Speech Envelope Enhancement Instantaneously Effaces Atypical Speech Perception in Dyslexia:

Attentional modulation of neural sound tracking in children with and without dyslexia

Auditory selective attention forms an important foundation of children's learning by enabling the prioritisation and encoding of relevant stimuli. It may also influence reading development, which relies on metalinguistic skills including the awareness of the sound structure of spoken language. Reports of attentional impairments and speech perception difficulties in noisy environments in dyslexic readers are also suggestive of the putative contribution of auditory attention to reading development. To date, it is unclear whether non-speech selective attention and its underlying neural mechanisms are impaired in children with dyslexia and to which extent these deficits relate to individual reading and speech perception abilities in suboptimal listening conditions. In this EEG study, we assessed non-speech sustained auditory selective attention in 106 7-to-12-year-old children with and without dyslexia. Children attended to one of two tone streams, detecting occasional sequence repeats in the attended stream, and performed a speech-in-speech perception task. Results show that when children directed their attention to one stream, inter-trial-phase-coherence at the attended rate increased in fronto-central sites; this, in turn, was associated with better target detection. Behavioural and neural indices of attention did not systematically differ as a function of dyslexia diagnosis. However, behavioural indices of attention did explain individual differences in reading fluency and speech-in-speech perception abilities: both these skills were impaired in dyslexic readers. Taken together, our results show that children with dyslexia do not show group-level auditory attention deficits but these deficits may represent a risk for developing reading impairments and problems with speech perception in complex acoustic environments. RESEARCH HIGHLIGHTS: Non-speech sustained auditory selective attention modulates EEG phase coherence in children with/without dyslexia Children with dyslexia show difficulties in speech-in-speech perception Attention relates to dyslexic readers' speech-in-speech perception and reading skills Dyslexia diagnosis is not linked to behavioural/EEG indices of auditory attention.

Dynamics of cognitive predictors during reading acquisition in a sample of children overrepresented for dyslexia risk

Literacy acquisition is a complex process with genetic and environmental factors influencing cognitive and neural processes associated with reading. Previous research identified factors that predict word reading fluency (WRF), including phonological awareness (PA), rapid automatized naming (RAN), and speech-in-noise perception (SPIN). Recent theoretical accounts suggest dynamic interactions between these factors and reading, but direct investigations of such dynamics are lacking. Here, we investigated the dynamic effect of phonological processing and speech perception on WRF. More specifically, we evaluated the dynamic influence of PA, RAN, and SPIN measured in kindergarten (the year prior to formal reading instruction), first grade (the first year of formal reading instruction) and second grade on WRF in second and third grade. We also assessed the effect of an indirect proxy of family risk for reading difficulties using a parental questionnaire (Adult Reading History Questionnaire, ARHQ). We applied path modeling in a longitudinal sample of 162 Dutch-speaking children of whom the majority was selected to have an increased family and/or cognitive risk for dyslexia. We showed that parental ARHQ had a significant effect on WRF, RAN and SPIN, but unexpectedly not on PA. We also found effects of RAN and PA directly on WRF that were limited to first and second grade respectively, in contrast to previous research reporting pre-reading PA effects and prolonged RAN effects throughout reading acquisition. Our study provides important new insights into early prediction of later word reading abilities and into the optimal time window to target a specific reading-related subskill during intervention.

Atypical speech production of multisyllabic words and phrases by children with developmental dyslexia

The prevalent "core phonological deficit" model of dyslexia proposes that the reading and spelling difficulties characterizing affected children stem from prior developmental difficulties in processing speech sound structure, for example, perceiving and identifying syllable stress patterns, syllables, rhymes and phonemes. Yet spoken word production appears normal. This suggests an unexpected disconnect between speech input and speech output processes. Here we investigated the output side of this disconnect from a speech rhythm perspective by measuring the speech amplitude envelope (AE) of multisyllabic spoken phrases. The speech AE contains crucial information regarding stress patterns, speech rate, tonal contrasts and intonational information. We created a novel computerized speech copying task in which participants copied aloud familiar spoken targets like "Aladdin." Seventy-five children with and without dyslexia were tested, some of whom were also receiving an oral intervention designed to enhance multi-syllabic processing. Similarity of the child's productions to the target AE was computed using correlation and mutual information metrics. Similarity of pitch contour, another acoustic cue to speech rhythm, was used for control analyses. Children with dyslexia were significantly worse at producing the multi-syllabic targets as indexed by both similarity metrics for computing the AE. However, children with dyslexia were not different from control children in producing pitch contours. Accordingly, the spoken production of multisyllabic phrases by children with dyslexia is atypical regarding the AE. Children with dyslexia may not appear to listeners to exhibit speech production difficulties because their pitch contours are intact. RESEARCH HIGHLIGHTS: Speech production of syllable stress patterns is atypical in children with dyslexia. Children with dyslexia are significantly worse at producing the amplitude envelope of multi-syllabic targets compared to both age-matched and reading-level-matched control children. No group differences were found for pitch contour production between children with dyslexia and age-matched control children. It may be difficult to detect speech output problems in dyslexia as pitch contours are relatively accurate.

Neural responses to natural and enhanced speech edges in children with and without dyslexia

Sensory-neural studies indicate that children with developmental dyslexia show impairments in processing acoustic speech envelope information. Prior studies suggest that this arises in part from reduced sensory sensitivity to amplitude rise times (ARTs or speech "edges") in the envelope, accompanied by less accurate neural encoding of low-frequency envelope information. Accordingly, enhancing these characteristics of the speech envelope may enhance neural speech processing in children with dyslexia. Here we applied an envelope modulation enhancement (EME) algorithm to a 10-min story read in child-directed speech (CDS), enhancing ARTs and also enhancing low-frequency envelope information. We compared neural speech processing (as measured using MEG) for the EME story with the same story read in natural CDS for 9-year-old children with and without dyslexia. The EME story affected neural processing in the power domain for children with dyslexia, particularly in the delta band (0.5-4 Hz) in the superior temporal gyrus. This may suggest that prolonged experience with EME speech could ameliorate some of the impairments shown in natural speech processing by children with dyslexia.

The importance of temporal-fine structure to perceive time-compressed speech with and without the restoration of the syllabic rhythm

Intelligibility of time-compressed (TC) speech decreases with increasing speech rate. However, intelligibility can be restored by 'repackaging' the TC speech by inserting silences between the syllables so that the original 'rhythm' is restored. Although restoration of the speech rhythm affects solely the temporal envelope, it is unclear to which extent repackaging also affects the perception of the temporal-fine structure (TFS). Here we investigate to which extent TFS contributes to the perception of TC and repackaged TC speech in quiet. Intelligibility of TC sentences with a speech rate of 15.6 syllables per second (sps) and the repackaged sentences, by adding 100 ms of silence between the syllables of the TC speech (i.e., a speech rate of 6.1 sps), was assessed for three TFS conditions: the original TFS and the TFS conveyed by an 8- and 16-channel noise vocoder. An overall positive effect on intelligibility of both the repackaging process and of the amount of TFS available to the listener was observed. Furthermore, the benefit associated with the repackaging TC speech depended on the amount of TFS available. The results show TFS contributes significantly to the perception of fast speech even when the overall rhythm/envelope of TC speech is restored.

Neural synchronization and intervention in pre-readers who later on develop dyslexia

A growing number of studies has investigated temporal processing deficits in dyslexia. These studies largely focus on neural synchronization to speech. However, the importance of rise times for neural synchronization is often overlooked. Furthermore, targeted interventions, phonics-based and auditory, are being developed, but little is known about their impact. The current study investigated the impact of a 12-week tablet-based intervention. Children at risk for dyslexia received phonics-based training, either with (n = 31) or without (n = 31) auditory training, or engaged in active control training (n = 29). Additionally, neural synchronization and processing of rise times was longitudinally investigated in children with dyslexia (n = 26) and typical readers (n = 52) from pre-reading (5 years) to beginning reading age (7 years). The three time points in the longitudinal study correspond to intervention pre-test, post-test and consolidation, approximately 1 year after completing the intervention. At each time point neural synchronization was measured to sinusoidal stimuli and pulsatile stimuli with shortened rise times at syllable (4 Hz) and phoneme rates (20 Hz). Our results revealed no impact on neural synchronization at syllable and phoneme rate of the phonics-based and auditory training. However, we did reveal atypical hemispheric specialization at both syllable and phoneme rates in children with dyslexia. This was detected even before the onset of reading acquisition, pointing towards a possible causal rather than consequential mechanism in dyslexia. This study contributes to our understanding of the temporal processing deficits underlying the development of dyslexia, but also shows that the development of targeted interventions is still a work in progress.

Speech perception deficits and the effect of envelope-enhanced story listening combined with phonics intervention in pre-readers at risk for dyslexia

Developmental dyslexia is considered to be most effectively addressed with preventive phonics-based interventions, including grapheme-phoneme coupling and blending exercises. These intervention types require intact speech perception abilities, given their large focus on exercises with auditorily presented phonemes. Yet some children with (a risk for) dyslexia experience problems in this domain due to a poorer sensitivity to rise times, i.e., rhythmic acoustic cues present in the speech envelope. As a result, the often subtle speech perception problems could potentially constrain an optimal response to phonics-based interventions in at-risk children. The current study therefore aimed (1) to extend existing research by examining the presence of potential speech perception deficits in pre-readers at cognitive risk for dyslexia when compared to typically developing peers and (2) to explore the added value of a preventive auditory intervention for at-risk pre-readers, targeting rise time sensitivity, on speech perception and other reading-related skills. To obtain the first research objective, we longitudinally compared speech-in-noise perception between 28 5-year-old pre-readers with and 30 peers without a cognitive risk for dyslexia during the second half of the third year of kindergarten. The second research objective was addressed by exploring growth in speech perception and other reading-related skills in an independent sample of 62 at-risk 5-year-old pre-readers who all combined a 12-week preventive phonics-based intervention (GraphoGame-Flemish) with an auditory story listening intervention. In half of the sample, story recordings contained artificially enhanced rise times (GG-FL_EE group, n = 31), while in the other half, stories remained unprocessed (GG-FL_NE group, n = 31; Clinical Trial Number S60962—https://www.uzleuven.be/nl/clinical-trial-center). Results revealed a slower speech-in-noise perception growth in the at-risk compared to the non-at-risk group, due to an emerged deficit at the end of kindergarten. Concerning the auditory intervention effects, both intervention groups showed equal growth in speech-in-noise perception and other reading-related skills, suggesting no boost of envelope-enhanced story listening on top of the effect of combining GraphoGame-Flemish with listening to unprocessed stories. These findings thus provide evidence for a link between speech perception problems and dyslexia, yet do not support the potential of the auditory intervention in its current form.

Language acquisition and speech rhythm patterns: an auditory neuroscience perspective

All human infants acquire language, but their brains do not know which language/s to prepare for. This observation suggests that there are fundamental components of the speech signal that contribute to building a language system, and fundamental neural processing mechanisms that use these components, which are shared across languages. Equally, disorders of language acquisition are found across all languages, with the most prevalent being developmental language disorder (approx. 7% prevalence), where oral language comprehension and production is atypical, and developmental dyslexia (approx. 7% prevalence), where written language acquisition is atypical. Recent advances in auditory neuroscience, along with advances in modelling the speech signal from an amplitude modulation (AM, intensity or energy change) perspective, have increased our understanding of both language acquisition and these developmental disorders. Speech rhythm patterns turn out to be fundamental to both sensory and neural linguistic processing. The rhythmic routines typical of childcare in many cultures, the parental practice of singing lullabies to infants, and the ubiquitous presence of BabyTalk (infant-directed speech) all enhance the fundamental AM components that contribute to building a linguistic brain.

Speech perception in noise in children with dyslexia: Does speech sound disorder matter?

The aim of this observational cohort study with a control group is to compare consonant perception skills in quiet and in noise in children with typical language and learning development and in children with dyslexia, with and without Speech Sound Disorder (SSD). Three groups were included: A control group of twenty children with normal reading abilities and typical language development, twelve children with dyslexia and typical language development and thirteen children with dyslexia and SSD. All subjects received a consonant recognition test in three different listening conditions (quiet, + 10 and 0 Signal-to-Noise Ratio). In all test conditions, children with dyslexia and SSD had significantly lower consonant recognition scores than the control group and the children with dyslexia and typical language development (p < .0001). The poorer performances observed in children with dyslexia and SSD may be explained by impaired phonological processing underlying both conditions.

Feasibility, Enjoyment, and Language Comprehension Impact of a Tablet- and GameFlow-Based Story-Listening Game for Kindergarteners: Methodological and Mixed Methods Study

BACKGROUND

Enjoyment plays a key role in the success and feasibility of serious gaming interventions. Unenjoyable games will not be played, and in the case of serious gaming, learning will not occur. Therefore, a so-called GameFlow model has been developed, which intends to guide (serious) game developers in the process of creating and evaluating enjoyment in digital (serious) games. Regarding language learning, a variety of serious games targeting specific language components exist in the market, albeit often without available assessments of enjoyment or feasibility.

OBJECTIVE

This study evaluates the enjoyment and feasibility of a tablet-based, serious story-listening game for kindergarteners, developed based on the principles of the GameFlow model. This study also preliminarily explores the possibility of using the game to foster language comprehension.

METHODS

Within the framework of a broader preventive reading intervention, 91 kindergarteners aged 5 years with a cognitive risk for dyslexia were asked to play the story game for 12 weeks, 6 days per week, either combined with a tablet-based phonics intervention or control games. The story game involved listening to and rating stories and responding to content-related questions. Game enjoyment was assessed through postintervention questionnaires, a GameFlow-based evaluation, and in-game story rating data. Feasibility was determined based on in-game general question response accuracy (QRA), reflecting the difficulty level, attrition rate, and final game exposure and training duration. Moreover, to investigate whether game enjoyment and difficulty influenced feasibility, final game exposure and training duration were predicted based on the in-game initial story ratings and initial QRA. Possible growth in language comprehension was explored by analyzing in-game QRA as a function of the game phase and baseline language skills.

RESULTS

Eventually, data from 82 participants were analyzed. The questionnaire and in-game data suggested an overall enjoyable game experience. However, the GameFlow-based evaluation implied room for game design improvement. The general QRA confirmed a well-adapted level of difficulty for the target sample. Moreover, despite the overall attrition rate of 39% (32/82), 90% (74/82) of the participants still completed 80% of the game, albeit with a large variation in training days. Higher initial QRA significantly increased game exposure (β=.35; P<.001), and lower initial story ratings significantly slackened the training duration (β=-0.16; P=.003). In-game QRA was positively predicted by game phase (β=1.44; P=.004), baseline listening comprehension (β=1.56; P=.002), and vocabulary (β=.16; P=.01), with larger QRA growth over game phases in children with lower baseline listening comprehension skills (β=-0.08; P=.04).

CONCLUSIONS

Generally, the story game seemed enjoyable and feasible. However, the GameFlow model evaluation and predictive relationships imply room for further game design improvements. Furthermore, our results cautiously suggest the potential of the game to foster language comprehension; however, future randomized controlled trials should further elucidate the impact on language comprehension.

Hearing loss is associated with delayed neural responses to continuous speech

We investigated the impact of hearing loss on the neural processing of speech. Using a forward modeling approach, we compared the neural responses to continuous speech of 14 adults with sensorineural hearing loss with those of age-matched normal-hearing peers. Compared to their normal-hearing peers, hearing-impaired listeners had increased neural tracking and delayed neural responses to continuous speech in quiet. The latency also increased with the degree of hearing loss. As speech understanding decreased, neural tracking decreased in both populations; however, a significantly different trend was observed for the latency of the neural responses. For normal-hearing listeners, the latency increased with increasing background noise level. However, for hearing-impaired listeners, this increase was not observed. Our results support the idea that the neural response latency indicates the efficiency of neural speech processing: more or different brain regions are involved in processing speech, which causes longer communication pathways in the brain. These longer communication pathways hamper the information integration among these brain regions, reflected in longer processing times. Altogether, this suggests decreased neural speech processing efficiency in HI listeners as more time and more or different brain regions are required to process speech. Our results suggest that this reduction in neural speech processing efficiency occurs gradually as hearing deteriorates. From our results, it is apparent that sound amplification does not solve hearing loss. Even when listening to speech in silence at a comfortable loudness, hearing-impaired listeners process speech less efficiently.

Neural auditory processing of parameterized speech envelopes

Speech perception depends highly on the neural processing of the speech envelope. Several auditory processing deficits are hypothesized to result in a reduction in fidelity of the neural representation of the speech envelope across the auditory pathway. Furthermore, this reduction in fidelity is associated with supra-threshold speech processing deficits. Investigating the mechanisms that affect the neural encoding of the speech envelope can be of great value to gain insight in the different mechanisms that account for this reduced neural representation, and to develop stimulation strategies for hearing prosthesis that aim to restore it. In this perspective, we discuss the importance of neural assessment of phase-locking to the speech envelope from an audiological view and introduce the Temporal Envelope Speech Tracking (TEMPEST) stimulus framework which enables the electrophysiological assessment of envelope processing across the auditory pathway in a systematic and standardized way. We postulate that this framework can be used to gain insight in the salience of speech-like temporal envelopes in the neural code and to evaluate the effectiveness of stimulation strategies that aim to restore temporal processing across the auditory pathway with auditory prostheses.

Ahead of maturation: Enhanced speech envelope training boosts rise time discrimination in pre-readers at cognitive risk for dyslexia

Dyslexia has frequently been related to atypical auditory temporal processing and speech perception. Results of studies emphasizing speech onset cues and reinforcing the temporal structure of the speech envelope, that is, envelope enhancement (EE), demonstrated reduced speech perception deficits in individuals with dyslexia. The use of this strategy as auditory intervention might thus reduce some of the deficits related to dyslexia. Importantly, reading-skill interventions are most effective when they are provided during kindergarten and first grade. Hence, we provided a tablet-based 12-week auditory and phonics-based intervention to pre-readers at cognitive risk for dyslexia and investigated the effect on auditory temporal processing with a rise time discrimination (RTD) task. Ninety-one pre-readers at cognitive risk for dyslexia (aged 5-6) were assigned to two groups receiving a phonics-based intervention and playing a story listening game either with (n = 31) or without (n = 31) EE or a third group playing control games and listening to non-enhanced stories (n = 29). RTD was measured directly before, directly after and 1 year after the intervention. While the groups listening to non-enhanced stories mainly improved after the intervention during first grade, the group listening to enhanced stories improved during the intervention in kindergarten and subsequently remained stable during first grade. Hence, an EE intervention improves auditory processing skills important for the development of phonological skills. This occurred before the onset of reading instruction, preceding the maturational improvement of these skills, hence potentially giving at risk children a head start when learning to read.

Digital Game-Based Phonics Instruction Promotes Print Knowledge in Pre-Readers at Cognitive Risk for Dyslexia

Dyslexia is targeted most effectively when (1) interventions are provided preventively, before the onset of reading instruction, and (2) remediation programs combine letter-sound training with phoneme blending. Given the growing potential of technology in educational contexts, there has been a considerable increase of letter-sound trainings embedded in digital serious games. One such intervention is GraphoGame. Yet, current evidence on the preventive impact of GraphoGame is limited by the lack of adaptation of the original learning content to the skills of pre-readers, short training duration, and a restricted focus on explicitly trained skills. Therefore, the current study aims at investigating the impact of a preventive, and pre-reading adapted GraphoGame training (i.e., GraphoGame-Flemish, GG-FL) on explicitly trained skills and non-specifically trained phonological and language abilities. Following a large-scale screening (N = 1225), the current study included 88 pre-reading kindergarteners at cognitive risk for dyslexia who were assigned to three groups training either with GG-FL (n = 31), an active control game (n = 29), or no game (n = 28). Before and after the 12-week intervention, a variety of reading-related skills were assessed. Moreover, receptive letter knowledge and phonological awareness were measured every three weeks during the intervention period. Results revealed significantly larger improvements in the GG-FL group on explicitly trained skills, i.e., letter knowledge and word decoding, without finding transfer-effects to untrained phonological and language abilities. Our findings imply a GG-FL-driven head start on early literacy skills in at-risk children. A follow-up study should uncover the long-term impact and the ability of GG-FL to prevent actual reading failure.

Perception of temporally enhanced and hearing aid processed speech in children with late-onset Auditory Neuropathy Spectrum Disorder

OBJECTIVE

To investigate phrase perception and subjective quality preference of temporal enhancement-based speech processing strategies: Deep-band modulation and Stretching, and hearing aid processed speech in adolescents with late-onset Auditory Neuropathy.

METHODS

15 participants with Auditory Neuropathy Spectrum Disorder were involved. Speech perception was assessed using unprocessed, deep-band modulated, stretched, and hearing aid processed conditions. Subjective preference was also assessed using the pair-wise comparison technique. Gap detection test was done using broadband noise to investigate the possible correlation with benefit from processing strategies.

RESULTS

As a group, no significant benefits were found with processed speech. Clinically relevant trends emerged on subdividing the group into good and poor performers. Deep-band modulation processing was significantly better than unprocessed speech in those with poorer speech recognition abilities. There was a trend for those with poorer temporal processing abilities to benefit more with deep-band modulation processing. In those with relatively better speech recognition abilities, processing showed no benefit, and hearing aid processed speech was inferior to unprocessed speech. Quality-wise, the unprocessed speech was preferred by all the participants. Among the processed conditions, deep-band modulation was preferred by most, followed by stretching and hearing aid processed speech.

CONCLUSION

Results indicate that temporal enhancement strategies may be beneficial for a subset of individuals with ANSD with poorer temporal processing and speech perception abilities. However, processing strategies need to take into account the quality aspect and not just intelligibility.

A Bridge over Troubled Listening: Improving Speech-in-Noise Perception by Children with Dyslexia

Developmental dyslexia is most commonly associated with phonological processing difficulties. However, children with dyslexia may experience poor speech-in-noise perception as well. Although there is an ongoing debate whether a speech perception deficit is inherent to dyslexia or acts as an aggravating risk factor compromising learning to read indirectly, improving speech perception might boost reading-related skills and reading acquisition. In the current study, we evaluated advanced speech technology as applied in auditory prostheses, to promote and eventually normalize speech perception of school-aged children with dyslexia, i.e., envelope enhancement (EE). The EE strategy automatically detects and emphasizes onset cues and consequently reinforces the temporal structure of the speech envelope. Our results confirmed speech-in-noise perception difficulties by children with dyslexia. However, we found that exaggerating temporal "landmarks" of the speech envelope (i.e., amplitude rise time and modulations)-by using EE-passively and instantaneously improved speech perception in noise for children with dyslexia. Moreover, the benefit derived from EE was large enough to completely bridge the initial gap between children with dyslexia and their typical reading peers. Taken together, the beneficial outcome of EE suggests an important contribution of the temporal structure of the envelope to speech perception in noise difficulties in dyslexia, providing an interesting foundation for future intervention studies based on auditory and speech rhythm training.

Impaired neural response to speech edges in dyslexia

Speech comprehension has been proposed to critically rely on oscillatory cortical tracking, that is, phase alignment of neural oscillations to the slow temporal modulations (envelope) of speech. Speech-brain entrainment is readjusted over time as transient events (edges) in speech lead to speech-brain phase realignment. Auditory behavioral research suggests that phonological deficits in dyslexia are linked to difficulty in discriminating speech edges. Importantly, research to date has not specifically examined neural responses to speech edges in dyslexia. In the present study, we used MEG to record brain activity from normal and dyslexic readers while they listened to speech. We computed phase locking values (PLVs) to evaluate phase entrainment between neural oscillations and the speech envelope time-locked to edge onsets. In both groups, we observed that edge onsets induced phase resets in the auditory oscillations tracking speech, thereby enhancing their entrainment to speech. Importantly, dyslexic readers showed weaker PLVs compared to normal readers in left auditory regions from ~.15 sec to ~.65 sec after edge onset. Our results indicate that the neural mechanism that adapts cortical entrainment to the speech envelope is impaired in dyslexia. These findings here are consistent with the temporal sampling theory of developmental dyslexia.