Speech ABR Research Articles

Speech evoked potentials in cochlear implant recipients with auditory neuropathy spectrum disorder

Purpose Cochlear implantation (CI) is now recognised as the most possible approach to help ANSD patients in improving their capability in hearing and speech communication. Because there are no reliable methods in clinical practice to identify the exact lesion site and mechanisms for a certain ANSD patient, the efficacy of CI is difficult to predict before surgery. This study was done to study speech ABR and CAEP P1 in ANSD subjects fitted with CIs and to compare results of both tests in ANSD versus SNHL subjects fitted with unilateral CIs, then correlate between both tests in both types of hearing loss. Method The current study was a case-control study, conducted on a total number of 45 subjects who were classified into three groups (one control and two study groups). The control group comprised 16 subjects with normal peripheral hearing sensitivity (NH group) who were age matched to both study groups. The study group comprised 29 children who underwent cochlear implantation. The study group were subdivided according to preoperative diagnosis of the type of their hearing loss into two groups (a group of children with sensorineural hearing loss; SNHL-CI) and (a group of children with Auditory neuropathy spectrum disorder; ANSD-CI). Both study groups were subjected to detailed history taking, aided warble-tone sound field audiometry, Speech-evoked potentials (P1 & ABR) and Questionnaire. Results There were statistically significant differences between the control group and both study subgroups regarding the P1 latencies. While; there were no statistically significant differences between {SNHL-CI group &ANSD-CI}. S-ABR waves were detected in 100% of control group, 75% of SNHL-CI group and 53.8% of ANSD-CI group. Sound-field S-ABR measured in the CI recipients indicated statistically significant delayed latencies than in the NH group. In addition, these results demonstrated that the frequency following response peak amplitude was significantly higher in CI recipients, than in the NH counterparts. Finally, the neural phase locking was significantly higher in CI recipients. Conclusion The findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech processing in CI recipients.

CZĘSTOTLIWOŚCIOWE POTENCJAŁY WOWOŁANE I DOŚWIADCZENIE MUZYCZNE - PRZEGLĄD

The aim of this review is to compare published FFR studies for groups of musicians and non-musicians. Musicians are taken to be those who have used their instrument at least twice a week for many years. The review considers sample size, age, gender, native language, preliminary and complementary assessments, equipment, stimuli, objective results, and conclusions of the studies. Medline/PubMed and Web of Science databases were accessed. Keywords were restricted to English Medical Subject Heading (MeSH) terms and included: auditory brainstem response, speech ABR, speech perception, frequency following response, musicians. The search identified 140 articles published between 2008 and 2015. After filtering the total number of papers according to inclusion and exclusion criteria, 11 studies remained. Analysis showed that individuals with musical experience, that is, play a musical instrument at least 2 to 3 hours per week, show an improved development of their FFR. Musical experience improves a broad range of abilities: detection, recognition, and discrimination of sound stimuli are processed more accurately and effectively in musicians. The improvement also relates to the encoding of speech, facilitating literacy. Assessment by FFR allows neural changes from musical training to be monitored.

An Analysis of The Parameters Used In Speech ABR Assessment Protocols.

The aim of this study was to assess the parameters of choice, such as duration, intensity, rate, polarity, number of sweeps, window length, stimulated ear, fundamental frequency, first formant, and second formant, from previously published speech ABR studies. To identify candidate articles, five databases were assessed using the following keyword descriptors: speech ABR, ABR-speech, speech auditory brainstem response, auditory evoked potential to speech, speech-evoked brainstem response, and complex sounds. The search identified 1288 articles published between 2005 and 2015. After filtering the total number of papers according to the inclusion and exclusion criteria, 21 studies were selected. Analyzing the protocol details used in 21 studies suggested that there is no consensus to date on a speech-ABR protocol and that the parameters of analysis used are quite variable between studies. This inhibits the wider generalization and extrapolation of data across languages and studies.

Speech-evoked brainstem response in normal adolescent and children speakers of Brazilian Portuguese

This study aimed to analyze the coding responses of speech sounds (syllable/da/) in children and adolescent speakers of Brazilian Portuguese with typical development and normal hearing, aged between 8 and 16 years, in order to establish normative data of speech ABR response. This normative data can be used as a reference for speech ABR responses and also to enable the diagnosis in individuals with different pathologies. The analyze for absolute latency of speech sounds, more specifically the syllable/da/, for speech-ABR in children and adolescent speakers of Brazilian Portuguese with typical development were: right ear - wave V (6,43–6,57), wave A (7,35–7,57), wave C (18,19–18,46), wave D (21,99–22,42), wave E (30,73–31,05), wave F (39,19–39,55) and wave O (47,75–48,24) and left ear - wave V (6,44–6,57), wave A (7,36–7,59), wave C (18,26–18,55), wave D (22,22 -22,50), wave E (30,58–30,97), wave F (39,05–39,35) and wave O (47,78–48,13). For the amplitude values (μv), the responses were within the following ranges: right ear - wave V (0,10–0,14), wave A (0,19–0,25), wave C (0,08–0,13), wave D (0,11–0,17), wave E (0,17–0,42), wave F (0,14–0,33) and wave O (0,11–0,31) and left ear - wave V (0,09–0,13), wave A (0,08–0,23), wave C (0,08–0,14), wave D (0,10–0,15), wave E (0,20–0,26), wave F (0,16–0,22) and wave O (0,12–0,20). For the values of complex VA (slope: μv/ms and area μv x ms) the follow values obtained were: right ear – slope (0,32–0,42) and area (0,29–0,38) and left ear – slope (0,30–0,39) and area (0,27–0,35).

Speech Auditory Brainstem Response through hearing aid stimulation

Millions of people across the world are hearing impaired, and rely on hearing aids to improve their everyday life. Objective audiometry could optimize hearing aid fitting, and is of particular interest for non-communicative patients. Speech Auditory Brainstem Response (speech ABR), a fine electrophysiological marker of speech encoding, is presently seen as a promising candidate for implementing objective audiometry; yet, unlike lower-frequency auditory-evoked potentials (AEPs) such as cortical AEPs or auditory steady-state responses (ASSRs), aided-speech ABRs (i.e. speech ABRs through hearing aid stimulation) have almost never been recorded. This may be due to their high-frequency components requesting a high temporal precision of the stimulation. We assess here a new approach to record high-quality and artifact-free speech ABR while stimulating directly through hearing aids. In 4 normal-hearing adults, we recorded speech ABR evoked by a /ba/ syllable binaurally delivered through insert earphones for quality control or through hearing aids. To assess the presence of a potential stimulus artifact, recordings were also done in mute conditions with the exact same potential sources of stimulus artifacts as in the main runs. Hearing aid stimulation led to artifact-free speech ABR in each participant, with the same quality as when using insert earphones, as shown with signal-to-noise (SNR) measurements. Our new approach consisting in directly transmitting speech stimuli through hearing aids allowed for a perfect temporal precision mandatory in speech ABR recordings, and could thus constitute a decisive step in hearing impairment investigation and in hearing aid fitting improvement.

The influence of cochlear spectral processing on the timing and amplitude of the speech-evoked auditory brain stem response

The speech-evoked auditory brain stem response (speech ABR) is widely considered to provide an index of the quality of neural temporal encoding in the central auditory pathway. The aim of the present study was to evaluate the extent to which the speech ABR is shaped by spectral processing in the cochlea. High-pass noise masking was used to record speech ABRs from delimited octave-wide frequency bands between 0.5 and 8 kHz in normal-hearing young adults. The latency of the frequency-delimited responses decreased from the lowest to the highest frequency band by up to 3.6 ms. The observed frequency-latency function was compatible with model predictions based on wave V of the click ABR. The frequency-delimited speech ABR amplitude was largest in the 2- to 4-kHz frequency band and decreased toward both higher and lower frequency bands despite the predominance of low-frequency energy in the speech stimulus. We argue that the frequency dependence of speech ABR latency and amplitude results from the decrease in cochlear filter width with decreasing frequency. The results suggest that the amplitude and latency of the speech ABR may reflect interindividual differences in cochlear, as well as central, processing. The high-pass noise-masking technique provides a useful tool for differentiating between peripheral and central effects on the speech ABR. It can be used for further elucidating the neural basis of the perceptual speech deficits that have been associated with individual differences in speech ABR characteristics.

Neural network-based adaptive noise cancellation for enhancement of speech auditory brainstem responses

The measurement of the speech-evoked auditory brainstem response (speech ABR) is a promising technique for evaluating auditory function. However, the speech ABR is severely contaminated by background noise related to other brain electrical activity. The most commonly used method to enhance the signal-to-noise ratio (SNR) of the response is coherent averaging, while recently adaptive filtering has also been reported. All of the applied methods are based on linear operations, but since the assumption of linearity may not be valid for neural activity, linear methods may not be adequate. In this paper, we present a new nonlinear adaptive noise cancellation (ANC) based on a multilayer perceptron neural network to enhance the speech ABR and compare its performance with a linear ANC algorithm based on least mean squares adaptive filtering. The effectiveness of the methods is tested using speech ABR data and is based on two different types of SNR measures, the local SNR at the fundamental frequency of the response and the overall SNR. The results show that the nonlinear neural network-based ANC can reduce the required recording time and performs better than the linear ANC especially when the SNR of the recorded speech ABR is low.

Classification of speech-evoked brainstem responses to English vowels

This study investigated whether speech-evoked auditory brainstem responses (speech ABRs) can be automatically separated into distinct classes. With five English synthetic vowels, the speech ABRs were classified using linear discriminant analysis based on features contained in the transient onset response, the sustained envelope following response (EFR), and the sustained frequency following response (FFR). EFR contains components mainly at frequencies well below the first formant, while the FFR has more energy around the first formant. Accuracies of 83.33% were obtained for combined EFR and FFR features and 38.33% were obtained for transient response features. The EFR features performed relatively well with a classification accuracy of 70.83% despite the belief that vowel discrimination is primarily dependent on the formants. The FFR features obtained a lower accuracy of 59.58% possibly because the second formant is not well represented in all the responses. Moreover, the classification accuracy based on the transient features exceeded chance level which indicates that the initial response transients contain vowel specific information. The results of this study will be useful in a proposed application of speech ABR to objective hearing aid fitting, if the separation of the brain’s responses to different vowels is found to be correlated with perceptual discrimination.

Topographic recordings of auditory evoked potentials to speech: subcortical and cortical responses.

Topographies of speech auditory brainstem response (speech ABR), a fine electrophysiological marker of speech encoding, have never been described. Yet, they could provide useful information to assess speech ABR generators and better characterize populations of interest (e.g., musicians, dyslexics). We present here a novel methodology of topographic speech ABR recording, using a 32-channel low sampling rate (5 kHz) EEG system. Quality of speech ABRs obtained with this conventional multichannel EEG system were compared to that of signals simultaneously recorded with a high sampling rate (13.3 kHz) EEG system. Correlations between speech ABRs recorded with the two systems revealed highly similar signals, without any significant difference between their signal-to-noise ratios (SNRs). Moreover, an advanced denoising method for multichannel data (denoising source separation) significantly improved SNR and allowed topography of speech ABR to be recovered.

Correlations between word intelligibility under reverberation and speech auditory brainstem responses in elderly listeners

ObjectiveTo investigate the relationship between speech auditory brainstem responses (speech ABRs) and word intelligibility under reverberation in elderly adults. MethodsWord intelligibility for words under four reverberation times (RTs) of 0, 0.5, 1.0, 1.5s, and speech ABRs to the speech syllable/da/ were obtained from 30 elderly listeners. Root mean square (RMS) amplitudes and discrete Fourier transform (DFT) amplitudes were calculated for ADD and SUB responses in the speech ABRs. ResultsNo significant correlations were found between the word intelligibility scores under reverberation and the ADD response components. However, in the SUB responses we found that the DFT amplitudes associated with H4-SUB, H5-SUB, H8-SUB, H9-SUB and H10-SUB significantly correlated with the word intelligibility scores for words under reverberation. With Bonferroni correction, the DFT amplitudes for H5-SUB and the intelligibility scores for words with the RT of 0.5s and 1.5s were significant. ConclusionsWord intelligibility under reverberation in elderly listeners is related to their ability to encode the temporal fine structure of speech. SignificanceThe results expand knowledge about subcortical responses of elderly listeners in daily-life listening situations. The SUB responses of speech ABR could be useful as an objective indicator to predict word intelligibility under reverberation.

Brainstem Auditory Responses to Resolved and Unresolved Harmonics of a Synthetic Vowel in Quiet and Noise

This study investigated speech auditory brainstem responses (speech ABR) with variants of a synthetic vowel in quiet and in background noise. Its objectives were to study the noise robustness of the brainstem response at the fundamental frequency F0 and at the first formant F1, evaluate how the resolved/unresolved harmonics regions in speech contribute to the response at F0, and investigate the origin of the response at F0 to resolved and unresolved harmonics in speech. In total, 18 normal-hearing subjects (11 women, aged 18-33 years) participated in this study. Speech ABRs were recorded using variants of a 300 msec formant-synthesized /a/ vowel in quiet and in white noise. The first experiment employed three variants containing the first three formants F1 to F3, F1 only, and F2 and F3 only with relative formant levels following those reported in the literature. The second experiment employed three variants containing F1 only, F2 only, and F3 only, with the formants equalized to the same level and the signal-to-noise ratio (SNR) maintained at -5 dB. Overall response latency was estimated, and the amplitude and local SNR of the envelope following response at F0 and of the frequency following response at F1 were compared for the different stimulus variants in quiet and in noise. The response at F0 was more robust to noise than that at F1. There were no statistically significant differences in the response at F0 caused by the three stimulus variants in both experiments in quiet. However, the response at F0 with the variant dominated by resolved harmonics was more robust to noise than the response at F0 with the stimulus variants dominated by unresolved harmonics. The latencies of the responses in all cases were very similar in quiet, but the responses at F0 due to resolved and unresolved harmonics combined nonlinearly when both were present in the stimulus. Speech ABR has been suggested as a marker of central auditory processing. The results of this study support earlier work on the differential susceptibility to noise of the F0 and F1 components of the evoked response. In the case of F0, the results support the view that in speech, the pitch of resolved harmonics and that of unresolved harmonics are processed in different but interacting pathways that converge in the upper brainstem. Pitch plays an important role in speech perception, and speech ABR can offer a window into the neural extraction of the pitch of speech and how it may change with hearing impairment.

F033 Cochlear implant artifacts in electrically evoked auditory brainstem responses critically depend on EEG amplifier settings

Speech elicited auditory brainstem responses (Speech ABR) have been shown to be an objective measurement of speech processing in the brainstem. Given the simultaneous stimulation and recording, and the similarities between the recording and the speech stimulus envelope, there is a great risk of artefactual recordings. This study sought to systematically investigate the source of artefactual contamination in Speech ABR response.In a first part, we measured the sound level thresholds over which artefactual responses were obtained, for different types of transducers and experimental setup parameters. A watermelon model was used to model the human head susceptibility to electromagnetic artefact. It was found that impedances between the electrodes had a great effect on electromagnetic susceptibility and that the most prominent artefact is due to the transducer’s electromagnetic leakage. The only artefact-free condition was obtained with insert-earphones shielded in a Faraday cage linked to common ground.In a second part of the study, using the previously defined artefact-free condition, we recorded speech ABR in unilateral deaf subjects and bilateral normal hearing subjects. In an additional control condition, Speech ABR was recorded with the insert-earphones used to deliver the stimulation, unplugged from the ears, so that the subjects did not perceive the stimulus. No responses were obtained from the deaf ear of unilaterally hearing impaired subjects, nor in the insert-out-of-the-ear condition in all the subjects, showing that Speech ABR reflects the functioning of the auditory pathways.

Contribution of Resolved and Unresolved Harmonic Regions to Brainstem Speech-Evoked Responses in Quiet and in Background Noise.

Speech auditory brainstem responses (speech ABR) reflect activity that is phase-locked to the harmonics of the fundamental frequency (F0) up to at least the first formant (F1). Recent evidence suggests that responses at F0 in the presence of noise are more robust than responses at F1, and are also dissociated in some learning-impaired children. Peripheral auditory processing can be broadly divided into resolved and unresolved harmonic regions. This study investigates the contribution of these two regions to the speech ABR, and their susceptibility to noise. We recorded, in quiet and in background white noise, evoked responses in twelve normal hearing adults in response to three variants of a synthetic vowel: i) Allformants, which contains all first three formants, ii) F1Only, which is dominated by resolved harmonics, and iii) F2&F3Only, which is dominated by unresolved harmonics. There were no statistically significant differences in the response at F0 due to the three variants of the stimulus in quiet, nor did the noise affect this response with the Allformants and F1Only variants. On the other hand, the response at F0 with the F2&F3Only variant was significantly weaker in noise than with the two other variants (p<0.001). With the response at F1, there was no difference with the Allformants and F1Only variants in quiet, but was expectedly weaker with the F2&F3Only variant (p<0.01). The addition of noise significantly weakened the response at F1 with the F1Only variant (p<0.05), but this weakening only tended towards significance with the Allformants variant (p=0.07). The results of this study indicate that resolved and unresolved harmonics are processed in different but interacting pathways that converge in the upper brainstem. The results also support earlier work on the differential susceptibility of responses at F0 and F1 to added noise.

Approche empirique pour déterminer les générateurs neurophysiologiques sous-jacents des potentiels évoqués auditifs engendrés par des sons de parole ( Speech ABR)

Auditory evoked potentials to speech (Speech auditory brainstem response [Speech ABR]) are a non-invasive way to investigate neurophysiological activity, at the level of the brainstem. The Speech ABR precise neurophyiological generators remain poorly defined. However, latencies and low-pass spectrum both suggest that these generators might lie in the upper brainstem (roughly between the cochlear nucleus and the inferior colliculus). Having considered the particular functional pattern of cells along the auditory pathway, specific stimuli have been synthesized to make out the acoustic sensitivity of Speech ABR components. Accordingly, hypotheses have been made on the probable neurophysiological generators, most likely to have elicited both Speech ABR components: onset response and frequency following response. Speech ABR have been recorded to pure tones, harmonic complex tones, /ba/ and /pa/ syllables, and their analogues (calculated as a sum of five weighted sine waves at the formant frequencies and amplitudes, and modulated by the syllables temporal envelopes). In addition, the Auditory Image Model (Patterson et al., 1995 [17]), simulating the neural activity at the auditory periphery, i.e. inferior colliculus input, suggests that both analogues and syllables elicit the same amount of energy, in contrast to the recorded FFR. This contradiction means that the neurophysiological signal processing leading to FFR is made beyond auditory periphery. Indeed, FFR synchronisation on F0 seems to be the result of an overall processing of the whole stimulus spectrum. This behaviour reminds the functional characteristics of disc-shape cells in the inferior colliculus, as described in a previous study of physiological periodicity coding (Periodicity analysis network, Voutsas et al., 2005 [42]).

Speech auditory brainstem response (speech ABR) characteristics depending on recording conditions, and hearing status: An experimental parametric study

Speech elicited auditory brainstem responses (Speech ABR) have been shown to be an objective measurement of speech processing in the brainstem. Given the simultaneous stimulation and recording, and the similarities between the recording and the speech stimulus envelope, there is a great risk of artefactual recordings. This study sought to systematically investigate the source of artefactual contamination in Speech ABR response. In a first part, we measured the sound level thresholds over which artefactual responses were obtained, for different types of transducers and experimental setup parameters. A watermelon model was used to model the human head susceptibility to electromagnetic artefact. It was found that impedances between the electrodes had a great effect on electromagnetic susceptibility and that the most prominent artefact is due to the transducer’s electromagnetic leakage. The only artefact-free condition was obtained with insert-earphones shielded in a Faraday cage linked to common ground. In a second part of the study, using the previously defined artefact-free condition, we recorded speech ABR in unilateral deaf subjects and bilateral normal hearing subjects. In an additional control condition, Speech ABR was recorded with the insert-earphones used to deliver the stimulation, unplugged from the ears, so that the subjects did not perceive the stimulus. No responses were obtained from the deaf ear of unilaterally hearing impaired subjects, nor in the insert-out-of-the-ear condition in all the subjects, showing that Speech ABR reflects the functioning of the auditory pathways.

Comparison of speech vs speech-analogue temporal encoding in human: An auditory brainstem response and categorical perception assessment

Temporal speech cues, such as periodicity and voice onset time (VOT), are particularly salient information for speech intelligibility. In addition, speech elicited auditory brainstem response (Speech ABR) to consonant vowels (CV) has been shown to mimic the temporal periodicity of the acoustic signal very accurately. Consequently, Speech ABR has been described as a potential objective tool to explore the temporal integration of speech excerpts in human brainstem. We aimed at putting in evidence the specialization of temporal encoding of speech vs nonspeech signals through clinical and behavioral measurements. A sum of five sinusoids, at the five formant frequencies, modulated by the corresponding CV temporal envelope, was taken as speech-analogue. Accordingly, Speech and Analogue ABRs components were compared, although a priori due to be similar. Furthermore, categorical perception assessment was processed to both analogue and full-speech continuums. If confirmed, these preliminary results (seven normal hearing adults for physiological ABRs and behavioral categorical perception) would bring further evidence of an early specialization of temporal processing of speech, in line with previous research [Kraus and Nicol, Trends in Neuroscience 28(4), 176--81 (2005)]. [Work supported by CNRS, Cochlear &amp; Univ.Lyon 1.]

The temporal relationship between speech auditory brainstem responses and the acoustic pattern of the phoneme /ba/ in normal-hearing adults

Objective To investigate the temporal relationship between speech auditory brainstem responses and acoustic pattern of the phoneme /ba/. Methods Speech elicited auditory brainstem responses (Speech ABR) to /ba/ were recorded in 23 normal-hearing subjects. Effect of stimulus intensity was assessed on Speech ABR components latencies in 11 subjects. The effect of different transducers on electromagnetic leakage was also measured. Results Speech ABR showed a reproducible onset response (OR) 6 ms after stimulus onset. The frequency following response (FFR) waveform mimicked the 500 Hz low pass filtered temporal waveform of phoneme /ba/ with a latency shift of 14.6 ms. In addition, the OR and FFR latencies decreased with increasing stimulus intensity, with a greater rate for FFR (−1.4 ms/10 dB) than for OR (−0.6 ms/10 dB). Conclusions A close relationship was found between the pattern of the acoustic stimulus and the FFR temporal structure. Furthermore, differences in latency behaviour suggest different generation mechanisms for FFR and OR. Significance The results provided further insight into the temporal encoding of basic speech stimulus at the brainstem level in humans.

Temporal relationship between speech auditory brainstem responses and phonemes envelopes

Auditory brainstem responses evoked by synthetic phonemes (speech-ABR) were recorded on normal hearing subjects stimulated monaurally on the right ear at 60 dB sensation level. The speech-ABR consists of an onset response (OR) followed by the frequency following response (FFR), which results of the summation of phase locking underlying activities in the auditory cells of the brainstem nuclei. The FFR mimicked accurately the envelope of the stimulus, defined as the absolute value of the stimulus filtered at the cutoff frequency of the speech ABR spectrum. However, the FFR was more shifted relative to the vowel than the OR did relative to the onset of the stimulus, which is close to the cochlear delay usually reported. Little interindividual discrepancies were found. Delay values give information about the sites of generation of the speech-ABR. This method may help to objectivate the temporal encoding of phonemes in the brainstem. Hence the potential assessing of speech intelligibility, as temporal speech envelopes retain perfect intelligibility [R. Drullman, J. Acoust. Soc. Am. 98, 1796–1798 (1995)]. [Work supported by CNRS.]

Preserved Hearing Following Vestibular Schwannoma Surgery

Audiologic test results were reviewed for 30 patients whose hearing was preserved following eighth nerve tumor surgery. Speech reception thresholds, 4,000-Hz thresholds, acoustic reflexes, and ABR wave I absolute latencies were generally unchanged or poorer following surgery; word recognition scores were essentially unchanged. By contrast, ABR waves III and V, and the I–III and I–V interpeak intervals, were generally improved postoperatively, including several patients who had clear waves following surgery despite absent preoperative responses. The improved ABR tracings likely indicate increased neural synchrony due to reduced pressure on the cochlear nerve following surgery, whereas the reduced hearing sensitivity probably reflects cochlear damage coincident to the surgery.