Family Risk Of Dyslexia Research Articles

Changing concepts of dyslexia: nature, treatment and comorbidity

Changing concepts of dyslexia: nature, treatment and comorbidity

Balance and reading are separate symptoms of dyslexia

Research into dyslexia has been characterized by controversy, but the issue of balance and whether or not it should be seen as causal in dyslexia has been one of the most heatedly debated issues in recent years. The consensus of research into balance and dyslexia over a 20-year period has been that balance deficits may be identified in around 50% of a sample of children with dyslexia and around 20% of a sample of adults with dyslexia. It has also been argued that any evidence of balance deficits may be attributed to comorbid attention deficit in the participants with dyslexia studied. However, recent evidence from the Sheffield group has established that deficits may be found in adults if the level of difficulty is manipulated in dual task paradigms1 and has demonstrated that balance difficulties are found in children and adults with dyslexia with age-appropriate tests even when attention-deficit–hyperactivity disorder is controlled for.2 Balance deficits have been linked to the cerebellum in the cerebellar deficit hypothesis of dyslexia,3 which argues that both balance and reading deficits in dyslexia may be explained by differences in processing, based on cerebellar dysfunction. This is an explanatory theory which provides an independent explanation of the other major theories of dyslexia, in particular the phonological deficit and double-deficit theories of dyslexia. The cerebellar hypothesis itself has generated further controversy, in particular as to whether the cerebellum is a causal factor in dyslexia or whether it should be seen as simply an ‘innocent bystander’. The basis for these disputes rests on a simple misunderstanding and confusion between reading deficits and dyslexia. The cerebellar deficit claims only that the language-related regions of the cerebellum are affected in dyslexia. These are generally considered to be lobule VI and VIIB in the neocerebellum – well away from the motor and balance regions in the cerebellum. Other cerebellar regions may also be affected, but this is not necessary. The ontogenetic causal chain for dyslexia,3 which outlines development from birth to 8 years, makes it clear that balance deficits are not directly linked to reading deficits, because they involve a separate route in the causal chain. The cerebellar deficit hypothesis would therefore predict a higher incidence of balance difficulties in dyslexia, but that these would not necessarily be directly correlated with reading difficulties. The balance difficulties are best seen as symptoms of dyslexia which may be identified before children fail to learn to read, and which are therefore particularly useful in screening tests for dyslexia, such as the Dyslexia Early Screening Test.4 This is precisely the pattern which is identified in the family study by Viholainen et al.5 The incidence of balance deficits in children with family risk for dyslexia is significantly higher than controls, but reading deficits are more highly significant in this group. This study provides further confirmation of the importance of family studies in our understanding of dyslexia. More recent research has suggested that it may be fruitful to subsume the cerebellar deficit hypothesis within a ‘neural systems’ framework that attempts to capture disorders of learning at the level of the systems that work together, rather than the specific brain structures.6 This framework suggests that for dyslexia the neural system involved is the language-specific procedural learning system. The framework provides a natural explanation for the comorbidities found in dyslexia and it may have the potential to reunite the developmental disabilities.

Coherent Motion Sensitivity and Reading Development in the Transition From Prereading to Reading Stage

Evidence suggests that sensitivity to coherent motion (CM) is related to reading, but its role in the etiology of developmental dyslexia remains unclear. In this longitudinal study, CM sensitivity was measured in 31 children at family risk for dyslexia and 31 low-risk controls. Children, diagnosed with dyslexia in third grade (mean age=8 years 3 months), demonstrated reduced CM sensitivity in kindergarten (mean age=5 years 8 months), before they had learned to read. Preschool CM thresholds in controls also uniquely predicted future literacy achievement. When reassessed in first grade, CM sensitivity in the dyslexic children was age appropriate, and CM thresholds in the controls no longer predicted literacy acquisition. These findings contribute to the debate about the developmental relations between visual processing and reading acquisition.

Time demands of caring for children with cerebral palsy: what are the implications for maternal mental health?

to read, and which are therefore particularly useful in screening tests for dyslexia, such as the Dyslexia Early Screening Test. This is precisely the pattern which is identified in the family study by Viholainen et al. The incidence of balance deficits in children with family risk for dyslexia is significantly higher than controls, but reading deficits are more highly significant in this group. This study provides further confirmation of the importance of family studies in our understanding of dyslexia. More recent research has suggested that it may be fruitful to subsume the cerebellar deficit hypothesis within a ‘neural systems’ framework that attempts to capture disorders of learning at the level of the systems that work together, rather than the specific brain structures. This framework suggests that for dyslexia the neural system involved is the languagespecific procedural learning system. The framework provides a natural explanation for the comorbidities found in dyslexia and it may have the potential to reunite the developmental disabilities.

Dutch children at family risk of dyslexia: precursors, reading development, and parental effects

The study concerns reading development and its precursors in a transparent orthography. Dutch children differing in family risk for dyslexia were followed from kindergarten through fifth grade. In fifth grade, at-risk dyslexic (n = 22), at-risk non-dyslexic (n = 45), and control children (n = 12) were distinguished. In kindergarten, the at-risk non-dyslexics performed better than the at-risk dyslexics, but worse than the controls on letter-knowledge and rapid naming. The groups did not differ on phonological awareness. At-risk dyslexics read less fluently from first grade onwards than the other groups. At-risk non-dyslexics' reading fluency was at an intermediate position between the other groups at the start of reading. By fifth grade they had reached a similar level as the controls on word reading, but still lagged behind on pseudoword reading. Results further showed that the parents of the groups of at-risk children differed in educational level and reading skills. Overall, the groups of at-risk children differed on pre-reading skills as well as on reading development. These differences do not seem to stem from differences in intellectual abilities or literacy environment. Instead, the better reading skills of parents of at-risk non-dyslexics suggest that these children might have a lower genetic liability.

Perception of Phonemic Length and Its Relation to Reading and Spelling Skills in Children With Family Risk for Dyslexia in the First Three Grades of School

To examine the ability to discriminate phonemic length and the association of this ability with reading accuracy, reading speed, and spelling accuracy in Finnish children throughout Grades 1-3. Reading-disabled (RDFR, n = 35) and typically reading children (TRFR, n = 69) with family risk for dyslexia and typically reading control children (TRC, n = 80) were tested once in each grade of Grades 1-3 using a phonemic length discrimination task. Reading, spelling, IQ, verbal short-term memory, phonological memory, and naming speed were assessed. The RDFR group made more errors in phonemic length discrimination than the TRC group in Grades 2 and 3. After taking into account variance in verbal short-term memory, phonological memory, and naming speed, discrimination ability explained unique variance of spelling accuracy in Grades 2 and 3 and reading accuracy in Grade 3 in the RDFR group. At the individual level, in Grade 2, 31.4% of the RDFR group and 14.7% of the TRFR group performed below -1.25 SDs in the phonemic length discrimination task. Problems in phonemic length discrimination could be one of the accumulating risk factors affecting development leading to dyslexia.

Speech and Language Difficulties in Children With and Without a Family History of Dyslexia

Comorbidity between SLI and dyslexia is well documented. Researchers have variously argued that dyslexia is a separate disorder from SLI, or that children with dyslexia show a subset of the difficulties shown in SLI. This study examines these hypotheses by assessing whether family history of dyslexia and speech and language difficulties are separable risk factors for literacy difficulties. Forty-six children with a family risk of dyslexia (FRD) and 36 children receiving speech therapy (SLT) were compared to 128 typically developing children. A substantial number (41.3%) of the children with FRD had received SLT. The nature of their difficulties did not differ in severity or form from those shown by the other children in SLT. However, both SLT and FRD were independent risk factors in predicting reading difficulties both concurrently and 6 months later. It is argued that the results are best explained in terms of Pennington's (2006) multiple deficits model.

Towards a further characterization of phonological and literacy problems in Dutch‐speaking children with dyslexia

This longitudinal study examined the development of phonology and literacy in Dutch-speaking children at family risk of dyslexia and in matched controls. Measures were administered in kindergarten (before the start of formal reading instruction), in first and in third grade. Children, diagnosed with dyslexia in third grade, showed impaired phonological awareness (PA), verbal short-term memory, and rapid automatic naming ability (RAN) at all time points, with the deficit in PA aggravating over time. These children also performed more poorly in letter knowledge, word and nonword reading accuracy and speed, and spelling at each time point. Children at family risk of dyslexia who did not fulfil criteria for dyslexia, scored more poorly than low-risk controls on the literacy and phonological measures that required the most fine-grained phonological representations. This suggests that the family risk of dyslexia is continuous rather than discrete. Hierarchical regression analyses demonstrated that PA and RAN were initially the most important instigators of reading accuracy and reading speed, respectively. After 2 years of reading instruction, only RAN predicted reading speed and accuracy. Letter knowledge, reading accuracy, and reading speed also contributed to the development of PA.

Visual deficits in pre-readers at familial risk for dyslexia

Visual processing deficits in dyslexic readers are argued to evolve as a consequence of reading failure. This study examines dorsal stream functioning of children before they commence formal reading instruction to determine whether visual deficits precede reading difficulties. Coherent motion and visual frequency doubling detection were measured in children at familial risk for dyslexia and in children unselected for family reading history. Here we show that children who are at family risk for dyslexia demonstrate dorsal stream deficits before they learn to read, whilst demonstrating no corresponding deficits in coherent form and static grating control tasks. Results indicate that the dorsal visual deficits observed in dyslexic readers are unlikely to be the result of reading failure.

Children at family risk of dyslexia: a follow‐up in early adolescence

This study is the follow-up in early adolescence of children born to families with a history of dyslexia (Gallagher, Frith, & Snowling, 2000). Fifty young people with a family history of dyslexia and 20 young people from control families were assessed at 12-13 years on a battery of tests of literacy and language skills, and they completed questionnaires tapping self-perception and print exposure. One parent from each family participated in an interview documenting family circumstances (including family literacy) and a range of environmental variables considered likely correlates of reading disability. They also rated their child's behavioural and emotional adjustment and their own health and well-being. Parental literacy levels were also measured. Forty-two per cent of the 'at-risk' sample had reading and spelling impairments. A significant proportion of the literacy-impaired group were affected by behavioural and emotional difficulties, although they were not low in terms of global self-esteem. The children in the at-risk subgroup who did not fulfil criteria for literacy impairment showed weak orthographic skills in adolescence and their reading was not fluent. There were no differences in the literacy levels or activities of the parents of impaired and unimpaired at-risk children, and no significant correlation between parent and child reading levels in the at-risk group. The impaired group read less than the other groups, their reading difficulties impacted learning at school and there was evidence that they also had an impact on family life and maternal well-being. The literacy difficulties of children at family-risk of dyslexia were longstanding and there was no evidence of catch-up in these skills between 8 and 13 years. The findings point to the role of gene-environment correlation in the determination of dyslexia.

Speech perception in preschoolers at family risk for dyslexia: Relations with low-level auditory processing and phonological ability

We tested categorical perception and speech-in-noise perception in a group of five-year-old preschool children genetically at risk for dyslexia, compared to a group of well-matched control children and a group of adults. Both groups of children differed significantly from the adults on all speech measures. Comparing both child groups, the risk group presented a slight but significant deficit in speech-in-noise perception, particularly in the most difficult listening condition. For categorical perception a marginally significant deficit was observed on the discrimination task but not on the identification task. Speech parameters were significantly related to phonological awareness and low-level auditory measures. Results are discussed within the framework of a causal model where low-level auditory problems are hypothesized to result in subtle speech perception problems that might interfere with the development of phonology and reading and spelling ability.

Coherent motion detection in preschool children at family risk for dyslexia

We tested sensitivity to coherent motion (CM) in random dot kinematograms in a group of 5-year-old preschool children genetically at risk for dyslexia, compared to a group of well-matched control children. No significant differences were observed, either in a group analysis or in an individual deviance analysis. Nonetheless, CM-thresholds were significantly related to emerging orthographic skills. In a previous study on the same subjects ( Boets, Wouters, van Wieringen, & Ghesquière, in press), we demonstrated that both risk groups already differed on measures of phonological awareness and letter knowledge. Moreover, auditory spectral processing (especially 2 Hz FM detection) was significantly related to phonological ability. In sum, the actual visual and previous auditory data combined, seem to suggest an exclusive relation between CM sensitivity and orthographic skills on the one hand, and FM sensitivity and phonological skills on the other.

Auditory temporal information processing in preschool children at family risk for dyslexia: Relations with phonological abilities and developing literacy skills

In this project, the hypothesis of an auditory temporal processing deficit in dyslexia was tested by examining auditory processing in relation to phonological skills in two contrasting groups of five-year-old preschool children, a familial high risk and a familial low risk group. Participants were individually matched for gender, age, non-verbal IQ, school environment, and parental educational level. Psychophysical thresholds were estimated for gap-detection, frequency modulation detection, and tone-in-noise detection using a three-interval forced-choice adaptive staircase paradigm embedded within a computer game. Phonological skills were measured by tasks assessing phonological awareness, rapid serial naming, and verbal short-term memory. Significant group differences were found for phonological awareness and letter knowledge. In contrast, none of the auditory tasks differentiated significantly between both groups. However, both frequency modulation and tone-in-noise detection were significantly related to phonological awareness. This relation with phonological skills was not present for gap-detection.

Family risk of dyslexia is continuous: individual differences in the precursors of reading skill.

The development of 56 children at family risk of dyslexia was followed from the age of 3 years, 9 months to 8 years. In the high-risk group, 66% had reading disabilities at age 8 years compared with 13% in a control group from similar, middle-class backgrounds. However, the family risk of dyslexia was continuous, and high-risk children who did not fulfil criteria for reading impairment at 8 years performed as poorly at age 6 as did high-risk impaired children on tests of grapheme-phoneme knowledge. The findings are interpreted within an interactive model of reading development in which problems in establishing a phonological pathway in dyslexic families may be compensated early by children who have strong language skills.

Early reading development in children at family risk for dyslexia.

In a 3-year longitudinal study, middle- to upper-middle-class preschool children at high family risk (HR group, N = 67) and low family risk (LR group, N = 57) for dyslexia (or reading disability, RD), were evaluated yearly from before kindergarten to the end of second grade. Both phonological processing and literacy skills were tested at each of four time points. Consistent with the well-known familiarity of RD, 34% of the HR group compared with 6% of the LR group became RD. Participants who became RD showed deficits in both implicit and explicit phonological processing skills at all four time points, clearly indicating a broader phonological deficit than is often found at older ages. The predictors of literacy skill did not vary by risk group. Both risk groups underwent a similar developmental shift from letter-name knowledge to phoneme awareness as the main predictor of later literacy skill. This shift, however, occurred 2 years later in the HR group. Familial risk was continuous rather than discrete because HR children who did not become RD performed worse than LR non-RD children on some phonological and literacy measures. Finally, later RD could be predicted with moderate accuracy at age 5 years, with the strongest predictor being letter-name knowledge.