Converging evidence for phonological and surface subtypes of reading disability.

Using regression-based procedures introduced by A. Castles and M. Coltheart (1993), the authors identified 17 phonological and 15 surface dyslexics from a sample of 68 reading-disabled 3rd-grade children by comparing them to chronological-age (CA) controls on exception word and pseudoword reading. However, when the dyslexic subtypes were defined by reference to reading-level (RL) controls, 17 phonological dyslexics were defined but only 1 surface dyslexic. When the CA-defined subtypes were compared to RL controls, the phonological dyslexics displayed superior exception word reading but displayed deficits in pseudoword naming, phonological sensitivity, working memory, and syntactic processing. The surface dyslexics, in contrast, displayed a cognitive profile remarkably similar to that of the RL controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A longitudinal study of reading development in dyslexic children.

The development of literacy skills was studied in 20 dyslexic children (7 years 7 months to 12 years 7 months). At Time 1, the dyslexic children performed worse on tests of reading, spelling, and phonological processing than chronological age-matched normal readers, but their performance was qualitatively similar to that of younger reading age-matched controls. The dyslexic children made poor progress over the following 2 years and, in comparison with reading age controls at Time 2, showed specific difficulties in nonword reading and repetition and made more dysphonetic spelling errors. The authors argue that this typical dyslexic profile becomes more defined with development and provides support for the theory that phonological deficits in dyslexia compromise the development of reading skills. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of dyslexics' phonological awareness deficits.

Examined the phonological awareness skills of dyslexic children, adults with childhood diagnoses of dyslexia, and good readers at various age levels. Comparisons of the dyslexics to good readers of the same age or the same reading level indicated that dyslexics do not acquire appropriate levels of phoneme awareness, regardless of their age or reading levels, although they eventually acquire appropriate levels of onset-rhyme awareness. Even adults with fairly high levels of word recognition skill show phoneme awareness deficits. For normal readers, reliable increases in phoneme awareness were associated with age and reading level, whereas for dyslexic Ss these associations were not reliable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abnormal callosal morphology in male adult dyslexics: relationships to handedness and phonological abilities

The classical notion that developmental dyslexia may somehow relate to impaired communication between hemispheres has not yet received convincing support. Sixteen dyslexic adults and 12 controls received a high resolution brain MRI scan for morphometric study of the corpus callosum. Automatized measurements of callosal area and calculation of indices defining the general morphology of the callosal mid-surface were performed. Each participant received global intelligence and reading achievement evaluation; dyslexics were further proposed specific neuropsychological tests specially designed to explore the mechanisms of reading impairment. It just appears from the group comparisons (1) that the dyslexics' corpus callosum displays a more circular and evenly thicker general shape, and (2) that the midsagittal surface is on the average larger than in controls, in particular in the isthmus. Moreover, the different morphometric characteristics of the dyslexic brain correlated with the degree of impairment on various tests exploring phonological abilities. In vivo morphometry of the corpus callosum may provide valuable hints for understanding developmental learning disorders and their consequences in adults.     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory temporal coding in dyslexia

Developmental dyslexia is generally believed to result from impaired linguistic processing rather than from deficits in low-level sensory function. Challenging this view, we studied the perception of non-verbal acoustic stimuli and low-level auditory evoked potentials in dyslexic adults. Compared with matched controls, dyslexics were selectively impaired in tasks (frequency discrimination and binaural unmasking) which rely on decoding neural discharges phase-locked to the fine structure of the stimulus. Furthermore, this ability to use phase-locking was related to reading ability. In addition, the evoked potential reflecting phase-locked discharges was significantly smaller in dyslexics. These results demonstrate a low-level auditory impairment in dyslexia traceable to the brainstem nuclei.     

Lexical access and phonological decoding in adult dyslexic subtypes.

Lexical access and phonological decoding were tested in 100 normal adult readers and 21 adult dyslexic individuals. Within the dyslexic sample, 11 dysphonetic dyslexic and 10 dyseidetic dyslexic participants were classified on the basis of spelling patterns. In the 1st experiment, adult dyseidetic readers showed a marked deficit on the lexical-access decision task in comparison with adult dysphonetic readers. In the 2nd experiment, the phonological-decoding decision task did not separate the subtypes. A lexical-access deficit in adult dyseidetic dyslexia cannot be explained in terms of a developmental delay. A phonological-decoding deficit in adult dyseidetic dyslexia may be explained by increased involvement of the lexical procedure in phonological assembly under an analogy strategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A quantitative-trait locus on chromosome 6p influences different aspects of developmental dyslexia

Recent application of nonparametric-linkage analysis to reading disability has implicated a putative quantitative-trait locus (QTL) on the short arm of chromosome 6. In the present study, we use QTL methods to evaluate linkage to the 6p25-21.3 region in a sample of 181 sib pairs from 82 nuclear families that were selected on the basis of a dyslexic proband. We have assessed linkage directly for several quantitative measures that should correlate with different components of the phenotype, rather than using a single composite measure or employing categorical definitions of subtypes. Our measures include the traditional IQ/reading discrepancy score, as well as tests of word recognition, irregular-word reading, and nonword reading. Pointwise analysis by means of sib-pair trait differences suggests the presence, in 6p21.3, of a QTL influencing multiple components of dyslexia, in particular the reading of irregular words (P=.0016) and nonwords (P=.0024). A complementary statistical approach involving estimation of variance components supports these findings (irregular words, P=.007; nonwords, P=.0004). Multipoint analyses place the QTL within the D6S422-D6S291 interval, with a peak around markers D6S276 and D6S105 consistently identified by approaches based on trait differences (irregular words, P=.00035; nonwords, P=.0035) and variance components (irregular words, P=.007; nonwords, P=.0038). Our findings indicate that the QTL affects both phonological and orthographic skills and is not specific to phoneme awareness, as has been previously suggested. Further studies will be necessary to obtain a more precise localization of this QTL, which may lead to the isolation of one of the genes involved in developmental dyslexia.     

Word-recognition skills of adults with childhood diagnoses of dyslexia.

This study investigated whether the same pattern of reading deficits that characterize dyslexic children continue to characterize this population as it reaches adulthood. Standardized and experimental reading tasks were administered to college students with childhood diagnoses of dyslexia, and to age-matched and reading-matched control subjects. Despite relatively high levels of reading comprehension, dyslexics showed inaccurate and particularly slow word-recognition skills. Dyslexics did not use age-appropriate, and in some cases reading-level-appropriate word recognition processes. They relied heavily on the use of spelling–sound information, syllabic information, and context for word recognition. Word-recognition difficulties reflected poor knowledge of spelling–sound correspondences. Adult dyslexics' patterns of performance were most similar to those of beginning skilled readers and to dyslexic children. The term arrest rather than deviance or delay best characterizes the word-recognition skills of adult dyslexics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitivity to dynamic auditory and visual stimuli predicts nonword reading ability in both dyslexic and normal readers

BACKGROUND: Developmental dyslexia is a specific disorder of reading and spelling that affects 3-9% of school-age children and adults. Contrary to the view that it results solely from deficits in processes specific to linguistic analysis, current research has shown that deficits in more basic auditory or visual skills may contribute to the reading difficulties of dyslexic individuals. These might also have a crucial role in the development of normal reading skills. Evidence for visual deficits in dyslexia is usually found only with dynamic and not static stimuli, implicating the magnocellular pathway or dorsal visual stream as the cellular locus responsible. Studies of such a dissociation between the processing of dynamic and static auditory stimuli have not been reported previously. RESULTS: We show that dyslexic individuals are less sensitive both to particular rates of auditory frequency modulation (2 Hz and 40 Hz but not 240 Hz) and to dynamic visual-motion stimuli. There were high correlations, for both dyslexic and normal readers, between their sensitivity to the dynamic auditory and visual stimuli. Nonword reading, a measure of phonological awareness believed crucial to reading development, was also found to be related to these sensory measures. CONCLUSIONS: These results further implicate neuronal mechanisms that are specialised for detecting stimulus timing and change as being dysfunctional in many dyslexic individuals. The dissociation observed in the performance of dyslexic individuals on different auditory tasks suggests a sub-modality division similar to that already described in the visual system. These dynamic tests may provide a non-linguistic means of identifying children at risk of reading failure.     

Word identification in reading proceeds from spelling to sound to meaning.

Van Orden (1987) reported that false positive errors in a categorization task are elevated for homophonic foils (e.g., {hare} for {a part of the human body}). Two new experiments replicate this finding and extend it to nonword homophone foils (e.g., {sute} for {an article of clothing}). False positive errors to nonword homophone foils substantially exceed false positive errors to nonhomophonic nonword spelling controls, showing that the phonological characteristics of the nonword foils are critical. Because nonwords are not represented in the lexicon, this new result implicates computed phonological codes as a source of the categorization errors. Additionally, in each of two experiments, matched word and nonword homophones produced virtually identical error rates. If stimulus nonword homophones are viewed as extremely unfamiliar words, compared with the relatively familiar stimulus word homophones, then our failure to observe an effect of stimulus familiarity strengthens the case that phonological coding plays a role in the identification of all printed words. The fact that the results are obtained in a categorization task that requires reading for meaning (rather than a lexical decision task) makes it difficult to avoid the conclusion that phonological mediation plays a role in normal reading of text for meaning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On subtypes of developmental dyslexia: Evidence from processing time and accuracy scores.

Determined the proportion of phonological dyslexics (Ph-DYS) and surface dyslexics (S-DYS) in a population of French dyslexics by applying A. Castles and M. Coltheart's (1993) regression method to 2 diagnostic measures: pseudo-word and irregular-word processing time. 31 dyslexics were matched to 19 average readers of the same age (aged 10 yrs, CA controls) and to 19 younger children of the same reading level (aged 8 yrs, RL controls). Compared to CA controls, there were more Ph-DYS than S-DYS. Compared to RL controls, there were still a high number of Ph-DYS. The reliability of these subtypes across different measures of phonological and orthographic skills was also examined. Compared to RL controls, both groups of dyslexics were found to be impaired only in phonological skills. The moment at which the 2 dissociated profiles emerged in the course of cognitive development was assessed by examining data that was collected when the children were 7 and 8 yrs old. The results show that only the S-DYS's orthographic deficit increased with development. The authors also looked at whether the Ph-DYS and S-DYS profiles were associated with other specific cognitive deficits. Specific deficits in phonemic awareness and in phonological short-term memory were found for both Ph-DYS and S-DYS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two routes or one in reading aloud? A connectionist dual-process model.

A connectionist study of word reading is described that emphasizes the computational demands of the spelling–sound mapping in determining the properties of the reading system. It is shown that the phonological assembly process can be implemented by a two-layer network, which easily extracts the regularities in the spelling–sound mapping for English from training data containing many exception words. It is argued that productive knowledge about spelling–sound relationships is more easily acquired and used if it is separated from case-specific knowledge of the pronunciation of known words. It is then shown how the interaction of assembled and retrieved phonologies can account for the combined effects of frequency and regularity–consistency and for the reading performance of dyslexic patients. It is concluded that the organization of the reading system reflects the demands of the task and that the pronunciations of nonwords and exception words are computed by different processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Understanding normal and impaired word reading: Computational principles in quasi-regular domains.

A connectionist approach to processing in quasi-regular domains, as exemplified by English word reading, is developed. Networks using appropriately structured orthographic and phonological representations were trained to read both regular and exception words, and yet were also able to read pronounceable nonwords as well as skilled readers. A mathematical analysis of a simplified system clarifies the close relationship of word frequency and spelling–sound consistency in influencing naming latencies. These insights were verified in subsequent simulations, including an attractor network that accounted for latency data directly in its time to settle on a response. Further analyses of the ability of networks to reproduce data on acquired surface dyslexia support a view of the reading system that incorporates a graded division of labor between semantic and phonological processes, and contrasts in important ways with the standard dual-route account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The representation of sublexical orthographic-phonologic correspondences: evidence from phonological dyslexia

Although there is considerable evidence that grapheme and body units are involved in assembling phonology from print, there is little evidence supporting the involvement of syllabic representations. We provide evidence on this point from a phonological dyslexic patient (ML) who, as a result of brain damage, is relatively unable to read nonwords. ML was found to be able to perform tasks assumed to reflect processes involved in assembled phonology (i.e. segmentation, orthographic-phonologic conversion, and blending) when the units involved were syllables, but demonstrated considerable difficulty when they were onset, body, or phoneme units. Additionally, both ML and matched controls were much better able to find words in an anagrams task (Treiman & Chafetz, 1987) when they resulted from the combination of segments corresponding to syllables than when they did not. It is suggested that the relationship between print and sound is represented at multiple levels (including the syllable) (Shallice, Warrington, & McCarthy, 1983) and that ML's nonword reading impairment is the result of disruption of representations below the level of the syllable.     

The double-deficit hypothesis for the developmental dyslexias.

The authors propose an alternative conceptualization of the developmental dyslexias, the double-deficit hypothesis (i.e., phonological deficits and processes underlying naming-speed deficits represent 2 separable sources of reading dysfunction). Data from cross-sectional, longitudinal, and cross-linguistic studies are reviewed supporting the presence of 2 single-deficit subtypes with more limited reading impairments and 1 double-deficit subtype with more pervasive and severe impairments. Naming-speed and phonological-awareness variables contribute uniquely to different aspects of reading according to this conception, with a model of visual letter naming illustrating both the multicomponential nature of naming speed and why naming speed should not be subsumed under phonological processes. Two hypotheses concerning relationships between naming-speed processes and reading are considered. The implications of processing speed as a second core deficit in dyslexia are described for diagnosis and intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-Term Effects of Phoneme Awareness and Letter Sound Training: An Intervention Study With Children at Risk for Dyslexia.

Positive long-term effects of phoneme awareness training in kindergarten were found in this study with children of dyslexic parents. Thirty-five at-risk children (attending 26 different classes) participated in an intensive 17-week program in their regular kindergarten classes designed to help them improve in phoneme awareness. Follow-up measures indicated that the trained children outperformed 47 untrained at-risk controls in both word and nonword reading in Grades 2, 3, and 7. For the very poorest readers, significant effects were found--even in Grade 7 reading comprehension. However, the trained at-risk children were found to lag behind a 2nd control group of 41 not-at-risk children in most aspects of reading. Treatment-resistant children had relatively poor phonological representations of known words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in contextual facilitation: evidence from dyslexia and poor reading comprehension

Ninety-two 7- to 10-year-old children read words presented in isolation or following a spoken sentence context. In absolute terms, poor readers showed more contextual facilitation than good readers. However, when the relative benefit of context was assessed, this was greater for children with better reading skills, and comprehension was a better predictor of contextual facilitation than decoding. Study 2 compared the performance of dyslexics with that of reading-age matched poor comprehenders and normal readers. The dyslexics showed greater contextual facilitation than the normal readers who, in turn, showed more priming than poor comprehenders. The results show that dyslexic children use context to compensate for poor decoding skills, whereas children with poor reading comprehension skills fail to benefit from context as much as normal readers.     

Treating the core deficits of developmental dyslexia: Evidence of transfer of learning after phonologically- and strategy-based reading training programs.

Individuals with dyslexia have difficulty generalizing from word identification training. This study compared 2 forms of word identification training to promote transfer of learning by children with dyslexia. 62 children were randomly assigned to 1 of the training programs or to a study skills control program. One program trained phonological analysis and blending skills and provided direct instruction of letter–sound correspondences; the other trained the acquisition, use, and monitoring of 4 metacognitive decoding strategies. Results provided clear evidence of transfer of learning after treatment of the core reading deficits of these children. Both training approaches were associated with large positive effects, transfer on several measures, and generalized achievement gains. The phonological program resulted in greater generalized gains in the phonological domain and the strategy program in broader-based transfer for real words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)