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Parida S, Yurasits K, Cancel VE, Zink ME, Mitchell C, Ziliak MC, Harrison AV, Bartlett EL, Parthasarathy A. Rapid and objective assessment of auditory temporal processing using dynamic amplitude-modulated stimuli. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.28.577641. [PMID: 38352339 PMCID: PMC10862703 DOI: 10.1101/2024.01.28.577641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Auditory neural coding of speech-relevant temporal cues can be noninvasively probed using envelope following responses (EFRs), neural ensemble responses phase-locked to the stimulus amplitude envelope. EFRs emphasize different neural generators, such as the auditory brainstem or auditory cortex, by altering the temporal modulation rate of the stimulus. EFRs can be an important diagnostic tool to assess auditory neural coding deficits that go beyond traditional audiometric estimations. Existing approaches to measure EFRs use discrete amplitude modulated (AM) tones of varying modulation frequencies, which is time consuming and inefficient, impeding clinical translation. Here we present a faster and more efficient framework to measure EFRs across a range of AM frequencies using stimuli that dynamically vary in modulation rates, combined with spectrally specific analyses that offer optimal spectrotemporal resolution. EFRs obtained from several species (humans, Mongolian gerbils, Fischer-344 rats, and Cba/CaJ mice) showed robust, high-SNR tracking of dynamic AM trajectories (up to 800Hz in humans, and 1.4 kHz in rodents), with a fivefold decrease in recording time and thirtyfold increase in spectrotemporal resolution. EFR amplitudes between dynamic AM stimuli and traditional discrete AM tokens within the same subjects were highly correlated (94% variance explained) across species. Hence, we establish a time-efficient and spectrally specific approach to measure EFRs. These results could yield novel clinical diagnostics for precision audiology approaches by enabling rapid, objective assessment of temporal processing along the entire auditory neuraxis.
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Affiliation(s)
- Satyabrata Parida
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kimberly Yurasits
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Victoria E. Cancel
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Maggie E. Zink
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Claire Mitchell
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Meredith C. Ziliak
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Audrey V. Harrison
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Edward L. Bartlett
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN, USA
| | - Aravindakshan Parthasarathy
- Department of Communication Science and Disorders, University of Pittsburgh, Pittsburgh, PA, USA
- Department of BioEngineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA
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Lai J, Alain C, Bidelman GM. Cortical-brainstem interplay during speech perception in older adults with and without hearing loss. Front Neurosci 2023; 17:1075368. [PMID: 36816123 PMCID: PMC9932544 DOI: 10.3389/fnins.2023.1075368] [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: 10/20/2022] [Accepted: 01/17/2023] [Indexed: 02/05/2023] Open
Abstract
Introduction Real time modulation of brainstem frequency-following responses (FFRs) by online changes in cortical arousal state via the corticofugal (top-down) pathway has been demonstrated previously in young adults and is more prominent in the presence of background noise. FFRs during high cortical arousal states also have a stronger relationship with speech perception. Aging is associated with increased auditory brain responses, which might reflect degraded inhibitory processing within the peripheral and ascending pathways, or changes in attentional control regulation via descending auditory pathways. Here, we tested the hypothesis that online corticofugal interplay is impacted by age-related hearing loss. Methods We measured EEG in older adults with normal-hearing (NH) and mild to moderate hearing-loss (HL) while they performed speech identification tasks in different noise backgrounds. We measured α power to index online cortical arousal states during task engagement. Subsequently, we split brainstem speech-FFRs, on a trial-by-trial basis, according to fluctuations in concomitant cortical α power into low or high α FFRs to index cortical-brainstem modulation. Results We found cortical α power was smaller in the HL than the NH group. In NH listeners, α-FFRs modulation for clear speech (i.e., without noise) also resembled that previously observed in younger adults for speech in noise. Cortical-brainstem modulation was further diminished in HL older adults in the clear condition and by noise in NH older adults. Machine learning classification showed low α FFR frequency spectra yielded higher accuracy for classifying listeners' perceptual performance in both NH and HL participants. Moreover, low α FFRs decreased with increased hearing thresholds at 0.5-2 kHz for clear speech but noise generally reduced low α FFRs in the HL group. Discussion Collectively, our study reveals cortical arousal state actively shapes brainstem speech representations and provides a potential new mechanism for older listeners' difficulties perceiving speech in cocktail party-like listening situations in the form of a miss-coordination between cortical and subcortical levels of auditory processing.
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Affiliation(s)
- Jesyin Lai
- Institute for Intelligent Systems, University of Memphis, Memphis, TN, United States,School of Communication Sciences and Disorders, University of Memphis, Memphis, TN, United States,Department of Diagnostic Imaging, St. Jude Children’s Research Hospital, Memphis, TN, United States
| | - Claude Alain
- Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto, ON, Canada,Department of Psychology, University of Toronto, Toronto, ON, Canada
| | - Gavin M. Bidelman
- Institute for Intelligent Systems, University of Memphis, Memphis, TN, United States,School of Communication Sciences and Disorders, University of Memphis, Memphis, TN, United States,Department of Speech, Language, and Hearing Sciences, Indiana University, Bloomington, IN, United States,Program in Neuroscience, Indiana University, Bloomington, IN, United States,*Correspondence: Gavin M. Bidelman,
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Märcher-Rørsted J, Encina-Llamas G, Dau T, Liberman MC, Wu PZ, Hjortkjær J. Age-related reduction in frequency-following responses as a potential marker of cochlear neural degeneration. Hear Res 2021; 414:108411. [PMID: 34929535 DOI: 10.1016/j.heares.2021.108411] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/28/2022]
Abstract
Healthy aging may be associated with neural degeneration in the cochlea even before clinical hearing loss emerges. Reduction in frequency-following responses (FFRs) to tonal carriers in older clinically normal-hearing listeners has previously been reported, and has been argued to reflect an age-dependent decline in temporal processing in the central auditory system. Alternatively, age-dependent loss of auditory nerve fibers (ANFs) may have little effect on audiometric sensitivity and yet compromise the precision of neural phase-locking relying on joint activity across populations of fibers. This peripheral loss may, in turn, contribute to reduced neural synchrony in the brainstem as reflected in the FFR. Here, we combined human electrophysiology and auditory nerve (AN) modeling to investigate whether age-related changes in the FFR would be consistent with peripheral neural degeneration. FFRs elicited by pure tones and frequency sweeps at carrier frequencies between 200 and 1200 Hz were obtained in older (ages 48-76) and younger (ages 20-30) listeners, both groups having clinically normal audiometric thresholds up to 6 kHz. The same stimuli were presented to a computational model of the AN in which age-related loss of hair cells or ANFs was modelled using human histopathological data. In the older human listeners, the measured FFRs to both sweeps and pure tones were found to be reduced across the carrier frequencies examined. These FFR reductions were consistent with model simulations of age-related ANF loss. In model simulations, the phase-locked response produced by the population of remaining fibers decreased proportionally with increasing loss of the ANFs. Basal-turn loss of inner hair cells also reduced synchronous activity at lower frequencies, albeit to a lesser degree. Model simulations of age-related threshold elevation further indicated that outer hair cell dysfunction had no negative effect on phase-locked AN responses. These results are consistent with a peripheral source of the FFR reductions observed in older normal-hearing listeners, and indicate that FFRs at lower carrier frequencies may potentially be a sensitive marker of peripheral neural degeneration.
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Affiliation(s)
- Jonatan Märcher-Rørsted
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - Gerard Encina-Llamas
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - Torsten Dau
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - M Charles Liberman
- Eaton-Peabody Laboratories and Department of Otolaryngology, Head and Neck Surgery, Massachusetts Eye and Ear, Boston, MA 02114 USA
| | - Pei-Zhe Wu
- Eaton-Peabody Laboratories and Department of Otolaryngology, Head and Neck Surgery, Massachusetts Eye and Ear, Boston, MA 02114 USA
| | - Jens Hjortkjær
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Kettegård Allé 30, DK-2650 Hvidovre, Denmark.
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Patro C, Kreft HA, Wojtczak M. The search for correlates of age-related cochlear synaptopathy: Measures of temporal envelope processing and spatial release from speech-on-speech masking. Hear Res 2021; 409:108333. [PMID: 34425347 PMCID: PMC8424701 DOI: 10.1016/j.heares.2021.108333] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 07/17/2021] [Accepted: 08/04/2021] [Indexed: 01/13/2023]
Abstract
Older adults often experience difficulties understanding speech in adverse listening conditions. It has been suggested that for listeners with normal and near-normal audiograms, these difficulties may, at least in part, arise from age-related cochlear synaptopathy. The aim of this study was to assess if performance on auditory tasks relying on temporal envelope processing reveal age-related deficits consistent with those expected from cochlear synaptopathy. Listeners aged 20 to 66 years were tested using a series of psychophysical, electrophysiological, and speech-perception measures using stimulus configurations that promote coding by medium- and low-spontaneous-rate auditory-nerve fibers. Cognitive measures of executive function were obtained to control for age-related cognitive decline. Results from the different tests were not significantly correlated with each other despite a presumed reliance on common mechanisms involved in temporal envelope processing. Only gap-detection thresholds for a tone in noise and spatial release from speech-on-speech masking were significantly correlated with age. Increasing age was related to impaired cognitive executive function. Multivariate regression analyses showed that individual differences in hearing sensitivity, envelope-based measures, and scores from nonauditory cognitive tests did not significantly contribute to the variability in spatial release from speech-on-speech masking for small target/masker spatial separation, while age was a significant contributor.
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Affiliation(s)
- Chhayakanta Patro
- Department of Psychology, University of Minnesota, N640 Elliott Hall, 75 East River Parkway, Minneapolis, MN 55455, USA.
| | - Heather A Kreft
- Department of Psychology, University of Minnesota, N640 Elliott Hall, 75 East River Parkway, Minneapolis, MN 55455, USA
| | - Magdalena Wojtczak
- Department of Psychology, University of Minnesota, N640 Elliott Hall, 75 East River Parkway, Minneapolis, MN 55455, USA
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Encina-Llamas G, Dau T, Epp B. On the use of envelope following responses to estimate peripheral level compression in the auditory system. Sci Rep 2021; 11:6962. [PMID: 33772043 PMCID: PMC7997911 DOI: 10.1038/s41598-021-85850-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/08/2021] [Indexed: 12/22/2022] Open
Abstract
Individual estimates of cochlear compression may provide complementary information to traditional audiometric hearing thresholds in disentangling different types of peripheral cochlear damage. Here we investigated the use of the slope of envelope following response (EFR) magnitude-level functions obtained from four simultaneously presented amplitude modulated tones with modulation frequencies of 80-100 Hz as a proxy of peripheral level compression. Compression estimates in individual normal hearing (NH) listeners were consistent with previously reported group-averaged compression estimates based on psychoacoustical and distortion-product oto-acoustic emission (DPOAE) measures in human listeners. They were also similar to basilar membrane (BM) compression values measured invasively in non-human mammals. EFR-based compression estimates in hearing-impaired listeners were less compressive than those for the NH listeners, consistent with a reduction of BM compression. Cochlear compression was also estimated using DPOAEs in the same NH listeners. DPOAE estimates were larger (less compressive) than EFRs estimates, showing no correlation. Despite the numerical concordance between EFR-based compression estimates and group-averaged estimates from other methods, simulations using an auditory nerve (AN) model revealed that compression estimates based on EFRs might be highly influenced by contributions from off-characteristic frequency (CF) neural populations. This compromises the possibility to estimate on-CF (i.e., frequency-specific or "local") peripheral level compression with EFRs.
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Affiliation(s)
- Gerard Encina-Llamas
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark (DTU), 2800, Kongens Lyngby, Denmark.
| | - Torsten Dau
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark (DTU), 2800, Kongens Lyngby, Denmark
| | - Bastian Epp
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark (DTU), 2800, Kongens Lyngby, Denmark
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Parthasarathy A, Hancock KE, Bennett K, DeGruttola V, Polley DB. Bottom-up and top-down neural signatures of disordered multi-talker speech perception in adults with normal hearing. eLife 2020; 9:e51419. [PMID: 31961322 PMCID: PMC6974362 DOI: 10.7554/elife.51419] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 12/15/2019] [Indexed: 12/16/2022] Open
Abstract
In social settings, speech waveforms from nearby speakers mix together in our ear canals. Normally, the brain unmixes the attended speech stream from the chorus of background speakers using a combination of fast temporal processing and cognitive active listening mechanisms. Of >100,000 patient records,~10% of adults visited our clinic because of reduced hearing, only to learn that their hearing was clinically normal and should not cause communication difficulties. We found that multi-talker speech intelligibility thresholds varied widely in normal hearing adults, but could be predicted from neural phase-locking to frequency modulation (FM) cues measured with ear canal EEG recordings. Combining neural temporal fine structure processing, pupil-indexed listening effort, and behavioral FM thresholds accounted for 78% of the variability in multi-talker speech intelligibility. The disordered bottom-up and top-down markers of poor multi-talker speech perception identified here could inform the design of next-generation clinical tests for hidden hearing disorders.
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Affiliation(s)
- Aravindakshan Parthasarathy
- Eaton-Peabody LaboratoriesMassachusetts Eye and Ear InfirmaryBostonUnited States
- Department of Otolaryngology – Head and Neck SurgeryHarvard Medical SchoolBostonUnited States
| | - Kenneth E Hancock
- Eaton-Peabody LaboratoriesMassachusetts Eye and Ear InfirmaryBostonUnited States
- Department of Otolaryngology – Head and Neck SurgeryHarvard Medical SchoolBostonUnited States
| | - Kara Bennett
- Bennett Statistical Consulting IncBallstonUnited States
| | - Victor DeGruttola
- Department of BiostatisticsHarvard TH Chan School of Public HealthBostonUnited States
| | - Daniel B Polley
- Eaton-Peabody LaboratoriesMassachusetts Eye and Ear InfirmaryBostonUnited States
- Department of Otolaryngology – Head and Neck SurgeryHarvard Medical SchoolBostonUnited States
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7
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Encina-Llamas G, Harte JM, Dau T, Shinn-Cunningham B, Epp B. Investigating the Effect of Cochlear Synaptopathy on Envelope Following Responses Using a Model of the Auditory Nerve. J Assoc Res Otolaryngol 2019; 20:363-382. [PMID: 31102010 PMCID: PMC6646444 DOI: 10.1007/s10162-019-00721-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 04/08/2019] [Indexed: 12/16/2022] Open
Abstract
The healthy auditory system enables communication in challenging situations with high levels of background noise. Yet, despite normal sensitivity to pure tones, many listeners complain about having difficulties in such situations. Recent animal studies demonstrated that noise overexposure that produces temporary threshold shifts can cause the loss of auditory nerve (AN) fiber synapses (i.e., cochlear synaptopathy, CS), which appears to predominantly affect medium- and low-spontaneous rate (SR) fibers. In the present study, envelope following response (EFR) magnitude-level functions were recorded in normal hearing (NH) threshold and mildly hearing-impaired (HI) listeners with thresholds elevated above 2 kHz. EFRs were elicited by sinusoidally amplitude modulated (SAM) tones presented in quiet with a carrier frequency of 2 kHz, modulated at 93 Hz, and modulation depths of 0.85 (deep) and 0.25 (shallow). While EFR magnitude-level functions for deeply modulated tones were similar for all listeners, EFR magnitudes for shallowly modulated tones were reduced at medium stimulation levels in some NH threshold listeners and saturated in all HI listeners for the whole level range. A phenomenological model of the AN was used to investigate the extent to which hair-cell dysfunction and/or CS could explain the trends observed in the EFR data. Hair-cell dysfunction alone, including postulated elevated hearing thresholds at extended high frequencies (EHF) beyond 8 kHz, could not account for the recorded EFR data. Postulated CS led to simulations generally consistent with the recorded data, but a loss of all types of AN fibers was required within the model framework. The effects of off-frequency contributions (i.e., away from the characteristic place of the stimulus) and the differential loss of different AN fiber types on EFR magnitude-level functions were analyzed. When using SAM tones in quiet as the stimulus, model simulations suggested that (1) EFRs are dominated by the activity of high-SR fibers at all stimulus intensities, and (2) EFRs at medium-to-high stimulus levels are dominated by off-frequency contributions.
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Affiliation(s)
- Gerard Encina-Llamas
- Hearing Systems section, Department of Health Technology, Technical University of Denmark (DTU), Kongens Lyngby, Denmark.
| | - James M Harte
- Interacoustics Research Unit, Kongens Lyngby, Denmark
| | - Torsten Dau
- Hearing Systems section, Department of Health Technology, Technical University of Denmark (DTU), Kongens Lyngby, Denmark
| | - Barbara Shinn-Cunningham
- Carnegie Mellon Neuroscience Institute, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Bastian Epp
- Hearing Systems section, Department of Health Technology, Technical University of Denmark (DTU), Kongens Lyngby, Denmark
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Parthasarathy A, Bartlett EL, Kujawa SG. Age-related Changes in Neural Coding of Envelope Cues: Peripheral Declines and Central Compensation. Neuroscience 2019; 407:21-31. [DOI: 10.1016/j.neuroscience.2018.12.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 11/30/2018] [Accepted: 12/03/2018] [Indexed: 12/22/2022]
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Kommajosyula SP, Cai R, Bartlett E, Caspary DM. Top-down or bottom up: decreased stimulus salience increases responses to predictable stimuli of auditory thalamic neurons. J Physiol 2019; 597:2767-2784. [PMID: 30924931 DOI: 10.1113/jp277450] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 03/25/2019] [Indexed: 01/29/2023] Open
Abstract
KEY POINTS Temporal imprecision leads to deficits in the comprehension of signals in cluttered acoustic environments, and the elderly are shown to use cognitive resources to disambiguate these signals. To mimic ageing in young rats, we delivered sound signals that are temporally degraded, which led to temporally imprecise neural codes. Instead of adaptation to repeated stimuli, with degraded signals, there was a relative increase in firing rates, similar to that seen in aged rats. We interpret this increase with repetition as a repair mechanism for strengthening the internal representations of degraded signals by the higher-order structures. ABSTRACT To better understand speech in challenging environments, older adults increasingly use top-down cognitive and contextual resources. The medial geniculate body (MGB) integrates ascending inputs with descending predictions to dynamically gate auditory representations based on salience and context. A previous MGB single-unit study found an increased preference for predictable sinusoidal amplitude modulated (SAM) stimuli in aged rats relative to young rats. The results suggested that the age-degraded/jittered up-stream acoustic code may engender an increased preference for predictable/repeating acoustic signals, possibly reflecting increased use of top-down resources. In the present study, we recorded from units in young-adult MGB, comparing responses to standard SAM with those evoked by less salient SAM (degraded) stimuli. We hypothesized that degrading the SAM stimulus would simulate the degraded ascending acoustic code seen in the elderly, increasing the preference for predictable stimuli. Single units were recorded from clusters of advanceable tetrodes implanted above the MGB of young-adult awake rats. Less salient SAM significantly increased the preference for predictable stimuli, especially at higher modulation frequencies. Rather than adaptation, higher modulation frequencies elicited increased numbers of spikes with each successive trial/repeat of the less salient SAM. These findings are consistent with previous findings obtained in aged rats suggesting that less salient acoustic signals engage the additional use of top-down resources, as reflected by an increased preference for repeating stimuli that enhance the representation of complex environmental/communication sounds.
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Affiliation(s)
- Srinivasa P Kommajosyula
- Southern Illinois University School of Medicine, , Department of Pharmacology, Springfield, IL, USA
| | - Rui Cai
- Southern Illinois University School of Medicine, , Department of Pharmacology, Springfield, IL, USA
| | - Edward Bartlett
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Donald M Caspary
- Southern Illinois University School of Medicine, , Department of Pharmacology, Springfield, IL, USA
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Parthasarathy A, Herrmann B, Bartlett EL. Aging alters envelope representations of speech-like sounds in the inferior colliculus. Neurobiol Aging 2018; 73:30-40. [PMID: 30316050 DOI: 10.1016/j.neurobiolaging.2018.08.023] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 08/13/2018] [Accepted: 08/27/2018] [Indexed: 11/29/2022]
Abstract
Hearing impairment in older people is thought to arise from impaired temporal processing in auditory circuits. We used a systems-level (scalp recordings) and a microcircuit-level (extracellular recordings) approach to investigate how aging affects the sensitivity to temporal envelopes of speech-like sounds in rats. Scalp-recorded potentials suggest an age-related increase in sensitivity to temporal regularity along the ascending auditory pathway. The underlying cellular changes in the midbrain were examined using extracellular recordings from inferior colliculus neurons. We observed an age-related increase in sensitivity to the sound's onset and temporal regularity (i.e., periodicity envelope) in the spiking output of inferior colliculus neurons, relative to their synaptic inputs (local field potentials). This relative enhancement for aged animals was most prominent for multi-unit (relative to single-unit) spiking activity. Spontaneous multi-unit, but not single-unit, activity was also enhanced in aged compared with young animals. Our results suggest that aging is associated with altered sensitivity to a sound's temporal regularities, and that these effects may be due to increased gain of neural network activity in the midbrain.
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Affiliation(s)
- Aravindakshan Parthasarathy
- Departments of Biological Sciences and Biomedical Engineering, Purdue University, West Lafayette, IN, USA; Department of Otolaryngology, Harvard Medical School, and Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
| | - Björn Herrmann
- Department of Psychology & Brain and Mind Institute, The University of Western Ontario, London, Ontario, Canada
| | - Edward L Bartlett
- Departments of Biological Sciences and Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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Lai J, Bartlett EL. Masking Differentially Affects Envelope-following Responses in Young and Aged Animals. Neuroscience 2018; 386:150-165. [PMID: 29953908 PMCID: PMC6076866 DOI: 10.1016/j.neuroscience.2018.06.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 05/31/2018] [Accepted: 06/04/2018] [Indexed: 11/21/2022]
Abstract
Age-related hearing decline typically includes threshold shifts as well as reduced wave I auditory brainstem response (ABR) amplitudes due to cochlear synaptopathy/neuropathy, which may compromise precise coding of suprathreshold speech envelopes. This is supported by findings with older listeners, who have difficulties in envelope and speech processing, especially in noise. However, separating the effects of threshold elevation, synaptopathy, and degradation by noise on physiological representations may be difficult. In the present study, the effects of notched, low- and high-pass noise on envelope-following responses (EFRs) in aging were compared when sound levels (aged: 85-dB SPL; young: 60- to 80-dB SPL) were matched between groups peripherally, by matching wave I ABR amplitudes, or centrally by matching EFR amplitudes. Low-level notched noise reduced EFRs to sinusoidally amplitude-modulated (SAM) tones in young animals for notch widths up to 2 octaves. High-pass noise above the carrier frequency reduced EFRs. Young animals showed EFR reductions at lower noise levels. Low-pass noise did not reduce EFRs in either young or aged animals. High-pass noise may affect EFR amplitudes in young animals more than aged by reducing the contributions of high-frequency-sensitive inputs. EFRs to SAM tones in modulated noise (NAM) suggest that neurons of young animals can synchronize to NAM at lower sound levels and maintain dual AM representations better than older animals. The overall results show that EFR amplitudes are strongly influenced by aging and the presence of a competing sound that likely reduces or shifts the pool of responsive neurons.
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Affiliation(s)
- Jesyin Lai
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA; Oregon Hearing Research Center, Oregon Health and Science University, Portland, OR 97239, USA
| | - Edward L Bartlett
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
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Synaptopathy in the Aging Cochlea: Characterizing Early-Neural Deficits in Auditory Temporal Envelope Processing. J Neurosci 2018; 38:7108-7119. [PMID: 29976623 DOI: 10.1523/jneurosci.3240-17.2018] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 06/27/2018] [Accepted: 06/28/2018] [Indexed: 12/12/2022] Open
Abstract
Aging listeners, even in the absence of overt hearing loss measured as changes in hearing thresholds, often experience impairments processing temporally complex sounds such as speech in noise. Recent evidence has shown that normal aging is accompanied by a progressive loss of synapses between inner hair cells and auditory nerve fibers. The role of this cochlear synaptopathy in degraded temporal processing with age is not yet understood. Here, we used population envelope following responses, along with other hair cell- and neural-based measures from an age-graded series of male and female CBA/CaJ mice to study changes in encoding stimulus envelopes. By comparing responses obtained before and after the application of the neurotoxin ouabain to the inner ear, we demonstrate that we can study changes in temporal processing on either side of the cochlear synapse. Results show that deficits in neural coding with age emerge at the earliest neural stages of auditory processing and are correlated with the degree of cochlear synaptopathy. These changes are seen before losses in neural thresholds and particularly affect the suprathreshold processing of sound. Responses obtained from more central sources show smaller differences with age, suggesting compensatory gain. These results show that progressive cochlear synaptopathy is accompanied by deficits in temporal coding at the earliest neural generators and contribute to the suprathreshold sound processing deficits observed with age.SIGNIFICANCE STATEMENT Aging listeners often experience difficulty hearing and understanding speech in noisy conditions. The results described here suggest that age-related loss of cochlear synapses may be a significant contributor to those performance declines. We observed aberrant neural coding of sounds in the early auditory pathway, which was accompanied by and correlated with an age-progressive loss of synapses between the inner hair cells and the auditory nerve. Deficits first appeared before changes in hearing thresholds and were largest at higher sound levels relevant to real world communication. The noninvasive tests described here may be adapted to detect cochlear synaptopathy in the clinical setting.
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Yao JD, Sanes DH. Developmental deprivation-induced perceptual and cortical processing deficits in awake-behaving animals. eLife 2018; 7:33891. [PMID: 29873632 PMCID: PMC6005681 DOI: 10.7554/elife.33891] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 06/04/2018] [Indexed: 01/02/2023] Open
Abstract
Sensory deprivation during development induces lifelong changes to central nervous system function that are associated with perceptual impairments. However, the relationship between neural and behavioral deficits is uncertain due to a lack of simultaneous measurements during task performance. Therefore, we telemetrically recorded from auditory cortex neurons in gerbils reared with developmental conductive hearing loss as they performed an auditory task in which rapid fluctuations in amplitude are detected. These data were compared to a measure of auditory brainstem temporal processing from each animal. We found that developmental HL diminished behavioral performance, but did not alter brainstem temporal processing. However, the simultaneous assessment of neural and behavioral processing revealed that perceptual deficits were associated with a degraded cortical population code that could be explained by greater trial-to-trial response variability. Our findings suggest that the perceptual limitations that attend early hearing loss are best explained by an encoding deficit in auditory cortex.
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Affiliation(s)
- Justin D Yao
- Center for Neural Science, New York University, New York, United States
| | - Dan H Sanes
- Center for Neural Science, New York University, New York, United States.,Department of Psychology, New York University, New York, United States.,Department of Biology, New York University, New York, United States.,Neuroscience Institute, NYU Langone Medical Center, New York, United States
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Lai J, Sommer AL, Bartlett EL. Age-related changes in envelope-following responses at equalized peripheral or central activation. Neurobiol Aging 2017; 58:191-200. [PMID: 28753474 PMCID: PMC5581704 DOI: 10.1016/j.neurobiolaging.2017.06.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 06/18/2017] [Accepted: 06/18/2017] [Indexed: 11/20/2022]
Abstract
Previous work has debated about the comparisons of hearing abilities faced with alterations in hearing thresholds and evoked potentials between groups following acoustic trauma- or age-related changes. This study compares envelope-following responses (EFRs) of young and aged rats when sound levels were matched according to (1) wave I amplitudes of auditory brainstem responses (ABRs) elicited by 8-kHz tones or (2) EFR amplitudes evoked by sinusoidally amplitude-modulated (SAM) tones at 100% depth. Matched wave I amplitudes across age corresponded to approximately 20-dB sound level differences. For matched wave I, no age-related differences were observed in wave V amplitudes. However, EFRs recorded in silence were enhanced with aging at 100% but not at 25% depth, consistent with enhanced central gain in aging. For matched EFRs, there were no age-related differences in EFRs of amplitude modulation (AM) depth and AM frequency processing. These results suggest novel, objective measures beyond threshold to compensate for differences in auditory nerve activation and to differentiate peripheral and central contributions of EFRs.
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Affiliation(s)
- Jesyin Lai
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Alexandra L Sommer
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Edward L Bartlett
- Department of Biological Sciences and the Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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Responses to Predictable versus Random Temporally Complex Stimuli from Single Units in Auditory Thalamus: Impact of Aging and Anesthesia. J Neurosci 2017; 36:10696-10706. [PMID: 27733619 DOI: 10.1523/jneurosci.1454-16.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 08/27/2016] [Indexed: 12/12/2022] Open
Abstract
Human aging studies suggest that an increased use of top-down knowledge-based resources would compensate for degraded upstream acoustic information to accurately identify important temporally rich signals. Sinusoidal amplitude-modulated (SAM) stimuli have been used to mimic the fast-changing temporal features in speech and species-specific vocalizations. Single units were recorded from auditory thalamus [medial geniculate body (MGB)] of young awake, aged awake, young anesthetized, and aged anesthetized rats. SAM stimuli were modulated between 2 and 1024 Hz with the modulation frequency (fm) changed randomly (RAN) across trials or sequentially (SEQ) after several repeated trials. Units were found to be RAN-preferring, SEQ-preferring, or nonselective based on total firing rate. Significant anesthesia and age effects were found. The majority (86%) of young anesthetized units preferred RAN SAM stimuli; significantly fewer young awake units (51%, p < 0.0001) preferred RAN SAM signals with 16% preferring SEQ SAM. Compared with young awake units, there was a significant increase of aged awake units preferring SEQ SAM (30%, p < 0.05). We examined RAN versus SEQ differences across fms by measuring selective fm areas under the rate modulation transfer function curve. The largest age-related differences from awake animals were found for mid-to-high fms in MGB units, with young units preferring RAN SAM while aged units showed a greater preference for SEQ-presented SAM. Together, these findings suggest that aged MGB units/animals employ increased top-down mediated stimulus context to enhance processing of "expected" temporally rich stimuli, especially at more challenging higher fms. SIGNIFICANCE STATEMENT Older individuals compensate for impaired ascending acoustic information by increasing use of cortical cognitive and attentional resources. The interplay between ascending and descending influences in the thalamus may serve to enhance the salience of speech signals that are degraded as they ascend to the cortex. The present findings demonstrate that medial geniculate body units from awake rats show an age-related preference for predictable modulated signals relative to randomly presented signals, especially at higher, more challenging modulation frequencies. Conversely, units from anesthetized animals, with little top-down influences, strongly preferred randomly presented modulated sequences. These results suggest a neuronal substrate for an age-related increase in experience/attentional-based influences in processing temporally complex auditory information in the auditory thalamus.
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