Evidence for frequent divergence impairment in French dyslexic children: deficit of convergence relaxation or of divergence per se?

Aim There is a controversy as to whether dyslexic children present visuo-motor disabilities such as vergence and accommodative problems assessed with orthoptic tests. The purpose of this study is to re-examine this issue in a large population of children. Methods Extensive orthoptic evaluation was made in 57 dyslexic and 46 non-dyslexic (“normal”) age-matched children. Convergence and divergence capacities were evaluated at two distances (30 cm and 400 cm). Results Binocular vision measured with stereo-acuity tests was normal in dyslexics. In contrast, the near point of convergence was significantly more remote in dyslexics; most importantly, divergence at both far and near distance was significantly more reduced in dyslexics (median value 4 pD and 10 pD, respectively, at far and near) than in “normals” (median value 6 pD and 12 pD, at far and near). Conclusion The existence of the divergence deficit at far distance indicates the presence of deficit of divergence per se, independently from convergence and accommodation relaxation. This result is novel and corroborated by physiological studies indicating distinct control of convergence and divergence, both at the cortical and subcortical premotor level. We conclude that vergence deficits are frequently present in dyslexics, and that dyslexics should be re-educated; training should address distinctively convergence and divergence subsystems.     

阅读困难儿童脑功能侧化的研究—汉语双耳分听测试

本研究以汉语字词作为刺激材料，利用双耳分听的手段，探讨阅读困难儿童脑功能侧化，发现阅读困难儿童处理简单汉语刺激表现出左耳优势（ｌｅｆｔｅａｒａｄｖａｎｔａｇｅ），与对照组没有差异，而处理复杂汉语刺激则未表现出耳优势（Ｎｏｅａｒａｄｖａｎｔａｇｅ），与对照组差异有显著性。支持阅读困难儿童双侧半球均过度激活的假说。     

Atypical organisation of the auditory cortex in dyslexia as revealed by MEG

Neuroanatomical and -radiological studies have converged to suggest an atypical organisation in the temporal bank of the left-hemispheric Sylvian fissure for dyslexia. Against the background of this finding, we applied high temporal resolution magnetoencephalography (MEG) to investigate functional aspects of the left-hemispheric auditory cortex in 11 right-handed dyslexic children (aged 8–13 years) and nine matched normal subjects (aged 8–14 years). Event-related field components during a passive oddball paradigm with pure tones and consonant–vowel syllables were evaluated. The first major peak of the auditory evoked response, the M80, showed identical topographical distributions in both groups. In contrast, the generating brain structures of the later M210 component were located more anterior to the earlier response in children with dyslexia only. Control children exhibited the expected activation of more posterior source locations of the component that appeared later in the processing stream. Since the group difference in the relative location of the M210 source seemed to be independent of stimulus category, it is concluded that dyslexics and normally literate children differ as to the organisation of their left-hemispheric auditory cortex.     

Network dynamics in dyslexia: Review and implications for remediation

Extant neurobiological theories of dyslexia appear fractional in focusing on isolated brain regions, mechanisms, and functional pathways. A synthesis of current research shows support for an Interactive Specialization (IS) model of dyslexia involving the dysfunctional orchestration of a widely-distributed, attentionally-controlled, hierarchical, and interhemispheric circuit of intercommunicating neuronal networks. This circuitry is comprised principally of the frontostriatal-parietal cognitive control system of networks, the posterior corpus callosum, and the left arcuate fasciculus. During development, the coalescence of these functionally specialized regions, acting together, may be essential to preventing the core phonemic and phonological processing deficits defining the dyslexic phenotype. Research demonstrating an association of each with processing phonology presents the foundational outline for a comprehensive, integrative theory of dyslexia and suggests the importance of inclusive remedial efforts aimed at promoting interactions among all three networking territories.     

Dissociation between exact and approximate addition in developmental dyslexia

Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact.     

Exploring the disclosure decisions made by physiotherapists with a specific learning difficulty

Objectives

To explore the disclosure decisions made in the workplace by physiotherapy staff with a specific learning difficulty (SpLD).

Do reading processes differ in transparent versus opaque orthographies? A study of acquired dyslexia in Welsh/English bilinguals

In English, the relationship between the written and spoken forms of words is relatively opaque, leading to proposals that skilled reading requires two procedures: (a) a sublexical grapheme/phoneme conversion process allowing the correct reading of regular words (CAT) and new or pseudowords (ZAT); (b) a lexical process necessary to read irregular words accurately (TWO) and assumed to be the dominant process for familiar words. However, it has been argued that the sublexical process may be sufficient in highly transparent languages such as Welsh. If this is the case, damage to the sublexical process may lead to more severe deficits in transparent languages due to the lack of an alternative lexical process. To test this hypothesis, we compared Welsh and English oral reading and written-word recognition and comprehension in seven bilingual stroke participants with comparably impaired pseudoword reading in English and Welsh. Performance was remarkably similar across languages. Irrespective of the language tested, words were read more accurately than pseudowords. Lexical decision and word comprehension were as accurate in Welsh and in English, and when imageability effects were present they were of a similar size in both languages. This study does not support the hypothesis that orthographic transparency determines the nature of cognitive reading processes, but rather suggests that readers develop a sight vocabulary through reading experience irrespective of orthographic transparency.     

How to improve reading skills in dyslexics: The effect of high frequency rTMS

The latest progress in understanding remediation of dyslexia underlines how some changes in brain are a necessary mechanism of improvement. We wanted to determine whether high frequency repetitive transcranial magnetic stimulation (hf-rTMS) over areas that are underactive during reading in dyslexics, would improve reading of dyslexic adults. We applied 5Hz-TMS over both left and right inferior parietal lobule (IPL) and superior temporal gyrus (STG) prior to word, non-word and text reading aloud.     

Writing to dictation and handwriting performance among Chinese children with dyslexia: Relationships with orthographic knowledge and perceptual-motor skills

The purpose of this study was to investigate the relationships between writing to dictation, handwriting, orthographic, and perceptual-motor skills among Chinese children with dyslexia. A cross-sectional design was used. A total of 45 third graders with dyslexia were assessed. Results of stepwise multiple regression models showed that Chinese character naming was the only predictor associated with word dictation (β = .32); handwriting speed was related to deficits in rapid automatic naming (β = ?.36) and saccadic efficiency (β = ?.29), and visual-motor integration predicted both of the number of characters exceeded grid (β = ?.41) and variability of character size (β = ?.38). The findings provided support to a multi-stage working memory model of writing for explaining the possible underlying mechanism of writing to dictation and handwriting difficulties.