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PubMed2006

[Role of the organ of vision in the course of developmental dyslexia].

PURPOSE: To present and describe the role of the organ of vision in the course of developmental dyslexia. MATERIAL AND METHODS: A comprehensive review of contemporary literature about the etiopathogenesis and the clinical symptoms of dyslexia was conducted. RESULTS: Developmental dyslexia in other words is the specific difficulty of a person with reading and writing caused by a deficit in the development of perceptive and motoric functions as well as the coordination of these functions. The etiopathogenesis of dyslexia is not definitely determined. Currently developmental dyslexia is thought to be determined by environmental and genetic factors. In accessible literature it is noted that a total of 5-17.5% of all people is effected by dyslexia. It is widely regarded that 63% of all sufferers of dyslexia develop the auditory type of dyslexia with an additional 9% having the visual type of dyslexia, while the rest develop a mixed type. The basis of visual dyslexia lies in the disorder of visual perception linked to the disorders of visual and motoric coordination as well as visual and spatial integration. People with developmental dyslexia tend to evolve numerous changes in the magnocellular pathway, eyeball movements, accommodation as well as binocular vision.

Auditory Perception↗
PubMed2004

Time reproduction in finger tapping tasks by children with attention-deficit hyperactivity disorder and/or dyslexia.

AIM: Deficits in timing and sequencing behaviour in children with dyslexia and with attention-deficit hyperactivity disorder have already been identified. However many studies have not controlled for comorbidity between dyslexia and ADHD. This study investigated timing performance of children with either dyslexia or ADHD, or ADHD + dyslexia or unaffected children using a finger tapping paradigm. METHOD: Four groups of children (ADHD x Dyslexia) with a total of 68 children were compared using a four factorial design with two between-subject factors (ADHD (yes/no), dyslexia (yes/no)) and two within-subject factors, inter-stimulus interval (263, 500, 625, 750, 875 and 1000 ms) and tapping condition (free tapping, synchronous tapping, and unpaced tapping). In addition the complexity of rhythm reproduction pattern (unpaced tapping) was varied (simple/complex). RESULTS: No significant differences were found either in the ability of the ADHD or the dyslexia groups to sustain a self-chosen free tapping rate or to generate a stable inter-response interval either by synchronising to a signal or in reproducing a given interval without the previous pacing signal. Response averages showed the expected asynchrony and variability. In rhythm pattern reproduction the groups did not differ significantly in their ability to reproduce rhythms. However, a significant two way interaction effect between dyslexia and complexity was apparent indicating that the difference in levels of performance for simple versus complex rhythms was more pronounced for dyslexia than for the two other groups. CONCLUSION: The results indicate that motor timing ability in the millisecond range below 1000 ms in children with ADHD and/or dyslexia is intact. The performance of the comorbid group was revealed to be similar to the performance of the single disorder groups, but both the dyslexic groups were relatively worse than either the ADHD-only or the unimpaired group at reproducing complex versus simple rhythms.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

Phonological dyslexia and phonological impairment: an exception to the rule?

The condition known as phonological dyslexia involves very poor reading of non-words, with otherwise good word reading performance [e.g. Derouesné & Beauvois, 1979; Sartori, G., Barry, C., & Job, R. (1984). Phonological dyslexia: A review. In R. N. Malatesha & H. A. Whitaker (Eds.), Dyslexia: A global issue. The Hague: Martinus Nijhoff Publishers]. Theoretical accounts of this non-word reading impairment suggest disruption to either a component of a non-lexical orthographic-phonological reading route [that is specifically involved in reading non-words; Coltheart, M., Rastle, K., Perry, C., Langdon, R., & Zeigler, J. (2001). A dual route cascaded model of visual word recognition and reading aloud. Psychological Review, 108, 204-256] or to generalised phonological processes on which novel reading is heavily dependent [Farah, M., Stowe, R. M., & Levinson, K. L. (1996). Phonological dyslexia: Loss of a reading-specific component of cognitive architecture? Cognitive Neuropsychology, 13, 849-868; Harm, M. W., & Seidenberg, M. S. (1999). Phonology, reading acquisition, and dyslexia: Insights from connectionist models. Psychological Review, 106, 491-528]. The present paper questions the latter hypothesis: that phonological dyslexia always occurs in connection with some other form of phonologically based disruption (i.e. in a 'cluster' of impairments that are not necessarily reading-specific). Contrary to this view, several recent studies have reported that phonological dyslexia can occur without corresponding generalised phonological impairment [e.g. Caccappolo-van Vliet, E., Miozzo, M., & Stern, Y. (2004a). Phonological dyslexia without phonological impairment? Cognitive Neuropsychology, 21, 820-839; Caccappollo-van Vliet, E., Miozzo, M., & Stern, Y. (2004b). Phonological dyslexia: A test case for reading models. Psychological Science, 15, 583-590]. However, the work is subject to a number of criticisms. The following study examines performance of a phonological dyslexic case (JH) on a variety of phonological based tasks and, unlike many other studies, components of phonological short-term memory. Despite clear impairments in reading non-words, good performance on a variety of phonological tasks makes the possibility of generalised phonologically based disruption unlikely. The view that JH's good phonological skill was dependent on the use of spelling based strategies was also excluded. As a result, JH's pattern of performance provides clear evidence that phonological dyslexia can occur without any generalised phonological impairment.

Articulation Disorders↗
PubMed2005

Are specific language impairment and dyslexia distinct disorders?

PURPOSE: The purpose of this study was to determine whether specific language impairment (SLI) and dyslexia are distinct developmental disorders. METHOD: Study 1 investigated the overlap between SLI identified in kindergarten and dyslexia identified in 2nd, 4th, or 8th grades in a representative sample of 527 children. Study 2 examined phonological processing in a subsample of participants, including 21 children with dyslexia only, 43 children with SLI only, 18 children with SLI and dyslexia, and 165 children with typical language/reading development. Measures of phonological awareness and nonword repetition were considered. RESULTS: Study 1 showed limited but statistically significant overlap between SLI and dyslexia. Study 2 found that children with dyslexia or a combination of dyslexia and SLI performed significantly less well on measures of phonological processing than did children with SLI only and those with typical development. Children with SLI only showed only mild deficits in phonological processing compared with typical children. CONCLUSIONS: These results support the view that SLI and dyslexia are distinct but potentially comorbid developmental language disorders. A deficit in phonological processing is closely associated with dyslexia but not with SLI when it occurs in the absence of dyslexia.

Adolescent↗
PubMed1992

Evidence that dyslexia may represent the lower tail of a normal distribution of reading ability.

BACKGROUND: Dyslexia is now widely believed to be a biologically based disorder that is distinct from other, less specific reading problems. According to this view, reading ability is considered to follow a bimodal distribution, with dyslexia as the lower mode. We hypothesized that, instead, reading ability follows a normal distribution, with dyslexia at the lower end of the continuum. METHODS AND RESULTS: We used data from the Connecticut Longitudinal Study, a sample survey of 414 Connecticut children who entered kindergarten in 1983 and were followed as a longitudinal cohort. Dyslexia was defined in terms of a discrepancy score, which represents the difference between actual reading achievement and achievement predicted on the basis of measures of intelligence. Data were available from intelligence tests administered in grades 1, 3, and 5 and achievement tests administered yearly in grades 1 through 6. For each child there were 108 possible discrepancy scores ([3 x 3 years] x [2 x 6 years]) based on combinations of the ability scores (full-scale, verbal, and performance IQ) in each of three years and two achievement scores (reading and mathematics) in each of six years. We demonstrated that each of the discrepancy scores followed a univariate normal distribution and that the interrelation of two different discrepancy scores followed a bivariate normal distribution. At most, only 9 of 108 discrepancy scores (8.3 percent) and 171 of 3402 pairs of discrepancy scores (5.0 percent) were significantly different (at the 5 percent level) from the expected scores--well within the expected values for data with univariate and bivariate normal distributions, respectively. We also examined the stability of dyslexia over time. The normal-distribution model predicted (and the data indicated) that only 7 of the 25 children (28 percent) classified as having dyslexia in grade 1 would also be classified as having dyslexia in grade 3. CONCLUSIONS: Reading difficulties, including dyslexia, occur as part of a continuum that also includes normal reading ability. Dyslexia is not an all-or-none phenomenon, but like hypertension, occurs in degrees. The variability inherent in the diagnosis of dyslexia can be both quantified and predicted with use of the normal-distribution model.

Child↗
PubMed2005

Executive functions in children with dyslexia.

There is little data available concerning the executive functions of children with dyslexia. The small number of existing studies in this field focus on single aspects of these functions such as working memory. The aim of the present study was therefore to assess a variety of aspects of executive functioning in children with dyslexia. Forty-two children with dyslexia and 42 non-dyslexic children were examined using a neuropsychological test battery. The test battery consisted of standardised tests examining the assessment of working memory, concept formation, inhibition, flexibility, problem solving and fluency functions. Comparison between the test performance of non-dyslexic children and children with dyslexia revealed obvious difficulties of children with dyslexia in tests measuring working memory. Inhibition of inappropriate reactions was impaired in children with dyslexia in more demanding tests, but not in simple ones. Furthermore, children with dyslexia displayed impairments of both verbal and figural fluency functions. While in comparison to non-dyslexic children no disturbances of concept formation were observed, problem solving seemed to be partially impaired. The present findings suggest that children with dyslexia demonstrate impairments in a variety of executive functions. This should be considered in the development of new concepts in the treatment of dyslexia.

Attention↗
PubMed2006

The disclosure of dyslexia in clinical practice: experiences of student nurses in the United Kingdom.

Heightened awareness and increasingly sophisticated psychological tests have seen a dramatic rise in the numbers of people diagnosed with dyslexia. Accordingly, there is a reported increase in the numbers of students with dyslexia entering Higher Education (HE) in the United Kingdom (UK) [Singleton, C.H., Chair, 1999. Dyslexia in higher education: policy, provision and practice. Report of the national working party on dyslexia in higher education. University of Hull on behalf of the Higher Education Funding Councils of England and Scotland, Hull], [Higher Education Statistics Agency. HESA. Available from: (accessed 21.12.05)]. Studies researching the effects of dyslexia on the clinical practice of nurses are almost non-existent. This paper reports part of a UK study exploring the clinical experiences of student nurses with dyslexia. In depth interviewing of 18 adult branch student nurses revealed a range of difficulties encountered and a variety of coping mechanisms to manage these. Other than in exceptional circumstances there is no legal requirement to disclose a dyslexia diagnosis. The decision to conceal or disclose their dyslexia was particularly prominent and contentious for these participants. This related to the attitudes of co-workers, concerns for patient safety, expectations of support, confidentiality issues and potential discrimination. Dyslexia continues to attract an unwarranted stigma and can adversely affect the learning experience. The need for disability awareness training in the workplace and improved education/service partnerships to support these students is considered crucial.

Adaptation, Psychological↗
PubMed2006

[Genetics of dyslexia].

Dyslexia is a very common developmental disorder. The aetiology of this complex disorder must in large part still be clarified. Dyslexia segregates in families and the risk for a sibling to become dyslexic is 3.5-fold increased. Different phenotypic dimensions are correlated with dyslexia. These are mainly phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, and rapid naming. The correlated dimensions segregate in families and were found to be heritable. The heritability of word reading lies between 50% and 60%, and that of spelling between 50% and 70%. Based on genome wide linkage analyses, nine candidate gene regions (DYX1-DYX9) could be identified. Recently, four candidate genes, DCDC2, KIAA0319, ROBO1 and DYX1C1 were identified by systematic association analyses. All these genes play a function role in neuronal migration, making them promising candidate genes for dyslexia. However, a functionally relevant mutation has not yet been identified. The comorbidity between dyslexia and ADHD and between dyslexia and SLI could be explained, at least in part, by genetic factors. For future research, all relevant factors playing a functional role in dyslexia should be investigated in sufficiently large samples. This research should integrate genetic, neurobiological, and environmental factors. For an understanding of causes, it is very helpful to understand the interaction between different factors, namely gene-environmental and gene-gene interaction. In a recent project funded by the EU in the Sixth Framework (www.neurodys.com), the worldwide largest sample of children with dyslexia will be sampled and investigated. The goal of this project is to investigate the biological basis of dyslexia in order to improve the basis for the development of successful diagnostics and therapies.

Adolescent↗
PubMed2000

Use of temporal envelope cues by children with developmental dyslexia.

This study evaluates the ability to process auditory temporal-envelope cues in a group of 6 children with dyslexia (mean age: 10;10 years;months). To address this issue, we measured (a) temporal modulation transfer functions (TMTFs), that is, the detection thresholds of sinusoidal amplitude modulation (SAM) applied to a white noise carrier, as a function of modulation frequency, fm (fm was 4, 16, 64, 256, and 1,024 Hz) and (b) identification performance for vowel-consonant-vowel (VCV) stimuli over 5 sessions. VCV stimuli were either unprocessed or digitally processed to remove the original spectral information, resulting in a time-varying speech envelope amplitude modulating a noise carrier. The same tests were conducted in 6 normal control children (mean age: 11;6 years;months) and 6 normal control adults (mean age: 24;8 years;months). SAM thresholds were similar in normal children and adults. For both normal groups, TMTFs were low pass in shape and showed low between-listener variability. TMTFs measured in children with dyslexia showed higher between-listener variability: TMTFs were band pass in 2 children, flat in 1 child, and low pass in the 3 others. Overall, SAM thresholds were higher in children with dyslexia than in normal children at fm = 4 and 1,024 Hz. Unprocessed-speech identification performance was nearly perfect in normal children and adults, and impaired in children with dyslexia. "Speech-envelope noise" identification performance was poorer in normal children and children with dyslexia than in normal adults. Performance improved across sessions in normal children and adults, but remained constant in children with dyslexia. Compared to normal children, children with dyslexia showed poorer reception of voicing, manner, and place of articulation for unprocessed speech and poorer reception of voicing for "speech-envelope noise." Taken together, these results support the hypothesis that some children with dyslexia may show abnormal auditory temporal-envelope processing. Such a deficit, in turn, may explain the difficulties of children with dyslexia with speech perception.

Adolescent↗
PubMedDate not supplied

Neuropsychological treatment of dyslexia in the classroom setting.

The purpose of this study was to validate Bakker's (1990, 1992) clinical neuropsychological balance model of dyslexia when implemented in a traditional general education classroom environment. The sample included 45 middle school, right-handed boys and girls (mean age = 12.78) with L-type dyslexia (excessively fast readers who make substantive reading errors), P-type dyslexia (displaying accurate but slow and laborious reading), and M-type dyslexia (readers who commit a combination of L-type and P-type dyslexia errors). The experimental groups (L and P type dyslexia) were presented with hemisphere specific stimulation (HSS) and hemispheric alluding stimuli (HAS). HSS involves the presentation of words into the right visual field (RVF) or the left visual field (LVF) or through tactile exercises with the right or left hand. HAS is achieved by constructing semantically and phonetically challenging letters and words. The children with M-type dyslexia served as a control group and received traditional decoding and comprehension exercises. The readers were exposed to a specific treatment model for 16 weeks, depending on their reading accuracy and comprehension. Statistical analyses indicated that, although there were no significant changes in word recognition for the dyslexia subtypes, the readers with L-type, P-type, and M-type dyslexia exhibited significant improvement in reading accuracy and comprehension as assessed by results from pretest to posttest. These results suggest that Bakker's clinical neuropsychological intervention can be effectively applied to the general education setting as well.

Adolescent↗
PubMed2001

Developmental dyslexia: an update on genes, brains, and environments.

The science of reading and developmental dyslexia has experienced spectacular advances during the last few years. Five aspects of this research are discussed in the article. (1) The holistic phenomenon of reading is complex. Many lower-level psychological processes (e.g., phonemic awareness, phonological decoding, ability to process stimuli rapidly and automatize this process, memory, ability to recognize words) contribute to a single act of reading. Conceptualizing the complex process of reading through its partly overlapping but partly independent components--which contribute to, but do not fully explain, the holistic process of reading--provides an excellent model for understanding complex hierarchies of higher mental functions. Those who master reading skills successfully and those who have difficulties doing so differ in a wide range of reading-related processes. The central deficit experienced by poor readers appears to be related to phonological processing (a complex hierarchy of functions related to processing phonemes), whereas characteristics of automatization processes seem to moderate the reading outcome for people whose phonological skills are weak. (2) There are new data addressing models of dyslexia in languages other than English. The most fascinating finding is that the model implicating phonological deficit as central to dyslexia, and the lack of ability to automatize as leading to troubled reading, appears to be universal, regardless of the specific language. However, there is an interaction effect between the characteristics of a particular language and the developmental model of dyslexia. In phonologically more difficult languages (e.g., English), the most pronounced weakness appears to occur in phonological processing, whereas in phonologically easier languages (e.g., German), the crucial role in the manifestation of dyslexia is played by the lack of the skills needed to achieve automatization. (3) There is abundant evidence that reading (i.e., any single act of reading as well as reading as a holistic process) is "cooked" by the brain. Although no unified brain map of reading has been developed, some specific areas of the brain have been implicated in different reading-related cognitive processes by different laboratories and on different samples. (4) Indisputable evidence has been accumulated suggesting the involvement of the genome in developmental dyslexia. As of now, specific regions of the genome have been identified as being intimately involved with a number of different reading-related processes. Today the field of developmental dyslexia is the only area of genetic studies of human abilities and disabilities in which linkages to the genome have been robustly replicated in independent laboratories. (5) Finally, evidence suggests that developmental dyslexia might be only one of the manifestations of a deep, underlying, anatomical syndrome. The comorbidity of developmental dyslexia with both internalizing and externalizing behavioral disturbances, as well as with other learning disabilities, underscores the need for wide-ranging cognitive and behavioral approaches in the remediation programs offered to dyslexic children.

Adolescent↗
PubMed2003

[Developmental dyslexia].

Developmental dyslexia makes up an important proportion of the known learning disorders. Until the late 1970s most research on dyslexia was carried out by educators and educational psychologists, but soon after the publication of some dyslexic cases with focal disorders of neuronal migration to the cerebral cortex, interest in the neurobiological and neurocognitive underpinnings of dyslexia grew, especially in Europe and North America. There are at least two types of developmental dyslexia--phonological and surface. Surface dyslexia refers to a disorder in which the difficulty lies in reading irregular words, whereas phonological dyslexia is characterized by difficulty with pseudowords. Phonological dyslexia is the more common of the two types. Surface dyslexia does not present a major problem in a language such as Spanish, where the number of irregular words is indeed very small. Still, in languages such as English, where irregular words are common, the phonological type of developmental dyslexia is much more common. Phonologic dyslexics have problems with phonological awareness, that is, the conscious knowledge and manipulation of speech sounds, which is the most proximate explanation for their difficulty in reading pseudowords. Many, but not all, phonologic dyslexics also have problems processing rapidly changing sounds, even if not linguistic, and some slow sounds, too. The same group tends to have visual problems, especially involving the so-called magnocellular pathway of the visual system, which, among others, has the role of analyzing movement. Accompanying these perceptual and cognitive deficits, phonologic dyslexics also show abnormal brain activation to phonological tasks, as shown in functional magnetic resonance studies (figure). In addition, dyslexic brains show focal malformations, ectopias and microgyria, of the cerebral cortex, involving mainly the left perisylvian region and the word form area in the temporo-occipital junction. There are also changes in the composition of neurons in the lateral and medial geniculate nuclei of the thalamus. Experimental studies indicate that the thalamic changes are a consequence of the focal malformations, and that they are responsible for the sound processing deficits. None of these discoveries have changed the therapeutic modalities in this condition, but it is hoped that this will be the next area of progress.

Brain↗
PubMed2006

Impaired balance in developmental dyslexia? A meta-analysis of the contending evidence.

BACKGROUND: Developmental dyslexia is typically defined by deficits in phonological skills, but it is also associated with anomalous performance on measures of balance. Although balance assessments are included in several screening batteries for dyslexia, the association between impairments in literacy and deficits in postural stability could be due to the high co-occurrence of dyslexia with other developmental disorders in which impairments of motor behaviour are also prevalent. METHODS: We identified 17 published studies that compared balance function between dyslexia and control samples and obtained effect-sizes for each. Contrast and association analyses were used to quantify the influence of hypothesised moderator variables on differences in effects across studies. RESULTS: The mean effect-size of the balance deficit in dyslexia was .64 (95% CI = .44-.78) with heterogeneous findings across the population of studies. Probable co-occurrence of other developmental disorders and variability in intelligence scores in the dyslexia samples were the strongest moderator variables of effect-size. CONCLUSIONS: Balance deficits are associated with dyslexia, but these effects are apparently more strongly related to third variables other than to reading ability. Deficits of balance may indicate increased risk of developmental disorder, but are unlikely to be uniquely associated with dyslexia.

Attention Deficit Disorder with Hyperactivity↗
PubMed2000

Two translocations of chromosome 15q associated with dyslexia.

Developmental dyslexia is characterised by difficulties in learning to read. As reading is a complex cognitive process, multiple genes are expected to contribute to the pathogenesis of dyslexia. The genetics of dyslexia has been a target of molecular studies during recent years, but so far no genes have been identified. However, a locus for dyslexia on chromosome 15q21 (DYX1) has been established in previous linkage studies. We have identified two families with balanced translocations involving the 15q21-q22 region. In one family, the translocation segregates with specific dyslexia in three family members. In the other family, the translocation is associated with dyslexia in one family member. We have performed fluorescence in situ hybridisation (FISH) studies to refine the position of the putative dyslexia locus further. Our results indicate that both translocation breakpoints on 15q map within an interval of approximately 6-8 Mb between markers D15S143 and D15S1029, further supporting the presence of a locus for specific dyslexia on 15q21.

Adolescent↗
PubMed2002

[Problems associated with dyslexia].

OBJECTIVE: In this article we review the disorders of development which affect learning and may be associated with dyslexia. DEVELOPMENT: Although the cognitive basis of dyslexia is a phonological deficit, it is not uncommonly associated with other disorders whose deficit is not necessarily related to the dyslexia from a physiopathological point of view. The problems which usually accompany dyslexia are: attention deficit with hyperactivity, dysgraphia, dyscalculia and disorders of the development of coordination. The starting point for understanding this comorbidity is finding broad, dysfunctional areas of the brains of dyslexic patients beyond those theoretically involved in dyslexia. Each of these disorders may or may not occur together with dyslexia. There are even some subtypes which are defined by being associated with dyslexia, leading to the conclusion that in some cases there are underlying common mechanisms. It is necessary to avoid confusion arising over dyslexia due to comorbidity with other conditions.

Agraphia↗
PubMed2006

Developmental and acquired dyslexias.

Marshall (1984) highlighted potential parallels between children with developmental disorders of reading and adults who had acquired reading disorders. He advocated the use of a cognitive neuropsychological framework in the investigation of children with developmental abnormalities of cognition, including those with developmental dyslexias. Developmental phonological dyslexia has been extensively described and is a pervasive disorder. The relationship between reading difficulty and phonological difficulties evident in explicit oral phonological tasks continues to be a focus for debate. Clear cases of developmental deep dyslexia have now been described and the syndrome has also been described as characterising early reading development in Williams syndrome (WS), where there are also semantic errors in other domains, including naming and receptive vocabulary and there may be a generalised difficulty with the activation of fine grain semantic specifications. In the domain of number, highly selective reading disorders characterised by high rates of semantic errors have been documented, indicating that semantic reading errors can be domain-specific. They can occur to number words despite intact ability to read Arabic numbers and they can occur to Arabic numbers and number words despite intact ability to read words in other domains. Current models of reading written words do not allow for such material-specific dissociation. Developmental surface dyslexia has also been described in a range of countries, languages and orthographies. Descriptions of cases for whom there is no phonological impairment in reading have generated contrary evidence for theories suggesting that phonological impairment underlies all developmental dyslexia. As reading develops in Williams Syndrome, phonological reading skills may improve with over-reliance on these leading to surface dyslexia. Surface dyslexia has also been reported in cases of developmental amnesia in which there are semantic memory impairments. Hyperlexia can take several forms including broad hyperdevelopment with elevated phonological reading abilities, lexico-semantic reading abilities and reading comprehension as in Turner's syndrome (TS). This advantage has early onset in school-starters. These specific modular effects do not have pervasive impact across systems but demonstrate the limitations of functional plasticity in developmental and genetic disorders. The framework Marshall (1984) outlined has provided a foundation for the development of systematic investigation of developmental disorders.

Adolescent↗
PubMed2005

Dyslexia in English as a second language.

This study focused on English as L2 in a group of Norwegian dyslexic 12 year olds, compared to an age and gender matched control group. Norwegian school children learn English from the first grades on. The subjects were assessed with a test battery of verbal and written tasks. First, they were given a comprehension task; second, a model sentence task; third, two pragmatic tasks, and fourth, three tasks of literacy. The verbal tasks were scored according to comprehension, morphology, syntax and semantics, while the literacy tasks were scored by spelling, translation and reading skills. It was hypothesized that the results of the control group and the dyslexia group would differ on all tasks, but that subgrouping the dyslexia group by comprehension skills would show heterogeneity within the dyslexia group. The data analyses confirmed these hypotheses. Significant differences were seen between the dyslexia group and the control group. However, the subgrouping revealed minor differences between the control group and the subgroup with good comprehension skills, and major differences between the control group and the subgroup with poor comprehension skills. Especially morphology and spelling were difficult for the dyslexia group. The results were tentatively discussed within the framework of biological and cognitive models of how to interpret L2 performance in dyslexia, underlining the importance of further research in L2 acquisition in dyslexia.

Child↗
PubMed1996

The visual deficit theory of developmental dyslexia.

Dyslexia is an impairment in reading that can result from an abnormal developmental process in the case of developmental dyslexia or cerebral insult in the case of acquired dyslexia. It has long been known that the clinical manifestations of developmental dyslexia are varied. In addition to their reading difficulties, individuals with developmental dyslexia exhibit impairments in their ability to process the phonological features of written or spoken language. Recently, it has been demonstrated with a variety of experimental approaches that these individuals are also impaired on a number of visual tasks involving visuomotor, visuospatial, and visual motion processing. The results of these studies, as well as the anatomical and physiological anomalies seen in the brains of individuals with dyslexia, suggest that the pathophysiology of developmental dyslexia is more complex than originally thought, extending beyond the classically defined language areas of the brain. Functional neuroimaging is a useful tool to more precisely delineate the pathophysiology of this reading disorder.

Awareness↗