reduction also suggest that stimulus duration should be considered in measuring suppression. In the present study, suppression was first measured psychoacoustically using stimuli that were too short to result in gain reduction. The potential effect of efferent cochlear gain reduction was then measured by using longer stimuli and presenting tonal or noise precursors before the shorter stimuli. Younger adults (ages 19-22 yr) and older adults (ages 57+ yr) with clinically normal hearing were tested. Suppression estimates decreased with longer stimuli or preceding sound which included the signal frequency, but did not decrease with preceding sound at the suppressor frequency. On average, the older group had lower suppression than the younger group, but this difference was not statistically significant.
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Affiliation(s)
- Erica L Hegland
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, Indiana 47907, USA
| | - Elizabeth A Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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19
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Beim JA, Oxenham AJ, Wojtczak M. Examining replicability of an otoacoustic measure of cochlear function during selective attention. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 144:2882. [PMID: 30522315 PMCID: PMC6246073 DOI: 10.1121/1.5079311] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 10/12/2018] [Accepted: 10/27/2018] [Indexed: 06/09/2023]
Abstract
Attention to a target stimulus within a complex scene often results in enhanced cortical representations of the target relative to the background. It remains unclear where along the auditory pathways attentional effects can first be measured. Anatomy suggests that attentional modulation could occur through corticofugal connections extending as far as the cochlea itself. Earlier attempts to investigate the effects of attention on human cochlear processing have revealed small and inconsistent effects. In this study, stimulus-frequency otoacoustic emissions were recorded from a total of 30 human participants as they performed tasks that required sustained selective attention to auditory or visual stimuli. In the first sample of 15 participants, emission magnitudes were significantly weaker when participants attended to the visual stimuli than when they attended to the auditory stimuli, by an average of 5.4 dB. However, no such effect was found in the second sample of 15 participants. When the data were pooled across samples, the average attentional effect was significant, but small (2.48 dB), with 12 of 30 listeners showing a significant effect, based on bootstrap analysis of the individual data. The results highlight the need for considering sources of individual differences and using large sample sizes in future investigations.
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Affiliation(s)
- Jordan A Beim
- Department of Psychology, N218 Elliott Hall, 75 East River Parkway, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Andrew J Oxenham
- Department of Psychology, N218 Elliott Hall, 75 East River Parkway, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Magdalena Wojtczak
- Department of Psychology, N218 Elliott Hall, 75 East River Parkway, University of Minnesota, Minneapolis, Minnesota 55455, USA
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20
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Francis NA, Zhao W, Guinan Jr. JJ. Auditory Attention Reduced Ear-Canal Noise in Humans by Reducing Subject Motion, Not by Medial Olivocochlear Efferent Inhibition: Implications for Measuring Otoacoustic Emissions During a Behavioral Task. Front Syst Neurosci 2018; 12:42. [PMID: 30271329 PMCID: PMC6146202 DOI: 10.3389/fnsys.2018.00042] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 08/24/2018] [Indexed: 12/12/2022] Open
Abstract
Otoacoustic emissions (OAEs) are often measured to non-invasively determine activation of medial olivocochlear (MOC) efferents in humans. Usually these experiments assume that ear-canal noise remains constant. However, changes in ear-canal noise have been reported in some behavioral experiments. We studied the variability of ear-canal noise in eight subjects who performed a two-interval-forced-choice (2IFC) sound-level-discrimination task on monaural tone pips in masker noise. Ear-canal noise was recorded directly from the unstimulated ear opposite the task ear. Recordings were also made with similar sounds presented, but no task done. In task trials, ear-canal noise was reduced at the time the subject did the discrimination, relative to the ear-canal noise level earlier in the trial. In two subjects, there was a decrease in ear-canal noise, primarily at 1-2 kHz, with a time course similar to that expected from inhibition by MOC activity elicited by the task-ear masker noise. These were the only subjects with spontaneous OAEs (SOAEs). We hypothesize that the SOAEs were inhibited by MOC activity elicited by the task-ear masker. Based on the standard rationale in OAE experiments that large bursts of ear-canal noise are artifacts due to subject movement, ear-canal noise bursts above a sound-level criterion were removed. As the criterion was lowered and more high- and moderate-level ear-canal noise bursts were removed, the reduction in ear-canal noise level at the time of the 2IFC discrimination decreased to almost zero, for the six subjects without SOAEs. This pattern is opposite that expected from MOC-induced inhibition (which is greater on lower-level sounds), but can be explained by the hypothesis that subjects move less and create fewer bursts of ear-canal noise when they concentrate on doing the task. In no-task trials for these six subjects, the ear-canal noise level was little changed throughout the trial. Our results show that measurements of MOC effects on OAEs must measure and account for changes in ear-canal noise, especially in behavioral experiments. The results also provide a novel way of showing the time course of the buildup of attention via the time course of the reduction in ear-canal noise.
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Affiliation(s)
- Nikolas A. Francis
- Speech and Hearing Bioscience and Technology, Harvard-Massachusetts Institute of Technology (MIT) Division of Health Sciences and Technology, Cambridge, MA, United States
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, United States
| | - Wei Zhao
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, United States
- Department of Otolaryngology, Harvard Medical School, Harvard University, Boston, MA, United States
| | - John J. Guinan Jr.
- Speech and Hearing Bioscience and Technology, Harvard-Massachusetts Institute of Technology (MIT) Division of Health Sciences and Technology, Cambridge, MA, United States
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, United States
- Department of Otolaryngology, Harvard Medical School, Harvard University, Boston, MA, United States
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21
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Boothalingam S, Kurke J, Dhar S. Click-Evoked Auditory Efferent Activity: Rate and Level Effects. J Assoc Res Otolaryngol 2018; 19:421-434. [PMID: 29736560 DOI: 10.1007/s10162-018-0664-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Accepted: 03/22/2018] [Indexed: 11/29/2022] Open
Abstract
There currently are no standardized protocols to evaluate auditory efferent function in humans. Typical tests use broadband noise to activate the efferents, but only test the contralateral efferent pathway, risk activating the middle ear muscle reflex (MEMR), and are laborious for clinical use. In an attempt to develop a clinical test of bilateral auditory efferent function, we have designed a method that uses clicks to evoke efferent activity, obtain click-evoked otoacoustic emissions (CEOAEs), and monitor MEMR. This allows for near-simultaneous estimation of cochlear and efferent function. In the present study, we manipulated click level (60, 70, and 80 dB peak-equivalent sound pressure level [peSPL]) and rate (40, 50, and 62.5 Hz) to identify an optimal rate-level combination that evokes measurable efferent modulation of CEOAEs. Our findings (n = 58) demonstrate that almost all click levels and rates used caused significant inhibition of CEOAEs, with a significant interaction between level and rate effects. Predictably, bilateral activation produced greater inhibition compared to stimulating the efferents only in the ipsilateral or contralateral ear. In examining the click rate-level effects during bilateral activation in greater detail, we observed a 1-dB inhibition of CEOAE level for each 10-dB increase in click level, with rate held constant at 62.5 Hz. Similarly, a 10-Hz increase in rate produced a 0.74-dB reduction in CEOAE level, with click level held constant at 80 dB peSPL. The effect size (Cohen's d) was small for either monaural condition and medium for bilateral, faster-rate, and higher-level conditions. We were also able to reliably extract CEOAEs from efferent eliciting clicks. We conclude that clicks can indeed be profitably employed to simultaneously evaluate cochlear health using CEOAEs as well as their efferent modulation. Furthermore, using bilateral clicks allows the evaluation of both the crossed and uncrossed elements of the auditory efferent nervous system, while yielding larger, more discernible, inhibition of the CEOAEs relative to either ipsilateral or contralateral condition.
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Affiliation(s)
- Sriram Boothalingam
- Department of Communication Sciences and Disorders, and The Waisman Center, University of Wisconsin, Madison, WI, USA.
| | - Julianne Kurke
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, USA
| | - Sumitrajit Dhar
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, and The Knowles Hearing Center, Northwestern University, Evanston, IL, USA
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22
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DeRoy Milvae K, Strickland EA. Psychoacoustic measurements of ipsilateral cochlear gain reduction as a function of signal frequency. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 143:3114. [PMID: 29857720 PMCID: PMC5967972 DOI: 10.1121/1.5038254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 03/09/2018] [Accepted: 04/30/2018] [Indexed: 05/19/2023]
Abstract
Forward masking experiments at 4 kHz have demonstrated that preceding sound can elicit changes in masking patterns consistent with a change in cochlear gain. However, the acoustic environment is filled with complex sounds, often dominated by lower frequencies, and ipsilateral cochlear gain reduction at frequencies below 4 kHz is largely unstudied in the forward masking literature. In this experiment, the magnitude of ipsilateral cochlear gain reduction was explored at 1, 2, and 4 kHz using forward masking techniques in an effort to evaluate a range of frequencies in listeners with normal hearing. Gain reduction estimates were not significantly different at 2 and 4 kHz using two forward masking measurements. Although the frequency was a significant factor in the analysis, post hoc testing supported the interpretation that gain reduction estimates measured without a masker were not significantly different at 1, 2, and 4 kHz. A second experiment provided evidence that forward masking in this paradigm at 1 kHz cannot be explained by excitation alone. This study provides evidence of ipsilateral cochlear gain reduction in humans at frequencies below the 4 kHz region.
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Affiliation(s)
- Kristina DeRoy Milvae
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, Indiana 47907, USA
| | - Elizabeth A Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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23
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Frequency specificity and left-ear advantage of medial olivocochlear efferent modulation: a study based on stimulus frequency otoacoustic emission. Neuroreport 2018; 28:775-778. [PMID: 28538522 DOI: 10.1097/wnr.0000000000000812] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The medial olivocochlear (MOC) bundle is an auditory nucleus that projects efferent nerve fibers to the outer hair cells (OHCs) for synaptic innervation. The aim of the present study was to investigate the possible existence of frequency and ear specificity in MOC efferent modulation, as well as how MOC activation influences cochlear tuning. Stimulus frequency otoacoustic emissions (SFOAEs) were used to study MOC efferent modulation. Therefore, the current experiment was designed to compare the degree of SFOAE suppression in the both ears of 20 individuals at 1, 2, 4, and 8 kHz. We also compared changes in Q10 values of SFOAE suppression tuning curves at 1, 2, and 4 kHz under contralateral acoustic stimulation (CAS) and no-CAS conditions. We observed a significant reduction in SFOAE magnitude in the CAS condition compared with the no-CAS condition at 1 and 2 kHz in the left ear. A significant difference in CAS suppression was also found between the left and right ears at 1 and 2 kHz, with larger CAS suppression in the left ear. CAS further produced a statistically significant increase in the Q10 value at 1 kHz and a significant reduction in Q10 values at 2 and 4 kHz. These findings suggest a left-ear advantage in terms of CAS-induced MOC efferent SFOAE suppression, with larger MOC efferent modulation for lower frequencies, and cochlear tuning was sharpened by means of MOC activation at lower frequencies and broadened at higher frequencies.
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Lopez-Poveda EA. Olivocochlear Efferents in Animals and Humans: From Anatomy to Clinical Relevance. Front Neurol 2018; 9:197. [PMID: 29632514 PMCID: PMC5879449 DOI: 10.3389/fneur.2018.00197] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 03/13/2018] [Indexed: 11/13/2022] Open
Abstract
Olivocochlear efferents allow the central auditory system to adjust the functioning of the inner ear during active and passive listening. While many aspects of efferent anatomy, physiology and function are well established, others remain controversial. This article reviews the current knowledge on olivocochlear efferents, with emphasis on human medial efferents. The review covers (1) the anatomy and physiology of olivocochlear efferents in animals; (2) the methods used for investigating this auditory feedback system in humans, their limitations and best practices; (3) the characteristics of medial-olivocochlear efferents in humans, with a critical analysis of some discrepancies across human studies and between animal and human studies; (4) the possible roles of olivocochlear efferents in hearing, discussing the evidence in favor and against their role in facilitating the detection of signals in noise and in protecting the auditory system from excessive acoustic stimulation; and (5) the emerging association between abnormal olivocochlear efferent function and several health conditions. Finally, we summarize some open issues and introduce promising approaches for investigating the roles of efferents in human hearing using cochlear implants.
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Affiliation(s)
- Enrique A Lopez-Poveda
- Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Salamanca, Spain.,Departamento de Cirugía, Facultad de Medicina, Universidad de Salamanca, Salamanca, Spain.,Instituto de Investigación Biomédica de Salamanca, Universidad de Salamanca, Salamanca, Spain
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25
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Olivocochlear efferents: Their action, effects, measurement and uses, and the impact of the new conception of cochlear mechanical responses. Hear Res 2017; 362:38-47. [PMID: 29291948 DOI: 10.1016/j.heares.2017.12.012] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 11/08/2017] [Accepted: 12/12/2017] [Indexed: 12/27/2022]
Abstract
The anatomy and physiology of olivocochlear (OC) efferents are reviewed. To help interpret these, recent advances in cochlear mechanics are also reviewed. Lateral OC (LOC) efferents innervate primary auditory-nerve (AN) fiber dendrites. The most important LOC function may be to reduce auditory neuropathy. Medial OC (MOC) efferents innervate the outer hair cells (OHCs) and act to turn down the gain of cochlear amplification. Cochlear amplification had been thought to act only through basilar membrane (BM) motion, but recent reports show that motion near the reticular lamina (RL) is amplified more than BM motion, and that RL-motion amplification extends to several octaves below the local characteristic frequency. Data on efferent effects on AN-fiber responses, otoacoustic emissions (OAEs) and human psychophysics are reviewed and reinterpreted in the light of the new cochlear-mechanical data. The possible origin of OAEs in RL motion is considered. MOC-effect measuring methods and MOC-induced changes in human responses are also reviewed, including that ipsilateral and contralateral sound can produce MOC effects with different patterns across frequency. MOC efferents help to reduce damage due to acoustic trauma. Many, but not all, reports show that subjects with stronger contralaterally-evoked MOC effects have better ability to detect signals (e.g. speech) in noise, and that MOC effects can be modulated by attention.
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Ma Z, Xia W, Liu F, Ma J, Sun S, Zhang J, Jiang N, Wang X, Hu J, Ma D. SLC44A4 mutation causes autosomal dominant hereditary postlingual non-syndromic mid-frequency hearing loss. Hum Mol Genet 2017; 26:383-394. [PMID: 28013291 DOI: 10.1093/hmg/ddw394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/11/2016] [Indexed: 01/28/2023] Open
Abstract
Clinical, genetic, and functional investigations were performed to identify the causative mutation in a distinctive Chinese family with postlingual non-syndromic mid-frequency sensorineural hearing loss. Whole-exome sequencing revealed SLC44A4, which encodes the choline transport protein, as the pathogenic gene in this family. In the zebrafish model, downregulation of slc44a4 using morpholinos led to significant abnormalities in the zebrafish inner ear and lateral line neuromasts and contributed, to some extent, to disabilities in hearing and balance. SH-SY5Y cells transfected with SLC44A4 showed higher choline uptake and acetylcholine release than that of cells transfected with mutant SLC44A4. We concluded that mutation of SLC44A4 may cause defects in the Choline- acetylcholine system, which is crucial to the efferent innervation of hair cells in the olivocochlear bundle for the maintenance of physiological function of outer hair cells and the protection of hair cells from acoustic injury, leading to hearing loss.
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Affiliation(s)
- Zhaoxin Ma
- Department of Otorhinolaryngology, Shanghai East Hospital, Tongji University, Shanghai, 200120, People's Republic of China
| | - Wenjun Xia
- Institute of Biomedical Science, Fudan University, Shanghai, 200032, People's Republic of China
| | - Fei Liu
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Jing Ma
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Shaoyang Sun
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Jin Zhang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Nan Jiang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Xu Wang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and
| | - Jiongjiong Hu
- Department of Otorhinolaryngology, Shanghai East Hospital, Tongji University, Shanghai, 200120, People's Republic of China
| | - Duan Ma
- Institute of Biomedical Science, Fudan University, Shanghai, 200032, People's Republic of China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Institute of Biomedical Sciences, Collaborative Innovation Center of Genetics and Development, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China and.,Children's Hospital, Fudan University, 200032, People's Republic of China
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27
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Bester CW, Robertson D, Taljaard D, Hammond G. Altered attentional filters in subjects with graded levels of sensorineural hearing loss. Hear Res 2017; 351:80-87. [PMID: 28610719 DOI: 10.1016/j.heares.2017.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 05/30/2017] [Accepted: 06/01/2017] [Indexed: 10/19/2022]
Abstract
Near-threshold tones (targets) in noise that are preceded by cues of the same frequency or occur with a high probability are detected better than tones of other frequencies that may occur with a lower probability (probes); the better detection of targets than probes defines the attentional filter. We measured attentional filters using a cued probe-signal procedure with a two-interval forced-choice (2IFC) method in normal-hearing subjects (N = 15) and subjects with sensorineural hearing loss (SNHL; N = 14) with a range of hearing levels. Attentional filters were altered in SNHL subjects, who detected low-frequency probes as well as targets at all hearing levels and who detected high-frequency probes increasingly well with increasing hearing level. These effects were present in both intervals of the 2IFC procedure. As auditory filters measured psychophysically are typically asymmetric in subjects with SNHL, these results suggest that the signal frequencies affected by the attentional filter are governed by the shapes of the auditory filters at and around the cue frequency. The normal-hearing subjects showed the expected attentional filters in the first interval and shallower filters in the second interval, suggesting that the cue-evoked attentional process is transient. In the first interval, both low- and high-frequency probes were detected better as hearing level increased over a narrow range (from -5 to 10 dB at the target frequency), with a resultant loss of attentional filtering. This finding adds to observations of variable auditory function in individuals with clinically normal hearing thresholds established by audiometry.
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Affiliation(s)
- Christofer W Bester
- The Auditory Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Nedlands, WA, 6009, Australia.
| | - Donald Robertson
- The Auditory Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Nedlands, WA, 6009, Australia
| | - Dunay Taljaard
- Ear Science Institute Australia, Subiaco, WA, 6008, Australia; Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA, 6009, Australia
| | - Geoff Hammond
- School of Psychology, The University of Western Australia, Nedlands, WA, 6009, Australia
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Verschooten E, Strickland EA, Verhaert N, Joris PX. Assessment of Ipsilateral Efferent Effects in Human via ECochG. Front Neurosci 2017; 11:331. [PMID: 28642679 PMCID: PMC5462931 DOI: 10.3389/fnins.2017.00331] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 05/26/2017] [Indexed: 11/16/2022] Open
Abstract
Development of electrophysiological means to assess the medial olivocochlear (MOC) system in humans is important to further our understanding of the function of that system and for the refinement and validation of psychoacoustical and otoacoustic emission methods which are thought to probe the MOC. Based on measurements in anesthetized animals it has been hypothesized that the MOC-reflex (MOCR) can enhance the response to signals in noise, and several lines of evidence support such a role in humans. A difficulty in these studies is the isolation of efferent effects. Efferent activation can be triggered by acoustic stimulation of the contralateral or ipsilateral ear, but ipsilateral stimulation is thought to be more effective. However, ipsilateral stimulation complicates interpretation of effects since these sounds can affect the perception of other ipsilateral sounds by mechanisms not involving olivocochlear efferents. We assessed the ipsilaterally evoked MOCR in human using a transtympanic procedure to record mass-potentials from the cochlear promontory or the niche of the round window. Averaged compound action potential (CAP) responses to masked probe tones of 4 kHz with and without a precursor (designed to activate the MOCR but not the stapedius reflex) were extracted with a polarity alternating paradigm. The masker was either a simultaneous narrow band noise masker or a short (20-ms) tonal ON- or OFF-frequency forward masker. The subjects were screened for normal hearing (audiogram, tympanogram, threshold stapedius reflex) and psychoacoustically tested for the presence of a precursor effect. We observed a clear reduction of CAP amplitude by the precursor, for different masking conditions. Even without an MOCR, this is expected because the precursor will affect the response to subsequent stimuli via neural adaptation. To determine whether the precursor also activated the efferent system, we measured the CAP over a range of masker levels, with or without precursor, and for different types of masker. The results show CAP reduction consistent with the type of gain reduction caused by the MOCR. These results generally support psychoacoustical paradigms designed to probe the efferent system as indeed activating the MOCR system, but not all observations are consistent with this mechanism.
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Affiliation(s)
- Eric Verschooten
- Laboratory of Auditory Neurophysiology, Department of Neurosciences, University of LeuvenLeuven, Belgium
| | - Elizabeth A. Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue UniversityWest Lafayette, IN, United States
| | - Nicolas Verhaert
- ExpORL Research Group, Department of Neurosciences, University of LeuvenLeuven, Belgium
| | - Philip X. Joris
- Laboratory of Auditory Neurophysiology, Department of Neurosciences, University of LeuvenLeuven, Belgium
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Bidelman GM, Schneider AD, Heitzmann VR, Bhagat SP. Musicianship enhances ipsilateral and contralateral efferent gain control to the cochlea. Hear Res 2016; 344:275-283. [PMID: 27964936 DOI: 10.1016/j.heares.2016.12.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/29/2016] [Accepted: 12/08/2016] [Indexed: 11/17/2022]
Abstract
Human hearing sensitivity is easily compromised with overexposure to excessively loud sounds, leading to permanent hearing damage. Consequently, finding activities and/or experiential factors that distinguish "tender" from "tough" ears (i.e., acoustic vulnerability) would be important for identifying people at higher risk for hearing damage. To regulate sound transmission and protect the inner ear against acoustic trauma, the auditory system modulates gain control to the cochlea via biological feedback of the medial olivocochlear (MOC) efferents, a neuronal pathway linking the lower brainstem and cochlear outer hair cells. We hypothesized that a salient form of auditory experience shown to have pervasive neuroplastic benefits, namely musical training, might act to fortify hearing through tonic engagement of these reflexive pathways. By measuring MOC efferent feedback via otoacoustic emissions (cochlear emitted sounds), we show that dynamic ipsilateral and contralateral cochlear gain control is enhanced in musically-trained individuals. Across all participants, MOC strength was correlated with the years of listeners' training suggested that efferent gain control is experience dependent. Our data provide new evidence that intensive listening experience(s) (e.g., musicianship) can strengthen the ipsi/contralateral MOC efferent system and sound regulation to the inner ear. Implications for reducing acoustic vulnerability to damaging sounds are discussed.
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Affiliation(s)
- Gavin M Bidelman
- School of Communication Sciences & Disorders, University of Memphis, Memphis, TN, USA; Institute for Intelligent Systems, University of Memphis, Memphis, TN, USA.
| | - Amy D Schneider
- School of Communication Sciences & Disorders, University of Memphis, Memphis, TN, USA
| | - Victoria R Heitzmann
- School of Communication Sciences & Disorders, University of Memphis, Memphis, TN, USA
| | - Shaum P Bhagat
- School of Communication Sciences & Disorders, University of Memphis, Memphis, TN, USA
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Bester C, Jayakody DMP, Hammond G, Robertson D. Selective attentional processes in cochlear implant recipients: Measurements of the attentional filter. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2016; 140:4091. [PMID: 28040033 DOI: 10.1121/1.4968783] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In normal hearing subjects, detection of near-threshold tones in noise is influenced by signal certainty. Thus, tones that are presented more frequently than others, and/or are preceded by a clearly audible cue tone of the same frequency (target tones) are detected better than other tones (probe tones). This auditory attentional filter was examined in six cochlear implant (CI) recipients, using acoustic stimuli and direct programmed electrode stimulation. Three of the subjects showed no evidence of an attentional filter. Three subjects showed a relatively higher detection rate of the target frequency or electrode stimulated during the attentional task, and in two of these subjects the target benefit was influenced by stimulus certainty. The absence of an attentional filter in some CI recipients is consistent with suggestions that the attentional filter may be generated by efferent modulation of outer hair cells, which would presumably be absent in CI recipients, however, the presence of some frequency-selective attentional effects and a near-normal attentional filter in two CI subjects imply that central processes can modulate signal detection in CI recipients according to stimulus certainty. Such central processes might serve as a neural substrate to improve signal detection in CI recipients.
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Affiliation(s)
- Christofer Bester
- School of Anatomy Physiology and Human Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Dona M P Jayakody
- Ear Sciences Institute Australia, 1 Salvado Road, Subiaco, Western Australia 6008, Australia
| | - Geoffrey Hammond
- School of Psychology, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Donald Robertson
- School of Anatomy Physiology and Human Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia
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Fletcher MD, Krumbholz K, de Boer J. Effect of Contralateral Medial Olivocochlear Feedback on Perceptual Estimates of Cochlear Gain and Compression. J Assoc Res Otolaryngol 2016; 17:559-575. [PMID: 27550069 PMCID: PMC5112214 DOI: 10.1007/s10162-016-0574-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/17/2016] [Indexed: 11/16/2022] Open
Abstract
The active cochlear mechanism amplifies responses to low-intensity sounds, compresses the range of input sound intensities to a smaller output range, and increases cochlear frequency selectivity. The gain of the active mechanism can be modulated by the medial olivocochlear (MOC) efferent system, creating the possibility of top-down control at the earliest level of auditory processing. In humans, MOC function has mostly been measured by the suppression of otoacoustic emissions (OAEs), typically as a result of MOC activation by a contralateral elicitor sound. The exact relationship between OAE suppression and cochlear gain reduction, however, remains unclear. Here, we measured the effect of a contralateral MOC elicitor on perceptual estimates of cochlear gain and compression, obtained using the established temporal masking curve (TMC) method. The measurements were taken at a signal frequency of 2 kHz and compared with measurements of click-evoked OAE suppression. The elicitor was a broadband noise, set to a sound pressure level of 54 dB to avoid triggering the middle ear muscle reflex. Despite its low level, the elicitor had a significant effect on the TMCs, consistent with a reduction in cochlear gain. The amount of gain reduction was estimated as 4.4 dB on average, corresponding to around 18 % of the without-elicitor gain. As a result, the compression exponent increased from 0.18 to 0.27.
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Affiliation(s)
- Mark D Fletcher
- Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
- School of Psychology, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
- Institute of Sound and Vibration Research, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK
| | - Katrin Krumbholz
- Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
| | - Jessica de Boer
- Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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Berezina-Greene MA, Guinan JJ. Electrically Evoked Medial Olivocochlear Efferent Effects on Stimulus Frequency Otoacoustic Emissions in Guinea Pigs. J Assoc Res Otolaryngol 2016; 18:153-163. [PMID: 27798720 DOI: 10.1007/s10162-016-0593-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 10/05/2016] [Indexed: 11/27/2022] Open
Abstract
Stimulus frequency otoacoustic emissions (SFOAEs) are produced by cochlear irregularities reflecting energy from the peak region of the traveling wave (TW). Activation of medial olivocochlear (MOC) efferents reduces cochlear amplification and otoacoustic emissions (OAEs). In other OAEs, MOC activation can produce enhancements. The extent of MOC enhancements of SFOAEs has not been previously studied. In anesthetized guinea pigs, we electrically stimulated MOC fibers and recorded their effects on SFOAEs. MOC stimulation mostly inhibited SFOAEs but sometimes enhanced them. Some enhancements were not near response dips and therefore cannot be explained by a reduction of wavelet cancelations. MOC stimulation always inhibited auditory-nerve compound action potentials showing that cochlear-amplifier gain was not increased. We propose that some SFOAE enhancements arise because shocks excite only a small number of MOC fibers that inhibit a few scattered outer hair cells thereby changing (perhaps increasing) cochlear irregularities and SFOAE amplitudes. Contralateral sound activation is expected to excite approximately one third of MOC efferents and may also change cochlear irregularities. Some papers suggest that large SFOAE components originate far basal of the TW peak, basal of the region that receives cochlear amplification. Using a time-frequency analysis, we separated SFOAEs into components with different latencies. At all SFOAE latencies, most SFOAE components were inhibited by MOC stimulation, but some were enhanced. The MOC inhibition of short-latency SFOAE components is consistent with these components being produced in the cochlear-amplified region near the TW peak.
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Affiliation(s)
- Maria A Berezina-Greene
- Eaton-Peabody Lab, Mass. Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3002, USA
- Harvard-MIT HST Speech and Hearing Bioscience and Technology Program, Cambridge, MA, USA
| | - John J Guinan
- Eaton-Peabody Lab, Mass. Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3002, USA.
- Harvard-MIT HST Speech and Hearing Bioscience and Technology Program, Cambridge, MA, USA.
- Harvard Medical School, Boston, MA, USA.
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Brown MC. Recording and labeling at a site along the cochlea shows alignment of medial olivocochlear and auditory nerve tonotopic mappings. J Neurophysiol 2016; 115:1644-53. [PMID: 26823515 PMCID: PMC4808113 DOI: 10.1152/jn.00842.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 01/28/2016] [Indexed: 11/22/2022] Open
Abstract
Medial olivocochlear (MOC) neurons provide an efferent innervation to outer hair cells (OHCs) of the cochlea, but their tonotopic mapping is incompletely known. In the present study of anesthetized guinea pigs, the MOC mapping was investigated using in vivo, extracellular recording, and labeling at a site along the cochlear course of the axons. The MOC axons enter the cochlea at its base and spiral apically, successively turning out to innervate OHCs according to their characteristic frequencies (CFs). Recordings made at a site in the cochlear basal turn yielded a distribution of MOC CFs with an upper limit, or "edge," due to usually absent higher-CF axons that presumably innervate more basal locations. The CFs at the edge, normalized across preparations, were equal to the CFs of the auditory nerve fibers (ANFs) at the recording sites (near 16 kHz). Corresponding anatomical data from extracellular injections showed spiraling MOC axons giving rise to an edge of labeling at the position of a narrow band of labeled ANFs. Overall, the edges of the MOC CFs and labeling, with their correspondences to ANFs, suggest similar tonotopic mappings of these efferent and afferent fibers, at least in the cochlear basal turn. They also suggest that MOC axons miss much of the position of the more basally located cochlear amplifier appropriate for their CF; instead, the MOC innervation may be optimized for protection from damage by acoustic overstimulation.
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Affiliation(s)
- M Christian Brown
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
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Roverud E, Strickland EA. The effects of ipsilateral, contralateral, and bilateral broadband noise on the mid-level hump in intensity discrimination. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 138:3245-3261. [PMID: 26627798 PMCID: PMC4662679 DOI: 10.1121/1.4935515] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 10/21/2015] [Accepted: 10/28/2015] [Indexed: 05/29/2023]
Abstract
Previous psychoacoustical and physiological studies indicate that the medial olivocochlear reflex (MOCR), a bilateral, sound-evoked reflex, may lead to improved sound intensity discrimination in background noise. The MOCR can decrease the range of basilar-membrane compression and can counteract effects of neural adaptation from background noise. However, the contribution of these processes to intensity discrimination is not well understood. This study examined the effect of ipsilateral, contralateral, and bilateral noise on the "mid-level hump." The mid-level hump refers to intensity discrimination Weber fractions (WFs) measured for short-duration, high-frequency tones which are poorer at mid levels than at lower or higher levels. The mid-level hump WFs may reflect a limitation due to basilar-membrane compression, and thus may be decreased by the MOCR. The noise was either short (50 ms) or long (150 ms), with the long noise intended to elicit the sluggish MOCR. For a tone in quiet, mid-level hump WFs improved with ipsilateral noise for most listeners, but not with contralateral noise. For a tone in ipsilateral noise, WFs improved with contralateral noise for most listeners, but only when both noises were long. These results are consistent with MOCR-induced WF improvements, possibly via decreases in effects of compression and neural adaptation.
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Affiliation(s)
- Elin Roverud
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, Indiana 47907, USA
| | - Elizabeth A Strickland
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, Indiana 47907, USA
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Stimulus Frequency Otoacoustic Emissions Provide No Evidence for the Role of Efferents in the Enhancement Effect. J Assoc Res Otolaryngol 2015; 16:613-29. [PMID: 26153415 DOI: 10.1007/s10162-015-0534-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 06/18/2015] [Indexed: 10/23/2022] Open
Abstract
Auditory enhancement refers to the perceptual phenomenon that a target sound is heard out more readily from a background sound if the background is presented alone first. Here we used stimulus-frequency otoacoustic emissions (SFOAEs) to test the hypothesis that activation of the medial olivocochlear efferent system contributes to auditory enhancement effects. The SFOAEs were used as a tool to measure changes in cochlear responses to a target component and the neighboring components of a multitone background between conditions producing enhancement and conditions producing no enhancement. In the "enhancement" condition, the target and multitone background were preceded by a precursor stimulus with a spectral notch around the signal frequency; in the control (no-enhancement) condition, the target and multitone background were presented without the precursor. In an experiment using a wideband multitone stimulus known to produce significant psychophysical enhancement effects, SFOAEs showed no changes consistent with enhancement, but some aspects of the results indicated possible contamination of the SFOAE magnitudes by the activation of the middle-ear-muscle reflex. The same SFOAE measurements performed using narrower-band stimuli at lower sound levels also showed no SFOAE changes consistent with either absolute or relative enhancement despite robust psychophysical enhancement effects observed in the same listeners with the same stimuli. The results suggest that cochlear efferent control does not play a significant role in auditory enhancement effects.
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Boothalingam S, Purcell DW. Influence of the stimulus presentation rate on medial olivocochlear system assays. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 137:724-32. [PMID: 25698007 DOI: 10.1121/1.4906250] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Click evoked otoacoustic emissions (CEOAEs) are commonly used both in research and clinics to assay the medial olivocochlear system (MOC). Clicks presented at rates >50 Hz in the contralateral ear have previously been reported to evoke contralateral MOC activity. However, in typical MOC assays, clicks are presented in the ipsilateral ear in conjunction with MOC elicitor (noise) in the contralateral ear. The effect of click rates in such an arrangement is currently unknown. A forward masking paradigm was used to emulate typical MOC assays to elucidate the influence of ipsilateral click presentation rates on MOC inhibition of CEOAEs in 28 normal hearing adults. Influence of five click rates (20.83, 25, 31.25, 41.67, and 62.5 Hz) presented at 55 dB peSPL was tested. Results indicate that click rates as low as 31.25 Hz significantly enhance contralateral MOC inhibition, possibly through the activation of ipsilateral and binaural MOC neurons with potential contributions from the middle ear muscle reflex. Therefore, click rates ≤25 Hz are recommended for use in MOC assays, at least for 55 dB peSPL click level.
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Affiliation(s)
- Sriram Boothalingam
- National Centre for Audiology, Western University, London, Ontario N6G 1H1, Canada
| | - David W Purcell
- National Centre for Audiology, Western University, London, Ontario N6G 1H1, Canada
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Fletcher M, de Boer J, Krumbholz K. Is off-frequency overshoot caused by adaptation of suppression? J Assoc Res Otolaryngol 2014; 16:241-53. [PMID: 25468405 PMCID: PMC4368652 DOI: 10.1007/s10162-014-0498-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 10/29/2014] [Indexed: 11/25/2022] Open
Abstract
This study is concerned with the mechanism of off-frequency overshoot. Overshoot refers to the phenomenon whereby a brief signal presented at the onset of a masker is easier to detect when the masker is preceded by a “precursor” sound (which is often the same as the masker). Overshoot is most prominent when the masker and precursor have a different frequency than the signal (henceforth referred to as “off-frequency overshoot”). It has been suggested that off-frequency overshoot is based on a similar mechanism as “enhancement,” which refers to the perceptual pop-out of a signal after presentation of a precursor that contains a spectral notch at the signal frequency; both have been proposed to be caused by a reduction in the suppressive masking of the signal as a result of the adaptive effect of the precursor (“adaptation of suppression”). In this study, we measured overshoot, suppression, and adaptation of suppression for a 4-kHz sinusoidal signal and a 4.75-kHz sinusoidal masker and precursor, using the same set of participants. We show that, while the precursor yielded strong overshoot and the masker produced strong suppression, the precursor did not appear to cause any reduction (adaptation) of suppression. Predictions based on an established model of the cochlear input–output function indicate that our failure to obtain any adaptation of suppression is unlikely to represent a false negative outcome. Our results indicate that off-frequency overshoot and enhancement are likely caused by different mechanisms. We argue that overshoot may be due to higher-order perceptual factors such as transient masking or attentional diversion, whereas enhancement may be based on mechanisms similar to those that generate the Zwicker tone.
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Wojtczak M, Beim JA, Oxenham AJ. Exploring the role of feedback-based auditory reflexes in forward masking by schroeder-phase complexes. J Assoc Res Otolaryngol 2014; 16:81-99. [PMID: 25338224 DOI: 10.1007/s10162-014-0495-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 10/02/2014] [Indexed: 10/24/2022] Open
Abstract
Several studies have postulated that psychoacoustic measures of auditory perception are influenced by efferent-induced changes in cochlear responses, but these postulations have generally remained untested. This study measured the effect of stimulus phase curvature and temporal envelope modulation on the medial olivocochlear reflex (MOCR) and on the middle-ear muscle reflex (MEMR). The role of the MOCR was tested by measuring changes in the ear-canal pressure at 6 kHz in the presence and absence of a band-limited harmonic complex tone with various phase curvatures, centered either at (on-frequency) or well below (off-frequency) the 6-kHz probe frequency. The influence of possible MEMR effects was examined by measuring phase-gradient functions for the elicitor effects and by measuring changes in the ear-canal pressure with a continuous suppressor of the 6-kHz probe. Both on- and off-frequency complex tone elicitors produced significant changes in ear canal sound pressure. However, the pattern of results was not consistent with the earlier hypotheses postulating that efferent effects produce the psychoacoustic dependence of forward-masked thresholds on masker phase curvature. The results also reveal unexpectedly long time constants associated with some efferent effects, the source of which remains unknown.
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Affiliation(s)
- Magdalena Wojtczak
- Department of Psychology, University of Minnesota, N218 Elliott Hall, 75 East River Rd., Minneapolis, MN, 55455, USA,
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Guinan JJ. Olivocochlear efferent function: issues regarding methods and the interpretation of results. Front Syst Neurosci 2014; 8:142. [PMID: 25161612 PMCID: PMC4129934 DOI: 10.3389/fnsys.2014.00142] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/23/2014] [Indexed: 11/19/2022] Open
Abstract
As studies of the olivocochlear (OC) efferent system have matured, issues have been identified that need to be taken into account in the design of new studies and in the interpretation of existing work. The need for high signal-to-noise ratios (SNRs), multiple alternations of conditions, and avoiding middle-ear-muscle activation have been previously highlighted. Less well-known issues include: Contralateral medial OC (MOC) effects may not be good proxies for ipsilateral (ipsi) MOC effects; MOC-induced changes in otoacoustic emissions (OAEs) may not accurately show MOC-induced changes in auditory-nerve (AN) responses; measuring OAE differences from before to after psychophysical trials yields the transient OAE change but not tonic MOC activation; tonic MOC activation may be measurable by several techniques including by OAE differences in trials in which the subject’s judgment was correct vs. trials that were incorrect; SNRs can be preserved by Bootstrap statistical tests; differences in task difficulty may outweigh differences in subject attention; lateral efferent effects are little understood and may be tied to MOC effects; to assess whether MOC strength predicts protection from acoustic trauma, prospective tests in humans are needed.
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Affiliation(s)
- John J Guinan
- Eaton Peabody Laboratory of Auditory Physiology, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary Boston, MA, USA ; Department of Otology and Laryngology, Harvard Medical School Boston, Massachusetts, USA
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40
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Henin S, Long GR, Thompson S. Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 136:272-283. [PMID: 24993213 DOI: 10.1121/1.4883361] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.
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Affiliation(s)
- Simon Henin
- Speech, Language and Hearing Sciences, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, New York 10016
| | - Glenis R Long
- Speech, Language and Hearing Sciences, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, New York 10016
| | - Suzanne Thompson
- Speech, Language and Hearing Sciences, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, New York 10016
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Brown MC. Single-unit labeling of medial olivocochlear neurons: the cochlear frequency map for efferent axons. J Neurophysiol 2014; 111:2177-86. [PMID: 24598524 DOI: 10.1152/jn.00045.2014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Medial olivocochlear (MOC) neurons are efferent neurons that project axons from the brain to the cochlea. Their action on outer hair cells reduces the gain of the "cochlear amplifier," which shifts the dynamic range of hearing and reduces the effects of noise masking. The MOC effects in one ear can be elicited by sound in that ipsilateral ear or by sound in the contralateral ear. To study how MOC neurons project onto the cochlea to mediate these effects, single-unit labeling in guinea pigs was used to study the mapping of MOC neurons for neurons responsive to ipsilateral sound vs. those responsive to contralateral sound. MOC neurons were sharply tuned to sound frequency with a well-defined characteristic frequency (CF). However, their labeled termination spans in the organ of Corti ranged from narrow to broad, innervating between 14 and 69 outer hair cells per axon in a "patchy" pattern. For units responsive to ipsilateral sound, the midpoint of innervation was mapped according to CF in a relationship generally similar to, but with more variability than, that of auditory-nerve fibers. Thus, based on CF mappings, most of the MOC terminations miss outer hair cells involved in the cochlear amplifier for their CF, which are located more basally. Compared with ipsilaterally responsive neurons, contralaterally responsive neurons had an apical offset in termination and a larger span of innervation (an average of 10.41% cochlear distance), suggesting that when contralateral sound activates the MOC reflex, the actions are different than those for ipsilateral sound.
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Affiliation(s)
- M Christian Brown
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
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Modeling the time-varying and level-dependent effects of the medial olivocochlear reflex in auditory nerve responses. J Assoc Res Otolaryngol 2013; 15:159-73. [PMID: 24306278 DOI: 10.1007/s10162-013-0430-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 11/17/2013] [Indexed: 10/25/2022] Open
Abstract
The medial olivocochlear reflex (MOCR) has been hypothesized to provide benefit for listening in noisy environments. This advantage can be attributed to a feedback mechanism that suppresses auditory nerve (AN) firing in continuous background noise, resulting in increased sensitivity to a tone or speech. MOC neurons synapse on outer hair cells (OHCs), and their activity effectively reduces cochlear gain. The computational model developed in this study implements the time-varying, characteristic frequency (CF) and level-dependent effects of the MOCR within the framework of a well-established model for normal and hearing-impaired AN responses. A second-order linear system was used to model the time-course of the MOCR using physiological data in humans. The stimulus-level-dependent parameters of the efferent pathway were estimated by fitting AN sensitivity derived from responses in decerebrate cats using a tone-in-noise paradigm. The resulting model uses a binaural, time-varying, CF-dependent, level-dependent OHC gain reduction for both ipsilateral and contralateral stimuli that improves detection of a tone in noise, similarly to recorded AN responses. The MOCR may be important for speech recognition in continuous background noise as well as for protection from acoustic trauma. Further study of this model and its efferent feedback loop may improve our understanding of the effects of sensorineural hearing loss in noisy situations, a condition in which hearing aids currently struggle to restore normal speech perception.
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Carcagno S, Semal C, Demany L. No Need for Templates in the Auditory Enhancement Effect. PLoS One 2013; 8:e67874. [PMID: 23826348 PMCID: PMC3694896 DOI: 10.1371/journal.pone.0067874] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 05/23/2013] [Indexed: 11/18/2022] Open
Abstract
The audibility of a target tone in a multitone background masker is enhanced by the presentation of a precursor sound consisting of the masker alone. There is evidence that precursor-induced neural adaptation plays a role in this perceptual enhancement. However, the precursor may also be strategically used by listeners as a spectral template of the following masker to better segregate it from the target. In the present study, we tested this hypothesis by measuring the audibility of a target tone in a multitone masker after the presentation of precursors which, in some conditions, were made dissimilar to the masker by gating their components asynchronously. The precursor and the following sound were presented either to the same ear or to opposite ears. In either case, we found no significant difference in the amount of enhancement produced by synchronous and asynchronous precursors. In a second experiment, listeners had to judge whether a synchronous multitone complex contained exactly the same tones as a preceding precursor complex or had one tone less. In this experiment, listeners performed significantly better with synchronous than with asynchronous precursors, showing that asynchronous precursors were poorer perceptual templates of the synchronous multitone complexes. Overall, our findings indicate that precursor-induced auditory enhancement cannot be fully explained by the strategic use of the precursor as a template of the following masker. Our results are consistent with an explanation of enhancement based on selective neural adaptation taking place at a central locus of the auditory system.
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Affiliation(s)
- Samuele Carcagno
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Université de Bordeaux and CNRS, Bordeaux, France
- * E-mail:
| | - Catherine Semal
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Université de Bordeaux and CNRS, Bordeaux, France
| | - Laurent Demany
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Université de Bordeaux and CNRS, Bordeaux, France
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Aguilar E, Eustaquio-Martin A, Lopez-Poveda EA. Contralateral efferent reflex effects on threshold and suprathreshold psychoacoustical tuning curves at low and high frequencies. J Assoc Res Otolaryngol 2013; 14:341-57. [PMID: 23423559 PMCID: PMC3642277 DOI: 10.1007/s10162-013-0373-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Accepted: 01/21/2013] [Indexed: 11/28/2022] Open
Abstract
Medial olivocochlear efferent neurons can control cochlear frequency selectivity and may be activated in a reflexive manner by contralateral sounds. The present study investigated the significance of the contralateral medial olivocochlear reflex (MOCR) on human psychoacoustical tuning curves (PTCs), a behavioral correlate of cochlear tuning curves. PTCs were measured using forward masking in the presence and in the absence of a contralateral white noise, assumed to elicit the MOCR. To assess MOCR effects on apical and basal cochlear regions over a wide range of sound levels, PTCs were measured for probe frequencies of 500 Hz and 4 kHz and for near- and suprathreshold conditions. Results show that the contralateral noise affected the PTCs predominantly at 500 Hz. At near-threshold levels, its effect was obvious only for frequencies in the tails of the PTCs; at suprathreshold levels, its effects were obvious for all frequencies. It was verified that the effects were not due to the contralateral noise activating the middle-ear muscle reflex or changing the postmechanical rate of recovery from forward masking. A phenomenological computer model of forward masking with efferent control was used to explain the data. The model supports the hypothesis that the behavioral results were due to the contralateral noise reducing apical cochlear gain in a frequency- and level-dependent manner consistent with physiological evidence. Altogether, this shows that the contralateral MOCR may be changing apical cochlear responses in natural, binaural listening situations.
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Affiliation(s)
- Enzo Aguilar
- />Instituto de Neurociencias de Castilla y León and Instituto de Investigaciones Biomédicas de Salamanca, Universidad de Salamanca, Calle Pintor Fernando Gallego 1, 37007 Salamanca, Spain
| | - Almudena Eustaquio-Martin
- />Instituto de Neurociencias de Castilla y León and Instituto de Investigaciones Biomédicas de Salamanca, Universidad de Salamanca, Calle Pintor Fernando Gallego 1, 37007 Salamanca, Spain
| | - Enrique A. Lopez-Poveda
- />Instituto de Neurociencias de Castilla y León and Instituto de Investigaciones Biomédicas de Salamanca, Universidad de Salamanca, Calle Pintor Fernando Gallego 1, 37007 Salamanca, Spain
- />Departamento de Cirugía, Facultad de Medicina, Universidad de Salamanca, 37007 Salamanca, Spain
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Auditory enhancement of increments in spectral amplitude stems from more than one source. J Assoc Res Otolaryngol 2012; 13:693-702. [PMID: 22766695 DOI: 10.1007/s10162-012-0339-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 06/13/2012] [Indexed: 10/28/2022] Open
Abstract
A component of a test sound consisting of simultaneous pure tones perceptually "pops out" if the test sound is preceded by a copy of itself with that component attenuated. Although this "enhancement" effect was initially thought to be purely monaural, it is also observable when the test sound and the precursor sound are presented contralaterally (i.e., to opposite ears). In experiment 1, we assessed the magnitude of ipsilateral and contralateral enhancement as a function of the time interval between the precursor and test sounds (10, 100, or 600 ms). The test sound, randomly transposed in frequency from trial to trial, was followed by a probe tone, either matched or mismatched in frequency to the test sound component which was the target of enhancement. Listeners' ability to discriminate matched probes from mismatched probes was taken as an index of enhancement magnitude. The results showed that enhancement decays more rapidly for ipsilateral than for contralateral precursors, suggesting that ipsilateral enhancement and contralateral enhancement stem from at least partly different sources. It could be hypothesized that, in experiment 1, contralateral precursors were effective only because they provided attentional cues about the target tone frequency. In experiment 2, this hypothesis was tested by presenting the probe tone before the precursor sound rather than after the test sound. Although the probe tone was then serving as a frequency cue, contralateral precursors were again found to produce enhancement. This indicates that contralateral enhancement cannot be explained by cuing alone and is a genuine sensory phenomenon.
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Zhao W, Dhar S. Frequency tuning of the contralateral medial olivocochlear reflex in humans. J Neurophysiol 2012; 108:25-30. [PMID: 22457463 DOI: 10.1152/jn.00051.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of the medial olivocochlear (MOC) efferents attenuates cochlear gain and reduces the amplitudes of mechanical, electrical, and neural cochlear outputs. The functional roles of the MOC efferents are not fully understood, especially in humans, despite postulations that they are involved in protection against acoustic trauma, facilitation of transient-sound perception, etc. Delineating the frequency tuning properties of the MOC efferents would provide critical evidence to support or refute these postulated functional roles. By utilizing spontaneous otoacoustic emissions (SOAEs), a cochlear measure sensitive to MOC modulation, we systematically demonstrate in humans that the contralateral MOC reflex is tuned to a fixed frequency band between 500 and 1,000 Hz independent of SOAE frequency. Our results question the role of the MOC reflex in protection against acoustic trauma or facilitation of transient-sound perception.
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Affiliation(s)
- Wei Zhao
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois, USA.
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