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Results for “Developmental dyslexia”

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PubMed1994

Dichotic listening performance under high and low lexical work load in subtypes of developmental dyslexia.

This study examined dichotic listening performance in different subtypes of developmental dyslexia under high and low verbal work load conditions. Free recall tests of digits and words were administered to 320 dyslexic children from grade 3 to grade 10 and their matched controls. Results indicate significant differences within subtypes. Surface dyslexics manifested extreme ear neglect or total performance collapse but only under high verbal work load conditions. Phonological dyslexia was distinguished by poor total performance both under high and low work load levels. Visuo-motor dyslexics, however, did not differ in any measure from their controls. These results lend support to the contention that the main neuropsychological factor impeding reading acquisition varies according to dyslexia subtype.

Adolescent↗

PubMed2003

Auditory and visual automatic attention deficits in developmental dyslexia.

Several studies have provided evidence for a phonological deficit in developmental dyslexia. However, recent studies provide evidence for a multimodal temporal processing deficit in dyslexia. In fact, dyslexics show both auditory and visual abnormalities, which could result from a more general problem in the perceptual selection of stimuli. Here we report the results of a behavioral study showing that children with dyslexia have both auditory and visual deficits in the automatic orienting of spatial attention. These findings suggest that a deficit of selective spatial attention may distort the development of phonological and orthographic representations that is essential for learning to read.

Acoustic Stimulation↗

PubMedDate not supplied

Treatment of developmental dyslexia: a review.

Remarkably few research articles on the treatment of developmental dyslexia were published during the last 25 years. Some treatment research arose from the temporal processing theory, some from the phonological deficit hypothesis and some more from the balance model of learning to read and dyslexia. Within the framework of that model, this article reviews the aetiology of dyslexia sub-types, the neuropsychological rationale for treatment, the treatment techniques and the outcomes of treatment research. The possible mechanisms underlying the effects of treatment are discussed.

Child↗

PubMed2001

Callosal transfer in different subtypes of developmental dyslexia.

Sixteen controls (age 6-13) and 20 native Italian children with developmental dyslexia (age 7-15) received a test of callosal transfer of tactile information. Among the dyslexic children, 7 had a diagnosis of L-type, 7 of P-type and 6 of M-type dyslexia according to Bakker's classification. Both control children and children with dyslexia made a significantly larger number of errors in the crossed localization condition (implying callosal transfer of tactile information) vs. the uncrossed condition. In the same condition, children with dyslexia made a significantly larger number of errors than controls. In the crossed localization condition L-types and M-types made a significantly larger number of errors than P-types and controls, while there was no significant difference in performance between P-types and controls. These findings are discussed in terms of defective callosal transfer or deficient somatosensory representation in children with L- and M-dyslexia.

Adolescent↗

PubMed2003

The perception of "sine-wave speech" by adults with developmental dyslexia.

Numerous studies have shown that, as a group, children or adults with developmental dyslexia perceive isolated syllables or words abnormally. Continuous speech containing reduced acoustic information also might prove perceptually difficult to such listeners. They might, however, exploit the intact syntactic and semantic features present in whole utterances, thereby compensating fully for impaired speech perception. "Sine-wave speech" sentences afford a test of these competing possibilities. The sentences contain only 4 frequency-modulated sine waves, lacking many acoustic cues present in natural speech. Adults with and without dyslexia were asked to orally reproduce 9 sine-wave utterances, each occurring in 4 immediately successive trials. Participants with dyslexia reported fewer words than did control listeners. Practice, phonological contrasts, and word position affected both groups similarly. Comprehension of sine-wave sentences seems impaired in many, but not all, adults with dyslexia. A reduced auditory memory capacity may contribute to this deficit.

Adult↗

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↗

PubMed2002

Executive functioning in adults and children with developmental dyslexia.

The performance of developmentally dyslexic children and adults was studied upon a range of tasks that involved executive functioning. Both adult and child samples of dyslexics were found to under-perform on the group-embedded figures test. This test required the identification of constituent parts from within complex visual arrays, with good performance necessitating the inhibition of the processing of the surrounding context. A general deficit on visual-spatial tasks was eliminated as an explanation as dyslexics performed normally upon a range of other non-verbal assessments. The dyslexics consistently demonstrated a deficit in digit span tasks, a decrement that was increased with distractors, again suggesting difficulties in inhibiting the processing of the surrounding context. A deficit was also identified upon a verbal fluency task without a deficit in vocabulary level. Additionally, a specific deficit in the recollection of the temporal order of the presentation of items was in evidence, without a deficit in the recognition of the items themselves. The findings taken as a whole suggest that dyslexic individuals show deficiencies in executive functions relating to inhibition of distractors and to sequencing of events, a set of tasks associated with left prefrontal cortex functioning in the acquired neuropsychology literature.

Adolescent↗

PubMed2003

Developmental dyslexia in different languages: language-specific or universal?

Most of the research on developmental dyslexia comes from English-speaking countries. However, there is accumulating evidence that learning to read English is harder than learning to read other European orthographies (Seymour, Aro, & Erskine, 2003). These findings therefore suggest the need to determine whether the main English findings concerning dyslexia can be generalized to other European orthographies, all of which have less irregular spelling-to-sound correspondences than English. To do this, we conducted a study with German- and English-speaking children (n=149) in which we investigated a number of theoretically important marker effects of the reading process. The results clearly show that the similarities between dyslexic readers using different orthographies are far bigger than their differences. That is, dyslexics in both countries exhibit a reading speed deficit, a nonword reading deficit that is greater than their word reading deficit, and an extremely slow and serial phonological decoding mechanism. These problems were of similar size across orthographies and persisted even with respect to younger readers that were at the same reading level. Both groups showed that they could process larger orthographic units. However, the use of this information to supplement grapheme-phoneme decoding was not fully efficient for the English dyslexics.

Adolescent↗

PubMed1991

Word-finding ability and design fluency in developmental dyslexia.

Certain oral as well as visual language disorders now appear characteristic of the developmental dyslexia syndrome. Recent research has revealed word-finding difficulties in dyslexic children but has left unanswered questions about specificity and causality. Verbal and non-verbal fluency in dyslexics and non-dyslexic CA- and RA-matched controls were measured by means of cued lexical retrieval and stick design tasks. Evidence for dyslexia-related difficulties was found only at the word form level of access. At the semantic level, dyslexics' word finding was superior. Non-verbal (design) fluency was normal. Such findings implicate long-term linguistic memory processes in dyslexia and are consistent with neurocognitive models that emphasize diffuse left hemisphere dysfunction.

Attention↗

PubMed1988

Developmental dyslexia and dysgraphia persistence in middle age.

J.R. is a middle-aged man whose developmental dyslexia and dysgraphia have persisted in a problematic fashion for the 30 years since he left school. He is a phonological dyslexic. Whereas surface dyslexics operate on reading units that are too small, Mr. R operates on units that are too large. Spelling exhibits both regularity and lexicality effects. These seemingly contradictory results are consistent with a two-route model of spelling in which each route is functioning with approximately 50% efficiency. Performance on paralinguistic rhyming tasks is poor and shows no recovery in comparison to younger developmental phonological dyslexics. Difficulties with higher-order sound segmentation, analysis, or organization may underly the lifelong literacy problems.

Agraphia↗

PubMed1991

Interventions based on the multiple connections model of reading for developmental dyslexia and acquired deep dyslexia.

This paper deals with intervention strategies for developmental and acquired dyslexia. In Study 1 two alternative strategies for developmental surface dyslexia (dysfunctional connection between the whole word orthographic code and the phonetic or name code) were compared. In both the initial study and replication study, a modification of the selective reminding technique was superior to a traditional multisensory technique in beginning readers, presumably because it facilitated word finding or prelexical access to a phonetic code. In Study 2 an adolescent with acquired deep dyslexia (dysfunctional connection between letter and phonemic codes) who had had his angular gyrus (site of grapheme-phoneme correspondence) surgically removed, recovered reading function after a four-month phonemic analysis training program. Further research is needed to evaluate the efficacy of theory-based intervention strategies in children with developmental reading disorders unrelated to focal lesions and in adults with acquired reading disorders related to focal lesions.

Journal Article↗

PubMed1986

Magnetic resonance imaging of brain anatomy in severe developmental dyslexia.

The brain anatomy of ten men (aged 18 to 28 years) with persistent, severe developmental dyslexia was examined with magnetic resonance imaging to explore the possibility of visualizing pathology not seen in previous computed tomographic scan studies. Nine of the ten examinations were clinically normal. One showed a focal finding thought to be incidental to dyslexia. The volume of the temporal lobes was judged to be symmetrical in nine of ten examinations, a finding supportive of previous computed tomographic scan and neuropathologic reports of unusual symmetries of posterior brain regions. Thus, despite its sensitivity, magnetic resonance imaging failed to identify a common focal pathology. The choice of imaging planes (particularly coronal) and lack of bone artifact may, however, prove useful for studying macroscopic asymmetries in dyslexia.

Adolescent↗

PubMed1996

Family patterns of developmental dyslexia. Part III: Spelling errors as behavioral phenotype.

The major trends in current research on developmental dyslexia assume that impaired phonological processing is the core deficit in this disorder. Our earlier studies indicated that half of all dyslexic persons have significant deficits of bimanual motor coordination, and that impaired temporal resolution in motor action may identify a vertically transmitted behavioral phenotype in familial dyslexia. This report examines the relationship between spelling errors as a measure of impaired phonological processing and motor coordination deficits in the same dyslexia families. Affected family members with motor coordination deficits made significantly more dysphonetic spelling errors than dyslexic family members without motor deficits, but there was no evidence that dysphonetic spelling is vertically transmitted in dyslexia families. On the other hand, affected offspring of affected parents with motor coordination deficits made relatively more dysphonetic spelling errors than the affected offspring of parents without motor coordination deficits. We suggest that dysphonetic spelling may be one outward expression of a vertically transmitted behavioral phenotype of impaired temporal resolution that is clearly expressed in coordinated motor action.

Child↗

PubMed2004

Developmental dyslexia: ERP correlates of anomalous phonological processing during spoken word recognition.

Ample evidence suggests that developmental dyslexia results from a phonological deficit that may not be reducible to a low-level auditory deficit. Yet, on-line phonological processing (in)capacities in dyslexics remain virtually unexplored, as studies have typically focused on either meta-phonological awareness tasks or, at the other extreme, basic perceptual tasks. The present study investigates event-related potential (ERP) correlates of implicit phonological processing during the recognition of spoken words in dyslexic and normally reading children (7-10 years). We examined general ERP morphology and alliteration priming effects on ERP measures in an auditory lexical decision task. Primes were words (Experiment 1) and non-words (Experiment 2). Alliteration priming effects suggested a distinct pattern of normal versus anomalous aspects of spoken word processing in dyslexic children. Whereas dyslexics showed deviant priming effects in earlier time windows encompassing the N1 and N2, later N400 priming effects were comparable to those of normal readers. The same pattern of results was also present in group comparisons of general ERP morphology. These findings suggest that dyslexics have selective processing anomalies at an earlier phonetic/phonological level, while processing at a later phonological/lexical level proceeds normally. In particular, our results indicate an anomalous contribution of phonological (word onset) information to the processing of spoken words, which may be related to time-course aspects of phonetic/phonological processing.

Acoustic Stimulation↗

PubMed1987

Regional cerebral blood flow in severe developmental dyslexia.

Regional cerebral blood flow was measured under three task conditions in 14 men with severe developmental dyslexia and their control subjects using a xenon 133 inhalation technique. No group differences in overall level or in pattern of gray matter flow were seen under relatively undemanding cognitive conditions. Despite minimal group differences in performance, the dyslexic group showed an increased hemispheric asymmetry (left greater than right) on a semantic classification task and a reduced anteroposterior difference on a line orientation task relative to controls. The exaggerated asymmetry suggests the possibility of less efficient information processing or inadequate bihemispheric integration. The reduced anteroposterior gradient may reflect a deficit in the ability of frontal systems to respond adequately to cognitive demands.

Adult↗

PubMed1986

Effects of piracetam on developmental dyslexia.

A new class of drugs (nootropics) are viewed from the perspective of their neuropsychological effect upon developmental dyslexia. Evidence from both the preclinical and clinical work conducted on Piracetam is briefly reviewed. The latest research on the effects of Piracetam in dyslexia shows a convergence of results. Attempts to replicate these results with dyslexia have only met with success in the areas of reading rate. In an attempt to find an independent replication of the Chase et al. (1984) finding, the author provides additional evidence on the effects of Piracetam on reading Rate X Accuracy in dyslexics.

Animals↗

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↗

PubMed1985

Developmental dyslexia: four consecutive patients with cortical anomalies.

We report the neuroanatomical findings in 4 consecutively studied brains of men with developmental dyslexia. The patients, who ranged in age between 14 and 32 years, were diagnosed as dyslexic during life. Nonrighthandedness and several autoimmune and atopic illnesses were present in the personal and family histories. All brains showed developmental anomalies of the cerebral cortex. These consisted of neuronal ectopias and architectonic dysplasias located mainly in perisylvian regions and affecting predominantly the left hemisphere. Furthermore, all brains showed a deviation from the standard pattern of cerebral asymmetry characterized by symmetry of the planum temporale. The neuroanatomical findings in these 4 patients are discussed with reference to developmental cortical anomalies, cerebral asymmetries, reorganization of the brain after early lesions, and the association between learning disorders, left handedness, and diseases of the immune system.

Adolescent↗