Acoustic change complex for frequency changes

Previous studies, using modulation stimuli, on the relative effects of frequency resolution and time resolution on CI users’ speech perception failed to reach a consistent conclusion. In this study, frequency change detection and temporal gap detection were used to investigate the frequency resolution and time resolution of CI users, respectively. Psychophysical and neurophysiological methods were used to simultaneously investigate the effects of frequency and time resolution on speech perception in post-lingual cochlear implant (CI) users. We investigated the effects of psychophysical results [frequency change detection threshold (FCDT), gap detection threshold (GDT)], and acoustic change complex (ACC) responses (evoked threshold, latency, or amplitude of ACC induced by frequency change or temporal gap) on speech perception [recognition rate of monosyllabic words, disyllabic words, sentences in quiet, and sentence recognition threshold (SRT) in noise]. Thirty-one adult post-lingual CI users of Mandarin Chinese were enrolled in the study. The stimuli used to induce ACCs to frequency changes were 800-ms pure tones (fundamental frequency was 1,000 Hz); the frequency change occurred at the midpoint of the tones, with six percentages of frequency changes (0, 2, 5, 10, 20, and 50%). Temporal silences with different durations (0, 5, 10, 20, 50, and 100 ms) were inserted in the middle of the 800-ms white noise to induce ACCs evoked by temporal gaps. The FCDT and GDT were obtained by two 2-alternative forced-choice procedures. The results showed no significant correlation between the CI hearing threshold and speech perception in the study participants. In the multiple regression analysis of the influence of simultaneous psychophysical measures and ACC responses on speech perception, GDT significantly predicted every speech perception index, and the ACC amplitude evoked by the temporal gap significantly predicted the recognition of disyllabic words in quiet and SRT in noise. We conclude that when the ability to detect frequency changes and the temporal gap is considered simultaneously, the ability to detect frequency changes may have no significant effect on speech perception, but the ability to detect temporal gaps could significantly predict speech perception.

Assessment of outcome measures after audiological computer-based auditory training in cochlear implant children

Background Cochlear implants (CI) can partially or totally revert the effects of sensory deprivation; thus enabling the development of auditory abilities. However, there remains a large amount of variability in speech perception outcome among CI users. Such variability may be attributed to the children’s diverse capabilities in detecting amplitude, temporal and spectral changes in the incoming complex speech signals in quiet and in difficult listening situations. Objective To study whether the newly introduced Acoustic Change Complex (ACC) cortical potential using short duration can be used to document such variability. If used as a tool for cortical discrimination, it will aid in evaluating young children who cannot be tested using behavioral measures. Patients and Methods Cortical auditory evoked potentials were recorded in forty five unilaterally-implanted children ranging in age from 6 to 12 years. Stimuli used to elicit ACC were short duration (500 msec.) speech and tonal stimuli. Spectral change was done using /i/ to /u/ vowels, while temporal change was done using variable gaps-in-1000 Hz tone, ranging from 5 msec. to 200 msec. Auditory evoked responses were compared to behavioral tests which included speech perception test (PBKG) and psychophysical test for temporal resolution. Results ACC potentials were successfully recorded in most of the children evaluated. Generally, ACC were significantly highly detected in temporal changes than spectral change. Individual data showed that poor behavioral performance was associated with higher ACC detection thresholds to gap in tone and poorer % detection to vowel change. Conclusion: ACC potential using short duration stimuli can be recorded in young implanted children in an ordinary clinical setting. However, more research is needed to document the complex behavioral-objective relationship and its ultimate link to speech perception and language development in young CI recipients.

Early representations of auditory features often involve neuronal populations whose tuning is substantially wider than behavioral discrimination thresholds. Although behavioral discrimination performance can be sometimes achieved by single neurons when using the appropriate part of their (wide) tuning curves, neurons that encode the resulting high-acuity representations have rarely been described. Here we demonstrate the existence of neurons with extremely narrow tuning for interaural time differences (ITDs), a major physical cue for the azimuth of sound sources. The tuning width of ITD-tuned brainstem neurons is mostly determined by the properties of their acoustic input, and may be 10-100 times wider than behavioral thresholds. In contrast, we show that tuning widths of some neurons in the primary auditory cortex in the cat high-frequency auditory cortex (measured using transposed stimulus) can be very sharp and approach behavioral thresholds. Furthermore, while best ITDs of brainstem neurons often lie outside the range of naturally encountered ITDs (the ethological range), the range of best ITDs of the narrowly tuned cortical neurons corresponds well to the ethological range. Thus, our results suggest that the auditory cortex contains a high-resolution representation of ITDs that explicitly decodes the widely tuned brainstem representations.

Previous studies demonstrated prolonged development of degraded speech perception, perhaps due to the maturation of auditory and cognitive brain regions. We investigated the contributions of auditory cortical encoding, measured by the acoustic change complex (ACC), and cognition to speech perception in adolescents (10–17) and young adults (18–23). Speech conditions included the QuickSIN and perception of 6-band noise-vocoded sentences, followed either by silence or multitalker babble. The ACC was measured to a frequency change condition (1000–950 Hz) and gap detection condition (10 ms gap in noise). Cognitive testing was also administered. Separate hierarchical stepwise regressions were completed for each condition. Preliminary results suggest that testing order (silence or babble first) exclusively affected performance on the NV silence condition. Encoding of timing information (ACC for gaps) contributed to the NV silence condition only, whereas encoding of spectral information (ACC for frequency) contributed to both NV speech conditions. Strategy use and sustained attention contributed to both NV speech conditions but age did not explain any unique variance after all factors were included. For the QuickSIN, auditory working memory and vocabulary contributed to performance, and age continued to influence performance after accounting for all other factors. [Funded by NIDCD.]

Identifying the temporal and spectral information in sound is important for understanding speech; indeed, a person who has good spectral resolution usually shows good speech recognition performance. The spectral ripple discrimination (SRD) test is often used to behaviorally determine spectral resolution capacity. However, although the SRD test is useful, it is difficult to apply to populations who cannot execute the behavioral task, such as younger children and people with disabilities. In this study, an objective approach using spectral ripple (SR) stimuli to evoke the acoustic change complex (ACC) response was investigated to determine whether it could objectively evaluate the spectral resolution ability of subjects with normal hearing (NH) and those with hearing loss (HL). Ten subjects with NH and eight with HL were enrolled in this study. All subjects completed the behavioral SRD test and the objective SR-ACC test. Additionally, the HL subjects completed speech perception performance tests while wearing hearing aids. In the SRD test, the average thresholds were 6.48 and 1.52 ripples per octave (RPO) for the NH and HL groups, respectively, while in the SR-ACC test, they were 4.90 and 1.35 RPO, respectively. There was a significant difference in the average thresholds between the two groups for the SRD (p < 0.001) and the SR-ACC (p < 0.001) tests. A significant positive correlation was observed between the SRD and SR-ACC tests (ρ = 0.829, p < 0.001). In the HL group, there was a statistically significant relationship between speech recognition performance in noisy conditions and the SR-ACC threshold (ρ = 0.911, p < 0.001 in Sentence score of Korean Speech Audiometry (KSA)). The results supported the feasibility of the SR-ACC test to objectively evaluate auditory spectral resolution in individuals with HL. This test has potential for use in individuals with HL who are unable to complete the behavioral task associated with the SRD test; therefore, it is proposed as a more inclusive alternative to the SRD test.

The aim of this study was to evaluate (a) the effect of aging on spectral and temporal resolution, as measured both behaviorally and electrophysiologically, and (b) the contributions of spectral and temporal resolution and cognition to speech perception in younger and older adults. Eighteen younger and 18 older listeners with normal hearing or no more than mild-moderate hearing loss participated in this cross-sectional study. Speech recognition was assessed with the QuickSIN test and six-band noise-vocoded sentences. Frequency discrimination, temporal interval discrimination, and gap detection thresholds were obtained using a three-alternative forced-choice task. Cortical auditory evoked potentials were recorded in response to tonal frequency changes and to gaps in noise. Cognitive testing included nonverbal reasoning, vocabulary, working memory, and processing speed. There were age-related declines on many outcome measures, including speech perception in noise, cognition (nonverbal reasoning, processing speed), behavioral gap detection thresholds, and neural correlates of spectral and temporal processing (smaller P1 amplitudes and prolonged P2 latencies in response to frequency change; smaller N1-P2 amplitudes and longer P1, N1, P2 latencies to temporal gaps). Hearing thresholds and neural processing of spectral and temporal information were the main predictors of degraded speech recognition performance, in addition to cognition and perceptual learning. These factors accounted for 58% of the variability on the QuickSIN test and 41% of variability on the noise-vocoded speech. The results confirm and extend previous work demonstrating age-related declines in gap detection, cognition, and neural processing of spectral and temporal features of sounds. Neural measures of spectral and temporal processing were better predictors of speech perception than behavioral ones. https://doi.org/10.23641/asha.28883711.

To assess the accuracy of threshold estimates determined using the auditory brain stem responses (ABRs) to brief tones presented in notched noise in a group of infants and young children with normal hearing or sensorineural hearing loss (SNHL). The thresholds for ABRs to brief duration 500, 2000, and 4000 Hz tones presented in notched-noise masking were evaluated in infants and young children with normal hearing (N = 34) or SNHL (N = 54). Tone-evoked ABR thresholds were compared with behavioral thresholds obtained at follow-up audiologic assessments, for a total of 220 comparisons. ABR thresholds for the infants with bilateral normal hearing were 23.6, 12.9, and 12.6 dB nHL for 500, 2000 and 4000 Hz, respectively. Most (92 to 100%) infants with normal hearing showed ABRs to 30 dB nHL tones. Across all subjects (i.e., those with normal hearing and those with impaired hearing), high ( > or = 0.94) correlations were found between the ABR and behavioral thresholds. The mean differences between ABR (dB nHL) and behavioral (dB HL) thresholds across all subjects were 8.6, -0.4, and -4.3 dB for 500, 2000, and 4000 Hz, respectively. Overall, 98% of the ABR thresholds were within 30 dB of the behavioral thresholds, 93% were within 20 dB, and 80% were within 15 dB. These threshold results for the ABR to brief tones in notched noise obtained for infants and young children are similar to those obtained in similar studies of adults. The technique may be used clinically with reasonable accuracy to estimate pure-tone behavioral thresholds in infants and young children who are referred for diagnostic threshold ABR testing.

This study examined the relationship between behavioural thresholds as measured by pure tone audiometry and electrophysiological thresholds measured by the Auditory Steady-State Response (ASSR) in children with normal hearing and sensorineural hearing loss. After being assessed, 45 children of both sexes, ranging in age from 5 to 15, were split into four groups: 10 with moderate to moderately severe sensorineural hearing loss (G2M); 10 with steeply sloping sensorineural hearing loss (G2D); 10 with profound and severe sensorineural hearing loss (G2S); and 15 with normal hearing (G1). ASSR, tympanometry, acoustic reflex testing, pure tone audiometry, and speech audiometry (SRT and SDT) were performed. The electrophysiological maximum in the group with normal hearing thresholds varied from 19 to 27 dB NA. The correlation in the group with moderate to moderately severe hearing loss was 0.42-0.74. The correlation in the steeply sloping hearing loss group was 0.68-0.94. The correlation in the group of people with profound and severe hearing loss was 0.59-0.86. The normal hearing group's mean differences in ASSR threshold and audiometric threshold ranged from -0.3 to 12 dB, in the moderate and moderately severe hearing loss group from -9 to 2 dB, in the steeply sloping hearing loss group from 1.4 to 7.5 dB, and in the severe and profound hearing loss group from -0.40 to 8.5 dB. As expected, there was no strong relationship between behavioural and electrophysiological thresholds in the group with normal hearing. But in children with hearing loss, there was a strong correlation between electrophysiological and behavioural thresholds; this relationship was especially evident in children with severe and profound hearing loss and those with steeply sloping hearing loss.

Increased serum bilirubin levels during infancy increase the risk of hearing loss in infants. This study aimed to investigate the relationship between pure-tone audiometry hearing thresholds and thresholds estimated using auditory steady-state responses (ASSRs) in children with a history of neonatal hyperbilirubinemia, and to evaluate the usefulness of 90-Hz ASSR in estimating hearing thresholds in children. This study was conducted on 26 children (13 girls and 13 boys) who were aged 2.4-11 years and had a history of neonatal hyperbilirubinemia (bilirubin level >17 mg/dL). ASSR thresholds were compared with behavioral thresholds and were interpreted after considering the amount and type of hearing loss. Of the 26 children, 12 had normal hearing thresholds, and 14 had varying degrees of sensorineural hearing loss. In general, a high correlation (r ≥ 0.81, p < 0.01) was found between the ASSR and behavioral thresholds. The highest correlation was observed at 2,000 Hz (r = 0.88, p < 0.01). No significant difference was observed (p > 0.13) between mean behavioral and ASSR thresholds at 52 studied ears. The results of this study showed that 90-Hz ASSR assessments provide reliable estimates of behavioral hearing thresholds in children who have a history of neonatal hyperbilirubinemia and sensorineural hearing loss or normal hearing.

Effect of noise exposure on gap detection in rats

Ocena zgodności progów słyszenia w badaniach potencjałów słuchowych stanu ustalonego (ASSR), audiometrii tonalnej i słuchowych potencjałów wywołanych pnia mózgu (ABR) u młodych osób z prawidłowym słuchem

Projections of changes in tropical cyclone (TC) characteristics under climate change are of great interest to those affected by TCs. In a recent paper, Knutson et al. combined a large number of previous results to produce projections consisting of distributions of possible future TC frequencies, intensities, and rainfall rates. These distributions provide a great resource for users of TC information. However, to apply the distributions to impacts models may require the user to solve a number of technical challenges including modeling correlations, fitting distributions, interpolation, and converting the projections to properties at landfall. I consider the frequency and intensity changes, and implement solutions for each of these challenges using a combination of recently published research and a new methodology. This allows me to produce a dataset of TC projections that give frequency changes as a function of landfall region and intensity. Mean intensity changes can then be derived from frequency changes. The projections are presented in a format that allows them to be used in impacts models without further processing. The interpolation and landfall adjustments tend to increase the frequency changes. As a result, my projections give increasing mean frequencies of hurricane-strength landfalling TCs in four out of six global basins, with mean frequencies increasing by up to 16% for a 2°C increase in global mean surface temperature. My projections are highly uncertain, but include uncertainty estimates. They are designed to be a useful resource for anyone interested in possible future TC frequencies and intensities.

Children with hearing loss (HL) remain at risk for poorer language abilities than normal hearing (NH) children despite targeted interventions; reasons for these differences remain unclear. In NH children, research suggests speech discrimination is related to language outcomes, yet we know little about it in children with HL under the age of 2years. We utilized a vowel contrast, /a-i/, and a consonant-vowel contrast, /ba-da/, to examine speech discrimination in 47 NH infants and 40 infants with HL. At Mean age=3months, EEG recorded from 11 scalp electrodes was used to compute the time-frequency mismatched response (TF-MMRSE ) to the contrasts; at Mean age=9months, behavioral discrimination was assessed using a head turn task. A machine learning (ML) classifier was used to predict behavioral discrimination when given an arbitrary TF-MMRSE as input, achieving accuracies of 73% for exact classification and 92% for classification within a distance of one class. Linear fits revealed a robust relationship regardless of hearing status or speech contrast. TF-MMRSE responses in the delta (1-3.5Hz), theta (3.5-8Hz), and alpha (8-12Hz) bands explained the most variance in behavioral task performance. Our findings demonstrate the feasibility of using TF-MMRSE to predict later behavioral speech discrimination.

An auditory model, excitation-pattern model, was used in the present study to interpret the effects of signal frequency on intensity discrimination of tonal signals and vowel formant frequency discrimination. Excitation patterns were computed for standard and intensity-changed tones and for standard and formant-shifted vowels. Simulation models based on these excitation patterns were used to predict thresholds of intensity discrimination and thresholds of vowel formant discrimination for F1 and F2 frequency of four American English vowels. Predicted thresholds showed high correlations and low root-mean-square errors with thresholds measured from human listeners for an auditory metric calculating the excitation level near the target formant. Results indicated that normal-hearing listeners needed a relatively constant change in the internal representation of signals, e.g. excitation patterns, near the signal/formant frequency to discriminate changes in tonal intensity and vowel formant frequency, independent of signal frequency. In addition, the excitation-pattern model may be used more broadly to explain discrimination of acoustic signals in a variety of listening conditions.