Evidence for a specific cross-modal association deficit in dyslexia: an electrophysiological study of letter-speech sound processing

The phonological deficit theory of dyslexia assumes that degraded speech sound representations might hamper the acquisition of stable letter-speech sound associations necessary for learning to read. However, there is only scarce and mainly indirect evidence for this assumed letter-speech sound association problem. The present study aimed at clarifying the nature and the role of letter-speech sound association problems in dyslexia by analysing event-related potentials (ERP) of 11-year-old dyslexic children to speech sounds in isolation or combined with letters, which were presented either simultaneously with or 200 ms before the speech sounds. Recent studies with normal readers revealed that letters systematically modulated speech sound processing in an early (mismatch negativity or MMN) and late (Late Discriminatory Negativity or LDN) time-window. The amplitude of the MMN and LDN to speech sounds was enhanced when speech sounds were presented with letters. The dyslexic readers in the present study, however, did not exhibit any early influences of letters on speech sounds even after 4 years of reading instruction, indicating no automatic integration of letters and speech sounds. Interestingly, they revealed a systematic late effect of letters on speech sound processing, probably reflecting the mere association of letters and speech sounds. This pattern is strongly divergent from that observed in age-matched normal readers, who showed both early and late effects, but reminiscent of that observed in beginner normal readers in a previous study (Froyen, Bonte, van Atteveldt & Blomert, 2009). The finding that the quality of letter-speech sound processing is directly related to reading fluency urges further research into the role of audiovisual integration in the development of reading failure in dyslexia.     

The cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia

The present study was conducted to examine the cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia. Thirty Chinese dyslexic children in Hong Kong were compared with 30 average readers of the same chronological age (CA controls) and 30 average readers of the same reading level (RL controls) in a number of rapid naming, visual, phonological, and orthographic tasks. Chinese dyslexic children performed significantly worse than the CA controls but similarly to the RL controls on most of the cognitive tasks. The rapid naming deficit was found to be the most dominant type of cognitive deficit in Chinese dyslexic children. Over half of the dyslexic children exhibited deficits in 3 or more cognitive areas, and there was a significant association between the number of cognitive deficits and the degree of reading and spelling impairment. The present findings support the multiple-deficit hypothesis in Chinese developmental dyslexia.     

Visual rapid naming and phonological abilities: different subtypes in dyslexic children

One implication of the double-deficit hypothesis for dyslexia is that there should be subtypes of dyslexic readers that exhibit rapid naming deficits with or without concomitant phonological processing problems. In the current study, we investigated the validity of this hypothesis for Portuguese orthography, which is more consistent than English orthography, by exploring different cognitive profiles in a sample of dyslexic children. In particular, we were interested in identifying readers characterized by a pure rapid automatized naming deficit. We also examined whether rapid naming and phonological awareness independently account for individual differences in reading performance. We characterized the performance of dyslexic readers and a control group of normal readers matched for age on reading, visual rapid naming and phonological processing tasks. Our results suggest that there is a subgroup of dyslexic readers with intact phonological processing capacity (in terms of both accuracy and speed measures) but poor rapid naming skills. We also provide evidence for an independent association between rapid naming and reading competence in the dyslexic sample, when the effect of phonological skills was controlled. Altogether, the results are more consistent with the view that rapid naming problems in dyslexia represent a second core deficit rather than an exclusive phonological explanation for the rapid naming deficits. Furthermore, additional non-phonological processes, which subserve rapid naming performance, contribute independently to reading development.     

Developmental and acquired dyslexia: A comparison

Jorm (1979a) has drawn attention to similarities between developmental dyslexia and acquired deep dyslexia, an analogy which has been criticized by A. W. Ellis (1979). A series of three experiments compared the two syndromes, using the techniques applied by Patterson and Marcel (1977) to adult deep dyslexics, to study a group of 15 boys suffering from developmental dyslexia. Patterson and Marcel's patients were able to perform a lexical decision task but showed no evidence of phonemic encoding of nonwords; our dyslexic children performed this task very slowly and with reduced accuracy but showed clear evidence of phonemic coding of the nonword items. Patterson and Marcel observed that their patients could not read out orthographically regular nonwords; our dyslexic children were able to do this task, although more slowly and somewhat less accurately than their chronological age or reading age controls. Finally, Patterson and Marcel observed that highly imageable words were more likely to be read correctly than words of equal frequency but low imageability; we observed a similar effect in both our dyslexic group and in their reading age controls. This implies that the imageability effect may not be peculiar to dyslexics but may be characteristic of normal reading under certain conditions. It is concluded that developmental dyslexics differ from the patients studied by Patterson and Marcel in demonstrating a pattern of reading which, though slow, is qualitatively similar to the reading of normal readers of a younger age. As such, our results do not support Jorm's position.     

The Effect of Parents’ Literacy Skills and Children’s Preliteracy Skills on the Risk of Dyslexia

The combination of investigating child and family characteristics sheds light on the constellation of risk factors that can ultimately lead to dyslexia. This family-risk study examines plausible preschool risk factors and their specificity. Participants (N?=?196, 42 % girls) included familial risk (FR) children with and without dyslexia in Grade 3 and controls. First, we found impairments in phonological awareness, rapid naming, and letter knowledge in FR kindergartners with later dyslexia, and mild phonological-awareness deficits in FR kindergartners without subsequent dyslexia. These skills were better predictors of reading than arithmetic, except for rapid naming. Second, the literacy environment at home was comparable among groups. Third, having a dyslexic parent and literacy abilities of the non-dyslexic parent related to offspring risk of dyslexia. Parental literacy abilities might be viewed as indicators of offspring’s liability for literacy difficulties, since parents provide offspring with genetic and environmental endowment. We propose an intergenerational multiple deficit model in which both parents confer cognitive risks.     

Specific disorders and broader phenotypes: the case of dyslexia

Two studies investigating the cognitive phenotype of dyslexia are described. Study 1 compared three groups of English and Italian children on speed of processing tasks: (a) children with dyslexia, (b) generally delayed poor readers and (c) CA-controls. In tests of simple and choice reaction time and two visual scanning tasks, children with dyslexia performed like controls and significantly faster than generally delayed poor readers. A second prospective longitudinal investigation of children at family risk of dyslexia showed that problems of literacy development were less circumscribed, with affected children showing phonological deficits in the context of more general oral language difficulties. An important finding was that the risk of dyslexia was continuous in this sample; among at-risk children with normal literacy development, mild impairments of phonological skills were apparent early in development, and subtle difficulties with reading fluency and spelling emerged in early adolescence. A case series extended these findings to show that phonological deficits alone are insufficient to explain literacy difficulties, and it is children with multiple deficits (including language problems) that are more likely to succumb to reading failure.     

发展性阅读障碍亚类型研究进展

发展性阅读障碍是一种特殊的学习障碍,伴有多种认知缺陷并且存在不同的亚类型。依据相关的阅读模型理论,阅读障碍可划分为语音型和表层型。从认知缺陷角度出发,语音加工缺陷是主要的缺陷表现,以此为特征形成一种主要的阅读障碍的亚类型,同时还有以正字法加工缺陷和快速命名缺陷为主的其他亚类型。而以基本感知觉缺陷为标准,主要有以视觉加工缺陷和以听觉加工缺陷为主的两种亚类型。在汉语条件下,依据同样的阅读模型理论,语音型阅读障碍亚类型比例明显低于拼音文字条件下的。汉语阅读障碍也具有分别以语音加工缺陷、快速命名缺陷和正字法加工缺陷为主要认知缺陷的亚类型。未来有必要从神经机制角度进一步明确不同亚类型的神经基础。     

The roles of family history of dyslexia,language, speech production and phonological processing in predicting literacy progress

It is well established that speech, language and phonological skills are closely associated with literacy, and that children with a family risk of dyslexia (FRD) tend to show deficits in each of these areas in the preschool years. This paper examines what the relationships are between FRD and these skills, and whether deficits in speech, language and phonological processing fully account for the increased risk of dyslexia in children with FRD. One hundred and fifty‐three 4–6‐year‐old children, 44 of whom had FRD, completed a battery of speech, language, phonology and literacy tasks. Word reading and spelling were retested 6 months later, and text reading accuracy and reading comprehension were tested 3 years later. The children with FRD were at increased risk of developing difficulties in reading accuracy, but not reading comprehension. Four groups were compared: good and poor readers with and without FRD. In most cases good readers outperformed poor readers regardless of family history, but there was an effect of family history on naming and nonword repetition regardless of literacy outcome, suggesting a role for speech production skills as an endophenotype of dyslexia. Phonological processing predicted spelling, while language predicted text reading accuracy and comprehension. FRD was a significant additional predictor of reading and spelling after controlling for speech production, language and phonological processing, suggesting that children with FRD show additional difficulties in literacy that cannot be fully explained in terms of their language and phonological skills.     

Early naming deficits, developmental dyslexia, and a specific deficit hypothesis.

The present research represents the final 2 years of a 5-year longitudinal investigation of (a) confrontation-based, word-retrieval deficits in dyslexic children; (b) the role of vocabulary development in these deficits; (c) the relationship between confrontation naming performance and three carefully defined aspects of reading performance in the general population and in eight dyslexic case studies; and (d) the possible specificity of word-retrieval deficits in dyslexia. Results indicate enduring problems in word-retrieval processes for dyslexic children across the primary grades and into middle childhood. Second, these deficits cannot be explained by simple vocabulary deficits. Third, these results in conjunction with our earlier data consolidate a pattern of differential relationships between specific reading and confrontation naming skills that are based on development and on the level of processes involved. Trends within case studies suggest the more pronounced the retrieval deficit, the more global the reading impairment. And fourth, there appear to be some specific differences in the basis of word-retrieval problems between dyslexic and garden-variety or lower achieving readers. Results are discussed within a speculative framework that implicates problems in timing as a possible predetermining condition in the dyslexias.     

Infant ERPs separate children at risk of dyslexia who become good readers from those who become poor readers

Dyslexia is heritable and associated with phonological processing deficits that can be reflected in the event‐related potentials (ERPs). Here, we recorded ERPs from 2‐month‐old infants at risk of dyslexia and from a control group to investigate whether their auditory system processes /bAk/ and /dAk/ changes differently. The speech sounds were presented in an oddball paradigm. The children were followed longitudinally and performed a word reading fluency test in second grade. The infant ERPs were subsequently analyzed according to high or low reading fluency in order to find a neurophysiological precursor of poor reading fluency. The results show that the fluent reading children (from both the at‐risk and the control group) processed the speech sound changes differentially in infancy as indicated by a mismatch response (MMR). In the control group the MMR was frontally positive and in the fluent at‐risk group the MMR was parietally positive. The non‐fluent at‐risk group did not show an MMR. We conclude that at‐risk children who became fluent readers were better at speech processing in infancy than those who became non‐fluent readers. This indicates a very early speech processing deficit in the group of later non‐fluent readers.     

On the prevalence of magnocellular deficits in the visual system of non-dyslexic individuals

Numerous studies have found visual deficits associated with dyslexia. This has made it important to understand how these deficits may be related to reading difficulties. A widely held theory is that dyslexia is the result of a deficit in the magnocellular part of the visual system (earlier called the transient system). In support for this theory, the prevalence of magnocellular deficits has been reported to be high among dyslexic readers and very low among non-dyslexic ones. This creates the impression that in the population as a whole dyslexic individuals have magnocellular deficits and non-dyslexic individuals do not. However, we show that because the prevalence of dyslexia itself is low this need not be the case. On the basis of previously published data we have estimated the number of non-dyslexic and dyslexic individuals with magnocellular deficits. Our estimates indicate that there should be a large number of non-dyslexic individuals with magnocellular deficits. Paradoxically more individuals without dyslexia have magnocellular deficits than individuals with dyslexia. This poses a challenge to the view that dyslexia is the result of a magnocellular deficit.     

Imbalanced word-reading profiles in eighth-graders

This current study introduced a new method to investigate the prevalence and correlates of significant imbalances in the relative accuracy with which eighth-graders read nonwords (e.g., prauma) and exception words (e.g., vaccine). Substantial proportions of students showed imbalanced word-reading profiles, but these were not strongly tied to differences in reading and spelling achievement. Of the students without reading difficulties, 19% had imbalanced word-reading profiles favoring exception words and 17% had imbalanced word-reading profiles favoring nonwords. Of the poor readers, 39% met the criterion for phonological dyslexia (with imbalanced word-reading profiles favoring exception words) and 14% met the criterion for surface dyslexia (with imbalanced word-reading profiles favoring nonwords) in relation to the eighth-grade benchmark readers, but the incidence of these types of dyslexia varied with verbal ability. Of the poor readers with normal verbal ability, 60% were classified as phonological dyslexics and none was classified as surface dyslexic. In students low in verbal ability, surface dyslexia was more common. However, when imbalanced word-reading profiles were defined in relation to fourth-grade reading-level controls, only 12 phonological dyslexics and 1 surface dyslexic were identified. Relatively few cases of either type of developmental dyslexia appeared to be "pure."     

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.     

Crossmodal temporal order and processing acuity in developmentally dyslexic young adults

We investigated crossmodal temporal performance in processing rapid sequential nonlinguistic events in developmentally dyslexic young adults (ages 20-36 years) and an age- and IQ-matched control group in audiotactile, visuotactile, and audiovisual combinations. Two methods were used for estimating 84% correct temporal acuity thresholds: temporal order judgment (TOJ) and temporal processing acuity (TPA). TPA requires phase difference detection: the judgment of simultaneity/nonsimultaneity of brief stimuli in two parallel, spatially separate triplets. The dyslexic readers' average temporal performance was somewhat poorer in all six comparisons; in audiovisual comparisons the group differences were not statistically significant, however. A principal component analysis indicated that temporal acuity and phonological awareness are related in dyslexic readers. The impairment of temporal input processing seems to be a general correlative feature of dyslexia in children and adults, but the overlap in performance between dyslexic and normal readers suggests that it is not a sufficient reason for developmental reading difficulties.     

汉语发展性阅读障碍儿童视觉注意广度的发展及其对阅读流畅性的作用

以85名小学2~6年级儿童为研究对象,采用方差分析、分层回归探讨小学高、低年龄阶段发展性阅读障碍儿童视觉注意广度的发展变化,并以同年龄正常阅读者作为对照组;同时在不同年龄阶段探究视觉注意广度对阅读流畅性发展的预测作用。结果显示：（1）发展性阅读障碍儿童存在视觉注意广度缺陷,并呈现出在小学高年龄阶段更严重的趋势;（2）在阅读障碍儿童中,视觉注意广度对汉语流畅阅读的显著预测作用随发展增强;而对于正常阅读者,视觉注意广度仅显著预测低年龄段学生的句子朗读流畅阅读能力。以上结果表明视觉注意广度与汉语流畅阅读能力关系密切,今后汉语阅读障碍的相关干预研究可以尝试从视觉注意广度训练方面切入。     

Picture naming deficits in developmental dyslexia in German

Recent research with English developmental dyslexics comparing the picture naming performance of these children to the picture naming performance of non-dyslexic (‘garden variety’) poor readers, reading age matched controls and chronological age matched controls has suggested that a selective difficulty in retrieving the phonological codes of known names on demand underlies the picture naming deficit found in developmental dyslexia (Swan & Goswami, Picture naming deficits in developmental dyslexia: the phonological representations hypothesis, Brain and Language, 56 (1997), 334–353). If the underlying causal factors in dyslexia are independent of the orthography that the child is learning to read, then a difficulty in retrieving the phonological codes of known names on demand should also be found in developmental dyslexics who are learning to read other languages. We therefore set out to replicate Swan and Goswami’s study with a group of German developmental dyslexics. We were interested to see whether a phonological deficit is characteristic of dyslexia in all orthographies, even those, such as German, in which high orthographic transparency means that dyslexic children read with considerable accuracy.     

Discrimination of speech sounds by children with dyslexia: comparisons with chronological age and reading level controls

Previous studies have shown that children suffering from developmental dyslexia have a deficit in categorical perception of speech sounds. The aim of the current study was to better understand the nature of this categorical perception deficit. In this study, categorical perception skills of children with dyslexia were compared with those of chronological age and reading level controls. Children identified and discriminated /do-to/ syllables along a voice onset time (VOT) continuum. Results showed that children with dyslexia discriminated among phonemically contrastive pairs less accurately than did chronological age and reading level controls and also showed higher sensitivity in the discrimination of allophonic contrasts. These results suggest that children with dyslexia perceive speech with allophonic units rather than phonemic units. The origin of allophonic perception in the course of perceptual development and its implication for reading acquisition are discussed.     

Visual versus phonological abilities in Spanish dyslexic boys and girls

Phonological and visual theories propose different primary deficits as part of the explanation for dyslexia. Both theories were put to test in a sample of Spanish dyslexic readers. Twenty-one dyslexic and 22 typically-developing children matched on chronological age were administered phonological discrimination and awareness tasks and coherent motion perception tasks. No differences were found between groups on the coherent motion tasks, whereas dyslexic readers were impaired relative to controls on phonological discrimination tasks. Gender differences followed the opposite pattern, with no differences on phonological tasks, and dyslexic girls performing significantly worse than dyslexic boys in coherent motion perception. These results point to the importance of phonological deficits related to speech perception in Spanish, and to possible gender differences in the neurobiological bases for dyslexia.     

Mothers speak differently to infants at‐risk for dyslexia

Dyslexia is a neurodevelopmental disorder manifested in deficits in reading and spelling skills that is consistently associated with difficulties in phonological processing. Dyslexia is genetically transmitted, but its manifestation in a particular individual is thought to depend on the interaction of epigenetic and environmental factors. We adopt a novel interactional perspective on early linguistic environment and dyslexia by simultaneously studying two pre‐existing factors, one maternal and one infant, that may contribute to these interactions; and two behaviours, one maternal and one infant, to index the effect of these factors. The maternal factor is whether mothers are themselves dyslexic or not (with/without dyslexia) and the infant factor is whether infants are at‐/not‐at family risk for dyslexia (due to their mother or father being dyslexic). The maternal behaviour is mothers’ infant‐directed speech (IDS), which typically involves vowel hyperarticulation, thought to benefit speech perception and language acquisition. The infant behaviour is auditory perception measured by infant sensitivity to amplitude envelope rise time, which has been found to be reduced in dyslexic children. Here, at‐risk infants showed significantly poorer acoustic sensitivity than not‐at‐risk infants and mothers only hyperarticulated vowels to infants who were not at‐risk for dyslexia. Mothers’ own dyslexia status had no effect on IDS quality. Parental speech input is thus affected by infant risk status, with likely consequences for later linguistic development.     

Speech prosody and developmental dyslexia: Reduced phonological awareness in the context of intact phonological representations

Recent research indicates that awareness of the rhythmic patterns present in spoken language (i.e., prosody) may be an important and relatively overlooked predictor of reading ability. Two studies investigated the prosodic processing abilities of skilled adult readers and adults with developmental dyslexia. Participants with dyslexia showed reduced awareness of lexical and metrical stress and these skills were found to be significantly associated with, and predictive of, phonological decoding ability. In contrast, the same individuals showed normal patterns of stress based priming at magnitudes similar to controls. These results—suggesting reduced phonological awareness in the context of intact phonological representations—are consistent with recent findings reported in the domain of phonemic processing. Implications for the phonological deficit theory of dyslexia are discussed.