Auditory Temporal Processing Research Articles

Relationship between Verbal and Nonverbal Tests of Auditory Temporal Processing.

Audiologists may choose to evaluate auditory temporal processing in assessing auditory processing abilities. Some may decide to use measures of nonverbal stimuli such as tonal or noise gap detection. Others may decide to use verbal measures such as time compressed sentences (TCS). Many may choose to use both. Since people typically come to audiologists for auditory processing testing complaining of problems processing verbal stimuli, the question arises whether measures of nonverbal stimuli provide evidence regarding a person's abilities to processing verbal stimuli. That is, are there significant correlations between measures of verbal stimuli and nonverbal stimuli that are used to evaluate auditory temporal processing? The present investigation is an exploratory study using file review of 104 people seen for routine auditory processing evaluations by the authors. A file review was completed based on data from 104 people seen for auditory processing evaluations. The data from these 104 files were used to evaluate whether there are any correlations between verbal and nonverbal measures of auditory temporal processing. The verbal measure used was the TCS subtest of the SCAN-3 while the nonverbal measures included the gap detection screening from the SCAN-3 as well as the gaps-in-noise measures. Results from these tests were compared to determine whether any significant correlations were found based on results from Pearson product moment correlational analyses. None of the nonverbal measures were found to have a significant correlation with the TCS test findings based on the Pearson correlations used to analyze the data. Results indicate that there are no significant correlations (relationships) between measures of auditory temporal processing using nonverbal stimuli versus verbal stimuli based on the tests used in the present investigation. These findings lead to a conclusion that tests using nonverbal stimuli are measuring different auditory processes than the measure of verbal stimuli used in the present investigation. Since people typically come complaining about understanding verbal input, it is concluded that audiologists should use some verbal measure of auditory temporal processing in their auditory processing test battery.

Neural tracking of the fundamental frequency of the voice: The effect of voice characteristics.

Traditional electrophysiological methods to study temporal auditory processing of the fundamental frequency of the voice (f0) often use unnaturally repetitive stimuli. In this study, we investigated f0 processing of meaningful continuous speech. EEG responses evoked by stories in quiet were analysed with a novel method based on linear modelling that characterizes the neural tracking of the f0. We studied both the strength and the spatio-temporal properties of the f0-tracking response. Moreover, different samples of continuous speech (six stories by four speakers: two male and two female) were used to investigate the effect of voice characteristics on the f0 response. The results indicated that response strength is inversely related to f0 frequency and rate of f0 change throughout the story. As a result, the male-narrated stories in this study (low and steady f0) evoked stronger f0-tracking compared to female-narrated stories (high and variable f0), for which many responses were not significant. The spatio-temporal analysis revealed that f0-tracking response generators were not fixed in the brainstem but were voice-dependent as well. Voices with high and variable f0 evoked subcortically dominated responses with a latency between 7 and 12ms. Voices with low and steady f0 evoked responses that are both subcortically (latency of 13-15ms) and cortically (latency of 23-26ms) generated, with the right primary auditory cortex as a likely cortical source. Finally, additional experiments revealed that response strength greatly improves for voices with strong higher harmonics, which is particularly useful to boost the small responses evoked by voices with high f0.

Children with developmental language disorder: a frequency following response in the noise study

IntroductionChildren with developmental language disorder have been reported to have poor temporal auditory processing. This study aimed to examine the frequency following response. ObjectiveThis work aimed to investigate speech processing in quiet and in noise. MethodsTwo groups of children were included in this work: the control group (15 children with normal language development) and the study group (25 children diagnosed with developmental language disorder). All children were submitted to intelligence scale, language assessment, full audiological evaluation, and frequency following response in quiet and noise (+5QNR and +10QNR). ResultsResults showed no statically significant difference between both groups as regards IQ or PTA. In the study group, the advanced analysis of frequency following response showed reduced F0 and F2 amplitudes. Results also showed that noise has an impact on both the transient and sustained components of the frequency following response in the same group. ConclusionChildren with developmental language disorder have difficulty in speech processing especially in the presence of background noise. Frequency following response is an efficient procedure that can be used to address speech processing problems in children with developmental language disorder.

Recovery from forward masking in cochlear implant listeners: Effects of age and the electrode-neuron interface.

Older adults exhibit deficits in auditory temporal processing relative to younger listeners. These age-related temporal processing difficulties may be further exacerbated in older adults with cochlear implant (CIs) when CI electrodes poorly interface with their target auditory neurons. The aim of this study was to evaluate the potential interaction between chronological age and the estimated quality of the electrode-neuron interface (ENI) on psychophysical forward masking recovery, a measure that reflects single-channel temporal processing abilities. Fourteen CI listeners (age 15 to 88 years) with Advanced Bionics devices participated. Forward masking recovery was assessed on two channels in each ear (i.e., the channels with the lowest and highest signal detection thresholds). Results indicated that the rate of forward masking recovery declined with advancing age, and that the effect of age was more pronounced on channels estimated to interface poorly with the auditory nerve. These findings indicate that the quality of the ENI can influence the time course of forward masking recovery for older CI listeners. Channel-to-channel variability in the ENI likely interacts with central temporal processing deficits secondary to auditory aging, warranting further study of programming and rehabilitative approaches tailored to older listeners.

Auditory Phenotypic Variability in Friedreich\u2019s Ataxia Patients

Auditory neural impairment is a key clinical feature of Friedreich’s Ataxia (FRDA). We aimed to characterize the phenotypical spectrum of the auditory impairment in FRDA in order to facilitate early identification and timely management of auditory impairment in FRDA patients and to explore the relationship between the severity of auditory impairment with genetic variables (the expansion size of GAA trinucleotide repeats, GAA1 and GAA2), when controlled for variables such as disease duration, severity of the disease and cognitive status. Twenty-seven patients with genetically confirmed FRDA underwent baseline audiological assessment (pure-tone audiometry, otoacoustic emissions, auditory brainstem response). Twenty of these patients had additional psychophysical auditory processing evaluation including an auditory temporal processing test (gaps in noise test) and a binaural speech perception test that assesses spatial processing (Listening in Spatialized Noise-Sentences Test). Auditory spatial and auditory temporal processing ability were significantly associated with the repeat length of GAA1. Patients with GAA1 greater than 500 repeats had more severe auditory temporal and spatial processing deficits, leading to poorer speech perception. Furthermore, the spatial processing ability was strongly correlated with the Montreal Cognitive Assessment (MoCA) score. To our knowledge, this is the first study to demonstrate an association between genotype and auditory spatial processing phenotype in patients with FRDA. Auditory temporal processing, neural sound conduction, spatial processing and speech perception were more severely affected in patients with GAA1 greater than 500 repeats. The results of our study may indicate that auditory deprivation plays a role in the development of mild cognitive impairment in FRDA patients.

Central Auditory Tests to Track Cognitive Function in People With HIV: Longitudinal Cohort Study.

BackgroundThe development of neurocognitive deficits in people infected with HIV is a significant public health problem. Previous cross-sectional studies have shown that performance on central auditory tests (CATs) correlates with cognitive test results in those with HIV, but no longitudinal data exist for confirmation. We have been performing longitudinal assessments of central auditory and cognitive function on a cohort of HIV-positive and HIV-negative individuals in Dar es Salaam, Tanzania to understand how the central auditory system could be used to study and track the progress of central nervous system dysfunction.ObjectiveThe goal of the project was to determine if CATs can track the trajectory of cognitive function over time in people diagnosed with HIV.MethodsTests of peripheral and central auditory function as well as cognitive performance were performed on 382 individuals over the course of 3.5 years. Visits were scheduled every 6 months. CATs included tests of auditory temporal processing (gap detection) and speech perception in noise (Hearing in Noise Test and Triple Digit Test). Cognitive tests included the Montreal Cognitive Assessment (MoCA), Test of Variables of Attention (TOVA), and subtests from the Cogstate battery. HIV-positive subjects were divided into groups based on their CAT results at their final visit (bottom 20%, top 20%, middle 60%). Primary analyses focused on the comparison between HIV-positive individuals that performed worse on CATs (bottom 20%) and the overall HIV-positive group (middle 60%). Data were analyzed using linear mixed-effect models with time as the main fixed effect.ResultsThe group with the worst (bottom 20%) CAT performance showed a difference in trajectory for the MoCA (P=.003), TOVA (P<.048), and Cogstate (P<.046) over the course of the study period compared to the overall HIV-positive group. A battery of three CATs showed a significant difference in cognitive trajectory over a relatively short study period of 3.5 years independent of age (bottom 20% vs HIV-positive group).ConclusionsThe results of this study support the ability for CATs to track cognitive function over time, suggesting that central auditory processing can provide a window into central nervous system performance. CATs can be simple to perform, and are relatively insensitive to education and socioeconomic status because they only require repeating sentences, numbers, or detecting gaps in noise. These tests could potentially provide a time-efficient, low-cost method to screen for and monitor cognitive decline in patients with HIV, making them a useful surveillance tool for this major public health problem.

Auditory Brainstem Response to Paired Click Stimulation as an Indicator of Peripheral Synaptic Health in Noise-Induced Cochlear Synaptopathy.

IntroductionA defect in the cochlear afferent synapse between the inner hair cells and spiral ganglion neurons, after noise exposure, without changes in the hearing threshold has been reported. Animal studies on auditory evoked potentials demonstrated changes in the auditory brainstem response (ABR) measurements of peak I amplitude and the loss of synapses, which affect the temporal resolution of complex sounds. Human studies of auditory evoked potential have reported ambiguous results regarding the relationship between peak I amplitude and noise exposure. Paired click stimuli have been used to investigate the temporal processing abilities of humans and animals. In this study, we investigated the utility of measuring auditory evoked potentials in response to paired click stimuli to assess the temporal processing function of ribbon synapses in noise-induced cochlear synaptopathy.Materials and MethodsTwenty-two Sprague Dawley rats were used in this study, and synaptopathy was induced by narrow-band noise exposure (16 kHz with 1 kHz bandwidth, 105 dB sound pressure level for 2 h). ABRs to tone and paired click stimuli were measured before and 1, 3, 7, and 14 days after noise exposure. For histological analyses, hair cells and ribbon synapses were immunostained and the synapses quantified. The relationships among ABR peak I amplitude, number of synapses, and ABR to paired click stimuli were examined.ResultsOur results showed that ABR thresholds increase 1 day after noise exposure but fully recover to baseline levels after 14 days. Further, we demonstrated test frequency-dependent decreases in peak I amplitude and the number of synapses after noise exposure. These decreases were statistically significant at frequencies of 16 and 32 kHz. However, the ABR recovery threshold to paired click stimuli increased, which represent deterioration in the ability of temporal auditory processing. Our results indicate that the ABR recovery threshold is highly correlated with ABR peak I amplitude after noise exposure. We also established a direct correlation between the ABR recovery threshold and histological findings.ConclusionThe result from this study suggests that in animal studies, the ABR to paired click stimuli along with peak I amplitude has potential as an assessment tool for hidden hearing loss.

Factors related to the performance of elderly people in temporal ordering tests.

To describe the performance of elderly individuals in Pitch Pattern Sequence (PPS) and Duration Pattern Sequence (DPS) tests and research related factors. An observational, cross-sectional study conducted with elderly people aged 60 to 79 years. The participants underwent cognitive screening tests, interviews containing socio-demographic data and general health, as well as audiologic evaluation and temporal auditory processing (PPS and DPS) evaluation tests. A descriptive analysis of the association between the performance in temporal processing and the variables gender, age, level of education and audiometric alterations was conducted through multiple linear regression. 86 elderly people participated in the study, most of them female, with ages between 60 and 69. Male participants performed better in both tests as well as the participants with higher education, whereas no difference in performance was observed across the different age ranges. In the DPS, the participants with auditory alteration performed worse in relation to the ones with average frequencies of 0.5 to 4 kHz. The male gender and higher level of education were associated with better results in the temporal ordering tests, whereas auditory alteration was associated with worse performance only in the pitch pattern sequence test.

Dysfunctional auditory gamma oscillations in developmental dyslexia: A potential target for a tACS-based intervention.

Interventions in developmental dyslexia typically consist of orthography-based reading and writing trainings. However, their efficacy is limited and, consequently, the symptoms persist into adulthood. Critical for this lack of efficacy is the still ongoing debate about the core deficit in dyslexia and its underlying neurobiological causes. There is ample evidence on phonological as well as auditory temporal processing deficits in dyslexia and, on the other hand, cortical gamma oscillations in the auditory cortex as functionally relevant for the extraction of linguistically meaningful information units from the acoustic signal. The present work aims to shed more light on the link between auditory gamma oscillations, phonological awareness, and literacy skills in dyslexia. By mean of EEG, individual gamma frequencies were assessed in a group of children and adolescents diagnosed with dyslexia as well as in an age-matched control group with typical literacy skills. Furthermore, phonological awareness was assessed in both groups, while in dyslexic participants also reading and writing performance was measured. We found significantly lower gamma peak frequencies as well as lower phonological awareness scores in dyslexic participants compared to age-matched controls. Additionally, results showed a positive correlation between the individual gamma frequency and phonological awareness. Our data suggest a hierarchical structure of neural gamma oscillations, phonological awareness, and literacy skills. Thereby, the results emphasize altered gamma oscillation not only as a core deficit in dyslexia but also as a potential target for future causal interventions. We discuss these findings considering non-invasive brain stimulation techniques and suggest transcranial alternating current stimulation as a promising approach to normalize dysfunctional oscillations in dyslexia.

Effects of auditory processing training on speech perception and brainstem plastisity in adolescents with autism spectrum disorders.

ObjectiveAutism spectrum disorder (ASD) is a neurodevelopmental disorder. A major problem of ASD is speech perception impairment in the presence of background noise. Additionally, researchers have reported temporal auditory processing impairment in patients with ASD. In the present study, we evaluated the effects of a temporal-based training program on improvement of speech perception in the presence of noise using the speech auditory brainstem response (sABR).Materials & MethodsTwenty-eight adolescents with high functional ASD with the mean age of 14.35±1.86 years were randomly selected and divided into an ASD group (11 males and three females) and a control group (13 males and one female). All the subjects had a normal hearing and intelligence threshold and had no history of neurological disorder.A speech perception test was performed in signal-to-noise ratios of 0 and +10. The intervention group received a temporal processingbased auditory training program, and the control group received a conventional training program. A P-value of <0.05 was considered significant.ResultsAfter training, speech perception in the presence of noise was significantly higher (P <0.001) and the latency of all sABR waves was lower in the intervention group compared to the control group.ConclusionImprovement of speech perception in noisy environments and the reduced latency of sABR waves following a temporal processingbased training program highlight the role of brainstem neural plasticity in speech processing.

The gap prepulse inhibition of the acoustic startle (GPIAS) paradigm to assess auditory temporal processing: Monaural versus binaural presentation.

The Gap Prepulse Inhibition of the Acoustic Startle Reflex (GPIAS) is a paradigm used to assess auditory temporal processing in both animals and humans. It consists of the presentation of a silent gap embedded in noise and presented a few milliseconds before a startle sound. The silent gap produces the inhibition of the startle reflex, a phenomenon called gap-prepulse inhibition (GPI). This paradigm is also used to detect tinnitus in animal models. The lack of inhibition by the silent gaps is suggested to be indicative of the presence of tinnitus "filling-in" the gaps. The current research aims at improving the GPIAS technique by comparing the GPI produced by monaural versus binaural silent gaps in 29 normal-hearing subjects. Two gap durations (5 or 50ms), each embedded in two different frequency backgrounds (centered around 500 or 4 kHz). Both low- and high- frequency narrowband noises had a bandwidth of half an octave. Overall, the startle magnitude was greater for the binaural versus the monaural presentation, which might reflect binaural loudness summation. In addition, the GPI was similar between the monaural and the binaural presentations for the high-frequency background noise. However, the GPI was greater for the low-frequency background noise for the binaural, compared to the monaural, presentation. These findings suggest that monaural GPIAS might be more suited to detect tinnitus compared to the binaural presentation.

Effect of Kv3 channel modulators on auditory temporal resolution in aged Fischer 344 rats

AUT00063 and AUT00202 are novel pharmaceutical modulators of the Kv3 subfamily of voltage-gated K+ channels. Kv3.1 channels, which control fast firing of many central auditory neurons, have been shown to decline with age and this may contribute to age-related deficits in central auditory processing. In the present study, the effects of the two novel compounds that specifically modulate Kv3 channels on auditory temporal processing were examined in aged (19-25-month-old) and young-adult (3-5 month-old) Fischer 344 rats (F344) using a behavioral gap-prepulse inhibition (gap-PPI) paradigm. The acoustic startle response (ASR) and its inhibition induced by a gap in noise were measured before and after drug administration. Hearing thresholds in tested rats were evaluated by the auditory brainstem response (ABR). Aged F344 rats had significantly higher ABR thresholds, lower amplitudes of ASR, and weaker gap-PPI compared with young-adult rats. No influence of AUT00063 and AUT00202 administration was observed on ABR hearing thresholds in rats of both age groups. AUT00063 and AUT00202 had suppressive effect on ASR of F344 rats that was more pronounced with AUT00063. The degree of suppression depended on the dose and age of the rats. Both compounds significantly improved the gap-PPI performance in gap detection tests in aged rats. These results indicate that AUT00063 and AUT00202 may influence intrinsic firing properties of neurons in the central auditory system of aged animals and have the potential to treat aged-related hearing disorders.

Neural Generators Underlying Temporal Envelope Processing Show Altered Responses and Hemispheric Asymmetry Across Age.

Speech understanding problems are highly prevalent in the aging population, even when hearing sensitivity is clinically normal. These difficulties are attributed to changes in central temporal processing with age and can potentially be captured by age-related changes in neural generators. The aim of this study is to investigate age-related changes in a wide range of neural generators during temporal processing in middle-aged and older persons with normal audiometric thresholds. A minimum-norm imaging technique is employed to reconstruct cortical and subcortical neural generators of temporal processing for different acoustic modulations. The results indicate that for relatively slow modulations (<50 Hz), the response strength of neural sources is higher in older adults than in younger ones, while the phase-locking does not change. For faster modulations (80 Hz), both the response strength and the phase-locking of neural sources are reduced in older adults compared to younger ones. These age-related changes in temporal envelope processing of slow and fast acoustic modulations are possibly due to loss of functional inhibition, which is accompanied by aging. Both cortical (primary and non-primary) and subcortical neural generators demonstrate similar age-related changes in response strength and phase-locking. Hemispheric asymmetry is also altered in older adults compared to younger ones. Alterations depend on the modulation frequency and side of stimulation. The current findings at source level could have important implications for the understanding of age-related changes in auditory temporal processing and for developing advanced rehabilitation strategies to address speech understanding difficulties in the aging population.

Effects of age on psychophysical measures of auditory temporal processing and speech reception at low and high levels

Age-related cochlear synaptopathy (CS) has been shown to occur in rodents with minimal noise exposure, and has been hypothesized to play a crucial role in age-related hearing declines in humans. It is not known to what extent age-related CS occurs in humans, and how it affects the coding of supra-threshold sounds and speech in noise. Because in rodents CS affects mainly low- and medium-spontaneous rate (L/M-SR) auditory-nerve fibers with rate-level functions covering medium-high levels, it should lead to greater deficits in the processing of sounds at high than at low stimulus levels. In this cross-sectional study the performance of 102 listeners across the age range (34 young, 34 middle-aged, 34 older) was assessed in a set of psychophysical temporal processing and speech reception in noise tests at both low, and high stimulus levels. Mixed-effect multiple regression models were used to estimate the effects of age while partialing out effects of audiometric thresholds, lifetime noise exposure, cognitive abilities (assessed with additional tests), and musical experience. Age was independently associated with performance deficits on several tests. However, only for one out of 13 tests were age effects credibly larger at the high compared to the low stimulus level. Overall these results do not provide much evidence that age-related CS, to the extent to which it may occur in humans according to the rodent model of greater L/M-SR synaptic loss, has substantial effects on psychophysical measures of auditory temporal processing or on speech reception in noise.

The Role of Phonological, Auditory Sensory and Cognitive Skills on Word Reading Acquisition: A Cross-Linguistic Study.

Despite considerable evidence regarding the influence of orthography on reading processing, the impact of orthographic depth on reading predictors remains unclear. In addition, it also remains unknown the role of the orthography in the influence of auditory temporal processing and attention skills on word reading skills. The current study investigates the word reading predictors in a group of British and Brazilian children with typical development considering phonological, auditory sensory, short-term memory, and sustained attention skills. Rhyme and Alliteration skills predicted word reading in both groups; however, the correlation in the British group was more robust. Short-term memory was also correlated with reading in both groups; however, it was a significant word reading predictor only in the British group. The auditory sensory was not directly correlated with word reading in either group; however, it was involved with Rhyme and Alliteration performance only in the British group. Those results were discussed considering the complexity of the phonological structure and opaque orthography in English when compared to Portuguese, which indicates that the less transparent the orthography, the higher the importance of factors such as phonological awareness, short-term memory, and to some extent, auditory sensory processing skills on word reading acquisition. Those results emphasize the need to consider orthography and phonological features of a particular language when developing a reading assessment and treatments.

Consonant and vowel articulation accuracy in younger and middle-aged Spanish healthy adults.

Children acquire vowels earlier than consonants, and the former are less vulnerable to speech disorders than the latter. This study explores the hypothesis that a similar contrast exists later in life and that consonants are more vulnerable to ageing than vowels. Data was obtained with two experiments comparing the speech of Younger Adults (YAs) and Middle-aged Adults (MAs). In the first experiment an Automatic Speech Recognition (ASR) system was trained with a balanced corpus of 29 YAs and 27 MAs. The productions of each speaker were obtained in a Spanish language word (W) and non-word (NW) repetition task. The performance of the system was evaluated with the same corpus used for training using a cross validation approach. The ASR system recognized to a similar extent the Ws of both groups of speakers, but it was more successful with the NWs of the YAs than with those of the MAs. Detailed error analysis revealed that the MA speakers scored below the YA speakers for consonants and also for the place and manner of articulation features; the results were almost identical in both groups of speakers for vowels and for the voicing feature. In the second experiment a group of healthy native listeners was asked to recognize isolated syllables presented with background noise. The target speakers were one YA and one MA that had taken part in the first experiment. The results were consistent with those of the ASR experiment: the manner and place of articulation were better recognized, and vowels and voicing were worse recognized, in the YA speaker than in the MA speaker. We conclude that consonant articulation is more vulnerable to ageing than vowel articulation. Future studies should explore whether or not these early and selective changes in articulation accuracy might be caused by changes in speech perception skills (e.g., in auditory temporal processing).

Brain mapping of auditory steady-state responses: A broad view of cortical and subcortical sources.

Auditory steady‐state responses (ASSRs) are evoked brain responses to modulated or repetitive acoustic stimuli. Investigating the underlying neural generators of ASSRs is important to gain in‐depth insight into the mechanisms of auditory temporal processing. The aim of this study is to reconstruct an extensive range of neural generators, that is, cortical and subcortical, as well as primary and non‐primary ones. This extensive overview of neural generators provides an appropriate basis for studying functional connectivity. To this end, a minimum‐norm imaging (MNI) technique is employed. We also present a novel extension to MNI which facilitates source analysis by quantifying the ASSR for each dipole. Results demonstrate that the proposed MNI approach is successful in reconstructing sources located both within (primary) and outside (non‐primary) of the auditory cortex (AC). Primary sources are detected in different stimulation conditions (four modulation frequencies and two sides of stimulation), thereby demonstrating the robustness of the approach. This study is one of the first investigations to identify non‐primary sources. Moreover, we show that the MNI approach is also capable of reconstructing the subcortical activities of ASSRs. Finally, the results obtained using the MNI approach outperform the group‐independent component analysis method on the same data, in terms of detection of sources in the AC, reconstructing the subcortical activities and reducing computational load.

The relation between neurofunctional and neurostructural determinants of phonological processing in pre-readers

Phonological processing skills are known as the most robust cognitive predictor of reading ability. Therefore, the neural determinants of phonological processing have been extensively investigated by means of either neurofunctional or neurostructural techniques. However, to fully understand how the brain represents and processes phonological information, there is need for studies that combine both methods. The present study applies such a multimodal approach with the aim of investigating the pre-reading relation between neural measures of auditory temporal processing, white matter properties of the reading network and phonological processing skills. We administered auditory steady-state responses, diffusion-weighted MRI scans and phonological awareness tasks in 59 pre-readers. Our results demonstrate that a stronger rightward lateralization of syllable-rate (4 Hz) processing coheres with higher fractional anisotropy in the left fronto-temporoparietal arcuate fasciculus. Both neural features each in turn relate to better phonological processing skills. As such, the current study provides novel evidence for the existence of a pre-reading relation between functional measures of syllable-rate processing, structural organization of the arcuate fasciculus and cognitive precursors of reading development. Moreover, our findings demonstrate the value of combining different neural techniques to gain insight in the underlying neural systems for reading (dis)ability.

Spectral-Temporal Trade-Off in Vocoded Sentence Recognition: Effects of Age, Hearing Thresholds, and Working Memory.

Cochlear implant (CI) signal processing degrades the spectral components of speech. This requires CI users to rely primarily on temporal cues, specifically, amplitude modulations within the temporal envelope, to recognize speech. Auditory temporal processing ability for envelope modulations worsens with advancing age, which may put older CI users at a disadvantage compared with younger users. To evaluate how potential age-related limitations for processing temporal envelope modulations impact spectrally degraded sentence recognition, noise-vocoded sentences were presented to younger and older normal-hearing listeners in quiet. Envelope modulation rates were varied from 10 to 500 Hz by adjusting the low-pass filter cutoff frequency (LPF). The goal of this study was to evaluate if age impacts recognition of noise-vocoded speech and if this age-related limitation existed for a specific range of envelope modulation rates. Noise-vocoded sentence recognition in quiet was measured as a function of number of spectral channels (4, 6, 8, and 12 channels) and LPF (10, 20, 50, 75, 150, 375, and 500 Hz) in 15 younger normal-hearing listeners and 15 older near-normal-hearing listeners. Hearing thresholds and working memory were assessed to determine the extent to which these factors were related to recognition of noise-vocoded sentences. Younger listeners achieved significantly higher sentence recognition scores than older listeners overall. Performance improved in both groups as the number of spectral channels and LPF increased. As the number of spectral channels increased, the differences in sentence recognition scores between groups decreased. A spectral-temporal trade-off was observed in both groups in which performance in the 8- and 12-channel conditions plateaued with lower-frequency amplitude modulations compared with the 4- and 6-channel conditions. There was no interaction between age group and LPF, suggesting that both groups obtained similar improvements in performance with increasing LPF. The lack of an interaction between age and LPF may be due to the nature of the task of recognizing sentences in quiet. Audiometric thresholds were the only significant predictor of vocoded sentence recognition. Although performance on the working memory task declined with advancing age, working memory scores did not predict sentence recognition. Younger listeners outperformed older listeners for recognizing noise-vocoded sentences in quiet. The negative impact of age was reduced when ample spectral information was available. Age-related limitations for recognizing vocoded sentences were not affected by the temporal envelope modulation rate of the signal, but instead, appear to be related to a generalized task limitation or to reduced audibility of the signal.

Electrophysiological correlates of the spatial temporal order judgment task

The study investigated auditory temporal processing on a tens of milliseconds scale that is the interval when two consecutive stimuli are processed either together or as distinct events. Distinctiveness is defined by one’s ability to make correct order judgments of the presented sounds and is measured via the spatial temporal order judgement task (TOJ).The study aimed to identify electrophysiological indices of the TOJ performance. Tone pairs were presented with inter-stimulus intervals (ISI) varying between 25 and 75 ms while EEG was recorded. A pronounced amplitude change in the P2 interval was found between the event-related potential (ERP) of tone pairs having ISI = 55 and 65 ms, but it was a characteristic only of the group having poor behavioral thresholds. With the two groups combined, the amplitude change between these ERPs in the P2 interval showed a medium-size correlation with the behavioral threshold.