Children with developmental dyslexia have equivalent audiovisual speech perception performance but their perceptual weights differ.

Determinants of speech perception in children after cochlear implantation

Studies of children's speech perception have shown that young children process speech signals differently than adults. Specifically, the relative contributions made by various acoustic parameters to some linguistic decisions seem to differ for children and adults. Such findings have led to the hypothesis that there is a developmental shift in the perceptual weighting of acoustic parameters that results from experience with a native language (i.e., the Developmental Weighting Shift). This developmental shift eventually leads the child to adopt the optimal perceptual weighting strategy for the native language being learned (i.e., one that allows the listener to make accurate decisions about the phonemic structure or his or her native language). Although this proposal has intuitive appeal, there is at least one serious challenge that can be leveled against it: Perhaps age-related differences in speech perception can appropriately be explained by age-related differences in basic auditory-processing abilities. That is, perhaps children are not as sensitive as adults to subtle differences in acoustic structure and so make linguistic decisions based on the acoustic information that is most perceptually salient. The present study tested this hypothesis for the acoustic cues relevant to fricative identity in fricative-vowel syllables. Results indicated that 3-year-olds were not as sensitive to changes in these acoustic cues as adults are, but that these age-related differences in auditory sensitivity could not entirely account for age-related differences in perceptual weighting strategies.

Plasticity of temporal binding in children with autism spectrum disorder: A single case experimental design perceptual training study

This scoping review provides a descriptive synthesis of available evidence on children's audiovisual speech perception. We used eight databases to identify the experimental studies published 2000–2019, and reported the data using the guidelines of PRISMA-ScR designed for scoping reviews. While research conducted prior to 2000 provided a strong foundation in this area, the past two decades have brought technical advances that have allowed for more precise measurement of audiovisual speech perception. Thirty-eight studies were identified: 18 articles that focused on children with typical development, 9 focused on children with autism spectrum disorder, 8 focused on children with speech and language disorders, and 3 focused on children with hearing loss. Most of the studies identified were behavioral studies, while a minority reported on neuroanatomical correlates underlying the audiovisual speech perception. Through this scoping review, key gaps were identified that include few studies in clinical populations, a few studies on languages other than English, and variability in terminology to describe similar or overlapping concepts. Further research is needed to inform the development and mechanisms of audiovisual speech integration in children with different language development paths. In addition, the use of common terminology in future research would improve access to evidence and the communication of this knowledge for researchers and clinicians.

Purpose The extant literature suggests that individual differences in speech perception can be linked to broad receptive language phenotype. For example, a recent study found that individuals with a smaller receptive vocabulary showed diminished lexically guided perceptual learning compared to individuals with a larger receptive vocabulary. Here, we examined (a) whether such individual differences stem from variation in reliance on lexical information or variation in perceptual learning itself and (b) whether a relationship exists between lexical recruitment and lexically guided perceptual learning more broadly, as predicted by current models of lexically guided perceptual learning. Method In Experiment 1, adult participants (n = 70) completed measures of receptive and expressive language ability, lexical recruitment, and lexically guided perceptual learning. In Experiment 2, adult participants (n = 120) completed the same lexical recruitment and lexically guided perceptual learning tasks to provide a high-powered replication of the primary findings from Experiment 1. Results In Experiment 1, individuals with weaker receptive language ability showed increased lexical recruitment relative to individuals with higher receptive language ability; however, receptive language ability did not predict the magnitude of lexically guided perceptual learning. Moreover, the results of both experiments converged to show no evidence indicating a relationship between lexical recruitment and lexically guided perceptual learning. Conclusion The current findings suggest that (a) individuals with weaker language ability demonstrate increased reliance on lexical information for speech perception compared to those with stronger receptive language ability; (b) individuals with weaker language ability maintain an intact perceptual learning mechanism; and, (c) to the degree that the measures used here accurately capture individual differences in lexical recruitment and lexically guided perceptual learning, there is no graded relationship between these two constructs.

Smith and Lewicki, Neural Comp. 17, 19–45, 2005a; Adv. Neural. Inf. Process. Syst. 17, 1289–1296, 2005b; Nature, 439, 7079, 2006, demonstrated that mammalian hearing follows an efficient coding principle (Barlow, Sensory Communications, 217–234, 1961; Atick, Network, 3(2), 213–251, 1992; Simoncelli and Olshausen, Ann. Rev. Neurosci., 24, 1193–1216, 2001; Laughlin and Sejnowski, ‘‘Communications in Neuronal Networks,’’ Science, 301, 1870–1874 2003). Auditory neurons efficiently code for natural sounds in the environment, maximizing information rate while minimizing coding cost (Shannon, Science, 270, 303–304, 1948). Applying the same analysis to speech coding suggests that speech acoustics are optimally adapted to the mammalian auditory code (Smith and Lewicki, Neural Comp. 17, 19–45, 2005a; Adv. Neural. Inf. Process. Syst. 17, 1289–1296, 2005b; Nature, 439, 7079, 2006). The present work applies this efficient coding theory to the problem of speech perception in individuals using cochlear implants (CI), for which there exist vast individual differences in speech perception and spectral resolution (Zeng et al., Auditory Prostheses and Electric Hearing, 20, 1–14, 2004). A machine-learning method for CI filterbank design based on the efficient-coding hypothesis is presented. Further, a pair of experiments to evaluate this approach using noise-excited vocoder speech (Shannon et al., Bell Systems Technical Journal 27, 379–423, 623–656, 1995) is described. Participants’ recognition of continuous speech and isolated syllables is significantly more accurate for speech filtered through the theoretically-motivated efficient-coding filterbank relative to the standard cochleotopic filterbank, particularly for speech transients. These findings offer insight in CI design and provide behavioral evidence for efficient coding in human perception.

The function of rapid perceptual learning for speech in adult listeners is poorly understood. On the one hand, perceptual learning of speech results in rapid and long-lasting improvements in the perception of many types of distorted and degraded speech signals. On the other hand, this learning is highly specific to stimuli that were encountered during its acquisition. Therefore, it is unclear whether past perceptual learning could support future speech perception under ecological conditions. Here, we hypothesize that rapid perceptual learning is a resource that is recruited when new speech challenges are encountered and used to support perception under those specific conditions. We review three lines of evidence related to aspects of this hypothesis – about the specificity of learning, the general nature of associations between rapid perceptual learning and speech perception and rapid perceptual-learning in populations with poor perception under adverse conditions.

In audiovisual speech perception, visual information from a talker's face during mouth articulation is available before the onset of the corresponding audio speech, and thereby allows the perceiver to use visual information to predict the upcoming audio. This prediction from phonetically congruent visual information modulates audiovisual speech perception and leads to a decrease in N1 and P2 amplitudes and latencies compared to the perception of audio speech alone. Whether audiovisual experience, such as with musical training, influences this prediction is unclear, but if so, may explain some of the variations observed in previous research. The current study addresses whether audiovisual speech perception is affected by musical training, first assessing N1 and P2 event-related potentials (ERPs) and in addition, inter-trial phase coherence (ITPC). Musicians and non-musicians are presented the syllable, /ba/ in audio only (AO), video only (VO), and audiovisual (AV) conditions. With the predictory effect of mouth movement isolated from the AV speech (AV−VO), results showed that, compared to audio speech, both groups have a lower N1 latency and P2 amplitude and latency. Moreover, they also showed lower ITPCs in the delta, theta, and beta bands in audiovisual speech perception. However, musicians showed significant suppression of N1 amplitude and desynchronization in the alpha band in audiovisual speech, not present for non-musicians. Collectively, the current findings indicate that early sensory processing can be modified by musical experience, which in turn can explain some of the variations in previous AV speech perception research.

Whilst functional neuroimaging has been used to investigate cortical processing of degraded speech in adults, much less is known about how these signals are processed in children. An enhanced understanding of cortical correlates of poor speech perception in children would be highly valuable to oral communication applications, including hearing devices. We utilised vocoded speech stimuli to investigate brain responses to degraded speech in 29 normally hearing children aged 6–12 years. Intelligibility of the speech stimuli was altered in two ways by (i) reducing the number of spectral channels and (ii) reducing the amplitude modulation depth of the signal. A total of five different noise-vocoded conditions (with zero, partial or high intelligibility) were presented in an event-related format whilst participants underwent functional near-infrared spectroscopy (fNIRS) neuroimaging. Participants completed a word recognition task during imaging, as well as a separate behavioural speech perception assessment. fNIRS recordings revealed statistically significant sensitivity to stimulus intelligibility across several brain regions. More intelligible stimuli elicited stronger responses in temporal regions, predominantly within the left hemisphere, while right inferior parietal regions showed an opposite, negative relationship. Although there was some evidence that partially intelligible stimuli elicited the strongest responses in the left inferior frontal cortex, a region previous studies have suggested is associated with effortful listening in adults, this effect did not reach statistical significance. These results further our understanding of cortical mechanisms underlying successful speech perception in children. Furthermore, fNIRS holds promise as a clinical technique to help assess speech intelligibility in paediatric populations.

The aim of the study was to examine the role of phonological processing in people with and without dyslexia, who should have already mastered the skill of reading. We tested 98 high school students aged 16–18 years, including 49 with dyslexia and 49 without. The results indicate that the participants with dyslexia, as compared with participants without dyslexia, read single words and pseudowords less correctly and slower, which is consistent with literature on the subject. In addition, they scored significantly poorer in the phoneme blending, rapid automatic naming, and backward digit span task. In the criterion group, the relationship between phonological awareness and reading fluency was much stronger, and between rapid automatic naming and reading fluency slightly weaker than in the control group. This indicates a greater influence of long-term memory on reading in high school students without dyslexia.

Auditory processing and speech perception in children with specific language impairment: Relations with oral language and literacy skills

Studies of speech processing have generally made the implicit assumption that typically developed speakers can distinguish all sounds of their mother tongue in perception and production. As such, individual differences in speech processing is usually studied with speakers differing in training/experience (Strait & Kraus, 2011), or populations with developmental disorders (Facoetti et al., 2010), and few investigations have been conducted without the effects from training/experience among typically-developed individuals. However, sociolinguists have long recognized that native speakers vary in their ability to discriminate speech sounds in their language, and enormous variability exists especially during a sound change in progress.
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\nTaking the opportunity of an on-going tone merging in Hong Kong Cantonese, this thesis aims to systematically investigate individual differences of native speech perception, production, and their relationships with cognitive functions among typically-developed speakers. Three participant groups were recruited, who presented respectively the pattern of good perception and good production of all Cantonese tones [+Per+Pro], that of good perception of all tones but poor production of specifically the T2/T5 distinction [+Per-Pro], and that of poor perception and production of specifically the T2/T5 distinction [-Per-Pro]. Behavioral and neural measures of tone perception included reaction time, discrimination sensitivity index, and components of event-related potentials (ERPs) – the mismatch negativity (MMN), P3a, and rise time of amplitude envelope. Acoustic measurements were used to evaluate tone production in terms of both pitch and amplitude rise time. Components of attention and working memory in auditory and visual modalities are assessed with published cognitive test batteries.
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\nThe results show that, apart from the expected differences in accuracy and discrimination sensitivity of tone perception, both [+Per-Pro] and [-Per-Pro] took significantly longer to discriminate between tones than [+Per+Pro]. As for the performance in production, besides the differences in pitch offset, both [+Per-Pro] and [-Per-Pro] showed decreased differentiation in rise time between the two rising tones in production, compared with [+Per+Pro].With respect to the brain responses reflected in the MMN and P3a to pitch deviations among tones, [-Per-Pro] showed smaller and slower responses than one or both of the other two groups, but [+Per+Pro] and [+Per-Pro] did not differ from each other. However, both [+Per-Pro] and [-Per-Pro] showed weaker neural responses compared with [+Per+Pro] to the rise time of T5. In addition, [-Per-Pro] was poorer in tasks pertaining to the ability of attention switching/shifting regardless of modality than one or both of the other two groups, but [+Per+Pro] and [+Per-Pro] did not differ from each other.
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\nFurther correlation and regression analyses reveal that both pitch contour/height and rise time contributed to distinctive perception and production of rising tones, measures of perception (behavioral and neural) and production were correlated with each other, and attentional shifting in visual and auditory modalities significantly predicted performances of discrimination and production. Taken together, the findings of the present study suggest that attentional switching influences the quality of phonological representations, resulting in different degrees of distinctiveness in perception and production among typically-developed individuals.

While a large portion of the variance among listeners in auditory speech processing is associated with the audibility of components of the speech waveform, it is not possible to predict individual differences in speech perception strictly from the audiogram. Psychoacoustic measures of spectral-temporal acuity with nonspeech stimuli also have been shown to correlate only weakly (or not at all) with speech processing. In a replication and extension of an earlier study (Watson etal., J. Acoust. Soc. Am. Suppl. 1 71, S73) 100 normal-hearing college students were tested on speech perception tasks (nonsense syllables, words, sentences in a noise background) and on 6 spectral-temporal discrimination tasks using simple and complex nonspeech sounds. Factor analysis showed that the abilities that explain performance on the nonspeech tasks are quite distinct from those that account for performance on the four speech tasks. Performance was significantly correlated among speech tasks, and among nonspeech tasks. Either, (a) auditory spectral-temporal acuity for nonspeech sounds is orthogonal to speech processing abilities, OR (b) we have yet to identify the appropriate task or types of nonspeech stimuli that exercise the abilities required for speech recognition. [Work supported grants from NIH and AFOSR to Indiana University.]

INTRODUCTION Speech is multisensory. The addition of visual speech to auditory speech greatly improves comprehension, especially under noisy auditory conditions. However, the neural mechanism for this visual enhancement of auditory speech is poorly understood. We used electrocorticography (ECoG) to study how auditory, visual, and audiovisual speech is processed in the posterior superior temporal gyrus (pSTG), an area of auditory association cortex involved in audiovisual speech integration. We hypothesized that early visual mouth movements modulate audiovisual speech integration through a mechanism of cross-modal suppression, suggesting that the pSTG response to early mouth movements should correlate with comprehension benefits gained by the addition of visual speech to auditory speech. METHODS Words were presented under auditory-only (AUD), visual-only (VIS), and audiovisual (AV) conditions to epilepsy patients (n = 8) implanted with intracranial electrodes for phase-2 monitoring. We measured high-frequency broadband activity (75-150 Hz), a marker for local neuronal firing, in 28 electrodes over the pSTG. RESULTS The early neural response to visual-only words was compared to the reduction in neural response seen from AUD to AV words, a reduction correlated with an improvement in speech comprehension that occurs with the addition of visual to auditory speech. In words that showed a comprehension benefit with the addition of visual speech, there was a strong early response to visual speech and a correlation between early visual response and the AUD-AV difference (r = 0.64, P = 104). In words where visual speech did not provide any comprehension benefit, there was a weak early visual response and no correlation (r = 0.18, P = .35). CONCLUSION Words with a visual speech comprehension benefit also elicit a strong neural response to early visual speech in pSTG, while words with no comprehension benefit do not cause a strong early response. This suggests that cross-modal suppression of auditory association cortex (pSTG) by early visual plays an important role in audiovisual speech perception.

Objective: The aim of this study was to evaluate the influence of age on speech perception in children implanted before 5 years of age over the first 3 years after surgery. Material and Methods: A total of 31 children are divided into 2 groups; 12 were implanted before 2 and 19 implanted between 3 and 5 years of age. Assessment battery designed to measure speech perception was used to evaluate recipients at 12, 24 and 36 months after implantation. We used the following tests: 1. Closed and open-set for monosyllabic and polysyllabic words in quiet and noise 2 and Open-set sentence in quiet. Testing was performed with recorded voice in free field. Results: The mean value on the open-set for monosyllabic words for all patients increased with time. The difference between the values for each group at 12, 24 and 36 months was significant (p<0.001). As duration of cochlear implant use increased, speech perception also improved. The mean value on the open-set with polysyllabic words at 36 months for all patients (82.7%) was significantly higher than the mean value at 24 months (77.2%) (p=0.10). The mean value for this parameter at 36 months in children aged 3 to 5 years of age (82.1%) was significantly higher than the mean value at 24 months (74.2%) (p=0.08). Improvement in speech perception is faster if implantation occurs at a younger before 2 years of age. Conclusion: Age at time of implantation has a positive effect on speech perception, especially in situations such as background noise. Children implanted before 2 years of age have faster improvement in speech perception. Those who are implanted between 3 and 5 years of age showed delay 2 years postoperatively and significant improvement after this time. Three years after cochlear implantation there was no significant differences among them.