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PubMed2006

Deficient orthographic and phonological representations in children with dyslexia revealed by brain activation patterns.

BACKGROUND: The current study examined the neuro-cognitive network of visual word rhyming judgment in 14 children with dyslexia and 14 age-matched control children (8- to 14-year-olds) using functional magnetic resonance imaging (fMRI). METHODS: In order to manipulate the difficulty of mapping orthography to phonology, we used conflicting and non-conflicting trials. The words in conflicting trials either had similar orthography but different phonology (e.g., pint-mint) or similar phonology but different orthography (e.g., jazz-has). The words in non-conflicting trials had similar orthography and phonology (e.g., gate-hate) or different orthography and phonology (e.g., press-list). RESULTS: There were no differences in brain activation between the controls and children with dyslexia in the easier non-conflicting trials. However, the children with dyslexia showed less activation than the controls in left inferior frontal gyrus (BA 45/44/47/9), left inferior parietal lobule (BA 40), left inferior temporal gyrus/fusiform gyrus (BA 20/37) and left middle temporal gyrus (BA 21) for the more difficult conflicting trials. For the direct comparison of conflicting minus non-conflicting trials, controls showed greater activation than children with dyslexia in left inferior frontal gyrus (BA 9/45/46) and medial frontal gyrus (BA 8). Children with dyslexia did not show greater activation than controls for any comparison. CONCLUSIONS: Reduced activation in these regions suggests that children with dyslexia have deficient orthographic representations in ventral temporal cortex as well as deficits in mapping between orthographic and phonological representations in inferior parietal cortex. The greater activation for the controls in inferior frontal gyrus could reflect more effective top-down modulation of posterior representations.

Adolescent↗

PubMed2001

A dominant gene for developmental dyslexia on chromosome 3.

Developmental dyslexia is a neurofunctional disorder characterised by an unexpected difficulty in learning to read and write despite adequate intelligence, motivation, and education. Previous studies have suggested mostly quantitative susceptibility loci for dyslexia on chromosomes 1, 2, 6, and 15, but no genes have been identified yet. We studied a large pedigree, ascertained from 140 families considered, segregating pronounced dyslexia in an autosomal dominant fashion. Affected status and the subtype of dyslexia were determined by neuropsychological tests. A genome scan with 320 markers showed a novel dominant locus linked to dyslexia in the pericentromeric region of chromosome 3 with a multipoint lod score of 3.84. Nineteen out of 21 affected pedigree members shared this region identical by descent (corrected p<0.001). Previously implicated genomic regions showed no evidence for linkage. Sequencing of two positional candidate genes, 5HT1F and DRD3, did not support their role in dyslexia. The new locus on chromosome 3 is associated with deficits in all three essential components involved in the reading process, namely phonological awareness, rapid naming, and verbal short term memory.

Adolescent↗

PubMed2003

A genome scan for developmental dyslexia confirms linkage to chromosome 2p11 and suggests a new locus on 7q32.

Developmental dyslexia is a distinct learning disability with unexpected difficulty in learning to read despite adequate intelligence, education, and environment, and normal senses. The genetic aetiology of dyslexia is heterogeneous and loci on chromosomes 2, 3, 6, 15, and 18 have been repeatedly linked to it. We have conducted a genome scan with 376 markers in 11 families with 38 dyslexic subjects ascertained in Finland. Linkage of dyslexia to the vicinity of DYX3 on 2p was confirmed with a non-parametric linkage (NPL) score of 2.55 and a lod score of 3.01 for a dominant model, and a novel locus on 7q32 close to the SPCH1 locus was suggested with an NPL score of 2.77. The SPCH1 locus has previously been linked with a severe speech and language disorder and autism, and a mutation in exon 14 of the FOXP2 gene on 7q32 has been identified in one large pedigree. Because the language disorder associated with the SPCH1 locus has some overlap with the language deficits observed in dyslexia, we sequenced the coding region of FOXP2 as a candidate gene for our observed linkage in six dyslexic subjects. No mutations were identified. We conclude that DYX3 appears to be important for dyslexia susceptibility in many Finnish families, and a suggested linkage of dyslexia to chromosome 7q32 will need verification in other data sets.

Chromosome Mapping↗

PubMedDate not supplied

[Phonological and orthographic processes of reading and spelling in young adolescents and adults with and without dyslexia in German and English: impact on foreign language learning].

The present study addressed the question whether there is a relationship between phonological and orthographic processes of reading and spelling in adolescents and young adults with and without dyslexia in German and English. On the evidence of the Linguistic Coding Differences Hypothesis and results of the latest research in foreign language learning the hypothesis is tested if there is a relationship between phonological and orthographic knowledge on the one hand and decoding and spelling performance on the other hand in German adolescents and young adults reading and spelling German and English words. This hypothesis was tested with the statistical method of structural equation modeling and therefore the research population was divided into the following groups: group 1 with dyslexia in reading (n = 93), group 2 with dyslexia in spelling (n = 93), group 3 without dyslexia in reading (n = 95), and group 4 without dyslexia in spelling (n = 95). Results of data analysis show that the postulated prediction model fits only the data of the dyslexia group for reading and spelling, but not for the control group. Also the model for both groups does not fit. The results of the pilot study show that it is necessary to modify diagnostic instruments of measurement and to separate scales of phonological and orthographic processes.

Adolescent↗

PubMed2006

Evidence for ocular motor deficits in developmental dyslexia: application of the double-step paradigm.

PURPOSE: Dyslexia is a language-based learning disability characterized by difficulties with reading, spelling, and writing. Persons with dyslexia often have deficits in processing rapid temporal sensory information. There is also evidence of sensorimotor deficits in persons with dyslexia. Whether these deficits include ocular motor problems is still an open question. Some previous studies have shown an increased saccadic latency in dyslexics, whereas others have not reproduced this finding. The purpose of the present study was to investigate saccadic latency in young adults with dyslexia during the double-step paradigm, a task that requires rapid sequential visual information processing and saccade generation. The study hypothesis was that dyslexics have a longer saccadic latency in the second orthogonal saccade, a task that nondyslexics parallel process and perform rapidly. METHODS: Eight students with dyslexia and eight age-matched control subjects participated in the study. Their eye movements were monitored with the scleral search coil technique in simple saccade trials and in the double-step paradigm. The second saccade was either orthogonal or colinear to the first. Intersaccadic interval and latency were calculated for the second saccade. RESULTS: No difference in saccadic latency was found for colinear second saccades; however, dyslexics had significantly longer latencies for orthogonal second saccades. This included a subset of subjects who had longer latencies for orthogonal than for colinear saccades. CONCLUSIONS: The findings indicate that under certain conditions, when the demand for rapid visual information processing is high and a rapid saccade sequence is required, some persons with dyslexia show ocular motor deficits manifested by longer saccadic latencies.

Adult↗

PubMedDate not supplied

Naming difficulties in children with dyslexia: application of the tip-of-the-tongue paradigm.

The present study used the tip-of-the-tongue (TOT) experimental paradigm in a picture naming task to explore the source of the naming deficits of children with dyslexia. Compared with a control group of typically developing readers, the children with dyslexia showed fewer correct responses and spontaneous recalls, more don't know (DK) and TOT responses, and less accurate feeling of knowing (FOK) judgments. When they failed to retrieve a target word, the children with dyslexia did not differ from the control group in the partial semantic information they provided, but they gave less valid and more invalid partial phonological information. The children with dyslexia also benefited less from phonological cues. The phonologically related responses of the children with dyslexia elicited during the administration of the TOT procedure were related to their performance on a phonological awareness test. These findings suggest that the naming problems of children with dyslexia arise because of their difficulty in accessing the phonological word forms after the corresponding abstract lexical representation has been successfully accessed. The results are discussed in relation to the claim that two-stage models of naming can be profitably used in the early identification and treatment of reading disabilities.

Anomia↗

PubMedDate not supplied

Clock drawing in developmental dyslexia.

Although developmental dyslexia is often defined as a language-based reading impairment not attributable to low intelligence or educational or socioeconomic limitations, the behavioral manifestations of dyslexia are not restricted to the realm of language. Functional brain imaging studies have shed light on physiological differences associated with poor reading both inside and outside the classical language areas of the brain. Concurrently, clinically useful tests that elicit these nonlinguistic deficits are few. Specifically, the integrity of the dorsal visual pathway, which predominantly projects to the parietal cortex, remains underinvestigated, lacking easily administered tests. Here we present the Clock Drawing Test (CDT), used to test the visuoconstructive ability of children with and without dyslexia and garden-variety poor readers. Compared to typically reading children, many children with dyslexia and some garden-variety poor readers showed significant left neglect, as measured by the distribution of figures drawn on the left clock face. In the poor readers with dyslexia, we observed spatial construction deficits like those of patients with acquired right-hemisphere lesions. The results suggest that in some children with dyslexia, right-hemisphere dysfunction may compound the phonological processing deficits attributed to the left hemisphere. The CDT provides an easy opportunity to assess skills known to be associated with right-hemisphere parietal function. This test can be easily administered to children for both clinical and research purposes.

Child↗

PubMed1989

Visual persistence and adult dyslexia.

Visual persistence was investigated in adults with and without dyslexia in order to determine whether the adults with dyslexia demonstrate problems similar to those found in childhood dyslexia. Using a temporal separation threshold measure and procedures derived from signal detection theory, sensitivity to sequentially presented form information was determined for the two types of adults. The results showed that the sensitivity of the adults with dyslexia was impaired relative to that of the nondisabled adults when parts of a test stimulus were presented to adjacent retinal areas. This result suggests that, under certain conditions, visual persistence is longer for adults with dyslexia. The results are discussed within the context of a recent theory of dyslexia (Lovegrove, Martin & Slaghuis, 1986) that incorporates the operation of sustained and transient visual mechanisms.

Adolescent↗

PubMed1991

Effects of reading and writing on cerebral laterality in good readers and children with dyslexia.

The present study evaluated the idea that the hemisphere-specific cognitive demands of reading and writing may induce task-specific maladaptive patterns of language lateralization in children with dyslexia. Situation-specific lateralization was examined in a repeated measures design under three dichotic listening conditions: baseline, concurrent reading, and concurrent writing. Twelve males with phonological dyslexia, 8 to 12 years old, were compared to 12 age-matched and 12 younger reading-matched good readers. Lateralization patterns were examined for condition-specific relationships to pseudoword decoding, word recognition, reading comprehension, spelling, and arithmetic. The results show that dyslexia is not related to incomplete lateralization or to a failure to inhibit verbal processing in the right hemisphere during reading and writing. Reading increased the lateralization of the children with dyslexia, which had a negative relation to arithmetic; writing caused a decrease in lateralization, which was linked specifically to deficits in phonological decoding and visual word recognition. The results suggest that children with dyslexia suffer from a selective linguistic vulnerability to left-hemisphere interference from the idiosyncratic attentional and processing demands of particular school tasks. Dyslexia is a much more dynamic and environmentally sensitive disorder than previously thought.

Achievement↗

PubMedDate not supplied

Foundation-level dyslexia: assessment and treatment.

It is supposed that there is an early, foundation stage in beginning reading during which children acquire basic letter-sound knowledge, a capability for alphabetic processing, and a logographic sight vocabulary. An assessment of foundation processes was administered to Scottish children with reading difficulties (n = 51) and to reading-level-matched controls (n = 56). The results suggested that the foundation is normally in place by the time a reading age of about 7 years has been achieved. Foundation-level dyslexia is identifiable in children with reading difficulty whose reading ages fall below this level. Differing patterns of dyslexia were observed, depending on whether the primary effect was on letter-sound learning (literal dyslexia), the acquisition of the alphabetic process (alphabetic dyslexia), or retention of a sight vocabulary (logographic dyslexia). Balanced dyslexia, in which both alphabetic and logographic functions were impaired, was also found. Some implications for assessment and treatment are discussed.

Child↗

PubMed2007

Reasoning and dyslexia: a spatial strategy may impede reasoning with visually rich information.

Bacon, Handley, and Newstead (2003, 2004), have presented evidence for individual differences in reasoning strategies, with most people seeming to represent and manipulate problem information using either a verbal or a spatial strategy. There is also evidence that individuals with dyslexia are inclined to conceptualise information in a visuo-spatial, rather than a verbal, way (e.g. von Károlyi et al., 2003). If so, we might expect a higher proportion of individuals with dyslexia to be spatial reasoners, compared with individuals who do not have dyslexia. The study reported here directly compared strategies reported by these two groups of participants on a syllogistic reasoning task. Moreover, problem content was manipulated so that reasoning across concrete and abstract materials could be compared. The findings suggest that whilst most individuals without dyslexia use a verbal strategy, reasoners with dyslexia do tend to adopt a spatial approach, though their performance is impaired with visually concrete materials. However, when reasoning with more abstract content, they perform comparably with non-dyslexic controls. The paper discusses these results in the light of recent research which has suggested that visual images may impede reasoning, and considers how individuals with dyslexia may differ from other reasoners.

Adult↗

PubMedDate not supplied

[Dysphasia and dyslexia in the light of PASS theory].

INTRODUCTION: The PASS theory of intelligence understands the cognitive function as an information process or program that can be differentiated in planning, attention, successive and simultaneous. Every process is linked to an anatomical region: planning to frontal cortex, attention to frontal cortex and subcortical structures, successive to frontal cortex and non-frontal cortex and simultaneous to non-frontal cortex. Effective remediation is possible when a PASS pattern is known. OBJECTIVE: To verify whether dysphasia and dyslexia have a typical PASS pattern. PATIENTS AND METHODS: The subjects were divided in three groups comprising 12 children with dysphasia, 12 children with dyslexia and 10 children with dysphasia and dyslexia, all of them between 6 years and 12 years of age, the majority boys. All children were administered the DN:CAS test to define the PASS pattern. A control group with 45 normal children was used. RESULTS: Dysphasia shows poor successive and simultaneous process. Dyslexia shows poor successive process. The successive deficiency is poorer and in different way in dyslexia than in dysphasia which is inferable from comparative analysis between groups. CONCLUSIONS: Dysphasia and dyslexia show a typical PASS pattern that allows an appropriate remedial training as a neurocognitive approach. The PASS diagnosis is a psychogenetic diagnosis which is different from the usual diagnosis based on semiology or results obtained with tests that explore non-PASS cognitive function.

Aphasia↗

PubMed2004

[Educational implications of the cognitive impairment in developmental dyslexia].

AIMS: In this study we review the main theories put forward to account for developmental dyslexia, as well as the intervention procedures deriving from these theories that enjoy the most empirical support. DEVELOPMENT: Developmental dyslexia is a complex disorder that reflects cognitive impairment related to neurobiological anomalies, although researchers still do not agree on fundamental aspects regarding its aetiology. There are at present a number of different theories that can be grouped in two antagonistic lines of work. On the one hand, one of them considers that the exclusive and direct cause of dyslexia is a specific cognitive disorder. On the other hand, however, there are several theories that consider the impairments experienced by dyslexic patients to be part of a wide range of tasks and processes that are secondary to an underlying primary deficit. As a consequence of the progress made in the characterisation of dyslexia, an unprecedented effort has been made in recent decades in the development of intervention programmes and in the analysis of their effectiveness. CONCLUSIONS: Research into the explanation for dyslexia finds itself faced with the challenge of determining whether the different cognitive problems identified in dyslexic patients represent different cognitive routes towards the same dyslexic phenotype, whether they correspond to different types of dyslexia or whether they refer to the sum of the problems resulting from different comorbid conditions. Until this issue is resolved, as educators, we must carry out more comprehensive evaluations in order to determine the profile of the difficulties that are experienced in each particular case and to be able to tailor the interventions employed in this enigmatic problem.

Cognition Disorders↗

PubMed1984

New approaches to the developmental dyslexias.

Although Hinshelwood (10-15), at the turn of the century, was interested in both analysis of individual cases and comparisons between acquired and developmental dyslexia, the most widespread approach to the developmental dyslexias has been the investigation of large groups of dyslexics in comparison to normal readers on a variety of tests. These studies ignore the heterogeneity of the disorder. In contrast, progress has been made in the investigation of acquired disorders of reading by conducting individual psycholinguistic analyses of reading difficulties and utilizing input from cognitive psychology to construct explanatory models and theories. Two of the disorders described and elucidated by this approach are acquired surface dyslexia, in which there is an impairment in whole word recognition and overreliance on sounding out words to obtain their pronunciation and meaning, and acquired phonological dyslexia, in which whole word recognition is good but sounding out of words and nonwords is poor. This approach has recently been used with cases of developmental dyslexia. This chapter compares and contrasts the pattern of performance of different dyslexic children when investigated in this way. Two of the children described are developmental phonological dyslexics; one is a developmental surface dyslexic. The developmental phonological dyslexics are poorer at reading words than non-words; the developmental surface dyslexic performs equally well on both. The developmental surface dyslexic is significantly influenced by spelling-to-sound regularity; the developmental phonological dyslexics are unaffected by this linguistic dimension. The developmental surface dyslexic makes more neologistic responses than the developmental phonological dyslexics, and also makes more valid errors. The developmental phonological dyslexics make derivational, pseudoderivational, and visuosemantic errors. Both groups make visual errors. The developmental phonological dyslexics are significantly impaired when stimuli are presented in a way that prohibits global analysis; the developmental surface dyslexic is unaffected by this manipulation. The developmental surface dyslexic makes homophone confusions, but these are not made by the developmental phonological dyslexics. (ABSTRACT TRUNCATED AT 400 WORDS)

Child↗

PubMed1993

Dyslexia, left-handedness, and immune disorders.

OBJECTIVE: To illuminate a possible three-way association between dyslexia, immune disorders, and left-handedness. Geschwind's, Behan's, and Galaburda's hypotheses have been of special interest in this connection. DESIGN: Statistical analysis based on general assessment of the prevalence of the three aforementioned conditions. PARTICIPANTS: There were 734 children included from a total of 1165 in grade 6 (about 12 years of age) in the municipality of Stavanger, Norway. SETTING: Educational and demographic statistics indicate that the municipality of Stavanger is representative of the national population at large regarding the three conditions examined. MAIN OUTCOME MEASURES: A screening test with high reliability and validity was used to assess reading ability. It measured word recognition and phonological decoding. The questionnaires that recorded the students' handedness and immune disorders were filled in by the parents. Handedness was assessed by a Norwegian version of the Oldfield Inventory. A questionnaire concerning allergies and asthma was used to assess the prevalence of immune disorders. RESULTS: The bivariate analyses disclosed a significant association between handedness and dyslexia and a significant but weak association between handedness and immune disorders. No significant association was found between dyslexia and immune disorders. A triadic analysis yielded the following: 66.7% of the left-handed dyslexic children had immune disorders (P > .05); 42.1% of the left-handed children with immune disorders had dyslexia (P < .01); and 32% of the dyslexic children with immune disorders were left-handed (P < .05). CONCLUSIONS: There seems to be some association between dyslexia, left-handedness, and immune disorders. Of the three factors, handedness seems to be the most important association. The findings lend some support to the one interpretation of the hypotheses of Geschwind, Behan, and Galaburda.

Adolescent↗

PubMed1993

Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging.

OBJECTIVE: To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities. DESIGN: Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history. SETTINGS: Hospital pediatric neurology clinic and private reading clinic. PATIENTS AND OTHER PARTICIPANTS VOLUNTEERS: individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years). INTERVENTIONS: Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images. MAIN OUTCOME MEASURES: (1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum. RESULTS: All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12). CONCLUSIONS: Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.

Adolescent↗

PubMedDate not supplied

The use of orthographic and phonological strategies for the decoding of words in children with developmental dyslexia and average readers.

Children with developmental dyslexia are known to have problems with phonological awareness and, in particular, with phonological decoding. This study was aimed at determining the relationship between orthographic and phonological decoding strategies used by a group of children with developmental dyslexia and two groups of children who were average readers (matched on reading age and chronological age, respectively). The three groups of children, 12 in each, were presented with single words, either visually or orally. The children were asked to pronounce these words using either an orthographic (spelling) strategy following mental deletion of one letter, or a phonological (sounding) strategy following mental deletion of one sound. Analysis of variance (ANOVA) revealed that the reading age control group were more accurate when using phonological strategies than when using orthographic strategies, whereas the chronological age control group generally showed superior orthographic and phonological processing abilities compared with both the developmental dyslexia and reading age control groups. Compared with both chronological and reading age control groups, children in the developmental dyslexia group had more difficulty when using a phonological strategy, particularly when words were presented auditorily. However, compared with their performance on phonological tasks, the developmental dyslexia group performed at a level commensurate with their age when carrying out the orthographic tasks.

Child↗

PubMed1994

Family patterns of developmental dyslexia: clinical findings.

Two separate groups of dyslexia families were ascertained through probands attending special schools for dyslexic students. An additional control group of families was ascertained through randomly selected students attending public schools. The 3 groups were interviewed by questionnaire about the family's demographic characteristics, and about the incidence of reading and spelling disorders in all first and second order relatives. One group of dyslexia families was also examined by standardized intelligence and academic achievement tests. Developmental dyslexia was found to aggregate in families; there were 4-5 times as many affected males as females among clinically identified students attending the special schools, but the sex ratio of affected relatives after probands had been excluded was approximately 1.4 males for every female. Sibs were at greater risk for reading difficulties when one parent was affected than when neither parent was affected. Sibs were also at greater risk for academic difficulties, and affected sibs were more severely impaired, when the father rather than the mother was the affected parent. In dyslexia families with 2 affected parents, the sibs were at greater risk, and the affected sibs were more severely impaired, than in families where only one parent was affected. Moreover, in families with 2 affected parents, both of the parents were more severely impaired in reading and spelling than parents of the same sex in families with one affected parent. Some indirect evidence is presented that assortative mating may codetermine patterns of affectedness in dyslexia families.

Dyslexia↗