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Gransier R, Carlyon RP, Richardson ML, Middlebrooks JC, Wouters J. Artifact removal by template subtraction enables recordings of the frequency following response in cochlear-implant users. Sci Rep 2024; 14:6158. [PMID: 38486005 PMCID: PMC10940306 DOI: 10.1038/s41598-024-56047-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 03/01/2024] [Indexed: 03/18/2024] Open
Abstract
Electrically evoked frequency-following responses (eFFRs) provide insight in the phase-locking ability of brainstem of cochlear-implant (CI) users. eFFRs can potentially be used to gain insight in the individual differences in the biological limitation on temporal encoding of the electrically stimulated auditory pathway, which can be inherent to the electrical stimulation itself and/or the degenerative processes associated with hearing loss. One of the major challenge of measuring eFFRs in CI users is the process of isolating the stimulation artifact from the neural response, as both the response and the artifact overlap in time and have similar frequency characteristics. Here we introduce a new artifact removal method based on template subtraction that successfully removes the stimulation artifacts from the recordings when CI users are stimulated with pulse trains from 128 to 300 pulses per second in a monopolar configuration. Our results show that, although artifact removal was successful in all CI users, the phase-locking ability of the brainstem to the different pulse rates, as assessed with the eFFR differed substantially across participants. These results show that the eFFR can be measured, free from artifacts, in CI users and that they can be used to gain insight in individual differences in temporal processing of the electrically stimulated auditory pathway.
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Affiliation(s)
- Robin Gransier
- ExpORL, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, UK
| | - Matthew L Richardson
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
- Center for Hearing Research, University of California at Irvine, Irvine, CA, USA
| | - John C Middlebrooks
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
- Center for Hearing Research, University of California at Irvine, Irvine, CA, USA
- Departments of Neurobiology and Behavior, Biomedical Engineering, Cognitive Sciences, University of California at Irvine, Irvine, CA, USA
| | - Jan Wouters
- ExpORL, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium.
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Lu H, Mehta AH, Oxenham AJ. Methodological considerations when measuring and analyzing auditory steady-state responses with multi-channel EEG. CURRENT RESEARCH IN NEUROBIOLOGY 2022; 3:100061. [PMID: 36386860 PMCID: PMC9647176 DOI: 10.1016/j.crneur.2022.100061] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 07/11/2022] [Accepted: 10/19/2022] [Indexed: 11/06/2022] Open
Abstract
The auditory steady-state response (ASSR) has been traditionally recorded with few electrodes and is often measured as the voltage difference between mastoid and vertex electrodes (vertical montage). As high-density EEG recording systems have gained popularity, multi-channel analysis methods have been developed to integrate the ASSR signal across channels. The phases of ASSR across electrodes can be affected by factors including the stimulus modulation rate and re-referencing strategy, which will in turn affect the estimated ASSR strength. To explore the relationship between the classical vertical-montage ASSR and whole-scalp ASSR, we applied these two techniques to the same data to estimate the strength of ASSRs evoked by tones with sinusoidal amplitude modulation rates of around 40, 100, and 200 Hz. The whole-scalp methods evaluated in our study, with either linked-mastoid or common-average reference, included ones that assume equal phase across all channels, as well as ones that allow for different phase relationships. The performance of simple averaging was compared to that of more complex methods involving principal component analysis. Overall, the root-mean-square of the phase locking values (PLVs) across all channels provided the most efficient method to detect ASSR across the range of modulation rates tested here.
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Affiliation(s)
- Hao Lu
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, MN, 55455, USA
| | - Anahita H. Mehta
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, MN, 55455, USA
| | - Andrew J. Oxenham
- Department of Psychology, University of Minnesota, 75 East River Parkway, Minneapolis, MN, 55455, USA
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Shader MJ, Luke R, McKay CM. Contralateral dominance to speech in the adult auditory cortex immediately after cochlear implantation. iScience 2022; 25:104737. [PMID: 35938045 PMCID: PMC9352526 DOI: 10.1016/j.isci.2022.104737] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/12/2022] [Accepted: 07/07/2022] [Indexed: 11/06/2022] Open
Abstract
Sensory deprivation causes structural and functional changes in the human brain. Cochlear implantation delivers immediate reintroduction of auditory sensory information. Previous reports have indicated that over a year is required for the brain to reestablish canonical cortical processing patterns after the reintroduction of auditory stimulation. We utilized functional near-infrared spectroscopy (fNIRS) to investigate brain activity to natural speech stimuli directly after cochlear implantation. We presented 12 cochlear implant recipients, who each had a minimum of 12 months of auditory deprivation, with unilateral auditory- and visual-speech stimuli. Regardless of the side of implantation, canonical responses were elicited primarily on the contralateral side of stimulation as early as 1 h after device activation. These data indicate that auditory pathway connections are sustained during periods of sensory deprivation in adults, and that typical cortical lateralization is observed immediately following the reintroduction of auditory sensory input.
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Affiliation(s)
- Maureen J. Shader
- Purdue University, Department of Speech, Language, and Hearing Sciences, 715 Clinic Drive, West Lafayette, IN 47907, USA
- The University of Melbourne, Department of Medical Bionics, Parkville, VIC 3010, Australia
| | - Robert Luke
- Bionics Institute, 384-388 Albert St, East Melbourne, VIC 3002, Australia
- Macquarie University, Department of Linguistics, Faculty of Medicine, Health and Human Sciences, Macquarie Hearing, NSW 2109, Australia
| | - Colette M. McKay
- Bionics Institute, 384-388 Albert St, East Melbourne, VIC 3002, Australia
- The University of Melbourne, Department of Medical Bionics, Parkville, VIC 3010, Australia
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Neural Modulation Transmission Is a Marker for Speech Perception in Noise in Cochlear Implant Users. Ear Hear 2021; 41:591-602. [PMID: 31567565 DOI: 10.1097/aud.0000000000000783] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Cochlear implants (CIs) restore functional hearing in persons with a severe hearing impairment. Despite being one of the most successful bionic prosthesis, performance with CI (in particular speech understanding in noise) varies considerably across its users. The ability of the auditory pathway to encode temporal envelope modulations (TEMs) and the effect of degenerative processes associated with hearing loss on TEM encoding is assumed to be one of the reasons underlying the large intersubject differences in CI performance. The objective of the present study was to investigate how TEM encoding of the stimulated neural ensembles of human CI recipients is related to speech perception in noise (SPIN). DESIGN We used electroencephalography as a noninvasive electrophysiological measure to assess TEM encoding in the auditory pathway of CI users by means of the 40-Hz electrically evoked auditory steady state response (EASSR). Nine CI users with a wide range of SPIN outcome were included in the present study. TEM encoding was assessed for each stimulation electrode of each subject and new metrics; the CI neural modulation transmission difference (CIMTD) and the CI neural modulation transmission index (CIMTI) were developed to quantify the amount of variability in TEM encoding across the stimulated neural ensembles of the CI electrode array. RESULTS EASSR patterns varied across the CI electrode array and subjects. We found a strong correlation (r = 0.89, p = 0.001) between the SPIN outcomes and the variability in EASSR amplitudes across the array as assessed with CIMTD/CIMTI. CONCLUSIONS The results of the present study show that the 40-Hz EASSR can be used to objectively assess the neural encoding of TEMs in human CI recipients. Overall reduced or largely variable TEM encoding of the neural ensembles across the electrode array, as quantified with the CIMTD/CIMTI, is highly correlated with speech perception in noise outcome with a CI.
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Gransier R, Carlyon RP, Wouters J. Electrophysiological assessment of temporal envelope processing in cochlear implant users. Sci Rep 2020; 10:15406. [PMID: 32958791 PMCID: PMC7506023 DOI: 10.1038/s41598-020-72235-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 08/18/2020] [Indexed: 11/12/2022] Open
Abstract
Cochlear-implant (CI) users rely on temporal envelope modulations (TEMs) to understand speech, and clinical outcomes depend on the accuracy with which these TEMs are encoded by the electrically-stimulated neural ensembles. Non-invasive EEG measures of this encoding could help clinicians identify and disable electrodes that evoke poor neural responses so as to improve CI outcomes. However, recording EEG during CI stimulation reveals huge stimulation artifacts that are up to orders of magnitude larger than the neural response. Here we used a custom-built EEG system having an exceptionally high sample rate to accurately measure the artefact, which we then removed using linear interpolation so as to reveal the neural response during continuous electrical stimulation. In ten adult CI users, we measured the 40-Hz electrically evoked auditory steady-state response (eASSR) and electrically evoked auditory change complex (eACC) to amplitude-modulated 900-pulses-per-second pulse trains, stimulated in monopolar mode (i.e. the clinical default), and at different modulation depths. We successfully measured artifact-free 40-Hz eASSRs and eACCs. Moreover, we found that the 40-Hz eASSR, in contrast to the eACC, showed substantial responses even at shallow modulation depths. We argue that the 40-Hz eASSR is a clinically feasible objective measure to assess TEM encoding in CI users.
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Affiliation(s)
- Robin Gransier
- Department of Neurosciences, KU Leuven, ExpORL, Herestraat 49, Box 721, 3000, Leuven, Belgium.
| | - Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| | - Jan Wouters
- Department of Neurosciences, KU Leuven, ExpORL, Herestraat 49, Box 721, 3000, Leuven, Belgium
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Deprez H, Gransier R, Hofmann M, van Wieringen A, Wouters J, Moonen M. Independent component analysis for cochlear implant artifacts attenuation from electrically evoked auditory steady-state response measurements. J Neural Eng 2019; 15:016006. [PMID: 29211684 DOI: 10.1088/1741-2552/aa87ce] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Electrically evoked auditory steady-state responses (EASSRs) are potentially useful for objective cochlear implant (CI) fitting and follow-up of the auditory maturation in infants and children with a CI. EASSRs are recorded in the electro-encephalogram (EEG) in response to electrical stimulation with continuous pulse trains, and are distorted by significant CI artifacts related to this electrical stimulation. The aim of this study is to evaluate a CI artifacts attenuation method based on independent component analysis (ICA) for three EASSR datasets. APPROACH ICA has often been used to remove CI artifacts from the EEG to record transient auditory responses, such as cortical evoked auditory potentials. Independent components (ICs) corresponding to CI artifacts are then often manually identified. In this study, an ICA based CI artifacts attenuation method was developed and evaluated for EASSR measurements with varying CI artifacts and EASSR characteristics. Artifactual ICs were automatically identified based on their spectrum. MAIN RESULTS For 40 Hz amplitude modulation (AM) stimulation at comfort level, in high SNR recordings, ICA succeeded in removing CI artifacts from all recording channels, without distorting the EASSR. For lower SNR recordings, with 40 Hz AM stimulation at lower levels, or 90 Hz AM stimulation, ICA either distorted the EASSR or could not remove all CI artifacts in most subjects, except for two of the seven subjects tested with low level 40 Hz AM stimulation. Noise levels were reduced after ICA was applied, and up to 29 ICs were rejected, suggesting poor ICA separation quality. SIGNIFICANCE We hypothesize that ICA is capable of separating CI artifacts and EASSR in case the contralateral hemisphere is EASSR dominated. For small EASSRs or large CI artifact amplitudes, ICA separation quality is insufficient to ensure complete CI artifacts attenuation without EASSR distortion.
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Affiliation(s)
- Hanne Deprez
- STADIUS Center for Dynamical Systems, Signal Processing and Data Analytics, Department of Electrical Engineering (ESAT), KU Leuven, Kasteelpark Arenberg 10 bus 2440, 3001 LEUVEN, Belgium. Experimental ORL, Department of Neurosciences, KU Leuven, Herestraat 49 bus 721, 3000 LEUVEN, Belgium
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Prado-Gutiérrez P, Otero M, Martínez-Montes E, Weinstein A, Escobar MJ, El-Deredy W, Zañartu M. A Method for Tracking the Time Evolution of Steady-State Evoked Potentials. J Vis Exp 2019. [PMID: 31180347 PMCID: PMC7055073 DOI: 10.3791/59898] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Neural entrainment refers to the synchronization of neural activity to the periodicity of sensory stimuli. This synchronization defines the generation of steady-state evoked responses (i.e., oscillations in the electroencephalogram phase-locked to the driving stimuli). The classic interpretation of the amplitude of the steady-state evoked responses assumes a stereotypical time-invariant neural response plus random background fluctuations, such that averaging over repeated presentations of the stimulus recovers the stereotypical response. This approach ignores the dynamics of the steady-state, as in the case of the adaptation elicited by prolonged exposures to the stimulus. To analyze the dynamics of steady-state responses, it can be assumed that the time evolution of the response amplitude is the same in different stimulation runs separated by sufficiently long breaks. Based on this assumption, a method to characterize the time evolution of steady-state responses is presented. A sufficiently large number of recordings are acquired in response to the same experimental condition. Experimental runs (recordings) are column-wise averaged (i.e., runs are averaged but epoch within recordings are not averaged with the preceding segments). The column-wise averaging allows analysis of steady-state responses in recordings with remarkably high signal-to-noise ratios. Therefore, the averaged signal provides an accurate representation of the time evolution of the steady-state response, which can be analyzed in both the time and frequency domains. In this study, a detailed description of the method is provided, using steady-state visually evoked potentials as an example of a response. Advantages and caveats are evaluated based on a comparison with single-trial methods designed to analyze neural entrainment.
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Affiliation(s)
- Pavel Prado-Gutiérrez
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María;
| | - Mónica Otero
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María; Department of Electronic Engineering, Universidad Técnica Federico Santa María
| | | | - Alejandro Weinstein
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María; Centro de Investigación y Desarrollo en IngenierÍa, Universidad de Valparaíso
| | - María-José Escobar
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María; Department of Electronic Engineering, Universidad Técnica Federico Santa María
| | - Wael El-Deredy
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María; Centro de Investigación y Desarrollo en IngenierÍa, Universidad de Valparaíso
| | - Matías Zañartu
- Advanced Center for Electrical and Electronic Engineering (AC3E), Universidad Técnica Federico Santa María; Department of Electronic Engineering, Universidad Técnica Federico Santa María
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Abstract
OBJECTIVES Auditory steady state responses (ASSRs) are used in clinical practice for objective hearing assessments. The response is called steady state because it is assumed to be stable over time, and because it is evoked by a stimulus with a certain periodicity, which will lead to discrete frequency components that are stable in amplitude and phase over time. However, the stimuli commonly used to evoke ASSRs are also known to be able to induce loudness adaptation behaviorally. Researchers and clinicians using ASSRs assume that the response remains stable over time. This study investigates (1) the stability of ASSR amplitudes over time, within one recording, and (2) whether loudness adaptation can be reflected in ASSRs. DESIGN ASSRs were measured from 14 normal-hearing participants. The ASSRs were evoked by the stimuli that caused the most loudness adaptation in a previous behavioral study, that is, mixed-modulated sinusoids with carrier frequencies of either 500 or 2000 Hz, a modulation frequency of 40 Hz, and a low sensation level of 30 dB SL. For each carrier frequency and participant, 40 repetitions of 92 sec recordings were made. Two types of analyses were used to investigate the ASSR amplitudes over time: with the more traditionally used Fast Fourier Transform and with a novel Kalman filtering approach. Robust correlations between the ASSR amplitudes and behavioral loudness adaptation ratings were also calculated. RESULTS Overall, ASSR amplitudes were stable. Over all individual recordings, the median change of the amplitudes over time was -0.0001 μV/s. Based on group analysis, a significant but very weak decrease in amplitude over time was found, with the decrease in amplitude over time around -0.0002 μV/s. Correlation coefficients between ASSR amplitudes and behavioral loudness adaptation ratings were significant but low to moderate, with r = 0.27 and r = 0.39 for the 500 and 2000 Hz carrier frequency, respectively. CONCLUSIONS The decrease in amplitude of ASSRs over time (92 sec) is small. Consequently, it is safe to use ASSRs in clinical practice, and additional correction factors for objective hearing assessments are not needed. Because only small decreases in amplitudes were found, loudness adaptation is probably not reflected by the ASSRs.
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Somers B, Verschueren E, Francart T. Neural tracking of the speech envelope in cochlear implant users. J Neural Eng 2018; 16:016003. [PMID: 30444216 DOI: 10.1088/1741-2552/aae6b9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE When listening to speech, the brain tracks the speech envelope. It is possible to reconstruct this envelope from EEG recordings. However, in people who hear using a cochlear implant (CI), the artifacts caused by electrical stimulation of the auditory nerve contaminate the EEG. The objective of this study is to develop and validate a method for assessing the neural tracking of speech envelope in CI users. APPROACH To obtain EEG recordings free of stimulus artifacts, the electrical stimulation is periodically interrupted. During these stimulation gaps, artifact-free EEG can be sampled and used to train a linear envelope decoder. EEG recordings obtained during audible and inaudible (i.e. sub-threshold) stimulation were used to characterize the artifacts and their influence on the envelope reconstruction. MAIN RESULTS The present study demonstrates for the first time that neural tracking of the speech envelope can be measured in response to ongoing electrical stimulation. The responses were validated to be truly neural and not affected by stimulus artifact. SIGNIFICANCE Besides applications in audiology and neuroscience, the characterization and elimination of stimulus artifacts will enable future EEG studies involving continuous speech in CI users. Measures of neural tracking of the speech envelope reflect interesting properties of the listener's perception of speech, such as speech intelligibility or attentional state. Successful decoding of neural envelope tracking will open new possibilities to investigate the neural mechanisms of speech perception with a CI.
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Attina V, Mina F, Stahl P, Duroc Y, Veuillet E, Truy E, Thai-Van H. A New Method to Test the Efficiency of Cochlear Implant Artifacts Removal From Auditory Evoked Potentials. IEEE Trans Neural Syst Rehabil Eng 2017; 25:2453-2460. [PMID: 28692981 DOI: 10.1109/tnsre.2017.2723952] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Auditory evoked potentials are of great interest to objectively evaluate the audition in cochlear implant (CI) recipients. However, these measures are impeded by CI stimulation electrical artifacts present in the EEG. In the first part, this paper investigates the use of a hybrid model approximating CI patient data. This model gives access to both uncontaminated and denoised data, thus allowing for the evaluation of CI artifact removal methods. Here the efficiency of independent component analysis (ICA) is evaluated in the context of auditory steady-state responses (ASSRs). A dedicated experimental setup was developed to simultaneously record EEG data from a normal hearing (NH) participant and CI artifact data from a phantom equipped with a CI. Hybrid data were obtained as a linear mixture of both sources. Amplitude-modulated continuous tones were used as stimuli to elicit ASSRs. After denoising, the comparison of denoised hybrid data and original NH data showed high correlations between the two datasets, demonstrating the efficiency of ICA. In the second part, the ICA was applied to real clinical CI ASSR data. Results support the usefulness of the methodology as regards the performance evaluation of signal processing methods applied to CI patient data prior to clinical application.
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