Dyslexia Medical and Health News Headlines

A case study of the effect of age-of-acquisition on reading aloud in Chinese dyslexia.

Neurocase. 2008;14(3):276-89

Authors: Law SP, Wong W, Yeung O, Weekes BS

This paper reports the influence of age-of-acquisition (AoA) effects on the oral reading accuracy of a Chinese brain-injured individual, FWL, who has anomia and dyslexia resulting from moderate-to-severe semantic deficits. We found an effect of the phonological consistency of a character and tentative evidence for an interaction between AoA and consistency. These observations converge on previous reports of an effect of AoA on reading and spelling of alphabetic scripts and in the reading of Japanese Kanji, a non-alphabetic script. An effect of AoA is also the expected outcome of the arbitrary mapping hypothesis which assumes that the locus of the AoA effect resides in the connection between levels of representations in the lexical processing system. We consider alternative interpretations of the AoA effect being located at the representations themselves, including phonological output and the semantic system. We propose that future studies of dyslexic individuals who rely primarily on the semantic reading route for reading in Chinese may reveal effects of semantic variables, including those associated with the semantic radical in phonetic compound characters.

PMID: 18704834 [PubMed - in process]

Maturation of visual and auditory temporal processing in school-aged children.

J Speech Lang Hear Res. 2008 Aug;51(4):1002-15

Authors: Dawes P, Bishop DV

PURPOSE: To examine development of sensitivity to auditory and visual temporal processes in children and the association with standardized measures of auditory processing and communication. Methods Normative data on tests of visual and auditory processing were collected on 18 adults and 98 children aged 6-10 years of age. Auditory processes included detection of pitch from temporal cues using iterated rippled noise and frequency modulation detection at 2 Hz, 40 Hz, and 240 Hz. Visual processes were coherent form and coherent motion detection. Test-retest data were gathered on 21 children. RESULTS: Performance on perceptual tasks improved with age, except for fine temporal processing (iterated rippled noise) and coherent form perception, both of which were relatively stable over the age range. Within-subject variability (as assessed by track width) did not account for age-related change. There was no evidence for a common temporal processing factor, and there were no significant associations between perceptual task performance and communication level (Children's Communication Checklist, 2nd ed.; D. V. M. Bishop, 2003) or speech-based auditory processing (SCAN-C; R. W. Keith, 2000). CONCLUSIONS: The auditory tasks had different developmental trajectories despite a common procedure, indicating that age-related change was not solely due to responsiveness to task demands. The 2-Hz frequency modulation detection task, previously used in dyslexia research, and the visual tasks had low reliability compared to other measures.

PMID: 18658067 [PubMed - in process]

Working Memory Deficits in Children With Specific Learning Disorders.

J Learn Disabil. 2008 Jul 14;

Authors: Schuchardt K, Maehler C, Hasselhorn M

This article examines working memory functioning in children with specific developmental disorders of scholastic skills as defined by ICD-10. Ninety-seven second to fourth graders with a minimum IQ of 80 are compared using a 2 x 2 factorial (dyscalculia vs. no dyscalculia; dyslexia vs. no dyslexia) design. An extensive test battery assesses the three subcomponents of working memory described by Baddeley (1986): phonological loop, visual-spatial sketchpad, and central executive. Children with dyscalculia show deficits in visual-spatial memory; children with dyslexia show deficits in phonological and central executive functioning. When controlling for the influence of the phonological loop on the performance of the central executive, however, the effect is no longer significant. Although children with both reading and arithmetic disorders are consistently outperformed by all other groups, there is no significant interaction between the factors dyscalculia and dyslexia.

PMID: 18625783 [PubMed - as supplied by publisher]

Distinct information processing characteristics in dyslexia and ADHD during a covert orienting task: An event-related potential study.

Clin Neurophysiol. 2008 Jul 11;

Authors: Dhar M, Been PH, Minderaa RB, Althaus M

OBJECTIVE: A visuo-spatial orienting task was used to investigate the individual and joint contribution of the presence of dyslexia and attention-deficit hyperactivity disorder (ADHD) to information processing. METHODS: Sixteen control, 17 dyslexic, 16 ADHD, and 15 comorbid adults performed the task, comprising a valid, invalid, and no-cue condition. Performance measures were errors and reaction time (RT). A negative potential in response to cues and targets (N2), and a positive potential in response to targets (P3) were derived from the EEG. A 2x2 design was used with the factors dyslexic/non-dyslexic, and ADHD/non-ADHD. RESULTS: Dyslexic participants demonstrated a smaller cue-related N2, yet a greater target-related N2 in the valid condition. ADHD participants were discriminated by the P3 difference between the invalid and valid conditions. Comorbids differed from ADHD mainly in invalid-valid RT, and were similar to dyslexics in target N2 processing. CONCLUSIONS: Dyslexics were impaired in early information processing, and participants with ADHD differed for later processing stages. SIGNIFICANCE: This is the first ERP study of attentional processes in dyslexia to incorporate an ADHD and a comorbid group. Its results may contribute to differentiation of these clinical groups.

PMID: 18621578 [PubMed - as supplied by publisher]

Related Articles

Visual scanning and reading ability in normal and dyslexic children.

Behav Neurol. 2008;19(1-2):87-92

Authors: Ferretti G, Mazzotti S, Brizzolara D

Very few studies have investigated the development of visual search of aligned stimuli in relation to normal reading acquisition and in developmental dyslexia. In this study we used a new computerised experimental task which requires a visuo-motor response (RT) to a target appearing unpredictably in one out of seven different spatial positions on a horizontally aligned array of 18 geometrical figures. The aims of the study were to investigate: 1) the visual scanning development in normal children from pre-school to school age; 2) whether visual scanning performance in kindergarten children could predict reading acquisition; 3) the visual scanning abilities in a group of developmental dyslexic children. The main results were: 1) a significant decrement of RTs with age and a progressive increase of the left-to-right gradient with reading experience; 2) visual scanning abilities in kindergarten proved to be a good predictor of reading acquisition; 3) dyslexics were slow scanners and did not present the left-to-right strategy typical of normal readers. The results support the hypothesis of a relationship between visual scanning and reading abilities.

PMID: 18413924 [PubMed - in process]

Related Articles

The education of dyslexic children from childhood to young adulthood.

Annu Rev Psychol. 2008;59:451-75

Authors: Shaywitz SE, Morris R, Shaywitz BA

The past two decades have witnessed an explosion in our understanding of dyslexia (or specific reading disability), the most common and most carefully studied of the learning disabilities. We first review the core concepts of dyslexia: its definition, prevalence, and developmental course. Next we examine the cognitive model of dyslexia, especially the phonological theory, and review empiric data suggesting genetic and neurobiological influences on the development of dyslexia. With the scientific underpinnings of dyslexia serving as a foundation, we turn our attention to evidence-based approaches to diagnosis and treatment, including interventions and accommodations. Teaching reading represents a major focus. We first review those reading interventions effective in early grades, and then review interventions for older students. To date the preponderance of intervention studies have focused on word-level reading; newer studies are beginning to examine reading interventions that have gone beyond word reading to affect reading fluency and reading comprehension. The article concludes with a discussion of the critical role of accommodations for dyslexic students and the recent neurobiological evidence supporting the need for such accommodations.

PMID: 18154503 [PubMed - indexed for MEDLINE]

Visually-based temporal distortion in dyslexia.

Vision Res. 2008 Jun 25;

Authors: Johnston A, Bruno A, Watanabe J, Quansah B, Patel N, Dakin S, Nishida S

In this study, we show that invisible flicker adaptation reduces the perceived duration of a subsequently viewed stimulus in control subjects, but not in dyslexics. Dyslexics, like controls, show apparent duration compression after 20Hz flicker and show normal shifts in apparent temporal frequency after adaptation. However a subgroup of the test group, scoring low on both a test of phonological skill (spoonerisms) and a test of literacy (NART), show an apparent temporal expansion after 5Hz flicker adaptation, a finding not previously seen in controls. Recent studies have linked genes conferring susceptibility to a cluster of language and sensory deficits to anomalous neural migration, providing a tentative biological basis for dyslexia. However it has proved difficult to establish a clear link between sensory deficits and impaired reading. The results presented here point to an abnormal adaptation response within the early precortical stages of the magnocellular pathway, occurring in tandem with a deficit in word-level cognitive processing, providing psychophysical evidence for anomalous cortico-thalamic circuits in dyslexia.

PMID: 18589473 [PubMed - as supplied by publisher]