Thalamocortical Auditory Processing Across the Lifespan: A Study with Speech-Evoked Cortical Potentials.

Auditory cortical stimulability in non habilitated individuals – An evidence from CAEPs

Components of auditory event-related potentials (ERPs) may represent various aspects of the cortical processing of pitch. However, evidence hints an earlier representation of pitch perception in auditory ERPs of cortical origin. In this study, we examined whether earlier waves in cortical auditory evoked potentials (CAEPs) might reflect pitch-relevant features of both listeners and stimuli. CAEPs were elicited by pure tones and sweeping tones, and individual behavioral performance in pitch discrimination reflected by frequency difference limen (FDL) was also measured. Results show that CAEPs evoked by sweeping tones significantly correlate to FDL around ~50 ms, but CAEPs evoked by pure tones do not. Also, CAEPs are significantly affected by pitch-shift direction around ~130 ms. CAEPs evoked by ascending sweeping tones are larger in magnitude than those evoked by descending ones. Therefore, listeners' personal attributes relevant to pitch perception have already been reflected at a very early stage of cortical auditory processing, whilst certain pitch-related features of stimuli are recognized and represented at a later stage.

Central auditory system responses from children while listening to speech in noise

Auditory cortical activity to different voice onset times in cochlear implant users

Recording of free-field cortical auditory evoked potential (CAEP) responses to speech tokens was introduced into the audiology management for infants with a permanent childhood hearing impairment (PCHI) during 2011–2015 at a U.K. service. Children with bilateral PCHI were studied from two sequential cohorts. Thirty-four children had followed an audiology pathway prior to CAEP introduction, and 44 children followed a pathway after the introduction of CAEP and were tested with unaided and aided CAEP responses. Data analysis explored the age of diagnosis, hearing aid fitting, and referral for cochlear implant (CI) assessment for each of these groups. CAEP offered a novel educative process for the parents and audiologists supporting decision-making for hearing aid fitting and CI referral. Delays in hearing aid fitting and CI referral were categorized as being due to the audiologist’s recommendation or parental choice. Results showed that the median age of hearing aid fitting prior to CAEP introduction was 9.2 months. After the inclusion of CAEP recording in the infant pathways, it was 3.9 months. This reduction was attributable to earlier fitting of hearing aids for children with mild and moderate hearing losses, for which the median age fell from 19 to 5 months. Children with profound hearing loss were referred for CI assessment at a significantly earlier age following the introduction of CAEP. Although there has also been a national trend for earlier hearing aid fitting in children, the current study demonstrates that the inclusion of CAEP recording in the pathway facilitated earlier hearing aid fitting for milder impairments.

Cortical processing of speech sounds in individuals with cochlear hearing loss and auditory neuropathy.

Background: Dichotic listening (DL) technique is a behavioral non-invasive tool which is used in studying hemispheric lateralization. Previous studies using behavioral DL have hypothesized that individuals with learning disabilities (LD) exhibit a lack of cortical specialization for processing speech stimulus. However, there is no event related potential (ERP) evidence, hence the main objective of the study is to explore hemispheric asymmetry using cortical auditory evoked potential (CAEPs) in normal hearing adults and also to compare the same in children with LD and healthy controls. Methods: CAEPs were recorded in 16 normal hearing young adults, eight right-handed children with LD and their age matched controls. Two stop constants (/Pa/ - voiceless, bilabial, stop: /Ta/ - voiceless, alveolar, stop) were chosen for this experiment and presented in each ear and dichotically in two different orders (/pa-ta/, /ta-pa/). ERPs were processed using a standard pipeline, and electrodes readings over the left and right hemispheres were averaged to create left and right regions of interest (ROI). The CAEPs were analyzed for mean amplitude and peak latency of P1-N1-P2 components. Results: The current study results suggest no statistically significant difference between the two stimulus in monaural condition and absence of order effect in dichotic condition. In healthy controls the CAEP latencies were shorter over the left hemisphere in both monaural and dichotic conditions in adults and control children. However, it was very evident that such a difference was lacking in children with LD. Conclusions: Hemispheric asymmetry can be detected using CAEPs for speech stimulus. The measures are consistent and void of stimulus or order effect. Taken together, the findings of current study, both monaural and dichotic condition illustrates the hemispheric differences in processing speech stimuli in normal hearers. Absence of latency differences between hemispheres in children with LD indicate a lack of hemispheric asymmetry.

Introduction The study of electrophysiological auditory measures with different types of masking makes it possible to understand temporal processing skills and the processes involved in speech recognition in noise situations. The use of modulated masking in cortical measures of hearing enables the obtainment of analysis parameters of the masking release and its impact on neural auditory processing.Objective To investigate the behavior of cortical auditory evoked potentials (CAEPs) with modulated masking in the normal hearing population.Data synthesis A total of 2,159 articles were identified in the initial search; of these, 12 were selected for full reading. After excluding studies that did not meet the eligibility criteria, six articles were included in the present systematic review.The results show that the type of masking has an influence on cortical auditory behavior, indicating a different effect on neural posture rergarding CAEP responses. Modulated noise as masking in the CAEP record generated statistically higher and earlier responses compared with non-modulated/steady noise, evidenced by the results obtained in the meta-analysis with subgroup analysis. These responses may indicate an influence of the type of noise in the neural auditory coding.Conclusion Better responses were observed in modulated masking in terms of the behavior of CAEPs. Decreased latency and increased amplitude of cortical measurements with the use of modulated noise indicate a lower masking effect of this noise in cortical auditory processing, evidencing the masking release phenomenon.

Purpose Previous research suggests the existence of gap detection impairments because of tinnitus. The current study aimed to determine whether there was objective evidence of gap impairment in individuals with tinnitus by recording silent gap in white noise cortical auditory evoked potentials (CAEPs) in a chronic tinnitus group and a no-tinnitus group. The results were compared to previous gap-evoked potential and behavioral gap detection studies. Method Chronic tinnitus and no-tinnitus groups were formed by matching pairs of subjects ( n = 26) based on age, gender, and hearing thresholds. Behaviorally determined gap detection thresholds were used to define the electrophysiological gap duration conditions of subthreshold, threshold, and suprathreshold gaps in white noise. Amplitude, latency, and area of the CAEP were analyzed by group and condition using mixed-model analyses of variance. Results Across all participants, as the duration of the gap increased, amplitude and area of the CAEP increased. There were no significant differences by tinnitus status between groups for any outcome measures, except for a significant interaction between group and gap duration for P1 latency. Conclusions Silent gap-evoked CAEPs can be recorded in adults with and without tinnitus. Amplitude and area were sensitive to gap duration across groups; latency was not. Contrary to hypotheses, there was little evidence supporting differences in gap-evoked CAEPs between the tinnitus and control groups. Stimulus and other factors that may have contributed to the lack of a group difference in the current study are discussed, as well as implications for future studies of objective measures of tinnitus perception. Supplemental Material https://doi.org/10.23641/asha.7822601.

The goal of this study was to examine the degree to which age-related differences in early or automatic levels of auditory processing and attention-related processes explain age-related differences in auditory temporal processing. We hypothesized that age-related differences in attention and cognition compound age-related differences at automatic levels of processing, contributing to the robust age effects observed during challenging listening tasks. We examined age-related and individual differences in cortical event-related potential (ERP) amplitudes and latencies, processing speed, and gap detection from 25 younger and 25 older adults with normal hearing. ERPs were elicited by brief silent periods (gaps) in an otherwise continuous broadband noise and were measured under two listening conditions, passive and active. During passive listening, participants ignored the stimulus and read quietly. During active listening, participants button pressed each time they detected a gap. Gap detection (percent detected) was calculated for each gap duration during active listening (3, 6, 9, 12, and 15 msec). Processing speed was assessed using the Purdue Pegboard Test and the Connections Test. Repeated measures analyses of variance assessed effects of age on gap detection, processing speed, and ERP amplitudes and latencies. An "attention modulation" construct was created using linear regression to examine the effects of attention while controlling for age-related differences in auditory processing. Pearson correlation analyses assessed the extent to which attention modulation, ERPs, and processing speed predicted behavioral gap detection. Older adults had significantly poorer gap detection and slower processing speed than younger adults. Even after adjusting for poorer gap detection, the neurophysiological response to gap onset was atypical in older adults with reduced P2 amplitudes and virtually absent N2 responses. Moreover, individual differences in attention modulation of P2 response latencies and N2 amplitudes predicted gap detection and processing speed in older adults. That is, older adults with P2 latencies that decreased and N2 amplitudes that increased with active listening had faster processing speed and better gap detection than those older adults whose P2 latencies increased and N2 amplitudes decreased with attention. The results from the present study are broadly consistent with previous findings that older adults exhibit significantly poorer gap detection than younger adults in challenging tasks. Even after adjusting for poorer gap detection, older and younger adults showed robust differences in their electrophysiological responses to sound offset. Furthermore, the degree to which attention modulated the ERP was associated with individual variation in measures of processing speed and gap detection. Taken together, these results suggest an age-related deficit in early or automatic levels of auditory temporal processing and that some older adults may be less able to compensate for declines in processing by attending to the stimulus. These results extend our previous findings and support the hypothesis that age-related differences in cognitive or attention-related processing, including processing speed, contribute to an age-related decrease in gap detection.

Objective: The ability to hear in background noise is related to the processing of the incoming acoustic signal in the peripheral auditory system as well as the central auditory nervous system (CANS). Electrophysiological tests have the ability to demonstrate the underlying neural integrity of the CANS, but to date a lack of literature exists demonstrating the effects of background noise on auditory cortical potentials. Therefore, the purpose of this investigation was to systematically investigate the effects of white noise on tone burst-evoked late auditory evoked potentials (N1, P2, and P3) in normal hearing young adults. Study Design: Twenty young-adult normal-hearing individuals served as subjects. A comparison of the late auditory evoked potentials (N1, P2, and P3) was made at multiple signal-to-noise ratios (SNRs) (quiet, + 20, + 10, 0). N1, P2, and P3 were elicited and both amplitude and latency were measured for each of the potentials. A standard oddball paradigm with binaural stimulation was used to evoke the potentials. Repeated Measures Analyses of Variance (ANOVA) were conducted for both the experimental factors of amplitude and latency with within subjects factors of condition (quiet, + 20, + 10, 0). Results: Results indicated no significant differences in N1, P2, or P3 amplitude or latency between the quiet and + 20 SNR condition; however, at poorer SNRs significant N1, P2, and P3 amplitude and/or latency differences were observed. Conclusion: The results indicate a change in higher-order neural function related to the presence of increased noise in the environment.

To examine the differences in auditory evoked cortical responses that may underlie the tendency of some people to perceive tinnitus. The study hypothesis is that the mean ALR and P300 amplitudes in normal hearing adults who perceive temporary tinnitus after exposure to sustained silence will be larger than the mean ALR and P300 amplitudes in normal hearing adults who do not perceive temporary tinnitus after exposure to sustained silence. This was a prospective cross-sectional study. The approval for the study was obtained from the IRB and COVID ramp up committee of University of North Carolina Greensboro (UNCG). Participants completed comprehensive hearing screening and preand postsilence ALR and P300 recordings were obtained. After the first ALR/P300 recording participants were exposed to ten minutes of silence. Participants completed a Qualtrics questionnaire to report any tinnitus perception that emerged during silence exposure. Absolute N1, P2 and P300 waveform amplitudes and latencies were identified and were entered into an SPSS spreadsheet for data analysis. Thirty adult females with normal pure tone hearing thresholds and no history of persistent tinnitus were included in the study. The mean age of the participants was 22.5 ± 3.9 years. When exposed to silence, eight (26.7%) participants perceived temporary tinnitus. N1 and P300 waveforms were smaller in amplitude and faster in latency in the tinnitus perception group; however, the ALR and P300 waveform latencies and amplitudes did not statistically differ significantly between the participants who perceived temporary tinnitus in silence and those who did not (p>0.05). The difference in waveform morphology between the tinnitus perception group and the non-tinnitus perception group revealed a greater difference in P300 amplitude after exposure to silence. Differences in ALR and P300 latencies and amplitudes were observed between the tinnitus perception group and non-tinnitus perception group, with smaller P300 amplitudes appearing in the group perceiving tinnitus. While the results did not statistically significant, this pattern may reflect a mismatch between the neuronal response in the auditory cortex (N1 and P2 amplitudes and latencies) and the neuronal activity in the modulatory network regions (P300).

Effect of competing noise on cortical auditory evoked potentials elicited by speech sounds in 7- to 25-year-old listeners

Aging effects on functional auditory and visual processing using fMRI with variable sensory loading

Human middle-latency auditory evoked potentials: vertex and temporal components