Predicting Perception in Noise Using Cortical Auditory Evoked Potentials

Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits.     

Habituation and rate effect in the auditory cortical potentials evoked by trains of stimuli

Summary The effects of the stimulus repetition rate over the habituated auditory cortical evoked responses were studied. The stimulation pattern consisted of trains of pure tone bursts with interstimulus interval (ISI) of 1 s, and intertrain interval (ITI) of 5 s, delivered with constant time and intensity parameters during 93 min. The analysis of the responses was based upon across averaging of the trains, each single response being evaluated in the latency and amplitude parameters. Two time-dependent factors affected the responses in a distinct way: the habituation throughout the whole stimulation and the rate effect within the train. The linear regressions of the time/amplitude functions of the responses were calculated in relation to the duration of ISI and ITI. By introducing a correction factor depending on the repetition rate it was possible to evaluate the relationships between habituation and repetition rate. Changes in the repetition rate do not have any effect on the habituation process. The two phenomena are completely distinct, and they probably have neurophysiologic substrates corresponding to different levels in the central nervous system (CNS).     

Auditory brain stem response and cortical evoked potentials in children with type 1 diabetes mellitus

Conclusions: Delay in ABR and CAEPs wave latencies in children with type 1DM indicates that there is abnormality in the neural conduction in DM patients. The duration of DM has greater effect on auditory function than the control of DM.

Background: Diabetes mellitus (DM) is a common endocrine and metabolic disorder. Evoked potentials offer the possibility to perform a functional evaluation of neural pathways in the central nervous system.

Objectives: To investigate the effect of type 1 diabetes mellitus (T1DM) on auditory brain stem response (ABR) and cortical evoked potentials (CAEPs).

Method: This study included two groups: a control group (GI), which consisted of 20 healthy children with normal peripheral hearing, and a study group (GII), which consisted of 30 children with type I DM. Basic audiological evaluation, ABR, and CAEPs were done in both groups.

Results: Delayed absolute latencies of ABR and CAEPs waves were found. Amplitudes showed no significant difference between both groups. Positive correlation was found between ABR wave latencies and duration of DM. No correlation was found between ABR, CAEPs, and glycated hemoglobin.     

Prediction of hearing thresholds: Comparison of cortical evoked response audiometry and auditory steady state response audiometry techniques

The present study evaluated how well auditory steady state response (ASSR) and tone burst cortical evoked response audiometry (CERA) thresholds predict behavioral thresholds in the same participants. A total of 63 ears were evaluated. For ASSR testing, 100% amplitude modulated and 10% frequency modulated tone stimuli at a modulation frequency of 40Hz were used. Behavioral thresholds were closer to CERA thresholds than ASSR thresholds. ASSR and CERA thresholds were closer to behavioral thresholds at higher frequencies than at lower frequencies. Although predictions based on CERA thresholds are slightly more accurate than ASSR thresholds, the differences may not be clinically significant, particularly when the degree of individual variations is considered. Prediction of hearing thresholds became more accurate when hearing loss increased. Due to variations in prediction across participants, a single correction factor cannot be used. Other factors must be considered in selecting whether to use CERA or ASSR in predicting behavioral thresholds.     

The relationship between cortical auditory evoked potential (CAEP) detection and estimated audibility in infants with sensorineural hearing loss

Abstract

Objective: To determine the effectiveness of objective statistical detection in CAEP testing to evaluate audibility in young infants with sensorineural hearing loss. Design: CAEP recordings to speech-based stimuli were made at three presentation levels (55, 65, or 75 dB SPL) when a group of hearing-impaired infants were either aided or unaided. Later-obtained behavioral audiograms were used as the gold standard against which to evaluate the accuracy of the automatic detection of the presence/absence of CAEP responses. Study sample: Participants were 18 infants with confirmed sensorineural hearing loss. Results: Higher sensation levels led to a greater number of present CAEP responses being detected. More CAEP waveforms were detected in the aided condition than in the unaided condition. Conclusion: Our results suggest that the presence/absence of CAEP responses defined by the automatic statistical criterion was effective in showing whether increased sensation levels provided by amplification were sufficient to reach the cortex. This was clearly apparent from the significant increase in cortical detections when comparing unaided with aided testing.     

Processing intensity at rapid rates: evidence from auditory evoked potentials in 9-11-year-old children

OBJECTIVE: The ability to understand speech requires processing of rapidly changing acoustic information. Much more is known about processing the rapid spectro-temporal properties of speech than is known about processing of intensity, even though intensity is a fundamental cue for accurate speech perception. The purpose for the current study was to characterize, in 9-11-year-old typically language-developing children, the auditory event-related brain potentials elicited by different tone intensities when presented in complex environments (i.e., varying in frequency and intensity) at rapid rates. METHODS: Pure tones of four different intensity levels (66, 74, 78, and 86dB SPL) and five different stimulus frequencies were presented at a stimulus rate of 10Hz. The latency and amplitude of the auditory event-related brain potentials were measured. RESULTS: At this fast rate, a positive (P1) followed by a negative component was elicited. The lowest intensity sound elicited the lowest P1 amplitude and the highest intensity sound elicited the highest P1 amplitude. The P1 elicited by the two middle tone intensities had amplitudes that fell between the lowest and highest amplitudes but they were not significantly different from each other. The negative component following the P1 was unaffected by intensity variation. CONCLUSIONS: Intensity variation of sounds presented in a complex environment at a rapid rate modulated only the amplitude of the earliest obligatory auditory component (P1), consistent with our previous studies in which only the P1 could follow the rapid stimulation rate. P1 amplitude changes reflected the relative differences among the sounds, not the absolute differences in loudness among the sounds presented together in the sequence. The results suggest that the environment, or context, within which rapid sounds occur, influences the relative amplitude of the P1 in children.     

Assessment of auditory discrimination in hearing-impaired patients

Hearing loss can impair auditory discrimination, especially in noisy environments, requiring greater listening effort, which can impact socio-occupational life. To assess the impact of hearing loss in noisy environments, clinicians may use subjective or objective methods. Subjective methods, such as speech audiometry in noise, are used in clinical practice to assess reported discomfort. Objective methods, such as cortical auditory evoked potentials (CAEPs), are mainly used in research. Subjective methods mainly comprise speech audiometry in noise, in which the signal-to-noise ratio can be varied so as to determine the individual speech recognition threshold, with and without hearing rehabilitation, the aim being to highlight any improvement in auditory performance. Frequency discrimination analysis is also possible. Objective methods assess auditory discrimination without the patient's active participation. One technique used for patients with auditory rehabilitation is the study of auditory responses by CAEPs. This electrophysiological examination studies cortical auditory rehabilitation oddball paradigms, enabling wave recordings such as mismatch negativity, P300 or N400, and analysis of neurophysiological markers according to auditory performance. The present article reviews all these methods, in order to better understand and evaluate the impact of hearing loss in everyday life.     

Objective detection of auditory steady-state evoked potentials based on mutual information

Objective: Recently, we developed a metric to objectively detect human auditory evoked potentials based on the mutual information (MI) between neural responses and stimulus spectrograms. Here, the MI algorithm is evaluated further for validity in testing the auditory steady-state response (ASSR), a sustained potential used in objective audiometry. Design: MI was computed between spectrograms of ASSRs and their evoking stimuli to quantify the shared time-frequency information between neuroelectric activity and stimulus acoustics. MI was compared against two traditional ASSR detection metrics: F-test and magnitude-squared coherence (MSC). Study Sample: Using an empirically derived threshold (?_MI=1.45), MI was applied as a binary classifier to distinguish actual biological responses recorded in human participants (n=11) from sham recordings, containing only EEG noise (i.e., non-stimulus-control condition). Results: MI achieved high overall accuracy (>90%) in identifying true ASSRs from sham recordings, with true positive/true negative rates of 82/100%. During online averaging, comparison with two other indices (F-test, MSC) indicated that MI could detect ASSRs in roughly half the number of trials (i.e., ～400 sweeps) as the MSC and performed comparably to the F-test, but showed slightly better signal detection performance. Conclusions: MI provides an alternative, more flexible metric for efficient and automated ASSR detection.     

The detection of adult cortical auditory evoked potentials (CAEPs) using an automated statistic and visual detection

Abstract

The detection of adult cortical auditory evoked potentials (CAEPs) can be challenging when the stimulus is just audible. The effectiveness of a statistic compared with expert examiners in (1) detecting the presence of CAEPs when stimuli were present, and (2) reporting the absence of CAEPs when no stimuli were present, was investigated. CAEPs recorded from ten adults, using two speech-based stimuli, five stimulus presentation levels, and non-stimulus conditions, were given to four experienced examiners who were asked to determine if responses to auditory stimulation could be observed, and their degree of certainty in making their decision. These recordings were also converted to multiple dependent variables and Hotelling's T2 was applied to calculate the probability that the mean value of any linear combination of these variables was significantly different from zero. Results showed that Hotelling's T2 was equally sensitive to the best of individual experienced examiners in differentiating a CAEP from random noise. It is reasonable to assume that the difference in response detection for a novice examiner and Hotelling's T2 would be even greater.

Sumario

La detección de los potenciales evocados auditivos corticales (CAEP) del adulto puede ser un desafío cuando el estímulo es apenas audible. Se investigó la efectividad de una comparación estadística con examinadores expertos para (1) detectar la presencia del CAEP cuando el estimulo estuvo presente, y (2) reportar la ausencia del CAEP cuando ningún estímulo estaba presente. Los CAEP registrados para diez adultos, usando dos estímulos con base en lenguaje, cinco niveles de presentación del estímulo, y condiciones sin estímulo, fueron presentados a cuatro examinadores con experiencia, a quienes se solicitó que determinaran si las respuestas a estímulos auditivos podían ser observadas y su grado de certeza en la toma de sus decisiones. Estos registros fueron también convertidos a múltiples variables dependientes y se aplicó el T2 de Hotelling para calcular la probabilidad de que el valor medio de una combinación lineal de estas variables fuera significativamente diferente de cero. Los resultados mostraron que el T2 de Hotelling era igualmente sensible que lo mejor de los examinadores experimentados individuales para diferenciar un CAEP de un ruido aleatorio. Es razonable asumir que la diferencia en detección de respuestas para un examinador novato y el T2 de Hotelling serían aún mayor.     

Age-related differences in sensitivity to small changes in frequency assessed with cortical evoked potentials

As part of an ongoing study of age-related changes in auditory processing, sensitivity to small changes in frequency were assessed using the cortical auditory evoked potential, P1-N1-P2, in younger and older adults with normal hearing. Behavioral measures have shown age-related differences in intensity and frequency discrimination that are larger at lower than higher frequencies. However, substantial individual differences and equivocal results among studies have been reported. This variability may reflect differences in tasks and procedures, as well as subject variables, such as hearing sensitivity and level of attention. To minimize these subject variables, the P1-N1-P2 response was investigated using a passive listening paradigm. Subjects were 10 younger and 10 older adults. The P1-N1-P2 was elicited by a 150-ms change in frequency in otherwise continuous 500-Hz and 3000-Hz pure tones presented at 70dB SPL. P1-N1-P2 threshold was defined as the smallest change in frequency needed to evoke a P1-N1-P2 response. Furthermore, a frequency-dependent aging effect was observed for P1-N1-P2 thresholds, such that older subjects were significantly less sensitive to the frequency change than younger subjects, with significantly larger age-related differences at 500Hz than at 3000Hz. Age-related changes in response latencies and amplitude of the P1-N1-P2 response were also evident at 500 and 3000Hz. These results are consistent with age-related changes in the central auditory system and suggest that changes in frequency discrimination abilities of older adults may be, in part, related to changes in preattentive levels of auditory processing.     

听性脑干反应联合听觉多频稳态诱发反应在儿童听力筛查和诊断中的应用

目的利用听觉稳态诱发反应（auditory steady state evoked response,ASSER）联合听性脑干反应（auditory brainstem response,ABR）测试对婴幼儿进行听力检测,评价两种方法对婴幼儿听力损伤早期发现及损失程度评估的作用。方法对7 6例（1 5 2耳）畸变产物耳声发射（distortion product otoacoustic emission,DPOAE）复筛未通过的婴幼儿及门诊就诊疑有听力损失的婴幼儿进行ASSER和ABR测试,对结果进行比较。结果7 6例（1 5 2耳）婴幼儿ABR反应阈与ASSER高频反应阈比较,差异无统计学意义（P＆lt;0.0 5）。ABR在最大输出无反应而ASSER测试中各频率能引出反应。结论ASSER联合ABR检查可以更全面的评估婴幼儿的真实听力情况,对ABR无反应的患儿还应进行ASSER测试,有助于全面评估其听力损失程度。     

The effect of a hearing aid noise reduction algorithm on the acquisition of novel speech contrasts

Audiologists are reluctant to prescribe digital hearing aids with active digital noise reduction (DNR) to pre-verbal children due to their potential for an adverse effect on the acquisition of language. The present study investigated the relation between DNR and language acquisition by modeling pre-verbal language acquisition using adult listeners presented with a non-native speech contrast. Two groups of normal-hearing, monolingual Anglophone subjects were trained over four testing sessions to discriminate novel, difficult to discriminate, non-native Hindi speech contrasts in continuous noise, where one group listened to both speech items and noise processed with DNR, and where the other group listened to unprocessed speech in noise. Results did not reveal a significant difference in performance between groups across testing sessions. A significant learning effect was noted for both groups between the first and second testing sessions only. Overall, DNR does not appear to enhance or impair the acquisition of novel speech contrasts by adult listeners.     

Deprivation-induced cortical reorganization in children with cochlear implants

A basic finding in developmental neurophysiology is that some areas of the cortex cortical areas will reorganize following a period of stimulus deprivation. In this review, we discuss mainly electroencephalography (EEG) studies of normal and deprivation-induced abnormal development of the central auditory pathways in children and in animal models.We describe age cut-off for sensitive periods for central auditory development in congenitally deaf children who are fitted with a cochlear implant. We speculate on mechanisms of decoupling and reorganization which may underlie the end of the sensitive period. Finally, we describe new magentoencephalography (MEG) evidence of somatosensory cross-modal plasticity following long-term auditory deprivation.