On the relationship between speech- and nonspeech-evoked auditory brainstem responses

Speech auditory brainstem response in audiological practice: a systematic review

BACKGROUND

Speech-ABR is an auditory brainstem response that evaluates the integrity of the temporal and spectral coding of speech in the upper levels of the brainstem. It reflects the acoustic properties of the stimulus used and consists of seven major waves. Waves V and A represent the onset of the response; wave C transition region; D, E, and F waves periodic region (frequency following response); and wave O reflects the offset of the response.

PURPOSE

The aim of this study is to evaluate the clinical availability of the speech-ABR procedure through a literature review.

METHODS

Literature search was conducted in Pubmed, Google Scholar, Scopus and Science Direct databases. Clinical studies of the last 15 years have been included in this review and 60 articles have been reviewed.

RESULTS

As a result of the articles reviewed, it was seen that most of the studies on speech ABR were conducted with children and young people and generally focused on latency analysis measurements. Most used stimulus is the /da/ syllable.

CONCLUSIONS

Speech ABR can objectively measure the auditory cues important for speech recognition and has many clinical applications. It can be used as a biomarker for auditory processing disorders, learning disorders, dyslexia, otitis media, hearing loss, language disorders and phonological disorders. S-ABR is an effective procedure that can be used in speech and language evaluations in people with hearing aids or cochlear implant. It may also be of benefit to the aging auditory system's ability to encode temporal cues.

Auditory brainstem response deficits in learning disorders and developmental language disorder: a systematic review and meta-analysis

Although learning disorders (LD) and developmental language disorder (DLD) can be linked to overlapping psychological and behavioral deficits, such as phonological, morphological, orthographic, semantic, and syntactic deficits, as well as academic (e.g., reading) difficulties, they are currently separate diagnoses in the DSM-5 with explicit phenotypic differences. At a neural level, it is yet to be determined to what extent they have overlapping or distinct signatures. The identification of such neural markers/endophenotypes could be important for the development of physiological diagnostic tools, as well as an understanding of disorders across different dimensions, as recommended by the Research Domain Criteria Initiative (RDoC). The current systematic review and meta-analysis examined whether the two disorders can be differentiated based on the auditory brainstem response (ABR). Even though both diagnoses require hearing problems to be ruled out, a number of articles have demonstrated associations of these disorders with the auditory brainstem response. We demonstrated that both LD and DLD are associated with longer latencies in ABR Waves III, V, and A, as well as reduced amplitude in Waves V and A. However, multilevel subgroup analyses revealed that LD and DLD do not significantly differ for any of these ABR waves. Results suggest that less efficient early auditory processing is a shared mechanism underlying both LD and DLD.

Deficient neural encoding of speech sounds in term neonates born after fetal growth restriction

Infants born after fetal growth restriction (FGR)-an obstetric condition defined as the failure to achieve the genetic growth potential-are prone to neurodevelopmental delays, with language being one of the major affected areas. Yet, while verbal comprehension and expressive language impairments have been observed in FGR infants, children and even adults, specific related impairments at birth, such as in the ability to encode the sounds of speech, necessary for language acquisition, remain to be disclosed. Here, we used the frequency-following response (FFR), a brain potential correlate of the neural phase locking to complex auditory stimuli, to explore the encoding of speech sounds in FGR neonates. Fifty-three neonates born with FGR and 48 controls born with weight adequate-for-gestational age (AGA) were recruited. The FFR was recorded to the consonant-vowel stimulus (/da/) during sleep and quantified as the spectral amplitude to the fundamental frequency of the syllable and its signal-to-noise ratio (SNR). The outcome was available in 45 AGA and 51 FGR neonates, yielding no differences for spectral amplitudes. However, SNR was strongly attenuated in the FGR group compared to the AGA group at the vowel region of the stimulus. These findings suggest that FGR population present a deficit in the neural pitch tracking of speech sounds already present at birth. Our results pave the way for future research on the potential clinical use of the FFR in this population, so that if confirmed, a disrupted FFR recorded at birth may help deriving FGR neonates at risk for postnatal follow-ups.

Masking Level Difference and Electrophysiological Evaluation in Adults with Normal Hearing

Introduction  The auditory structures of the brainstem are involved in binaural interaction, which contributes to sound location and auditory figure-background perception. Objective  To investigate the performance of young adults in the masking level difference (MLD) test, brainstem auditory-evoked potentials (BAEPs) with click stimulus, and frequency-following response (FFR), as well as to verify the correlation between the findings, considering the topographic origin of the components of these procedures. Methods  A total of 20 female subjects between 18 and 30 years of age, with normal hearing and no complaints concerning central auditory processing underwent a basic audiological evaluation, as well as the MLD test, BAEP and FFR. Results  The mean result on the MLD test was of 10.70 dB. There was a statistically significant difference in the absolute latencies of waves I, III and V in the BAEPs of the ears. A change in the FFR characterized by the absence of the C, E and F waves was noticed. There was a statistically significant difference in the positive correlation of wave V in the BAEPs with the MLD. There was a statistically significant difference in the positive correlation of the mean MLD and the V, A and F components of the FFR. Conclusion  The mean MLD was adequate. In the BAEPs, we observed that the click stimulus transmission occurred faster in the right ear. The FFR showed absence of some components. The mean MLD correlated positively with the BAEPs and FFR.

Effects of Aging on the Subcortical Encoding of Stop Consonants

Purpose The main purpose of this study was to evaluate aging effects on the predominantly subcortical (brainstem) encoding of the second-formant frequency transition, an essential acoustic cue for perceiving place of articulation. Method Synthetic consonant-vowel syllables varying in second-formant onset frequency (i.e., /ba/, /da/, and /ga/ stimuli) were used to elicit speech-evoked auditory brainstem responses (speech-ABRs) in 16 young adults (M _age = 21 years) and 11 older adults (M _age = 59 years). Repeated-measures mixed-model analyses of variance were performed on the latencies and amplitudes of the speech-ABR peaks. Fixed factors were phoneme (repeated measures on three levels: /b/ vs. /d/ vs. /g/) and age (two levels: young vs. older). Results Speech-ABR differences were observed between the two groups (young vs. older adults). Specifically, older listeners showed generalized amplitude reductions for onset and major peaks. Significant Phoneme × Group interactions were not observed. Conclusions Results showed aging effects in speech-ABR amplitudes that may reflect diminished subcortical encoding of consonants in older listeners. These aging effects were not phoneme dependent as observed using the statistical methods of this study.

Phonetic discrimination mediates the relationship between auditory brainstem response stability and syntactic performance

Syntactic, lexical, and phonological/phonetic knowledge are vital aspects of macro level language ability. Prior research has predominantly focused on environmental or cortical sources of individual differences in these areas; however, a growing literature suggests an auditory brainstem contribution to language performance in both typically developing (TD) populations and children with autism spectrum disorder (ASD). This study investigates whether one aspect of auditory brainstem responses (ABRs), neural response stability, which is a metric reflecting trial-by-trial consistency in the neural encoding of sound, can predict syntactic, lexical, and phonetic performance in TD and ASD school-aged children. Pooling across children with ASD and TD, results showed that higher neural stability in response to the syllable /da/ was associated with better phonetic discrimination, and with better syntactic performance on a standardized measure. Furthermore, phonetic discrimination was a successful mediator of the relationship between neural stability and syntactic performance. This study supports the growing body of literature that stable subcortical neural encoding of sound is important for successful language performance.

Subcortical auditory neural synchronization is deficient in pre-reading children who develop dyslexia

Auditory processing of temporal information in speech is sustained by synchronized firing of neurons along the entire auditory pathway. In school-aged children and adults with dyslexia, neural synchronization deficits have been found at cortical levels of the auditory system, however, these deficits do not appear to be present in pre-reading children. An alternative role for subcortical synchronization in reading development and dyslexia has been suggested, but remains debated. By means of a longitudinal study, we assessed cognitive reading-related skills and subcortical auditory steady-state responses (80 Hz ASSRs) in a group of children before formal reading instruction (pre-reading), after 1 year of formal reading instruction (beginning reading), and after 3 years of formal reading instruction (more advanced reading). Children were retrospectively classified into three groups based on family risk and literacy achievement: typically developing children without a family risk for dyslexia, typically developing children with a family risk for dyslexia, and children who developed dyslexia. Our results reveal that children who developed dyslexia demonstrate decreased 80 Hz ASSRs at the pre-reading stage. This effect is no longer present after the onset of reading instruction, due to an atypical developmental increase in 80 Hz ASSRs between the pre-reading and the beginning reading stage. A forward stepwise logistic regression analysis showed that literacy achievement was predictable with an accuracy of 90.4% based on a model including three significant predictors, that is, family risk for dyslexia (R = .31), phonological awareness (R = .23), and 80 Hz ASSRs (R = .26). Given that (1) abnormalities in subcortical ASSRs preceded reading acquisition in children who developed dyslexia and (2) subcortical ASSRs contributed to the prediction of literacy achievement, subcortical auditory synchronization deficits may constitute a pre-reading risk factor in the emergence of dyslexia.

Sound-Field Speech Evoked Auditory Brainstem Response in Cochlear-Implant Recipients

Background and Objectives

Currently limited information is available on speech stimuli processing at the subcortical level in the recipients of cochlear implant (CI). Speech processing in the brainstem level is measured using speech-auditory brainstem response (S-ABR). The purpose of the present study was to measure the S-ABR components in the sound-field presentation in CI recipients, and compare with normal hearing (NH) children.

Subjects and Methods

In this descriptive-analytical study, participants were divided in two groups: patients with CIs; and NH group. The CI group consisted of 20 prelingual hearing impairment children (mean age=8.90 ± 0.79 years), with ipsilateral CIs (right side). The control group consisted of 20 healthy NH children, with comparable age and sex distribution. The S-ABR was evoked by the 40-ms synthesized /da/ syllable stimulus that was indicated in the sound-field presentation.

Results

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 (p<0.05). Finally, the neural phase locking were significantly lower in CI recipients (p<0.05).

Conclusions

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 process in CI recipients.

Tinnitus Impacts on Speech and Non-speech Stimuli

OBJECTIVE

To investigate how tinnitus affects the processing of speech and non-speech stimuli at the subcortical level.

STUDY DESIGN

Cross-sectional analytical study.

SETTING

Academic, tertiary referral center.

PATIENTS

Eighteen individuals with tinnitus and 20 controls without tinnitus matched based on their age and sex. All subjects had normal hearing sensitivity.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

The effect of tinnitus on the parameters of auditory brainstem responses (ABR) to non-speech (click-ABR), and speech (sABR) stimuli was investigated.

RESULTS

Latencies of click ABR in waves III, V, and Vn, as well as inter-peak latency (IPL) of I to V were significantly longer in individuals with tinnitus compared with the controls. Individuals with tinnitus demonstrated significantly longer latencies of all sABR waves than the control group. The tinnitus patients also exhibited a significant decrease in the slope of the V-A complex and reduced encoding of the first and higher formants. A significant difference was observed between the two groups in the spectral magnitudes, the first formant frequency range (F1) and a higher frequency region (HF).

CONCLUSIONS

Our findings suggest that maladaptive neural plasticity resulting from tinnitus can be subcortically measured and affects timing processing of both speech and non-speech stimuli. The findings have been discussed based on models of maladaptive plasticity and the interference of tinnitus as an internal noise in synthesizing speech auditory stimuli.

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.

Subclinical Auditory Neural Deficits in Patients With Type 1 Diabetes Mellitus

Supplemental Digital Content is available in the text.

Objectives:

Diabetes mellitus (DM) is associated with a variety of sensory complications. Very little attention has been given to auditory neuropathic complications in DM. The aim of this study was to determine whether type 1 DM (T1DM) affects neural coding of the rapid temporal fluctuations of sounds, and how any deficits may impact on behavioral performance.

Design:

Participants were 30 young normal-hearing T1DM patients, and 30 age-, sex-, and audiogram-matched healthy controls. Measurements included electrophysiological measures of auditory nerve and brainstem function using the click-evoked auditory brainstem response, and of brainstem neural temporal coding using the sustained frequency-following response (FFR); behavioral tests of temporal coding (interaural phase difference discrimination and the frequency difference limen); tests of speech perception in noise; and self-report measures of auditory disability using the Speech, Spatial and Qualities of Hearing Scale.

Results:

There were no significant differences between T1DM patients and controls in the auditory brainstem response. However, the T1DM group showed significantly reduced FFRs to both temporal envelope and temporal fine structure. The T1DM group also showed significantly higher interaural phase difference and frequency difference limen thresholds, worse speech-in-noise performance, as well as lower overall Speech, Spatial and Qualities scores than the control group.

Conclusions:

These findings suggest that T1DM is associated with degraded neural temporal coding in the brainstem in the absence of an elevation in audiometric threshold, and that the FFR may provide an early indicator of neural damage in T1DM, before any abnormalities can be identified using standard clinical tests. However, the relation between the neural deficits and the behavioral deficits is uncertain.

Effects of Manipulating the Amplitude of Consonant Noise Portion on Subcortical Representation of Voice Onset Time and Voicing Perception in Stop Consonants

Purpose The purpose of this study was to investigate whether speech perception would reflect small latency changes in subcortical speech representation. Method Twelve native Japanese listeners participated in the experiment. Those listeners participated in speech identification task and auditory brainstem response (ABR) measurement using /d/-/t/ continuum stimuli varying in voice onset time (VOT) with manipulation of the amplitude of initial noise (consonant) portion, the duration of which corresponded to VOT. Results Increasing the noise portion amplitude lengthened subcortical representation of VOT, which is the latency difference between ABRs synchronizing to the onsets of initial noise and following periodic (vowel) portions (VOT_ABR) and made listeners likely to perceive the stimuli with ambiguous VOT as a voiceless stop /t/. In addition, the amount of VOT_ABR lengthening was close to that of the VOT boundary shortening. Conclusion A few milliseconds of difference in subcortical speech representation are important for the perception of speech sounds with ambiguous acoustic cues. Supplemental Material https://doi.org/10.23641/asha.7728695.

Brainstem auditory evoked potentials with speech stimulus in neonates

INTRODUCTION

Brainstem auditory evoked potentials in response to complex sounds, such as speech sounds, investigate the neural representation of these sounds at subcortical levels, and faithfully reflect the stimulus characteristics. However, there are few studies that utilize this type of stimulus; for it to be used in clinical practice it is necessary to establish standards of normality through studies performed in different populations.

OBJECTIVE

To analyze the latencies and amplitudes of the waves obtained from the tracings of brainstem auditory evoked potentials using speech stimuli in Brazilian neonates with normal hearing and without auditory risk factors.

METHODS

21 neonates with a mean age of 9 days without risk of hearing loss and with normal results at the neonatal hearing screening were evaluated according to the Joint Committee on Infant Hearing protocols. Auditory evoked potentials were performed with speech stimuli (/da/ syllable) at the intensity of 80 dBNA and the latency and amplitude of the waves obtained were analyzed.

RESULTS

In the transient portion, we observed a 100% response rate for all analyzable waves (Wave I, Wave III, Wave V and Wave A), and these waves exhibited a latency <10ms. In the sustained portion, Wave B was identified in 53.12% of subjects; Wave C in 75%; Wave D in 90.62%; Wave E in 96.87%; Wave F in 87.5% and Wave O was identified in 87.5% of subjects. The observed latency of these waves ranged from 11.51ms to 52.16ms. Greater similarity was observed for the response latencies, as well as greater amplitude variation in the studied group.

CONCLUSIONS

Although the wave morphology obtained for brainstem evoked potentials with speech stimulation in neonates is quite similar to that of adults, a longer latency and greater variation in amplitude were observed in the waves analyzed.

Parameters for Applying the Brainstem Auditory Evoked Potential with Speech Stimulus: Systematic Review

Introduction  Studies using the Brainstem Auditory Evoked Potential with speech stimulus are increasing in Brazil, and there are divergences between the methodologies used for testing.

Objectives  To analyze the parameters used in the study of the Brainstem Auditory Evoked Potentials with speech stimulus.

Data Synthesis  The survey was performed using electronic databases. The search strategy was as follows: “Evoked potentials, auditory” OR “Brain stem” OR “Evoked potentials, auditory, brain stem” AND “Speech.” The survey was performed from June to July of 2016. The criteria used for including articles in this study were: being written in Portuguese, English or Spanish; presenting the description of the testing parameters and the description of the sample. In the databases selected, 2,384 articles were found, and 43 articles met all of the inclusion criteria. The predominance of the following parameters was observed to achieve the potential during study: stimulation with the syllable /da/; monaural presentation with greater use of the right ear; intensity of 80 dB SPL; vertical placement of electrodes; use of in-ear headphones; patient seated, distracted in awake state; alternating polarity; use of speech synthesizer software for the elaboration of stimuli; presentation rate of 10.9/s; and sampling rate of 20 kHz.

Conclusions  The theme addressed in this systematic review is relatively recent. However, the results are significant enough to encourage the use of the procedure in clinical practice and advise clinicians about the most used procedures in each parameter.

Perceptual Encoding in Auditory Brainstem Responses: Effects of Stimulus Frequency

PURPOSE

A central question about auditory perception concerns how acoustic information is represented at different stages of processing. The auditory brainstem response (ABR) provides a potentially useful index of the earliest stages of this process. However, it is unclear how basic acoustic characteristics (e.g., differences in tones spanning a wide range of frequencies) are indexed by ABR components. This study addresses this by investigating how ABR amplitude and latency track stimulus frequency for tones ranging from 250 to 8000 Hz.

METHOD

In a repeated-measures experimental design, listeners were presented with brief tones (250, 500, 1000, 2000, 4000, and 8000 Hz) in random order while electroencephalography was recorded. ABR latencies and amplitudes for Wave V (6-9 ms) and in the time window following the Wave V peak (labeled as Wave VI; 9-12 ms) were measured.

RESULTS

Wave V latency decreased with increasing frequency, replicating previous work. In addition, Waves V and VI amplitudes tracked differences in tone frequency, with a nonlinear response from 250 to 8000 Hz and a clear log-linear response to tones from 500 to 8000 Hz.

CONCLUSIONS

Results demonstrate that the ABR provides a useful measure of early perceptual encoding for stimuli varying in frequency and that the tonotopic organization of the auditory system is preserved at this stage of processing for stimuli from 500 to 8000 Hz. Such a measure may serve as a useful clinical tool for evaluating a listener's ability to encode specific frequencies in sounds.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.6987422.

Auditory Deficits in Patients With Mild and Moderate Obstructive Sleep Apnea Syndrome: A Speech Syllable Evoked Auditory Brainstem Response Study

Objectives

The energy consumption process of cochlea and neural signal transduction along the auditory pathway are highly dependent on blood oxygen supply. At present, it is under debate on whether the obstructive sleep apnea syndrome (OSAS) would affect the auditory function since the patients suffer from low oxygen saturation. Moreover, it is difficult to detect the functional state of auditory in less severe stage of OSAS. Recently, speech-evoked auditory brainstem response (speech-ABR) has been reported to be a new electrophysiological tool in characterizing the auditory dysfunction. The aim of the present study is to evaluate the auditory processes in adult patients with mild and moderate OSAS by speech-ABR.

Methods

An experimental group of 31 patients with mild to moderate OSAS, and a control group without OSAS diagnosed by apnea hypopnea index in polysomnogram were recruited. All participants underwent otologic examinations and tests of pure-tone audiogram, distortion product otoacoustic emissions, click-evoked auditory brainstem response (click-ABR) and speech-ABR, respectively.

Results

The results of pure-tone audiogram, distortion product otoacoustic emissions, and click-ABR in OSAS group showed no significant differences compared with the control group (P>0.05). Speech-ABRs for OSAS participants and controls showed similar morphological waveforms and typical peak structures. There were significant group differences for the onset and offset transient peaks (P<0.05), where OSAS group had longer latencies for peak V (6.69± 0.33 ms vs. 6.39±0.23 ms), peak C (13.48±0.30 ms vs. 13.31±0.23 ms), and peak O (48.27±0.39 ms vs. 47.60± 0.40 ms) compared to the control group. The latency of these peaks showed significant correlations with apnea hypopnea index for peak V (r=0.37, P=0.040), peak C (r=0.36, P=0.045), as well as peak O (r=0.55, P=0.001).

Conclusion

These findings indicate that some auditory dysfunctions may be present in patients with mild and moderate OSAS, and the damages were aggravated with the severity of OSAS, which suggests that speech-ABR may be a potential biomarker in the diagnosis and evaluation at early stage of OSAS.

Brainstem Evoked Potential Indices of Subcortical Auditory Processing After Mild Traumatic Brain Injury

OBJECTIVES

The primary aim of this study was to assess subcortical auditory processing in individuals with chronic symptoms after mild traumatic brain injury (mTBI) by measuring auditory brainstem responses (ABRs) to standard click and complex speech stimuli. Consistent with reports in the literature of auditory problems after mTBI (despite normal-hearing thresholds), it was hypothesized that individuals with mTBI would have evidence of impaired neural encoding in the auditory brainstem compared to noninjured controls, as evidenced by delayed latencies and reduced amplitudes of ABR components. We further hypothesized that the speech-evoked ABR would be more sensitive than the click-evoked ABR to group differences because of its complex nature, particularly when recorded in a background noise condition.

DESIGN

Click- and speech-ABRs were collected in 32 individuals diagnosed with mTBI in the past 3 to 18 months. All mTBI participants were experiencing ongoing injury symptoms for which they were seeking rehabilitation through a brain injury rehabilitation management program. The same data were collected in a group of 32 age- and gender-matched controls with no history of head injury. ABRs were recorded in both left and right ears for all participants in all conditions. Speech-ABRs were collected in both quiet and in a background of continuous 20-talker babble ipsilateral noise. Peak latencies and amplitudes were compared between groups and across subgroups of mTBI participants categorized by their behavioral auditory test performance.

RESULTS

Click-ABR results were not significantly different between the mTBI and control groups. However, when comparing the control group to only those mTBI subjects with measurably decreased performance on auditory behavioral tests, small differences emerged, including delayed latencies for waves I, III, and V. Similarly, few significant group differences were observed for peak amplitudes and latencies of the speech-ABR when comparing at the whole group level but were again observed between controls and those mTBI subjects with abnormal behavioral auditory test performance. These differences were seen for the onset portions of the speech-ABR waveforms in quiet and were close to significant for the onset wave. Across groups, quiet versus noise comparisons were significant for most speech-ABR measures but the noise condition did not reveal more group differences than speech-ABR in quiet, likely because of variability and overall small amplitudes in this condition for both groups.

CONCLUSIONS

The outcomes of this study indicate that subcortical neural encoding of auditory information is affected in a significant portion of individuals with long-term problems after mTBI. These subcortical differences appear to relate to performance on tests of auditory processing and perception, even in the absence of significant hearing loss on the audiogram. While confounds of age and slight differences in audiometric thresholds cannot be ruled out, these preliminary results are consistent with the idea that mTBI can result in neuronal changes within the subcortical auditory pathway that appear to relate to functional auditory outcomes. Although further research is needed, clinical audiological evaluation of individuals with ongoing post-mTBI symptoms is warranted for identification of individuals who may benefit from auditory rehabilitation as part of their overall treatment plan.

Subcortical encoding of speech cues in children with congenital blindness

BACKGROUND

Congenital visual deprivation underlies neural plasticity in different brain areas, and provides an outstanding opportunity to study the neuroplastic capabilities of the brain.

OBJECTIVES

The present study aimed to investigate the effect of congenital blindness on subcortical auditory processing using electrophysiological and behavioral assessments in children.

METHODS

A total of 47 children aged 8-12 years, including 22 congenitally blind (CB) children and 25 normal-sighted (NS) control, were studied. All children were tested using an auditory brainstem response (ABR) test with both click and speech stimuli. Speech recognition and musical abilities were tested using standard tools.

RESULTS

Significant differences were observed between the two groups in speech ABR wave latencies A, F and O (p≤0.043), wave amplitude F (p = 0.039), V-A slope (p = 0.026), and three spectral magnitudes F0, F1 and HF (p≤0.002). CB children showed a superior performance compared to NS peers in all the subtests and the total score of musical abilities (p≤0.003). Moreover, they had significantly higher scores during the nonsense syllable test in noise than the NS children (p = 0.034). Significant negative correlations were found only in CB children between the total music score and both wave A (p = 0.039) and wave F (p = 0.029) latencies, as well as nonsense-syllable test in noise and the wave A latency (p = 0.041).

CONCLUSION

Our results suggest that neuroplasticity resulting from congenital blindness can be measured subcortically and has a heightened effect on temporal, musical and speech processing abilities. The findings have been discussed based on models of plasticity and the influence of corticofugal modulation in synthesizing complex auditory stimuli.

Association Between Sex and Speech Auditory Brainstem Responses in Adults, and Relationship to Sex Hormone Levels

BACKGROUND The aim of this study was to investigate the association between sex and speech-ABR in adults, and its relationship to sex hormone levels. MATERIAL AND METHODS Speech-ABR were elicited with the consonant-vowel syllable (/da/) in a total of 35 adults. Reproductive hormone levels were also measured. RESULTS The transient response of the speech-ABR (waves V, A, and O) in females show a shorter latency (waves V, A and O) and a larger amplitude (waves V and A) than in males (P<0.05), except for the amplitude of peak O (P>0.05). The sustained response of females exhibited a larger amplitude (wave F, P<0.05) and a shorter latency (wave D, E, and F, P<0.05) than in males, except for the amplitude of peak D and E (P>0.05). The latencies of speech-ABR were positively correlated with testosterone level (P<0.05), and were negatively correlated with estradiol (E2) levels (P<0.05), except for wave E (P>0.05). The E2 showed a positive correlation with the absolute value of amplitude of the speech-ABR (P < 0.05). On the contrary, total testosterone showed a negative correlation with the absolute value of amplitude the speech-ABR (P<0.05), except for wave D and wave O (P>0.05). CONCLUSIONS Sex differences in speech-ABR are significant in adults. The latencies and amplitude of the speech-ABR waves were correlated with the E2 concentration and testosterone level. The sex hormones likely affect speech encoding in the brainstem.

Mild Cognitive Impairment Is Characterized by Deficient Brainstem and Cortical Representations of Speech

Mild cognitive impairment (MCI) is recognized as a transitional phase in the progression toward more severe forms of dementia and is an early precursor to Alzheimer's disease. Previous neuroimaging studies reveal that MCI is associated with aberrant sensory-perceptual processing in cortical brain regions subserving auditory and language function. However, whether the pathophysiology of MCI extends to speech processing before conscious awareness (brainstem) is unknown. Using a novel electrophysiological approach, we recorded both brainstem and cortical speech-evoked brain event-related potentials (ERPs) in older, hearing-matched human listeners who did and did not present with subtle cognitive impairment revealed through behavioral neuropsychological testing. We found that MCI was associated with changes in neural speech processing characterized as hypersensitivity (larger) brainstem and cortical speech encoding in MCI compared with controls in the absence of any perceptual speech deficits. Group differences also interacted with age differentially across the auditory pathway; brainstem responses became larger and cortical ERPs smaller with advancing age. Multivariate classification revealed that dual brainstem-cortical speech activity correctly identified MCI listeners with 80% accuracy, suggesting its application as a biomarker of early cognitive decline. Brainstem responses were also a more robust predictor of individuals' MCI severity than cortical activity. Our findings suggest that MCI is associated with poorer encoding and transfer of speech signals between functional levels of the auditory system and advance the pathophysiological understanding of cognitive aging by identifying subcortical deficits in auditory sensory processing mere milliseconds (<10 ms) after sound onset and before the emergence of perceptual speech deficits.SIGNIFICANCE STATEMENT Mild cognitive impairment (MCI) is a precursor to dementia marked by declines in communication skills. Whether MCI pathophysiology extends below cerebral cortex to affect speech processing before conscious awareness (brainstem) is unknown. By recording neuroelectric brain activity to speech from brainstem and cortex, we show that MCI hypersensitizes the normal encoding of speech information across the hearing brain. Deficient neural responses to speech (particularly those generated from the brainstem) predicted the presence of MCI with high accuracy and before behavioral deficits. Our findings advance the neurological understanding of MCI by identifying a subcortical biomarker in auditory-sensory processing before conscious awareness, which may be a precursor to declines in speech understanding.

Reading ability reflects individual differences in auditory brainstem function, even into adulthood

Research with developmental populations suggests that the maturational state of auditory brainstem encoding is linked to reading ability. Specifically, children with poor reading skills resemble biologically younger children with respect to their auditory brainstem responses (ABRs) to speech stimulation. Because ABR development continues into adolescence, it is possible that the link between ABRs and reading ability changes or resolves as the brainstem matures. To examine these possibilities, ABRs were recorded at varying presentation rates in adults with diverse, yet unimpaired reading levels. We found that reading ability in adulthood related to ABR Wave V latency, with more juvenile response morphology linked to less proficient reading ability, as has been observed for children. These data add to the evidence indicating that auditory brainstem responses serve as an index of the sound-based skills that underlie reading, even into adulthood.

Neurophysiological aspects of brainstem processing of speech stimuli in audiometric-normal geriatric population

Objective:

Poor auditory speech perception in geriatrics is attributable to neural de-synchronisation due to structural and degenerative changes of ageing auditory pathways. The speech-evoked auditory brainstem response may be useful for detecting alterations that cause loss of speech discrimination. Therefore, this study aimed to compare the speech-evoked auditory brainstem response in adult and geriatric populations with normal hearing.

Methods:

The auditory brainstem responses to click sounds and to a 40 ms speech sound (the Hindi phoneme |da|) were compared in 25 young adults and 25 geriatric people with normal hearing. The latencies and amplitudes of transient peaks representing neural responses to the onset, offset and sustained portions of the speech stimulus in quiet and noisy conditions were recorded.

Results:

The older group had significantly smaller amplitudes and longer latencies for the onset and offset responses to |da| in noisy conditions. Stimulus-to-response times were longer and the spectral amplitude of the sustained portion of the stimulus was reduced. The overall stimulus level caused significant shifts in latency across the entire speech-evoked auditory brainstem response in the older group.

Conclusion:

The reduction in neural speech processing in older adults suggests diminished subcortical responsiveness to acoustically dynamic spectral cues. However, further investigations are needed to encode temporal cues at the brainstem level and determine their relationship to speech perception for developing a routine tool for clinical decision-making.

Construction of Hindi Speech Stimuli for Eliciting Auditory Brainstem Responses

Speech-evoked auditory brainstem responses (spABRs) provide considerable information of clinical relevance to describe auditory processing of complex stimuli at the sub cortical level. The substantial research data have suggested faithful representation of temporal and spectral characteristics of speech sounds. However, the spABR are known to be affected by acoustic properties of speech, language experiences and training. Hence, there exists indecisive literature with regards to brainstem speech processing. This warrants establishment of language specific speech stimulus to describe the brainstem processing in specific oral language user. The objective of current study is to develop Hindi speech stimuli for recording auditory brainstem responses. The Hindi stop speech of 40 ms containing five formants was constructed. Brainstem evoked responses to speech sound |da| were gained from 25 normal hearing (NH) adults having mean age of 20.9 years (SD = 2.7) in the age range of 18-25 years and ten subjects (HI) with mild SNHL of mean 21.3 years (SD = 3.2) in the age range of 18-25 years. The statistically significant differences in the mean identification scores of synthesized for speech stimuli |da| and |ga| between NH and HI were obtained. The mean, median, standard deviation, minimum, maximum and 95 % confidence interval for the discrete peaks and V-A complex values of electrophysiological responses to speech stimulus were measured and compared between NH and HI population. This paper delineates a comprehensive methodological approach for development of Hindi speech stimuli and recording of ABR to speech. The acoustic characteristic of stimulus |da| was faithfully represented at brainstem level in normal hearing adults. There was statistically significance difference between NH and HI individuals. This suggests that spABR offers an opportunity to segregate normal speech encoding from abnormal speech processing at sub cortical level, which implies that alterations in brainstem responses have clinical significance to identify the subjects with possible processing disorders.

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).

The Role of Age-Related Declines in Subcortical Auditory Processing in Speech Perception in Noise

Older adults, even those without hearing impairment, often experience increased difficulties understanding speech in the presence of background noise. This study examined the role of age-related declines in subcortical auditory processing in the perception of speech in different types of background noise. Participants included normal-hearing young (19 - 29 years) and older (60 - 72 years) adults. Normal hearing was defined as pure-tone thresholds of 25 dB HL or better at octave frequencies from 0.25 to 4 kHz in both ears and at 6 kHz in at least one ear. Speech reception thresholds (SRTs) to sentences were measured in steady-state (SS) and 10-Hz amplitude-modulated (AM) speech-shaped noise, as well as two-talker babble. In addition, click-evoked auditory brainstem responses (ABRs) and envelope following responses (EFRs) in response to the vowel /ɑ/ in quiet, SS, and AM noise were measured. Of primary interest was the relationship between the SRTs and EFRs. SRTs were significantly higher (i.e., worse) by about 1.5 dB for older adults in two-talker babble but not in AM and SS noise. In addition, the EFRs of the older adults were less robust compared to the younger participants in quiet, AM, and SS noise. Both young and older adults showed a "neural masking release," indicated by a more robust EFR at the trough compared to the peak of the AM masker. The amount of neural masking release did not differ between the two age groups. Variability in SRTs was best accounted for by audiometric thresholds (pure-tone average across 0.5-4 kHz) and not by the EFR in quiet or noise. Aging is thus associated with a degradation of the EFR, both in quiet and noise. However, these declines in subcortical neural speech encoding are not necessarily associated with impaired perception of speech in noise, as measured by the SRT, in normal-hearing older adults.

Speech processing in children with cochlear implant

Cochlear implants (CIs) can be used effectively in the profoundly impaired children individuals.

OBJECTIVES

This work was designed to assess speech processing at brainstem and cortical level in children fitted with CIs to investigate the possible influence of brainstem processing of speech on the cortical processing in those children.

METHOD

Twenty children fitted with CIs underwent aided sound-field audiologic evaluation, speech evoked cortical auditory evoked potentials (S-CAEPs) and according to the results, children were classified into two groups: group I with good cortical response and group II with poor cortical response. This was followed by speech evoked ABR (S-ABR) recoding.

RESULTS

P1 component of CAEPs was recorded in all children while other component showed variable results. S-ABR was recorded in all children even those with poor S-CAEPs response who showed delayed D, E, F and O latencies. However, S-ABR amplitudes did not show any significant difference between both groups.

CONCLUSIONS

Children fitted with CI showed immediate cortical activation following device programming and this activity depends on the age of implantation as well as the child's age. S-ABR provides a new clinical tool that showed an important role of brainstem in complex sound processing that contribute to cortical processing.

Central load reduces peripheral processing: Evidence from incidental memory of background speech

Is there a trade-off between central (working memory) load and peripheral (perceptual) processing? To address this question, participants were requested to undertake an n-back task in one of two levels of central/cognitive load (i.e., 1-back or 2-back) in the presence of a to-be-ignored story presented via headphones. Participants were told to ignore the background story, but they were given a surprise memory test of what had been said in the background story, immediately after the n-back task was completed. Memory was poorer in the high central load (2-back) condition in comparison with the low central load (1-back) condition. Hence, when people compensate for higher central load, by increasing attentional engagement, peripheral processing is constrained. Moreover, participants with high working memory capacity (WMC) - with a superior ability for attentional engagement - remembered less of the background story, but only in the low central load condition. Taken together, peripheral processing - as indexed by incidental memory of background speech - is constrained when task engagement is high.

Sensitivity, specificity and efficiency of speech-evoked ABR

We determined the sensitivity, specificity and efficiency of speech-evoked Auditory Brainstem Response (ABR) as a diagnostic support for Auditory Processing Disorder (APD) and specific language impairment (SLI). Speech-evoked ABRs were elicited using the five-formant syllable/da/. The waveforms V, A, C, D, E, F, and O of all groups were analyzed. The sensitivity and specificity were calculated, and receiver operating characteristic analyses were performed to determine the optimum cut-off. Seventy-five children who were native speakers of Brazilian-Portuguese participated. The participants included 25 children with APD, 25 children with SLI and 25 with typical development. Statistical analysis demonstrated a cut-off for latency values of 6.48, 7.51, 17.82, 22.33, 30.79, 39.54 and 48.00 for V, A, C, D, E, F, and O waves, respectively. The A wave exhibited superior balance for the APD group. For the SLI group, the A, D and O waves exhibited the best balance. Furthermore, when analyzing the APD and SLI groups separately, better sensitivity values were observed for the SLI group than the APD group. Speech-evoked ABR is a useful test to identify auditory processing disorders and language impairment. Furthermore, this study represented an important step forward in establishing the clinical utility of speech-evoked ABR in Brazilian Portuguese-speaking children.

Effect of Repetition Rate on Speech Evoked Auditory Brainstem Response in Younger and Middle Aged Individuals

Speech evoked auditory brainstem responses depicts the neural encoding of speech at the level of brainstem. This study was designed to evaluate the neural encoding of speech at the brainstem in younger population and middle-aged population at three different repetition rates (6.9, 10.9 and 15.4). Speech evoked auditory brainstem response was recorded from 84 participants (young participants=42, middle aged participants=42) with normal hearing sensitivity. The latency of wave V and amplitude of the fundamental frequency, first formant frequency and second formant frequency was calculated. Results showed that the latency of wave V was prolonged for middle-aged individuals for all three-repetition rates compared to the younger participants. The results of the present study also revealed that there was no difference in encoding of fundamental frequency between middle aged and younger individuals at any of the repetition rates. However, increase in repetition rate did affect the encoding of the fundamental frequency in middle-aged individuals. The above results suggest a differential effect of repetition rate on wave V latency and encoding of fundamental frequency. Further, it was noticed that repetition rate did not affect the amplitude of first formant frequency or second formant frequency in middle aged participants compared to the younger participants.

Speech evoked auditory brainstem response in stuttering

Auditory processing deficits have been hypothesized as an underlying mechanism for stuttering. Previous studies have demonstrated abnormal responses in subjects with persistent developmental stuttering (PDS) at the higher level of the central auditory system using speech stimuli. Recently, the potential usefulness of speech evoked auditory brainstem responses in central auditory processing disorders has been emphasized. The current study used the speech evoked ABR to investigate the hypothesis that subjects with PDS have specific auditory perceptual dysfunction. Objectives. To determine whether brainstem responses to speech stimuli differ between PDS subjects and normal fluent speakers. Methods. Twenty-five subjects with PDS participated in this study. The speech-ABRs were elicited by the 5-formant synthesized syllable/da/, with duration of 40 ms. Results. There were significant group differences for the onset and offset transient peaks. Subjects with PDS had longer latencies for the onset and offset peaks relative to the control group. Conclusions. Subjects with PDS showed a deficient neural timing in the early stages of the auditory pathway consistent with temporal processing deficits and their abnormal timing may underlie to their disfluency.

Speech evoked auditory brainstem response findings in children with epilepsy

OBJECTIVES

Children with epilepsy are at a considerable risk of cognitive impairment and school failure. Previous studies have typically documented abnormal responses in children with epilepsy at cortical level using speech stimuli. Recent studies reported that abnormal neural encoding of a speech syllable could be detected at the level of the brainstem using speech-evoked auditory brainstem response (ABR). The aim of this study is to investigate speech-evoked (ABR) results in children with epilepsy.

METHODS

The study group consisted of 38 recently diagnosed epileptic children; none of them has received antiepileptic therapy. They were 22 males and 16 females with age 9.1 ± 3.1 years. The control group consisted of 38 healthy normal hearing children with matched age and gender distribution. All subjects underwent full history taking, basic audiologic evaluation including pure-tone, speech audiometry and immittance testing. Click ABR response was recorded monaurally from both ears at 90 dB nHL then speech ABR was recorded monaurally from each ear at 80 dB SPL.

RESULTS

Though the study group disclosed normal click ABR compared to age matched normative values, speech-evoked ABR revealed a delayed waves V and A latencies in both ears. These findings reflect abnormal neural encoding of speech at the level of brainstem. The younger the age of epileptic child the more prolonged wave A latency and increased V/A inter-latency values.

CONCLUSIONS

Speech-evoked ABR results denote abnormal timing in the brainstem; such brainstem abnormality could be detected by speech evoked ABR rather than conventional click evoked ABR.

Subcortical encoding of speech cues in children with attention deficit hyperactivity disorder

OBJECTIVE

There is little information about processing of nonspeech and speech stimuli at the subcortical level in individuals with attention deficit hyperactivity disorder (ADHD). The auditory brainstem response (ABR) provides information about the function of the auditory brainstem pathways. We aim to investigate the subcortical function in neural encoding of click and speech stimuli in children with ADHD.

METHODS

The subjects include 50 children with ADHD and 34 typically developing (TD) children between the ages of 8 and 12 years. Click ABR (cABR) and speech ABR (sABR) with 40 ms synthetic /da/ syllable stimulus were recorded.

RESULTS

Latencies of cABR in waves of III and V and duration of V-Vn (P⩽0.027), and latencies of sABR in waves A, D, E, F and O and duration of V-A (P⩽0.034) were significantly longer in children with ADHD than in TD children. There were no apparent differences in components the sustained frequency following response (FFR).

CONCLUSIONS

We conclude that children with ADHD have deficits in temporal neural encoding of both nonspeech and speech stimuli.

SIGNIFICANCE

There is a common dysfunction in the processing of click and speech stimuli at the brainstem level in children with suspected ADHD.

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

OBJECTIVE

To investigate the relationship between speech auditory brainstem responses (speech ABRs) and word intelligibility under reverberation in elderly adults.

METHODS

Word 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.

RESULTS

No 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.

CONCLUSIONS

Word intelligibility under reverberation in elderly listeners is related to their ability to encode the temporal fine structure of speech.

SIGNIFICANCE

The 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.

The Relationship Between Acceptable Noise Level and Electrophysiologic Auditory Brainstem and Cortical Signal to Noise Ratios

The following objectives of the study were formulated: i) to investigate differences in measured signal to noise ratios while recording speech-evoked auditory brainstem response (cABR) and cortical late latency response (LLR) in low and high acceptable noise level (ANL) groups; and ii) to compare peak to peak amplitude of cABR (V-A) and LLR (N1-P2) in low and high ANL groups. A total of 23 normal hearing participants was included in the study. One shot replicative and partly exploratory research design was utilized to study the effect of signal to noise ratio in a recorded waveform on afferent mechanism, assessed by cABR and LLR on participants having values of ANL of ≤7 (low ANL group) and ≥13 (high ANL group). There were no differences in signal to noise ratio in the recorded waveforms of cABR and LLR between low and high ANL groups at both brainstem and cortical levels. However, the peak to peak amplitude of V-A of cABR and N1-P2 of LLR were both statistically larger in the high ANL group compared to their counterpart. The signal to noise ratio in recorded waveforms did not differentiated cABR (V-A) or LLR (N1-P2) in low and high ANL groups. However, Larger peak to peak amplitudes in the high ANL group suggests differences higher processing centers in the upper brainstem to the auditory cortex. The findings of the study may be useful in determining the patient acceptability of noise.

Effects of congenital blindness on the subcortical representation of speech cues

Human modalities play a vital role in the way the brain produces mental representations of the world around us. Although congenital blindness limits the understanding of the environment in some aspects, blind individuals may have other superior capabilities from long-term experience and neural plasticity. This study investigated the effects of congenital blindness on temporal and spectral neural encoding of speech at the subcortical level. The study included 26 congenitally blind individuals and 24 normal-sighted individuals with normal hearing. Auditory brainstem response (ABR) was recorded with both click and speech synthetic 40-ms /da/ stimuli. No significant difference was observed between the two groups in wave latencies or amplitudes of click ABR. Latencies of speech ABR D (p=0.012) and O (p=0.014) waves were significantly shorter in blind individuals than in normal-sighted individuals. Amplitudes of the A (p<0.001) and E (p=0.001) speech ABR (sABR) waves were also significantly higher in blind subjects. Blind individuals had significantly better results for duration (p<0.001) amplitude (p=0.015) and slope of the V-A complex (p=0.004), signal-to-noise ratio (p<0.001), and amplitude of the stimulus fundamental frequency (F0) (p=0.009), first formant (F1) (p<0.001) and higher-frequency region (HF) (p<0.001) ranges. Results indicate that congenitally blind subjects have improved hearing function in response to the /da/ syllable in both source and filter classes of sABR. It is possible that these subjects have enhanced neural representation of vocal cord vibrations and improved neural synchronization in temporal encoding of the onset and offset parts of speech stimuli at the brainstem level. This may result from the compensatory mechanism of neural reorganization in blind subjects influenced from top-down corticofugal connections with the auditory cortex.

A case study of the changes in the speech-evoked auditory brainstem response associated with auditory training in children with auditory processing disorders

BACKGROUND

Studies related to plasticity and learning-related phenomena have primarily focused on higher-order processes of the auditory system, such as those in the auditory cortex and limited information is available on learning- and plasticity-related processes in the auditory brainstem.

DESIGN AND METHOD

A clinical electrophysiological test of speech-evoked ABR known as BioMARK has been developed to evaluate brainstem responses to speech sounds in children with language learning disorders. Fast ForWord (FFW) was used as an auditory intervention program in the current study and pre- intervention and post-intervention speech-evoked ABR (BioMARK) measures were compared in 2 school-aged children with auditory processing disorders (APD).

RESULTS AND CONCLUSIONS

Significant changes were noted from pre-intervention to post-intervention and reflect plasticity in the auditory brainstem's neural activity to speech stimuli.

Auditory brainstem response to complex sounds predicts self-reported speech-in-noise performance

PURPOSE

To compare the ability of the auditory brainstem response to complex sounds (cABR) to predict subjective ratings of speech understanding in noise on the Speech, Spatial, and Qualities of Hearing Scale (SSQ; Gatehouse & Noble, 2004) relative to the predictive ability of the Quick Speech-in-Noise test (QuickSIN; Killion, Niquette, Gudmundsen, Revit, & Banerjee, 2004) and pure-tone hearing thresholds.

METHOD

Participants included 111 middle- to older-age adults (range = 45-78) with audiometric configurations ranging from normal hearing levels to moderate sensorineural hearing loss. In addition to using audiometric testing, the authors also used such evaluation measures as the QuickSIN, the SSQ, and the cABR.

RESULTS

Multiple linear regression analysis indicated that the inclusion of brainstem variables in a model with QuickSIN, hearing thresholds, and age accounted for 30% of the variance in the Speech subtest of the SSQ, compared with significantly less variance (19%) when brainstem variables were not included.

CONCLUSION

The authors' results demonstrate the cABR's efficacy for predicting self-reported speech-in-noise perception difficulties. The fact that the cABR predicts more variance in self-reported speech-in-noise (SIN) perception than either the QuickSIN or hearing thresholds indicates that the cABR provides additional insight into an individual's ability to hear in background noise. In addition, the findings underscore the link between the cABR and hearing in noise.

The Potential Role of the cABR in Assessment and Management of Hearing Impairment

Hearing aid technology has improved dramatically in the last decade, especially in the ability to adaptively respond to dynamic aspects of background noise. Despite these advancements, however, hearing aid users continue to report difficulty hearing in background noise and having trouble adjusting to amplified sound quality. These difficulties may arise in part from current approaches to hearing aid fittings, which largely focus on increased audibility and management of environmental noise. These approaches do not take into account the fact that sound is processed all along the auditory system from the cochlea to the auditory cortex. Older adults represent the largest group of hearing aid wearers; yet older adults are known to have deficits in temporal resolution in the central auditory system. Here we review evidence that supports the use of the auditory brainstem response to complex sounds (cABR) in the assessment of hearing-in-noise difficulties and auditory training efficacy in older adults.

Sex differences in auditory subcortical function

OBJECTIVE

Sex differences have been demonstrated in the peripheral auditory system as well as in higher-level cognitive processing. Here, we aimed to determine if the subcortical response to a complex auditory stimulus is encoded differently between the sexes.

METHODS

Using electrophysiological techniques, we assessed the auditory brainstem response to a synthesized stop-consonant speech syllable [da] in 76 native-English speaking, young adults (38 female). Timing and frequency components of the response were compared between males and females to determine which aspects of the response are affected by sex.

RESULTS

A dissimilarity between males and females was seen in the neural response to the components of the speech stimulus that change rapidly over time; but not in the slower changing, lower frequency information in the stimulus. We demonstrate that, in agreement with the click-evoked brainstem response, females have earlier peaks relative to males in the subcomponents of the response representing the onset of the speech sound. In contrast, the response peaks comprising the frequency-following response, which encode the fundamental frequency (F(0)) of the stimulus, as well as the spectral amplitude of the response to the F(0), is not affected by sex. Notably, the higher-frequency elements of the speech syllable are encoded differently between males and females, with females having greater representation of spectrotemporal information for frequencies above the F(0).

CONCLUSIONS

Our results provide a baseline for interpreting the higher incidence of language impairment (e.g. dyslexia, autism, specific language impairment) in males, and the subcortical deficits associated with these disorders.

SIGNIFICANCE

These results parallel the subcortical encoding patterns that are documented for good and poor readers in that poor readers differ from good readers on encoding fast but not slow components of speech. This parallel may thus help to explain the higher incidence of reading impairment in males compared to females.

Central auditory nervous system dysfunction in infants with non-syndromic cleft lip and/or palate

OBJECTIVE

Peripheral hearing loss has been commonly reported in children with non-syndromic cleft lip and/or palate (NSCLP) but few studies have provided information about central auditory nervous system (CANS) functioning for this group. The main objective of this study was to explore CANS functioning in infants with NSCLP through analysis of auditory evoked potentials (AEPs).

METHODS

AEPs including auditory brainstem response (ABR), middle latency response (MLR), and mismatch negativity (MMN) recordings were conducted in 34 infants of Chinese ethnicity with NSCLP and an equivalent number of normal controls.

RESULTS

There was no significant difference in ABR (all measurements, including wave I, III, V latencies, I-V inter-wave latency, and wave V amplitude), or MLR (recordable components, Na, Pa latencies, and Na-Pa amplitude) findings between the two groups. However, infants with NSCLP had a significantly smaller MMN response than their normal controls, using MMN strength as the measurement.

CONCLUSIONS

Significant abnormal auditory evoked potential findings at the cortical level suggest that infants with NSCLP may be at risk of central auditory discrimination dysfunction. Further effort is needed to determine auditory processing abilities in infants with NSCLP.

What is the role of the medial olivocochlear system in speech-in-noise processing?

The medial olivocochlear (MOC) bundle reduces the gain of the cochlear amplifier through reflexive activation by sound. Physiological results indicate that MOC-induced reduction in cochlear gain can enhance the response to signals when presented in masking noise. Some previous studies suggest that this "antimasking" effect of the MOC system plays a role in speech-in-noise perception. The present study set out to reinvestigate this hypothesis by correlating measures of MOC activity and speech-in-noise processing across a group of normal-hearing participants. MOC activity was measured using contralateral suppression of otoacoustic emissions (OAEs), and speech-in-noise processing was measured by measuring the effect of noise masking on performance in a consonant-vowel (CV) discrimination task and on auditory brain stem responses evoked by a CV syllable. Whereas there was a significant correlation between OAE suppression and both measures of speech-in-noise processing, the direction of this correlation was opposite to that predicted by the antimasking hypothesis, in that individuals with stronger OAE suppression tended to show greater noise-masking effects on CV processing. The current results indicate that reflexive MOC activation is not always beneficial to speech-in-noise processing. We propose an alternative to the antimasking hypothesis, whereby the MOC system benefits speech-in-noise processing through dynamic (e.g., attention- and experience-dependent), rather than reflexive, control of cochlear gain.