Subtypes Of Developmental Dyslexia Research Articles

Subtypes of Developmental Dyslexia

In light of teaching students with dyslexia and other learning difficulties (LD), neuroscientists claim that such deficiencies happen due to a neural base, depending on biological and environmental factors, and experience developing properties and improving reading skills. The research claims two types of dyslexia: developmental (or innate) and deep (or acquired due to brain traumas or diseases). This article researches developmental dyslexia (DD), which may be primary and secondary. DD is divided into two main subtypes: surface and phonological While reading; our brains must "rewire" neural circuits initially used for other tasks, such as visual and speech processing and attention and cognition. Psycholinguistics investigates the cognitive process of perception, production, and general use of language. This article revises teaching English in light of neuroscience, psycholinguistics, and appropriate methods to train working memory and other ways to overcome DD and its subtypes.

Attention dysfunction subtypes of developmental dyslexia.

BackgroundPrevious studies indicate that many different aspects of attention are impaired in children diagnosed with developmental dyslexia (DD). The objective of the present study was to identify cognitive profiles of DD on the basis of attentional test performance.Material/Methods78 children with DD (30 girls, 48 boys, mean age of 12 years ±8 months) and 32 age- and sex-matched non-dyslexic children (14 girls, 18 boys) were examined using a battery of standardized tests of reading, phonological and attentional processes (alertness, covert shift of attention, divided attention, inhibition, flexibility, vigilance, and visual search). Cluster analysis was used to identify subtypes of DD.ResultsDyslexic children showed deficits in alertness, covert shift of attention, divided attention, flexibility, and visual search. Three different subtypes of DD were identified, each characterized by poorer performance on the reading, phonological awareness, and visual search tasks. Additionally, children in cluster no. 1 displayed deficits in flexibility and divided attention. In contrast to non-dyslexic children, cluster no. 2 performed poorer in tasks involving alertness, covert shift of attention, divided attention, and vigilance. Cluster no. 3 showed impaired covert shift of attention.ConclusionsThese results indicate different patterns of attentional impairments in dyslexic children. Remediation programs should address the individual child’s deficit profile.

EEG correlates of clinical subtypes of developmental dyslexia: Independent component analysis study

P.H.T. Leppanen, K. Lohvansuu, J. Bartling, J. Bruder, F. Honbolygo, J.A. Hamalainen, S. Iannuzzi, R. Nenert, J.-F. Demonet, G. Schulte-Korne, V. Csepe Department of Psychology, University of Jyvaskyla, Finland Research Institute for Psychology, Hungarian Academy of Science, Hungary Department of Child and Adolescent Psychiatry and Psychotherapy, University Hospital Munich, Munich, Germany Memory Center Department of Clinical Neuroscience CHUV University Hospital Lausanne, Switzerland

Subtypes of developmental dyslexia in transparent orthographies: A comment on Lachmann and Van Leeuwen (2008)

Lachmann and Van Leeuwen (2008) proposed two diagnostic subtypes of developmental dyslexia in a language with transparent orthography (German). The classification was based on reading time, rather than reading errors, for lists of words and nonwords. The two subtypes were “frequent-word reading impaired” (FWRI) and “nonword reading impaired” (NWRI). Notably, FWRI were very slow in reading high-frequency words but as fast as controls in reading nonwords; ca. one-third of these children showed this “reversed lexicality effect” in a particularly marked fashion (i.e., read nonwords two to three times faster than high-frequency words). Since Italian is a highly transparent language, we applied this classification to 87 third- and sixth-grade dyslexics from various previously published studies. Some children showed a marked lexicality effect, while others showed small or no difference between word and nonword reading speed. However, regardless of stimulus length, grade and presence/absence of a previous language delay, no child showed a marked reversed lexicality effect; more generally, no child could be classified as FWRI. These findings indicate that the search for subtypes of developmental dyslexia in transparent orthographies still constitutes an open question.

Surface and phonological developmental dyslexia in Greek

The present study examined whether equivalents of surface and phonological subtypes of developmental dyslexia could be found among a sample of 84 poor readers aged 9–12 years in Greece. Word reading latency was used as a measure of lexical skill, and nonword reading accuracy was used as a measure of nonlexical skill. A simple regression of word reading latencies on nonword reading accuracy scores was performed for 42 developing readers. A total of 2 poor readers with accurate nonword reading plus slow word reading relative to controls (equivalents of surface dyslexia) and 2 poor readers with inaccurate nonword reading plus fast accurate word reading relative to controls (equivalents of phonological dyslexia) were identified from amongst the sample of poor readers. Further testing of these 4 cases on measures of irregular-word and nonword spelling revealed additional evidence of a dissociation between lexical and nonlexical impairments. These results support the notion that dual-route models can be used to explore individual differences among dyslexic readers in transparent orthographic systems such as Greek. An attempt is also made to interpret the results in terms of a double deficit theory of dyslexia (Wimmer, Mayringer, & Landerl, 2000; Wolf & Bowers, 1999).

Cognitive profiling and preliminary subtyping in Chinese developmental dyslexia

The present study examined the cognitive profile and subtypes of developmental dyslexia in a nonalphabetic script, Chinese. One hundred and forty-seven Chinese primary school children with developmental dyslexia were tested on a number of literacy and cognitive tasks. The results showed that rapid naming deficit and orthographic deficit were the two most dominant types of cognitive deficits in Chinese developmental dyslexia, and that rapid naming and orthographic processing had significant unique contributions to literacy performance. Seven subtypes of dyslexia – global deficit, orthographic deficit, phonological memory deficit, mild difficulty, and three other subtypes with rapid-naming-related deficits – were identified using scores of the cognitive tasks as classification measures in cluster analyses. These subtypes were validated with a behaviour checklist and three literacy measures. The authors suggested that orthographic and rapid naming deficits in Chinese dyslexic children might pose an interrelated problem in developing orthographic knowledge and representation. Therefore, orthographic-related difficulties may be the crux of the problem in Chinese developmental dyslexia.

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.

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

Phonological dyslexics (Ph-DYS) are characterized by a phonological deficit, while surface dyslexics (S-DYS) are characterized by an orthographic deficit. Four issues were addressed in this study. First, we determined the proportion of Ph-DYS and S-DYS in a population of French dyslexics by applying Castles and Coltheart's (1993) regression method to two previously unused diagnostic measures: pseudo-word and irregular-word processing time. Thirty-one dyslexics were matched to 19 average readers of the same age (10 years, CA controls) and to 19 younger children of the same reading level (8 years, 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; however, the S-DYS profile almost disappeared. Next, we examined the reliability of these subtypes across different measures of phonological and orthographic skills. Compared to RL controls, both groups of dyslexics were found to be impaired only in phonological skills, either in processing time (Ph-DYS) or in accuracy (S-DYS). Then we assessed the moment at which the two dissociated profiles emerged in the course of cognitive development. In order to do so, we examined earlier longitudinal data, collected when the children were 7 and 8 years old, and found that only the S-DYS's orthographic deficit increased with development. Last, we 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. These data suggest that developmental dyslexia could be largely accounted for by an underlying phonological impairment.

Visual and Auditory Processing Impairments in Subtypes of Developmental Dyslexia: A Discussion

There has been a large body of research exploring sensory processing deficits in dyslexia, in both the visual and the auditory domains. Recently, there has also been evidence to suggest that dyslexia may be a heterogeneous disorder, with different patterns of dyslexia being identifiable. In this paper, we examine the relationship between these two bodies of research. First, we briefly review the evidence for sensory processing impairments in dyslexia, in both the visual and the auditory domains. Second, we consider how such deficits might affect the development of different component processes in reading and, therefore, be associated with different subtypes of dyslexia. Finally, we present some illustrative data, which points to the importance of considering different component processes of reading when investigating sensory processing deficits in dyslexia.

Subtypes of developmental dyslexia and lexical acquisition

Although much has been learned about the nature and etiology of impairments in sublexical translation skills, less is known about the difficulties of children who are poor at recognising words as whole orthographic units. In the research described here, an attempt was made to look closely at the process these poor readers go through when trying to acquire new lexical information. Groups of poor readers were required to learn the pronunciations of a set of “irregular” nonsense words over a series of training sessions. There was an imperfect correspondence between the orthographic and phonological forms of these items, so grapheme-phoneme conversion rules could not be used (e. g., macht was pronounced “mot”). The results indicated that this learning task distinguishes between poor readers with a specific lexical deficit and those with a different type of reading difficulty. Ways in which this kind of task might usefully be employed in future research in this area are discussed.

Family patterns of developmental dyslexia, part II: behavioral phenotypes.

The motor control of bimanual coordination and motor speech was compared between first degree relatives from families with at least 2 dyslexic family members, and families where probands were the only affected family members. Half of affected relatives had motor coordination deficits; and they came from families in which probands also showed impaired motor coordination. By contrast, affected relatives without motor deficits came from dyslexia families where probands did not have motor deficits. Motor coordination deficits were more common and more severe among affected offspring in families where both parents were affected than among affected offspring in families where only one parent was affected. However, motor coordination deficits were also more common and more severe in affected parents when both parents were affected than among affected parents in families where only one parent was affected. We conclude that impaired temporal resolution in motor action identifies a behavioral phenotype in some subtypes of developmental dyslexia. The observed pattern of transmission for motor deficits and reading impairment in about half of dyslexia families was most congruent with a genetic model of dyslexia in which 2 codominant major genes cosegregate in dyslexia pedigrees where the proband is also motorically impaired.

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.

Dichotic listening performance in subtypes of developmental dyslexia and a left temporal lobe brain tumor contrast group

This study examined dichotic listening performance in three subtypes of developmental dyslexia and in children with left temporal lobe brain tumors (clinical contrast group). Each child was administered a free-recall CV syllable dichotic paradigm (30 pairs). Analysis of variance and Tukey-HSD pairwise follow-up comparison indicated that the dichotic listening performance of the left temporal lobe brain tumor contrast group (strong LEA/right ear suppression) was significantly different from those of the visual-spatial/dyseidetic (strong REA/left ear depression) and mixed (moderate REA/bilateral ear suppression) dyslexic subtypes. The language disorder/dysphonetic dyslexic subtype demonstrated a REA with right ear depression. Closer inspection of the individual performances of the language disorder/dysphonetic dyslexic subtype revealed a bimodal distribution with 12 subjects demonstrating a strong LEA/right ear suppression and 8 subjects exhibiting a strong REA/left ear depression. These results lend support for the contention that the dyslexic population is heterogeneous in nature with each subgroup exhibiting (1) a distinct neuropsychological test profile and reading pattern and (2) a pattern of performance on the dichotic listening task which is consistent with what would be expected based upon the pattern of dysfunction exhibited on neuropsychological evaluation.

Dyslexics and normal beginning readers read by different strategies: a comparison of strategy distributions in dyslexic and normal readers1

Research on subtypes of developmental dyslexia often implies that dyslexics fall into discrete groups with different reading strategies and underlying deficits. Recently this assumption has been questioned (Stanovich 1989). However, the distributions of reading strategies in groups of dyslexic and normal readers have never been compared. With this aim, the present study compared the individual reading strategies in a group of 26 severely impaired developmental dyslexics with strategies in a reading‐level‐matched group of 26 younger, normal readers. It was found that reading skills and strategies were distributed over a continuum in both groups. The dyslexic subjects were specifically impaired in phonological processing, however, and half of them read by means of more whole‐word oriented strategies than any of the normal controls. These findings contest current subtype theory and clinical practice (e.g. Boder & Jarrico 1982).

Subtypes of developmental dyslexia: The influence of definitional variables

The purpose of this study was to investigate the hypothesis that the manner in which a reading disability is defined will influence the conclusions that are made about the characteristics of the disability. To test this hypothesis, learning disabled and normally achieving children, aged 6 to 14, were administered tasks measuring grammatical, shortterm memory, phonological, reading, and visual-spatial skills. The poor readers were divided into groups of poor readers with 1. inadequate phonics skills, 2. inadequate word recognition skills, 3. adequate word recognition skills but low reading comprehension scores, and 4. adequate word recognition scores but a slow reading speed.

Cerebral dominance and subtypes of developmental dyslexia

Evidence of different syndromes of developmental dyslexia raises the question of the interaction between dyslexic types and patterns of cerebral dominance. Some of the proposed classifications of dyslexia, and most notably the one proposed by Boder (1971), strongly suggest that dyslexic subtypes, that can be identified clinically by reading-spelling patterns, may possess different or opposite cerebral dominance patterns. Thus, research of cerebral dominance in dyslexia (i.e., Orton’s hypothesis) should involve careful selection and classification of subjects. When this is done it can be shown that electrophysiological measures can identify cerebral-dominance abnormalities in at least one subtype of developmental dyslexia.