Are speech perception deficits associated with developmental dyslexia?

Event Related Potentials to Native Speech Contrasts Predicts Word Reading Abilities in Early School-Aged Children

Speech perception skills have been implicated in the development of phoneme-grapheme correspondence, yet the exact nature of speech perception and word reading ability remains unknown. We investigate phonological sensitivity to native (English) and nonnative (Spanish) speech syllables within an auditory oddball paradigm using event related potentials (ERPs) collected from lateral temporal electrode sites in 33 monolingual English-speaking children aged 6-8 years (N=33). We further explore the relationship between ERPs to English word reading abilities for this group. Results revealed that language stimuli (English, Spanish), ERP condition (standard, deviant), and hemisphere (left, right) all influenced the lateral N1 component. ERPs recorded from deviant English stimuli were significantly more negative within the left hemisphere compared to all other recorded ERPs. Mean amplitude differences within the N1 in left lateral electrode sites recorded in response to English phoneme contrasts significantly predicted English word reading abilities within this sample. Results indicate that speech perception of native contrasts recorded in left temporal electrode sites for the N1 component are linked to English word reading abilities in early school-aged children.

Preliminary Speech Perception Performance Profiles of School-Age Children With Childhood Apraxia of Speech, Speech Sound Disorder, and Typical Development

PURPOSE

Limited research exists assessing speech perception in school-age children with speech sound disorder (SSD) and childhood apraxia of speech (CAS); despite early evidence that speech perception may lead to error-prone motor planning/programming. In this study, we examine speech perception performance in school-age children with and without speech production deficits.

METHOD

Speech perception was assessed using the Wide Range Acoustic Accuracy Scale to determine the just-noticeable difference in discrimination for three consonant-vowel syllable contrasts (/bɑ/-/wɑ/, /dɑ/-/gɑ/, /ɹɑ/-/wɑ/), each varying along a single acoustic parameter for seven children with CAS with rhotic errors, seven children with SSD with rhotic errors, and seven typically developing (TD) children.

RESULTS

Findings revealed statistically significant mean differences between perceptual performance of children with CAS when compared to TD children for discrimination of /ɹɑ/-/wɑ/ contrasts. Large effect sizes were also observed for comparisons of /ɹɑ/-/wɑ/ contrasts between children with CAS, SSD, and TD peers. Additionally, large effect sizes were observed for /dɑ/-/gɑ/ contrasts between children with CAS and SSD and TD children despite nonsignificant mean differences in group performance.

CONCLUSIONS

Overall, mean outcome scores suggest that school-age children with CAS and persistent rhotic errors demonstrated less accurate speech perception skills relative to TD children for the /ɹɑ/-/wɑ/ contrasts. However, the relatively small sample sizes per group limit the extent to which these findings may be generalized to the broader population.

Do developmental dyslexia and congenital amusia share underlying impairments?

Developmental dyslexia and congenital amusia have common characteristics. Yet, their possible association in some individuals has been addressed only scarcely. Recently, two converging studies reported a sizable comorbidity rate between these two neurodevelopmental disorders (Couvignou et al., Cognitive Neuropsychology 2019; Couvignou & Kolinsky, Neuropsychologia 2021). However, the reason for their association remains unclear. Here, we investigate the hypothesis of shared underlying impairments between dyslexia and amusia. Fifteen dyslexic children with amusia (DYS+A), 15 dyslexic children without amusia (DYS-A), and two groups of 25 typically developing children matched on either chronological age (CA) or reading level (RL) were assessed with a behavioral battery aiming to investigate phonological and pitch processing capacities at auditory memory, perceptual awareness, and attentional levels. Overall, our results suggest that poor auditory serial-order memory increases susceptibility to comorbidity between dyslexia and amusia and may play a role in the development of the comorbid phenotype. In contrast, the impairments observed in the DYS+A children for auditory item memory, perceptual awareness, and attention might be a consequence of their reduced reading experience combined with weaker musical skills. Comparing DYS+A and DYS-A children suggests that the latter are more resourceful and/or have more effective compensatory strategies, or that their phenotype results from a different developmental trajectory. We will discuss the relevance of these findings for delving into the etiology of these two developmental disorders and address their implications for future research and practice.

Altered engagement of the speech motor network is associated with reduced phonological working memory in autism

Nonword repetition, a common clinical measure of phonological working memory, involves component processes of speech perception, working memory, and speech production. Autistic children often show behavioral challenges in nonword repetition, as do many individuals with communication disorders. It is unknown which subprocesses of phonological working memory are vulnerable in autistic individuals, and whether the same brain processes underlie the transdiagnostic difficulty with nonword repetition. We used functional magnetic resonance imaging (fMRI) to investigate the brain bases for nonword repetition challenges in autism. We compared activation during nonword repetition in functional brain networks subserving speech perception, working memory, and speech production between neurotypical and autistic children. Autistic children performed worse than neurotypical children on nonword repetition and had reduced activation in response to increasing phonological working memory load in the supplementary motor area. Multivoxel pattern analysis within the speech production network classified shorter vs longer nonword-repetition trials less accurately for autistic than neurotypical children. These speech production motor-specific differences were not observed in a group of children with reading disability who had similarly reduced nonword repetition behavior. These findings suggest that atypical function in speech production brain regions may contribute to nonword repetition difficulties in autism.

Don't force it! Gradient speech categorization calls for continuous categorization tasks

Research on speech categorization and phoneme recognition has relied heavily on tasks in which participants listen to stimuli from a speech continuum and are asked to either classify each stimulus (identification) or discriminate between them (discrimination). Such tasks rest on assumptions about how perception maps onto discrete responses that have not been thoroughly investigated. Here, we identify critical challenges in the link between these tasks and theories of speech categorization. In particular, we show that patterns that have traditionally been linked to categorical perception could arise despite continuous underlying perception and that patterns that run counter to categorical perception could arise despite underlying categorical perception. We describe an alternative measure of speech perception using a visual analog scale that better differentiates between processes at play in speech categorization, and we review some recent findings that show how this task can be used to better inform our theories.

Decoding of speech information using EEG in children with dyslexia: Less accurate low-frequency representations of speech, not "Noisy" representations

The amplitude envelope of speech carries crucial low-frequency acoustic information that assists linguistic decoding. The sensory-neural Temporal Sampling (TS) theory of developmental dyslexia proposes atypical encoding of speech envelope information < 10 Hz, leading to atypical phonological representations. Here a backward linear TRF model and story listening were employed to estimate the speech information encoded in the electroencephalogram in the canonical delta, theta and alpha bands by 9-year-old children with and without dyslexia. TRF decoding accuracy provided an estimate of how faithfully the children's brains encoded low-frequency envelope information. Between-group analyses showed that the children with dyslexia exhibited impaired reconstruction of speech information in the delta band. However, when the quality of speech encoding for each child was estimated using child-by-child decoding models, then the dyslexic children did not differ from controls. This suggests that children with dyslexia encode neither "noisy" nor "normal" representations of the speech signal, but different representations.

Reading Skills in Children With Suspected Childhood Apraxia of Speech and Children With Reading Disorders: Same or Different?

PURPOSE

The primary aim of this study was to compare decoding and literacy-related skills of children with suspected childhood apraxia of speech (sCAS) to children with reading disorders (RD) and no history of speech sound disorder (RD-no SSD) to determine if the groups differ in decoding and the endophenotypes that contribute to RD. We also explored the association between language impairment (LI) and decoding and literacy-related skills within the participant group with sCAS.

METHOD

Participants were school-age children and adolescents, 8-14 years of age, with a diagnosis of sCAS (n = 13) or RD-no SSD (n = 16). The sCAS and RD-no SSD groups were compared on measures of single-word decoding, oral language, motor-speech skills, phonological processing, and speech-in-noise perception, employing t tests and analysis of covariance. The sCAS + LI and sCAS-only groups were compared on similar measures using t tests.

RESULTS

Compared to the RD-no SSD group, the sCAS group performed significantly worse on measures of phonological processing, multisyllable word repetition, diadochokinetic rate, and speech-in-noise perception. The groups did not differ on measures of single-word decoding, with mean scores for both groups falling below average. All participants with sCAS + LI demonstrated deficits in literacy and literacy-related skills compared to a smaller percentage of the sCAS-only group.

CONCLUSIONS

Children with sCAS and children with RD-no SSD demonstrate similar impairments in literacy. However, the endophenotypes underlying these difficulties can differ between the groups. Deficits in skills needed for literacy may require specifically tailored interventions to address reading difficulties for children with sCAS, especially for those with comorbid LI.

Phonotactic and lexical factors in talker discrimination and identification

Previous research has shown that listeners are better at processing talker information in their native language compared to an unfamiliar language, a phenomenon known as the language familiarity effect. Several studies have explored two mechanisms that support this effect: lexical status and phonological familiarity. Further support for the importance of phonological knowledge comes from studies showing that participants with poorer reading skills perform worse on talker processing tasks. Previous research also suggested that speech perception in individuals with poor reading skills may be task dependent, with poorer performance on identification tasks compared to discrimination tasks. In the current study, we explore talker perception while manipulating lexicality (words, nonwords) and phonotactic probability (high, low) in participants who differ in reading ability and phonological working memory using a talker discrimination task (Experiment 1) and a talker identification task (Experiment 2). Results from these experiments revealed an effect of lexical status and phonotactic probability in both the discrimination and the identification tasks. Effects of phonological working memory were found only for the identification task, where participants with higher scores identified more talkers correctly. These results suggest that listeners use both phonological and lexical information when processing talker information. The task-modulated results show that listeners with poorer phonological working memory perform worse on talker identification tasks that tap into long-term memory representations, but not on discrimination tasks that can be completed with more peripheral processing. This may suggest a more general link between phonological working memory and learning talker categories.

Later but Not Weaker: Neural Categorization of Native Vowels of Children at Familial Risk of Dyslexia

Although allophonic speech processing has been hypothesized to be a contributing factor in developmental dyslexia, experimental evidence is limited and inconsistent. The current study compared the categorization of native similar sounding vowels of typically developing (TD) children and children at familial risk (FR) of dyslexia. EEG response was collected in a non-attentive passive oddball paradigm from 35 TD and 35 FR Dutch 20-month-old infants who were matched on vocabulary. The children were presented with two nonwords “giep” [ɣip] and “gip” [ɣIp] that contrasted solely with respect to the vowel. In the multiple-speaker condition, both nonwords were produced by twelve different speakers while in the single-speaker condition, single tokens of each word were used as stimuli. For both conditions and for both groups, infant positive mismatch response (p-MMR) was elicited, and the p-MMR amplitude was comparable between the two groups, although the FR children had a later p-MMR peak than the TD children in the multiple-speaker condition. These findings indicate that FR children are able to categorize speech sounds, but that they may do so in a more effortful way than TDs.

Comparison of temporal fine structure sensitivity and concurrent vowel perception between children with and without reading disability

Background: Children with reading disabilities (RD) exhibit difficulty in perceiving speech in background noise due to poor auditory stream segregation. There is a dearth of literature on measures of temporal fine structure sensitivity (TFS) and concurrent vowel perception abilities to assess auditory stream segregation in children with reading disabilities. Hence the present study compared temporal fine structure sensitivity (TFS) and concurrent vowel perception abilities between children with and without reading deficits.

Method: The present research consisted of a total number of 30 participants, 15 children with reading disabilities (RD) and fifteen typically developing (TD) children within the age range of 7-14 years and were designated as Group 1 and Group 2 respectively. Both groups were matched for age, grade, and classroom curricular instructions. The groups were evaluated for TFS and concurrent vowel perception abilities and the performance was compared using independent ‘t’ test and repeated measure ANOVA respectively.

Results: Results revealed that the children with RD performed significantly (p < 0.001) poorer than TD children on both TFS and concurrent vowel identification task. On concurrent vowel identification tasks, there was no significant interaction found between reading ability and F0 difference suggesting that the trend was similar in both the groups.

Conclusion: The study concludes that the children with RD show poor temporal fine structure sensitivity and concurrent vowel identification scores compared to age and grade matched TD children owing to poor auditory stream segregation in children with RD.

Poor reading is characterized by a more connected network with wrong hubs

Using graph theory, we examined topological organization of the language network in Chinese children with poor reading during an auditory rhyming task and a visual spelling task, compared to reading-matched controls and age-matched controls. First, poor readers (PR) showed reduced clustering coefficient in the left inferior frontal gyrus (IFG) and higher nodal efficiency in the bilateral superior temporal gyri (STG) during the visual task, indicating a less functionally specialized cluster around the left IFG and stronger functional links between bilateral STGs and other regions. Furthermore, PR adopted additional right-hemispheric hubs in both tasks, which may explain increased global efficiency across both tasks and lower normalized characteristic shortest path length in the visual task for the PR. These results underscore deficits in the left IFG during visual word processing and conform previous findings about compensation in the right hemisphere in children with poor reading.

The cognitive basis of dyslexia in school-aged children: A multiple case study in a transparent orthography

This study focuses on the role of numerous cognitive skills such as phonological awareness (PA), rapid automatized naming (RAN), visual and selective attention, auditory skills, and implicit learning in developmental dyslexia. We examined the (co)existence of cognitive deficits in dyslexia and assessed cognitive skills’ predictive value for reading. First, we compared school‐aged children with severe reading impairment (n = 51) to typical readers (n = 71) to explore the individual patterns of deficits in dyslexia. Children with dyslexia, as a group, presented low PA and RAN scores, as well as limited implicit learning skills. However, we found no differences in the other domains. We found a phonological deficit in 51% and a RAN deficit in 26% of children with dyslexia. These deficits coexisted in 14% of the children. Deficits in other cognitive domains were uncommon and most often coexisted with phonological or RAN deficits. Despite having a severe reading impairment, 26% of children with dyslexia did not present any of the tested deficits. Second, in a group of children presenting a wide range of reading abilities (N = 211), we analysed the relationship between cognitive skills and reading level. PA and RAN were independently related to reading abilities. Other skills did not explain any additional variance. The impact of PA and RAN on reading skills differed. While RAN was a consistent predictor of reading, PA predicted reading abilities particularly well in average and good readers with a smaller impact in poorer readers.

Structural neural correlates of individual differences in categorical perception

Listeners perceive speech sounds categorically. While group-level differences in categorical perception have been observed in children or individuals with reading disorders, recent findings suggest that typical adults vary in how categorically they perceive sounds. The current study investigated neural sources of individual variability in categorical perception of speech. Fifty-seven participants rated phonetic tokens on a visual analogue scale; categoricity and response consistency were measured and related to measures of brain structure from MRI. Increased surface area of the right middle frontal gyrus predicted more categorical perception of a fricative continuum. This finding supports the idea that frontal regions are sensitive to phonetic category-level information and extends it to make behavioral predictions at the individual level. Additionally, more gyrification in bilateral transverse temporal gyri predicted less consistent responses on the task, perhaps reflecting subtle variation in language ability across the population.

Clinical experience and categorical perception of children's speech

BACKGROUND

Accurate and detailed records of children's speech are a critical component of competent service delivery in speech-language pathology/speech and language therapy (SLP/SLT). Previous research has shown that during speech-sound acquisition, children gradually learn to produce sounds in adult-like manners. Continuous rating scales are a way to track this gradual learning.

AIMS

To examine whether clinical experience affects the ability and willingness to rate children's speech production using continuous rating scales.

METHODS & PROCEDURES

An online survey was administered to 81 US-based SLPs/SLTs, binned into more- and less-experienced groups, and 20 non-SLPs/SLTs. The survey included a speech-sound rating task in which participants rated the production of place of articulation in children's productions of word-initial /θ/, /s/, /ʃ/, /d/, /ɡ/, /t/ and /k/ on a nine-point equally appearing interval scale. We examined the extent to which these were accurate (i.e., the extent to which they matched laboratory measures of production characteristics) and the extent to which the ratings were gradual (i.e., they used the entire rating scales, rather than just the endpoints).

MAIN CONTRIBUTION

There were no consistent differences between non-SLPs/SLTs, less-experienced SLPs/SLTs and more-experienced SLPs/SLTs in a measure of the accuracy of responses. More consistent differences were found in the extent to which listeners used the endpoints of the scale: greater experience was associated with greater use of the endpoint values.

CONCLUSIONS & IMPLICATIONS

More-experienced SLPs/SLTs are less likely to use the entire range of continuous rating scales to rate children's speech accuracy than less-experienced SLPs/SLTs or clinically untrained listeners. Implications for service delivery are discussed. What this paper adds What is already known on the subject Children's productions of individual sounds, like /k/, become gradually more adult-like over the course of development. For a child who has a [t] for /k/ error, this gradual development means that children's productions become progressively less like /t/ and more like /k/ over development. Phonetic transcription does not capture this gradual development. In contrast, studies have shown that continuous ratings of children's speech (such as rating productions on a scale anchored by the text "the 't' sound" at one end and "the 'k' sound" at the other end) can capture this gradual development. What this paper adds to existing knowledge To determine continuous ratings are clinically feasible, we must first determine whether clinical experience affects people's use of continuous rating scales to rate children's speech. We conducted an on-line speech perception experiment in which 81 speech-language pathologists/speech and language therapists (SLPs/SLTs) and 20 non-SLPs/SLTs rated 60 productions by children on continuous rating scales. The 60 stimuli included many sounds that had been independently verified to be intermediate productions (i.e., a target /k/ that was neither completely /k/-like nor completely /t/-like). Non-SLPs/SLTs and less-experienced SLPs/SLTs rated those intermediate sounds with intermediate ratings (i.e., somewhere on the midpoint of a continuous scale). In contrast, more-experienced SLPs/SLTs were more likely to rate those sounds as instances of endpoints (i.e., as either /k/ or /t/). What are the potential or actual clinical implications of this work? This finding suggests that clinical experience is paradoxically associated with a reduced tendency to use the entire range of responses on continuous rating scales. This finding suggests that we must better understand the cause of this reduced tendency, so that clinicians at all levels can use continuous rating scales equally effectively.

Effects of computerized grapho-phonological training on literacy acquisition and vocabulary knowledge in children with an immigrant background learning German as L2

As a consequence of globalization and migration, the number of children receiving literacy instruction in their second language (L2) is high and still increasing. Therefore, teachers need instruction methods that are effective in both L1 and L2 learners. Here, we investigate the effectiveness of a computerized training program combining phoneme perception, phonological awareness, and systematic phonics, in a sample of second-graders (N = 26) instructed in German as L2. Based on prior evidence concerning (1) literacy acquisition in L2 and (2) effects of literacy development on oral language abilities, we expected significant training effects on children’s literacy skills and vocabulary knowledge. The children of the training group worked through the program during school lessons, 20 min per day, for a period of 8 weeks. The controls continued to receive standard classroom instruction. German tests of phonological awareness, reading, spelling, and vocabulary were performed at three time points (pretest, immediate posttest, and follow-up after 9 weeks). Analyses confirmed that improvements in phonological awareness, spelling, and vocabulary between pretest and posttest were stronger in the training group when compared to the controls. For spelling and vocabulary, these effects were still significant at follow-up. Effect sizes were medium to high. For the reading measures, no group differences were found. In sum, the results yield further evidence for the effectiveness of phonics-based literacy instruction in L2 learners, and for the beneficial effects of basic literacy skills on novel word learning.

Auditory processing deficit in individuals with dyslexia: A meta-analysis of mismatch negativity

Several previous studies have used mismatch negativity (MMN) to examine the auditory processing deficit in individuals with dyslexia. However, researchers have not clearly determined whether the deficit is general or specific and how it potentially changes with age. Meta-analysis was adopted to quantitatively identify the auditory processing deficit in individuals with dyslexia. By analysing 81 results within 25 publications that employed passive oddball paradigms to explore auditory processing in individuals with dyslexia, we identified that MMN impairment in auditory processing of speech was observed in children (Cohen's d = 0.296) and adults with dyslexia (Cohen's d = 0.486). Besides, adults with dyslexia showed atypical auditory processing of non-speech (Cohen's d = 0.409), which appeared to be related to the types of stimuli. Based on these findings, for individuals with dyslexia, the auditory processing deficit in speech will persist into adulthood, and the auditory processing deficit is general in adults with dyslexia. Because few studies used appropriate non-speech stimuli to examine the auditory processing in children with dyslexia, future studies should focus more on this area.

Differential activation of the visual word form area during auditory phoneme perception in youth with dyslexia

Developmental dyslexia is a learning disorder characterized by difficulties reading words accurately and/or fluently. Several behavioral studies have suggested the presence of anomalies at an early stage of phoneme processing, when the complex spectrotemporal patterns in the speech signal are analyzed and assigned to phonemic categories. In this study, fMRI was used to compare brain responses associated with categorical discrimination of speech syllables (P) and acoustically matched nonphonemic stimuli (N) in children and adolescents with dyslexia and in typically developing (TD) controls, aged 8-17 years. The TD group showed significantly greater activation during the P condition relative to N in an area of the left ventral occipitotemporal cortex that corresponds well with the region referred to as the "visual word form area" (VWFA). Regression analyses using reading performance as a continuous variable across the full group of participants yielded similar results. Overall, the findings are consistent with those of previous neuroimaging studies using print stimuli in individuals with dyslexia that found reduced activation in left occipitotemporal regions; however, the current study shows that these activation differences seen during reading are apparent during auditory phoneme discrimination in youth with dyslexia, suggesting that the primary deficit in at least a subset of children may lie early in the speech processing stream and that categorical perception may be an important target of early intervention in children at risk for dyslexia.

Training a non-native vowel contrast with a distributional learning paradigm results in improved perception and production

Previous distributional learning research suggests that adults can improve perception of a non-native contrast more efficiently when exposed to a bimodal than a unimodal distribution. Studies have also suggested that perceptual learning can transfer to production. The current study tested whether the addition of visual images to reinforce the contrast and active learning with feedback would result in lcearning in both conditions and would transfer to gains in production. Native English-speaking adults heard stimuli from a bimodal or unimodal /o/-/œ/ continuum. No group differences were found on a discrimination task, possibly suggesting that the supports eliminated previously documented group differences. On an identification task, listeners in the bimodal group showed better performance than the unimodal group on the endpoint stimuli. Production results indicated that both groups showed increased Euclidean distance between the target vowels after training, suggesting that perceptual training improved production skills in both conditions. Contrary to expectations, degree of perception and production learning were not correlated. Together, these results suggest that a bimodal distribution may aid learning, but that adding images to reinforce the contrast and active learning to the training paradigm could mitigate disadvantages found previously for participants exposed to a unimodal distribution.

Remediation of Allophonic Perception and Visual Attention Span in Developmental Dyslexia: A Joint Assay

Categorical perception of phonemes and visual attention span are cognitive processes that contribute independently to poor reading skills in developmental dyslexia. We here explored whether training programs specifically targeting one or the other process do improve reading performance in dyslexic children. The dyslexic participants were trained using either the RapDys© program designed to improve phonemic perception or the MAEVA© program targeting visual attention span. Each participant was provided the two programs successively for intensive training. Results show specific effects of RapDys© on phonemic discrimination and pseudo-word reading. MAEVA© specifically improved visual attention span and irregular word reading. Phonemic awareness and regular word reading improved after application of both training programs, suggesting similar positive effects of both methods although effects of concomitant phonic training cannot be ruled out (as there was no control group). The overall findings suggest that both categorical perception and visual attention span remediation contribute to reading.

Categorical phoneme labeling in children with dyslexia does not depend on stimulus duration

It is established that individuals with dyslexia are less consistent at auditory phoneme categorization than typical readers. One hypothesis attributes these differences in phoneme labeling to differences in auditory cue integration over time, suggesting that the performance of individuals with dyslexia would improve with longer exposure to informative phonetic cues. Here, the relationship between phoneme labeling and reading ability was investigated while manipulating the duration of steady-state auditory information available in a consonant-vowel syllable. Children with dyslexia obtained no more benefit from longer cues than did children with typical reading skills, suggesting that poor task performance is not explained by deficits in temporal integration or temporal sampling.

Are Temporal and Tonal Musical Skills Related to Phonological Awareness and Literacy Skills? - Evidence From Two Cross-Sectional Studies With Children From Different Age Groups

Temporal and spectral auditory processing abilities are required for efficient and unimpaired processing of speech and might thus be associated with the development of phonological and literacy skills in children. Indeed, studies with unselected children have found links between these basic auditory processing abilities and the development of phonological awareness, reading, and spelling. Additionally, associations between the processing of temporal or spectral/tonal information in music and phonological awareness/literacy have been reported, but findings concerning relations between music processing and spelling are rather sparse. To gain more insights into the specific, potentially age-dependent relevance of various temporal (e.g., rhythm, tempo) and tonal (e.g., pitch, melody) musical subdomains for phonological awareness and literacy, we adapted five music-processing tasks (three temporal, two tonal) for use with tablet computers and used them in two cross-sectional studies with German children from two age groups: Study 1 was conducted with preschool children (about 5 years of age; without formal reading and spelling instruction) and focused on associations between music processing and phonological awareness. In Study 2, third-graders (about 8 years of age) were investigated concerning relations between music processing, phonological awareness, reading comprehension, and spelling. In both studies, rhythm reproduction and pitch perception turned out to be significant predictors of phonological awareness in stepwise regression analyses. Although various associations between music processing and literacy were found for third-graders in Study 2, after phonological awareness was accounted for, only rhythm reproduction made a unique contribution to literacy skills, namely, to alphabetic spelling skills. Hence, both studies indicate that temporal (i.e., rhythm reproduction) and spectral/tonal (i.e., pitch perception) musical skills are distinctly and uniquely related to phonological awareness in children from different age groups (preschool vs. Grade 3). The finding that rhythm reproduction, an auditory temporal processing skill integrating perceptual and motor aspects of rhythm processing, was especially tightly linked to phonological awareness and literacy corroborates other findings on associations between rhythm processing and literacy development and is of interest from the viewpoint of current theories of developmental dyslexia. The potential relevance of our results for applied research concerning early diagnosis and training of literacy-related skills is discussed.

Reading-Induced Shifts in Speech Perception in Dyslexic and Typically Reading Children

One of the proposed mechanisms underlying reading difficulties observed in developmental dyslexia is impaired mapping of visual to auditory speech representations. We investigate these mappings in 20 typically reading and 20 children with dyslexia aged 8–10 years using text-based recalibration. In this paradigm, the pairing of visual text and ambiguous speech sounds shifts (recalibrates) the participant’s perception of the ambiguous speech in subsequent auditory-only post-test trials. Recent research in adults demonstrated this text-induced perceptual shift in typical, but not in dyslexic readers. Our current results instead show significant text-induced recalibration in both typically reading children and children with dyslexia. The strength of this effect was significantly linked to the strength of perceptual adaptation effects in children with dyslexia but not typically reading children. Furthermore, additional analyses in a sample of typically reading children of various reading levels revealed a significant link between recalibration and phoneme categorization. Taken together, our study highlights the importance of considering dynamic developmental changes in reading, letter-speech sound coupling and speech perception when investigating group differences between typical and dyslexic readers.

Longitudinal relationships between speech perception, phonological skills and reading in children at high-risk of dyslexia

Speech perception deficits are commonly reported in dyslexia but longitudinal evidence that poor speech perception compromises learning to read is scant. We assessed the hypothesis that phonological skills, specifically phoneme awareness and RAN, mediate the relationship between speech perception and reading. We assessed longitudinal predictive relationships between categorical speech perception, phoneme awareness, RAN, language, attention and reading at ages 5½ and 6½ years in 237 children many of whom were at high risk of reading difficulties. Speech perception at 5½ years correlated with language, attention, phoneme awareness and RAN concurrently and was a predictor of reading at 6½ years. There was no significant indirect effect of speech perception on reading via phoneme awareness, suggesting that its effects are separable from those of phoneme awareness. Children classified with dyslexia at 8 years had poorer speech perception than age-controls at 5½ years and children with language disorders (with or without dyslexia) had more severe difficulties with both speech perception and attention control. Categorical speech perception tasks tap factors extraneous to perception, including decision-making skills. Further longitudinal studies are needed to unravel the complex relationships between categorical speech perception tasks and measures of reading and language and attention.

Reading ability and phoneme categorization

Dyslexia is associated with abnormal performance on many auditory psychophysics tasks, particularly those involving the categorization of speech sounds. However, it is debated whether those apparent auditory deficits arise from (a) reduced sensitivity to particular acoustic cues, (b) the difficulty of experimental tasks, or (c) unmodeled lapses of attention. Here we investigate the relationship between phoneme categorization and reading ability, with special attention to the nature of the cue encoding the phoneme contrast (static versus dynamic), differences in task paradigm difficulty, and methodological details of psychometric model fitting. We find a robust relationship between reading ability and categorization performance, show that task difficulty cannot fully explain that relationship, and provide evidence that the deficit is not restricted to dynamic cue contrasts, contrary to prior reports. Finally, we demonstrate that improved modeling of behavioral responses suggests that performance does differ between children with dyslexia and typical readers, but that the difference may be smaller than previously reported.

Behavioral and electrophysiological investigation of speech perception deficits in silence, noise and envelope conditions in developmental dyslexia

The present study investigated whether children with developmental dyslexia showed specific deficits in the perception of three phonetic features (voicing, place, and manner of articulation) in optimal (silence) and degraded listening conditions (envelope-coded speech versus noise), using both standard behavioral and electrophysiological measures. Performance of children with dyslexia was compared to that of younger typically developing children who were matched in terms of reading age. Results showed no significant group differences in response accuracy except for the reception of place-of-articulation in noise. However, dyslexic children responded more slowly than typically developing children across all conditions with larger deficits in noise than in envelope than in silence. At the neural level, dyslexic children exhibited reduced N1 components in silence and the reduction of N1 amplitude was more pronounced for voicing than for the other phonetic features. In the envelope condition, the N1 was localized over the right hemisphere and it was larger for typically developing readers than for dyslexic children. Finally, in stationary noise, the N1 to place of articulation was clearly delayed in children with dyslexia, which suggests a temporal de-organization in the most adverse listening conditions. The results clearly show abnormal neural processing to speech sounds in all conditions. They are discussed in the context of recent theories on perceptual noise exclusion, neural noise and temporal sampling.

Cortical Responses to Chinese Phonemes in Preschoolers Predict Their Literacy Skills at School Age

We investigated whether preschoolers with poor phonological awareness (PA) skills had impaired cortical basis for detecting speech feature, and whether speech perception influences future literacy outcomes in preschoolers. We recorded ERP responses to speech in 52 Chinese preschoolers. The results showed that the poor PA group processed speech changes differentially compared to control group in mismatch negativity (MMN) and late discriminative negativity (LDN). Furthermore, speech perception in kindergarten could predict literacy outcomes after literacy acquisition. These suggest that impairment in detecting speech features occurs before formal reading instruction, and that speech perception plays an important role in reading development.

Revisiting the "enigma" of musicians with dyslexia: Auditory sequencing and speech abilities

Previous research has suggested a link between musical training and auditory processing skills. Musicians have shown enhanced perception of auditory features critical to both music and speech, suggesting that this link extends beyond basic auditory processing. It remains unclear to what extent musicians who also have dyslexia show these specialized abilities, considering often-observed persistent deficits that coincide with reading impairments. The present study evaluated auditory sequencing and speech discrimination in 52 adults comprised of musicians with dyslexia, nonmusicians with dyslexia, and typical musicians. An auditory sequencing task measuring perceptual acuity for tone sequences of increasing length was administered. Furthermore, subjects were asked to discriminate synthesized syllable continua varying in acoustic components of speech necessary for intraphonemic discrimination, which included spectral (formant frequency) and temporal (voice onset time [VOT] and amplitude envelope) features. Results indicate that musicians with dyslexia did not significantly differ from typical musicians and performed better than nonmusicians with dyslexia for auditory sequencing as well as discrimination of spectral and VOT cues within syllable continua. However, typical musicians demonstrated superior performance relative to both groups with dyslexia for discrimination of syllables varying in amplitude information. These findings suggest a distinct profile of speech processing abilities in musicians with dyslexia, with specific weaknesses in discerning amplitude cues within speech. Because these difficulties seem to remain persistent in adults with dyslexia despite musical training, this study only partly supports the potential for musical training to enhance the auditory processing skills known to be crucial for literacy in individuals with dyslexia. (PsycINFO Database Record

Short-term Memory in Childhood Dyslexia: Deficient Serial Order in Multiple Modalities

In children with dyslexia, deficits in working memory have not been well-specified. We assessed second-grade children with dyslexia, with and without concomitant specific language impairment, and children with typical development. Immediate serial recall of lists of phonological (non-word), lexical (digit), spatial (location) and visual (shape) items were included. For the latter three modalities, we used not only standard span but also running span tasks, in which the list length was unpredictable to limit mnemonic strategies. Non-word repetition tests indicated a phonological memory deficit in children with dyslexia alone compared with those with typical development, but this difference vanished when these groups were matched for non-verbal intelligence and language. Theoretically important deficits in serial order memory in dyslexic children, however, persisted relative to matched typically developing children. The deficits were in recall of (1) spoken digits in both standard and running span tasks and (2) spatial locations, in running span only. Children with dyslexia with versus without language impairment, when matched on non-verbal intelligence, had comparable serial order memory, but differed in phonology. Because serial orderings of verbal and spatial elements occur in reading, the careful examination of order memory may allow a deeper understanding of dyslexia and its relation to language impairment. Copyright © 2017 John Wiley & Sons, Ltd.

Word Learning Deficits in Children With Dyslexia

PURPOSE

The purpose of this study is to investigate word learning in children with dyslexia to ascertain their strengths and weaknesses during the configuration stage of word learning.

METHOD

Children with typical development (N = 116) and dyslexia (N = 68) participated in computer-based word learning games that assessed word learning in 4 sets of games that manipulated phonological or visuospatial demands. All children were monolingual English-speaking 2nd graders without oral language impairment. The word learning games measured children's ability to link novel names with novel objects, to make decisions about the accuracy of those names and objects, to recognize the semantic features of the objects, and to produce the names of the novel words. Accuracy data were analyzed using analyses of covariance with nonverbal intelligence scores as a covariate.

RESULTS

Word learning deficits were evident for children with dyslexia across every type of manipulation and on 3 of 5 tasks, but not for every combination of task/manipulation. Deficits were more common when task demands taxed phonology. Visuospatial manipulations led to both disadvantages and advantages for children with dyslexia.

CONCLUSION

Children with dyslexia evidence spoken word learning deficits, but their performance is highly dependent on manipulations and task demand, suggesting a processing trade-off between visuospatial and phonological demands.

Increased Response to Altered Auditory Feedback in Dyslexia: A Weaker Sensorimotor Magnet Implied in the Phonological Deficit

PURPOSE

The purpose of this study was to examine whether developmental dyslexia (DD) is characterized by deficiencies in speech sensory and motor feedforward and feedback mechanisms, which are involved in the modulation of phonological representations.

METHOD

A total of 42 adult native speakers of Dutch (22 adults with DD; 20 participants who were typically reading controls) were asked to produce /bep/ while the first formant (F1) of the /e/ was not altered (baseline), increased (ramp), held at maximal perturbation (hold), and not altered again (after-effect). The F1 of the produced utterance was measured for each trial and used for statistical analyses. The measured F1s produced during each phase were entered in a linear mixed-effects model.

RESULTS

Participants with DD adapted more strongly during the ramp phase and returned to baseline to a lesser extent when feedback was back to normal (after-effect phase) when compared with the typically reading group. In this study, a faster deviation from baseline during the ramp phase, a stronger adaptation response during the hold phase, and a slower return to baseline during the after-effect phase were associated with poorer reading and phonological abilities.

CONCLUSION

The data of the current study are consistent with the notion that the phonological deficit in DD is associated with a weaker sensorimotor magnet for phonological representations.

Perception-production relations in later development of American English rhotics

It is known that some adult listeners have more sharply defined perceptual categories than others, and listeners with more precise auditory targets are also more precise in their production of contrasts. There is additionally evidence that children who have not yet mastered production of a contrast show diminished performance on perceptual measures of the same contrast. To date, however, few studies have investigated developmental perception-production relations using the fine-grained measures typical of adult studies. Existing evidence suggests that perception and production can be closely connected in development, but this relationship may break down as perception and articulation mature at different rates. This study evaluated perception and production of the English /r-w/ contrast in 40 typically-developing children aged 9-14. Perceptual sensitivity was measured with a logistic function fitted over responses in a forced-choice identification task using two synthetic 10-step continua from rake to wake. Participants also produced rhotic and non-rhotic words. Across participants, there was a significant correlation between perceptual acuity and rhoticity in production, although this effect was only observed for one of two continua tested. These results provide preliminary evidence compatible with the hypothesis that children with a more refined auditory target for a sound also produce that sound more accurately.

Electrophysiological and phonological change detection measures of auditory word processing in normal Persian-speaking children

OBJECTIVE

Auditory phoneme discrimination is a basic and important prerequisite for acquiring speech, reading, and spelling skills. Children, who are unable to perceive auditory phoneme discrimination, cannot develop phonemic representations. Therefore, the early identification of these deficits and application of effective therapeutic approaches is a necessity. We need to assess appropriately word or sound discrimination in normal populations using an objective passive task such as mismatch negativity (MMN). Therefore, the aim of the present study was to investigate MMN responses using speech stimuli (words) in 6-7 year-old normal Persian-speaking children.

METHODS

Ten right-handed Persian-speaking children with normal visual and auditory acuity, aged from 6 to 7 years, participated in the study. Recording of electroencephalography (EEG) was done by 64 A g/AgCl electrodes. A new auditory paradigm was used with three deviant stimuli (/gam/,/jam/, and/tam/) which differed in the first consonant from a repeated standard word (/dam/). A total of 1500 stimuli, 750 standards and 750 deviants (250 each deviant), were presented by Cogent 2000 running in MATLAB software using two loud speakers.

RESULTS

MMN peaked over the fronto-central sites at around 380-424 ms after the onset of the stimulus. The comparison of the MMN amplitudes elicited by three deviants revealed a significant "initial phoneme type" effect in Fz and Cz (p < 0.05). This negativity was found to be larger for manner and voicing deviants compared with that of the place of articulation (p < 0.001) on midline scalps. The comparison of the MMN latencies revealed no significant main effect of all variables (p > 0.05). Also, the results revealed that only the MMN amplitude for the/gam/deviant correlated with the percentage of correct responses (R = -0.86, p < 0.01).

CONCLUSION

The current study showed that words can elicit MMN responses in ∼200 ms after the onset of changes. We can objectively evaluate children's neural speech sound discrimination using the developed paradigm in a natural word context. This paradigm can be useful objectively for investigating distinctive features of sounds and phonological discrimination development in normal children.

Bias in the perception of phonetic detail in children's speech: A comparison of categorical and continuous rating scales

Previous research has shown that continuous rating scales can be used to assess phonetic detail in children's productions, and could potentially be used to detect covert contrasts. Two experiments examined whether continuous rating scales have the additional benefit of being less susceptible to task-related biasing than categorical phonetic transcriptions. In both experiments, judgements of children's productions of /s/ and /θ/ were interleaved with two types of rating tasks designed to induce bias: continuous judgements of a parameter whose variation is itself relatively more continuous (gender typicality of their speech) in one biasing condition, and categorical judgements of a parameter that is relatively less continuous (the vowel they produced) in the other biasing condition. One experiment elicited continuous judgements of /s/ and /θ/ productions, while the other elicited categorical judgements. The results of Experiment 1 showed that the influence of acoustic characteristics on continuous judgements of /s/ and /θ/ was stable across biasing conditions. In contrast, the results of Experiment 2 showed that the influence of acoustic characteristics on categorical judgements of /s/ and /θ/differed systematically across biasing conditions. These results suggest that continuous judgements are psychometrically superior to categorical judgements, as they are more resistant to task-related bias.

Is There a Relationship Between Speech Identification in Noise and Categorical Perception in Children With Dyslexia?

PURPOSE

Children with dyslexia have been suggested to experience deficits in both categorical perception (CP) and speech identification in noise (SIN) perception. However, results regarding both abilities are inconsistent, and the relationship between them is still unclear. Therefore, this study aimed to investigate the relationship between CP and the psychometric function of SIN perception.

METHOD

Sixteen children with dyslexia, 16 chronological-age controls, and 16 reading-level controls were evaluated in CP of a voicing continuum and in consonant identification in both stationary and fluctuating noises.

RESULTS

There was a small but significant impairment in speech identification performance of children with dyslexia in stationary noise compared with chronological age-matched controls (but not reading level-matched controls). However, their performance increased in a fluctuating background, hence suggesting normal masking and unmasking effects and preserved sensory processing of speech information. Regarding CP, location of the phoneme boundary differed in the children with dyslexia compared with both control groups. However, scrutinizing individual profiles failed to reveal consistently poor performance in SIN and CP tasks. In addition, there was no significant correlation between CP, SIN perception, and reading scores in the group with dyslexia.

CONCLUSIONS

The relationship between the SIN deficit and CP, and how they potentially affect reading in children with dyslexia, remains unclear. However, these results are inconsistent with the notion that children with dyslexia suffer from a low-level temporal processing deficit and rather suggest a role of nonsensory (e.g., attentional) factors in their speech perception difficulties.

Direct Viewing of Dyslexics' Compensatory Strategies in Speech in Noise Using Auditory Classification Images

A vast majority of dyslexic children exhibit a phonological deficit, particularly noticeable in phonemic identification or discrimination tasks. The gap in performance between dyslexic and normotypical listeners appears to decrease into adulthood, suggesting that some individuals with dyslexia develop compensatory strategies. Some dyslexic adults however remain impaired in more challenging listening situations such as in the presence of background noise. This paper addresses the question of the compensatory strategies employed, using the recently developed Auditory Classification Image (ACI) methodology. The results of 18 dyslexics taking part in a phoneme categorization task in noise were compared with those of 18 normotypical age-matched controls. By fitting a penalized Generalized Linear Model on the data of each participant, we obtained his/her ACI, a map of the time-frequency regions he/she relied on to perform the task. Even though dyslexics performed significantly less well than controls, we were unable to detect a robust difference between the mean ACIs of the two groups. This is partly due to the considerable heterogeneity in listening strategies among a subgroup of 7 low-performing dyslexics, as confirmed by a complementary analysis. When excluding these participants to restrict our comparison to the 11 dyslexics performing as well as their average-reading peers, we found a significant difference in the F3 onset of the first syllable, and a tendency of difference on the F4 onset, suggesting that these listeners can compensate for their deficit by relying upon additional allophonic cues.

Transcranial Alternating Current Stimulation (tACS) differentially modulates speech perception in young and older adults

BACKGROUND

Normal aging is accompanied by a functional decline in processing temporal features of spoken language, such as voice onset time (VOT). On an electrophysiological level, this finding is paralleled by altered patterns of gamma oscillations.

OBJECTIVE

Using 40 Hz transcranial alternating current stimulation (tACS) over the bilateral auditory cortex, this study aims to compare the effect of tACS to modulate VOT-processing in samples of healthy young and older adults.

METHODS

Twenty-five healthy young (age 20-35 years) and 20 older adults (age 60-75 years) participated in this study. Presented with an auditory phoneme categorization task participants received 40 Hz and 6 Hz tACS on two consecutive sessions.

RESULTS

While 40 Hz tACS diminished task accuracy in young adults, older adults benefitted from this stimulation resulting in a more precise phonetic categorization.

CONCLUSION

The results of the study are discussed with respect to the non-linear relationship between gamma oscillations in the vicinity of the auditory cortex and VOT-processing. The present findings are promising in the context of an intervention for subjects with impaired ability to process temporal acoustic features in the speech signal.

Relationships between Categorical Perception of Phonemes, Phoneme Awareness, and Visual Attention Span in Developmental Dyslexia

We tested the hypothesis that the categorical perception deficit of speech sounds in developmental dyslexia is related to phoneme awareness skills, whereas a visual attention (VA) span deficit constitutes an independent deficit. Phoneme awareness tasks, VA span tasks and categorical perception tasks of phoneme identification and discrimination using a d/t voicing continuum were administered to 63 dyslexic children and 63 control children matched on chronological age. Results showed significant differences in categorical perception between the dyslexic and control children. Significant correlations were found between categorical perception skills, phoneme awareness and reading. Although VA span correlated with reading, no significant correlations were found between either categorical perception or phoneme awareness and VA span. Mediation analyses performed on the whole dyslexic sample suggested that the effect of categorical perception on reading might be mediated by phoneme awareness. This relationship was independent of the participants’ VA span abilities. Two groups of dyslexic children with a single phoneme awareness or a single VA span deficit were then identified. The phonologically impaired group showed lower categorical perception skills than the control group but categorical perception was similar in the VA span impaired dyslexic and control children. The overall findings suggest that the link between categorical perception, phoneme awareness and reading is independent from VA span skills. These findings provide new insights on the heterogeneity of developmental dyslexia. They suggest that phonological processes and VA span independently affect reading acquisition.

Relation between Phonological Processing, Auditory Processing and Speech Perception among Bilingual Poor Readers

BACKGROUND AND OBJECTIVES

A deficit in phonological processing abilities has been hypothesized as a cause of reading deficits among poor readers, but the precise etiology of this deficit is still unknown. Many studies have investigated the relation of auditory processing and speech perception with phonological processing, while the relation between these are not well understood. Thus, the present study was carried out to investigate the relation between these abilities among poor readers.

SUBJECTS AND METHODS

A total of 20 children between 7-12 years of age participated in the study. Among these 10 were typically developing children and 10 were poor readers. Auditory processing, speech perception in noise and phonological processing skills were assessed in both the groups.

RESULTS

Auditory processing was not significantly different between children in both the groups. In contrast, phonological awareness, verbal short-term memory and rapid automatized naming, which reflect phonological processing, and speech perception in noise were found to be significantly affected in poor readers. In addition, the results showed a significant correlation between phonological processing and speech perception in noise.

CONCLUSIONS

The present study found a significant relationship between speech perception in noise and phonological processing, while there was no relationship between auditory processing and phonological processing. This finding suggests that poor speech perception among poor readers may be one of the contributing factors for phonological processing deficits, which in turn leads to reading difficulties.

Incidental learning of sound categories is impaired in developmental dyslexia

Developmental dyslexia is commonly thought to arise from specific phonological impairments. However, recent evidence is consistent with the possibility that phonological impairments arise as symptoms of an underlying dysfunction of procedural learning. The nature of the link between impaired procedural learning and phonological dysfunction is unresolved. Motivated by the observation that speech processing involves the acquisition of procedural category knowledge, the present study investigates the possibility that procedural learning impairment may affect phonological processing by interfering with the typical course of phonetic category learning. The present study tests this hypothesis while controlling for linguistic experience and possible speech-specific deficits by comparing auditory category learning across artificial, nonlinguistic sounds among dyslexic adults and matched controls in a specialized first-person shooter videogame that has been shown to engage procedural learning. Nonspeech auditory category learning was assessed online via within-game measures and also with a post-training task involving overt categorization of familiar and novel sound exemplars. Each measure reveals that dyslexic participants do not acquire procedural category knowledge as effectively as age- and cognitive-ability matched controls. This difference cannot be explained by differences in perceptual acuity for the sounds. Moreover, poor nonspeech category learning is associated with slower phonological processing. Whereas phonological processing impairments have been emphasized as the cause of dyslexia, the current results suggest that impaired auditory category learning, general in nature and not specific to speech signals, could contribute to phonological deficits in dyslexia with subsequent negative effects on language acquisition and reading. Implications for the neuro-cognitive mechanisms of developmental dyslexia are discussed.

Objective measurement of high-level auditory cortical function in children

OBJECTIVE

This study examined whether the N2 latency of the cortical auditory evoked potential (CAEP) could be used as an objective indicator of temporal processing ability in normally hearing children.

METHODS

The N2 latency was evoked using three temporal processing paradigms: (1) differences in voice-onset-times (VOTs); (2) speech-in-noise using the CV/da/embedded in broadband noise (BBN) with varying signal-to-noise ratios (SNRs); and (3) 16Hz amplitude-modulated (AM) BBN presented (i) alone and (ii) following an unmodulated BBN, using four modulation depths. Thirty-four school-aged children with normal hearing, speech, language and reading were stratified into two groups: 5-7 years (n=13) and 8-12 years (n=21).

RESULTS

The N2 latency shifted significantly and systematically with differences in VOT and SNR, and was significantly different in the two AM-BBN conditions.

CONCLUSIONS

For children without an N1 peak in the cortical waveform, the N2 peak can be used as a sensitive measure of temporal processing for these stimuli.

SIGNIFICANCE

N2 latency of the CAEP can be used as an objective measure of temporal processing ability in a paediatric population with temporal processing disorder who are difficult to assess via behavioural response.

Evidence for a general auditory processing deficit in developmental dyslexia from a discrimination paradigm using speech versus nonspeech sounds matched in complexity

PURPOSE

It is unknown whether phonological deficits are the primary cause of developmental dyslexia or whether they represent a secondary symptom resulting from impairments in processing basic acoustic parameters of speech. This might be due, in part, to methodological difficulties. Our aim was to overcome two of these difficulties: the comparability of stimulus material and task in speech versus nonspeech conditions.

METHOD

In this study, the authors (a) assessed auditory processing of German vowel center stimuli, spectrally rotated versions of these stimuli, and bands of formants; (b) used the same task for linguistic and nonlinguistic conditions; and (c) varied systematically temporal and spectral parameters inherent in the German vowel system. Forty-two adolescents and adults with and without reading disabilities participated.

RESULTS

Group differences were found for all linguistic and nonlinguistic conditions for both temporal and spectral parameters. Auditory deficits were identified in most but not all participants with dyslexia. These deficits were not restricted to speech stimuli-they were also found for nonspeech stimuli with equal and lower complexity compared with the vowel stimuli. Temporal deficits were not observed in isolation.

CONCLUSION

These results support the existence of a general auditory processing impairment in developmental dyslexia.

Phonological, temporal and spectral processing in vowel length discrimination is impaired in German primary school children with developmental dyslexia

It is still unclear whether phonological processing deficits are the underlying cause of developmental dyslexia, or rather a consequence of basic auditory processing impairments. To avoid methodological confounds, in the current study the same task and stimuli of comparable complexity were used to investigate both phonological and basic auditory (temporal and spectral) processing in dyslexia. German dyslexic children (Grades 3 and 4) were compared to age- and grade-matched controls in a vowel length discrimination task with three experimental conditions: In a phonological condition, natural vowels were used, differing both with respect to temporal and spectral information (in German, vowel length is phonemic, and vowel length differences are characterized by both temporal and spectral information). In a temporal condition, spectral information differentiating between the two vowels of a pair was eliminated, whereas in a spectral condition, temporal differences were removed. As performance measure, the sensitivity index d' was computed. At the group level, dyslexic children's performance was inferior to that of controls for phonological as well as temporal and spectral vowel length discrimination. At an individual level, nearly half of the dyslexic sample was characterized by deficits in all three conditions, but there were also some children showing no deficits at all. These results reveal on the one hand that phonological processing deficits in dyslexia may stem from impairments in processing temporal and spectral information in the speech signal. On the other hand they indicate, however, that not all dyslexic children might be characterized by phonological or auditory processing deficits.