Association of reading disability on chromosome 6p22 in the Afrikaner population.

The genetic basis of reading disability (RD) has long been established through family and twin studies. More recently genetic linkage studies have identified genomic regions that appear to harbor susceptibility genes for RD. Association studies have been shown to have greater power for detecting genes of modest effect, particularly in genetically isolated populations. Hence, a case control study of RD was undertaken in the Afrikaner population in South Africa. Sixty-eight microsatellite markers in regions where linkages had been reported in previous studies were genotyped on 122 children with reading disability and 112 typically reading controls drawn from the same school population. A single allele of marker D6S299 showed a highly significant association with the RD phenotype (D6S299[229], P-value 0.000014). Other markers on other chromosomes also showed suggestive associations. Of particular interest were markers on chromosomes 1 and 15. These two regions have been implicated in studies of populations that formed the founding population in the Afrikaner population.

Reading problems, psychiatric disorders, and functional impairment from mid- to late adolescence.

OBJECTIVE: To examine psychiatric morbidity and functional impairment of adolescents with and without poor reading skills during mid- to late adolescence. METHOD: The sample consisted of 188 adolescents, 94 with poor reading skills and 94 with typical reading skills, screened from a larger sample in the public schools at age 15. To assess psychiatric disorders, participants were assessed annually with the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Epidemiologic Version (up to 4.5 years; maximum age, 20 years). Functional impairment was assessed with the Child and Adolescent Functional Assessment Scale. RESULTS: Adolescents with poor reading skills evidenced higher rates of current attention-deficit/hyperactivity, affective, and anxiety disorders, particularly social phobia and generalized anxiety disorder. Anxiety disorders but not affective disorders were related to reading status after controlling for attention-deficit/hyperactivity disorder. Adolescents with poor reading evidenced more functional impairment across multiple areas than youths with typical reading skills, even after considering the presence of comorbid attention-deficit/hyperactivity disorder. CONCLUSIONS: The increased psychiatric morbidity and functional impairment of adolescents with reading problems highlight the importance of developing interventions that help these youths address reading deficits and associated vulnerabilities during the last years of secondary school.

Suicidality, school dropout, and reading problems among adolescents.

The purpose of this study was to examine the risk of suicidal ideation and suicide attempts and school dropout among youth with poor reading in comparison to youth with typical reading (n = 188) recruited from public schools at the age of 15. In a prospective naturalistic study, youth and parents participated in repeated research assessments to obtain information about suicide ideation and attempts, psychiatric and sociodemographic variables, and school dropout. Youth with poor reading ability were more likely to experience suicidal ideation or attempts and more likely to drop out of school than youth with typical reading, even after controlling for sociodemographic and psychiatric variables. Suicidality and school dropout were strongly associated with each other. Prevention efforts should focus on better understanding the relationship between these outcomes, as well as on the developmental paths leading up to these behaviors among youth with reading difficulties.

Altered temporal profile of visual-auditory multisensory interactions in dyslexia.

Recent studies have demonstrated that dyslexia is associated with deficits in the temporal encoding of sensory information. While most previous studies have focused on information processing within a single sensory modality, it is clear that the deficits seen in dyslexia span multiple sensory systems. Surprisingly, although the development of linguistic proficiency involves the rapid and accurate integration of auditory and visual cues, the capacity of dyslexic individuals to integrate information between the different senses has not been systematically examined. To test this, we studied the effects of task-irrelevant auditory information on the performance of a visual temporal-order-judgment (TOJ) task. Dyslexic subjects' performance differed significantly from that of control subjects, specifically in that they integrated the auditory and visual information over longer temporal intervals. Such a result suggests an extended temporal "window" for binding visual and auditory cues in dyslexic individuals. The potential deleterious effects of this finding for rapid multisensory processes such as reading are discussed.

Severity of emotional and behavioral problems among poor and typical readers.

The purpose of this study was to examine the severity of behavioral and emotional problems among adolescents with poor and typical single word reading ability (N = 188) recruited from public schools and followed for a median of 2.4 years. Youth and parents were repeatedly assessed to obtain information regarding the severity and course of symptoms (depression, anxiety, somatic complaints. aggression, delinquent behaviors, inattention), controlling for demographic variables and diagnosis or ADHD. After adjustment for demographic variables and ADHD, poor readers reported higher levels of depression, trait anxiety, and somatic complaints than typical readers, but there were no difference, in reported self-reported delinquent or aggressive behaviors. Parent reports indicated no difference, in depression, anxiety or aggression between the two groups but indicated more inattention, somatic complaints, and delinquent behaviors for the poor readers. School and health professionals should carefully assess youth with poor reading for behavioral and emotional symptoms and provide services when indicated.

Predictive assessment of reading.

Study 1 retrospectively analyzed neuropsychological and psychoeducational tests given to N=220 first graders, with follow-up assessments in third and eighth grade. Four predictor constructs were derived: (1) Phonemic Awareness, (2) Picture Vocabulary, (3) Rapid Naming, and (4) Single Word Reading. Together, these accounted for 88%, 76%, 69%, and 69% of the variance, respectively, in first, third, and eighth grade Woodcock Johnson Broad Reading and eighth grade Gates-MacGinitie. When Single Word Reading was excluded from the predictors, the remaining predictors still accounted for 71%, 65%, 61%, and 65% of variance in the respective outcomes. Secondary analyses of risk of low outcome showed sensitivities/specificities of 93.0/91.0, and 86.4/84.9, respectively, for predicting which students would be in the bottom 15% and 30% of actual first grade WJBR. Sensitivities/specificities were 84.8/83.3 and 80.2/81.3, respectively, for predicting the bottom 15% and 30% of actual third grade WJBR outcomes; eighth grade outcomes had sensitivities/specificities of 80.0/80.0 and 85.7/83.1, respectively, for the bottom 15% and 30% of actual eighth grade WJBR scores. Study 2 cross-validated the concurrent predictive validities in an N=500 geographically diverse sample of late kindergartners through third graders, whose ethnic and racial composition closely approximated the national early elementary school population. New tests of the same four predictor domains were used, together taking only 15 minutes to administer by teachers; the new Woodcock-Johnson III Broad Reading standard score was the concurrent criterion, whose testers were blind to the predictor results. This cross-validation showed 86% of the variance accounted for, using the same regression weights as used in Study 1. With these weights, sensitivity/specificity values for the 15% and 30% thresholds were, respectively, 91.3/88.0 and 94.1/89.1. These validities and accuracies are stronger than others reported for similar intervals in the literature.

Neural changes following remediation in adult developmental dyslexia.

Brain imaging studies have explored the neural mechanisms of recovery in adults following acquired disorders and, more recently, childhood developmental disorders. However, the neural systems underlying adult rehabilitation of neurobiologically based learning disabilities remain unexplored, despite their high incidence. Here we characterize the differences in brain activity during a phonological manipulation task before and after a behavioral intervention in adults with developmental dyslexia. Phonologically targeted training resulted in performance improvements in tutored compared to nontutored dyslexics, and these gains were associated with signal increases in bilateral parietal and right perisylvian cortices. Our findings demonstrate that behavioral changes in tutored dyslexic adults are associated with (1) increased activity in those left-hemisphere regions engaged by normal readers and (2) compensatory activity in the right perisylvian cortex. Hence, behavioral plasticity in adult developmental dyslexia involves two distinct neural mechanisms, each of which has previously been observed either for remediation of developmental or acquired reading disorders.

Continuing the search for dyslexia genes on 6p.

This study is a continuation and extension of the work with Orton Developmental Dyslexia (DD) pedigrees [Grigorenko et al., 1997; 2000, Grigorenko et al., 2001]. This study utilized an extended sample (N = 176) and a well-saturated map of chromosome 6p (30 markers). Six phenotypes were constructed to span a range of dyslexia-related cognitive processes. These phenotypes were: (1) Phonemic Awareness (of spoken words); (2) Phonological Decoding (of printed nonwords); (3) Rapid Automatized Naming (of colored squares or object drawings); (4) Single Word Reading (orally, of printed real words); (5) Phonemic Awareness/Decoding/Single-Word Reading pathway; and (6) Phonemic Awareness/Rapid Naming/Single-Word Reading pathway. The study resulted in two major findings. First, considering the distributions of the genetic linkage indicators across all phenotypes examined, there appear to be three regions of interest (around markers D6S109, D6S1261, and in the D6S105-D6S265 region). Any of these regions could serve as a starting point in the search for specific gene candidates contributing to the manifestation of DD, yet they all might be echo peaks of a single peak, the boundary of which is difficult to establish due to the limited power of this sample. Second, the DD-related linkage in 6p21.3 appears to be most closely related to the manifestations of DD through phonemic awareness and single-word reading deficits.

Clock drawing in developmental dyslexia.

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