Reading and reading-related skills in children using cochlear implants: prospects for the influence of cued speech.

We assessed the reading and reading-related skills (phonemic awareness and phonological short-term memory) of deaf children fitted with cochlear implants (CI), either exposed to cued speech early (before 2 years old) (CS+) or never (CS-). Their performance was compared to that of 2 hearing control groups, 1 matched for reading level (RL), and 1 matched for chronological age (CA). Phonemic awareness and phonological short-term memory were assessed respectively through a phonemic similarity judgment task and through a word span task measuring phonological similarity effects. To assess the use of sublexical and lexical reading procedures, children read pseudowords and irregular words aloud. Results showed that cued speech improved performance on both the phonemic awareness and the reading tasks but not on the phonological short-term memory task. In phonemic awareness and reading, CS+ children obtained accuracy and rapidity scores similar to CA controls, whereas CS- children obtained lower scores than hearing controls. Nevertheless, in phonological short-term memory task, the phonological similarity effect of both CI groups was similar. Overall, these results support the use of cued speech to improve phonemic awareness and reading skills in CI children.

Allophonic perception of VOT contrasts in Spanish children with dyslexia.

INTRODUCTION: Previous studies have evidenced a different mode of speech perception in dyslexia, characterized by the use of allophonic rather than phonemic units. People with dyslexia perceive phonemic features (such as voicing) less accurately than typical readers, but they perceive allophonic features (i.e., language-independent differences between speech sounds) more accurately. METHOD: In this study, we investigated the perception of voicing contrasts in a sample of 204 Spanish children with or without dyslexia. Identification and discrimination data were collected for synthetic sounds varying along three different voice onset time (VOT) continua (ba/pa, de/te, and di/ti). Empirical data will be contrasted with a mathematical model of allophonic perception building up from neural oscillations and auditory temporal processing. RESULTS: Children with dyslexia exhibited a general deficit in categorical precision; that is, they discriminated among phonemically contrastive pairs (around 0-ms VOT) less accurately than did chronological age controls, irrespective of the stimulus continuum. Children with dyslexia also exhibited a higher sensitivity in the discrimination of allophonic features (around ±30-ms VOT), but only for the stimulus continuum that was based on a nonlexical contrast (ba/pa). CONCLUSION: Fitting the neural network model to the data collected for this continuum suggests that allophonic perception is due to a deficit in "subharmonic coupling" between high-frequency oscillations. Relationships with "temporal sampling framework" theory are discussed.

The impact of alphabetic literacy on the perception of speech sounds.

The aim of the present study was to evaluate the impact of literacy on phoneme perception. It built on previous research by using more controlled stimuli than in former studies and by independently examining the impacts of literacy and age on phoneme perception. Participants were adult and children beginning readers, and skilled adult readers. They were presented with identification and discrimination tasks, using a voicing continuum. In addition to examining their categorical perception of speech sounds and the precision of phonemic categories, participants' literacy level was carefully evaluated. The results confirmed that neither age nor literacy modulated categorical perception. However, level of literacy did have a significant impact on the precision of phonemic categories, which was independent from the influence of age.

French native speakers in the making: from language-general to language-specific voicing boundaries.

By examining voice onset time (VOT) discrimination in 4- and 8-month-olds raised in a French-speaking environment, the current study addresses the question of the role played by linguistic experience in the reshaping of the initial perceptual abilities. Results showed that the language-general -30- and +30-ms VOT boundaries are better discriminated than the 0-ms boundary in 4-month-olds, whereas 8-month-olds better discriminate the 0-ms boundary. These data support explanations of speech development stressing the effects of both language-general boundaries and linguistic environment (attunement theory and coupling theory). Results also suggest that the acquisition of the adult voicing boundary (at 0 ms VOT in French vs. +30 ms VOT in English) is faster and more linear in French than in English. This latter aspect of the results might be related to differences in the consistency of VOT distributions of voiced and voiceless stops between languages.

Discrimination of speech sounds based upon temporal envelope versus fine structure cues in 5- to 7-year-old children.

PURPOSE: To investigate the capacity of young children and adults with normal hearing to discriminate speech on the basis of either relatively slow (temporal envelope, E) or fast (temporal fine structure, TFS) auditory cues. METHOD: Vowel-consonant-vowel nonsense disyllables were processed to preserve either the E or the TFS information in 16 adjacent frequency bands. The band signals were then recombined and resulting stimuli were presented for discrimination to adults or 5-, 6-, and 7-year-old children using an odd-ball paradigm. Discrimination scores (d') and response latencies were measured in each listener. No training was given to listeners. RESULTS: Overall, discrimination scores were high (d' >or=1) in all speech-processing conditions, and did not differ across age groups. Overall, and irrespective of age, greater discrimination scores and shorter response latencies were observed for E speech than for TFS speech. CONCLUSIONS: These results suggest that normal-hearing children are able to encode and use E and TFS speech cues at adult levels by the age of 5 years. TFS- and E-coded speech stimuli might therefore prove to be a useful tool for the investigation of the developmental time course of speech perception, and for the early diagnosis of peripheral and central auditory processing disorders.

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.

Enhanced Sensitivity to Subphonemic Segments in Dyslexia: A New Instance of Allophonic Perception.

Although dyslexia can be individuated in many different ways, it has only three discernable sources: a visual deficit that affects the perception of letters, a phonological deficit that affects the perception of speech sounds, and an audio-visual deficit that disturbs the association of letters with speech sounds. However, the very nature of each of these core deficits remains debatable. The phonological deficit in dyslexia, which is generally attributed to a deficit of phonological awareness, might result from a specific mode of speech perception characterized by the use of allophonic (i.e., subphonemic) units. Here we will summarize the available evidence and present new data in support of the "allophonic theory" of dyslexia. Previous studies have shown that the dyslexia deficit in the categorical perception of phonemic features (e.g., the voicing contrast between /t/ and /d/) is due to the enhanced sensitivity to allophonic features (e.g., the difference between two variants of /d/). Another consequence of allophonic perception is that it should also give rise to an enhanced sensitivity to allophonic segments, such as those that take place within a consonant cluster. This latter prediction is validated by the data presented in this paper.

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.

Categorical perception of speech sounds in illiterate adults.

Children affected by dyslexia exhibit a deficit in the categorical perception of speech sounds, characterized by both poorer discrimination of between-category differences and by better discrimination of within-category differences, compared to normal readers. These categorical perception anomalies might be at the origin of dyslexia, by hampering the set up of grapheme-phoneme correspondences, but they might also be the consequence of poor reading skills, as literacy probably contributes to stabilizing phonological categories. The aim of the present study was to investigate this issue by comparing categorical perception performances of illiterate and literate people. Identification and discrimination responses were collected for a /ba-da/ synthetic place-of-articulation continuum and between-group differences in both categorical perception and in the precision of the categorical boundary were examined. The results showed that illiterate vs. literate people did not differ in categorical perception, thereby suggesting that the categorical perception anomalies displayed by dyslexics are indeed a cause rather than a consequence of their reading problems. However, illiterate people displayed a less precise categorical boundary and a stronger lexical bias, both also associated with dyslexia, which might, therefore, be a specific consequence of written language deprivation or impairment.

Review of neural rehabilitation programs for dyslexia: how can an allophonic system be changed into a phonemic one?

Neural investigations suggest that there are three possible core deficits in dyslexia: phonemic, grapho-phonemic, and graphemic. These investigations also suggest that the phonemic deficit resides in a different mode of speech perception which is based on allophonic (subphonemic) units rather than phonemic units. Here we review the results of remediation methods that tap into each of these core deficits, and examine how the methods that tap into the phonemic deficit might contribute to the remediation of allophonic perception. Remediation of grapho-phonemic deficiencies with a new computerized phonics training program (GraphoGame) might be able to surpass the limits of classical phonics training programs, particularly with regard to reading fluency. Remediation of visuo-graphemic deficiencies through exposure to enhanced letter spacing is also promising, although children with dyslexia continued to read more slowly than typical readers after this type of training. Remediation of phonemic deficiencies in dyslexia with programs based solely on phonemic awareness has a limited impact on reading. This might be due to the persistence of a covert deficit in phonemic perception. Methods based on slowed speech enhance the perception not only of phonemic features but also of allophonic features, and this is probably why they have not been found to be effective in meta-analyses. Training of phonemic perception with a perceptual fading paradigm, a method that improves precision in identification and discrimination around phonemic boundaries, has yielded promising results. However, studies with children at risk for dyslexia and dyslexic adults have found that even when behavioral data do not reflect allophonic perception, it can nevertheless be present in neural recordings. Further investigations should seek to confirm that the perceptual fading paradigm is beneficial for reading, and that it renders perception truly phonemic.

A psychophysical imaging method evidencing auditory cue extraction during speech perception: a group analysis of auditory classification images.

Although there is a large consensus regarding the involvement of specific acoustic cues in speech perception, the precise mechanisms underlying the transformation from continuous acoustical properties into discrete perceptual units remains undetermined. This gap in knowledge is partially due to the lack of a turnkey solution for isolating critical speech cues from natural stimuli. In this paper, we describe a psychoacoustic imaging method known as the Auditory Classification Image technique that allows experimenters to estimate the relative importance of time-frequency regions in categorizing natural speech utterances in noise. Importantly, this technique enables the testing of hypotheses on the listening strategies of participants at the group level. We exemplify this approach by identifying the acoustic cues involved in da/ga categorization with two phonetic contexts, Al- or Ar-. The application of Auditory Classification Images to our group of 16 participants revealed significant critical regions on the second and third formant onsets, as predicted by the literature, as well as an unexpected temporal cue on the first formant. Finally, through a cluster-based nonparametric test, we demonstrate that this method is sufficiently sensitive to detect fine modifications of the classification strategies between different utterances of the same phoneme.

Neural evidence of the allophonic mode of speech perception in adults with dyslexia.

OBJECTIVE: A growing body of evidence suggests that individuals with dyslexia perceive speech using allophonic rather than phonemic units and are thus sensitive to phonetic variations that are actually irrelevant in the ambient language. This study investigated speech perception difficulties in adults with dyslexia using behavioural and neural measurements with stimuli along a place-of-articulation continuum with well-defined allophonic boundaries. Adults without dyslexia served as control participants. METHODS: Categorical perception of a /bə - də/ place-of-articulation continuum was evaluated using both identification and discrimination tasks. In addition to these behavioural measures, mismatch negativity (MMN) was recorded for stimuli that came from either similar or different phoneme categories. RESULTS: The adults with dyslexia exhibited less consistent labelling than controls, but no heightened sensitivity to allophonic contrasts was observed at the behavioural level. Neural measurements revealed that stimuli from different phoneme categories elicited MMNs in both the adults with dyslexia and controls, whereas stimuli from the same category elicited an MMN in the adults with dyslexia only. CONCLUSION: The finding that adults with dyslexia have heightened sensitivity to allophonic contrasts in the form of neural activation supports the allophonic explanation of dyslexia. SIGNIFICANCE: Sensitivity to allophonic contrasts may be a valuable marker for dyslexia.

Deviant neural processing of phonotactic probabilities in adults with dyslexia.

During language acquisition in the first year of life, children become sensitive to phonotactic probabilities such as the likelihood of speech sound occurrences in the ambient language. Because this sensitivity is acquired at an early age, the extent to which the neural system that underlies speech processing in adults is tuned to these phonological regularities can reflect difficulties in processing language-specific phonological regularities that can persist into adulthood. Here, we examined the neural processing of phonotactic probabilities in 18 adults with dyslexia and 18 non-dyslexic controls using mismatch negativity, a pre-attentive neurophysiological response. Stimuli that differed in phonotactic probability elicited similar mismatch negativity responses among the adults with dyslexia, whereas the controls responded more strongly to stimuli with a high phonotactic probability than to stimuli with a low phonotactic probability, suggesting that controls - but not adults with dyslexia - are sensitive to the phonological regularities of the ambient language. These findings suggest that the underlying neural system in adults with dyslexia is not properly tuned to language-specific phonological regularities, which may partially account for the phonological deficits that are often reported in dyslexic individuals.

Perception of speech features by French-speaking children with cochlear implants.

PURPOSE: The present study investigates the perception of phonological features in French-speaking children with cochlear implants (CIs) compared with normal-hearing (NH) children matched for listening age. METHOD: Scores for discrimination and identification of minimal pairs for all features defining consonants (e.g., place, voicing, manner, nasality) and vowels (e.g., frontness, nasality, aperture) were measured in each listener. RESULTS: The results indicated no differences in "categorical perception," specified as a similar difference between discrimination and identification between CI children and controls. However, CI children demonstrated a lower level of "categorical precision," that is, lesser accuracy in both feature identification and discrimination, than NH children, with the magnitude of the deficit depending on the feature. CONCLUSIONS: If sensitive periods of language development extend well beyond the moment of implantation, the consequences of hearing deprivation for the acquisition of categorical perception should be fairly important in comparison to categorical precision because categorical precision develops more slowly than categorical perception in NH children. These results do not support the idea that the sensitive period for development of categorical perception is restricted to the first 1-2 years of life. The sensitive period may be significantly longer. Differences in precision may reflect the acoustic limitations of the cochlear implant, such as coding for temporal fine structure and frequency resolution.

Neural correlates of switching from auditory to speech perception.

Many people exposed to sinewave analogues of speech first report hearing them as electronic glissando and, later, when they switch into a 'speech mode', hearing them as syllables. This perceptual switch modifies their discrimination abilities, enhancing perception of differences that cross phonemic boundaries while diminishing perception of differences within phonemic categories. Using high-density evoked potentials and fMRI in a discrimination paradigm, we studied the changes in brain activity that are related to this change in perception. With ERPs, we observed that phonemic coding is faster than acoustic coding: The electrophysiological mismatch response (MMR) occurred earlier for a phonemic change than for an equivalent acoustic change. The MMR topography was also more asymmetric for a phonemic change than for an acoustic change. In fMRI, activations were also significantly asymmetric, favoring the left hemisphere in both perception modes. Furthermore, switching to the speech mode significantly enhanced activation in the posterior parts of the left superior gyrus and sulcus relative to the non-speech mode. When responses to a change of stimulus were studied, a cluster of voxels in the supramarginal gyrus was activated significantly more by a phonemic change than by an acoustic change. These results demonstrate that phoneme perception in adults relies on a specific and highly efficient left-hemispheric network, which can be activated in top-down fashion when processing ambiguous speech/non-speech stimuli.

Allophonic mode of speech perception in dyslexia.

Perceptual discrimination between speech sounds belonging to different phoneme categories is better than that between sounds falling within the same category. This property, known as "categorical perception," is weaker in children affected by dyslexia. Categorical perception develops from the predispositions of newborns for discriminating all potential phoneme categories in the world's languages. Predispositions that are not relevant for phoneme perception in the ambient language are usually deactivated during early childhood. However, the current study shows that dyslexic children maintain a higher sensitivity to phonemic distinctions irrelevant in their linguistic environment. This suggests that dyslexic children use an allophonic mode of speech perception that, although without straightforward consequences for oral communication, has obvious implications for the acquisition of alphabetic writing. Allophonic perception specifically affects the mapping between graphemes and phonemes, contrary to other manifestations of dyslexia, and may be a core deficit.

Development of phonological and orthographic processing in reading aloud, in silent reading, and in spelling: a four-year longitudinal study.

The development of phonological and orthographic processing was studied from the middle of Grade 1 to the end of Grade 4 (age 6; 6-10 years) using the effects of regularity and of lexicality in reading aloud and in spelling tasks, and using the effect of pseudohomophony in a silent reading task. In all the tasks, signs of reliance on phonological processing were found even when indicators of reliance on orthographic processing appeared. Multiple regression analyses were conducted to determine which early skills predict later reading achievement. Pseudoword and irregular word scores were used as measures for phonological and orthographic skills, respectively. Only middle of Grade 1 phonological reading skills accounted for independent variance in end of Grade 4 orthographic skills. Conversely, from the middle to the end of Grade 1, and from the end of Grade 1 to the end of Grade 4, both orthographic and phonological skills accounted for independent variance in later orthographic skills. In the prediction of phonological skills, only the unique contribution of earlier phonological skills was significant. Thus, phonological and orthographic processing appear to be reciprocally related, rather than independent components of written word recognition. However, very early reliance on the phonological procedure seems to be the bootstrapping mechanism for reading acquisition.