Dyslexia and the anchoring-deficit hypothesis

The 'core deficit' of dyslexia has been characterized by different researchers in terms of either phonological impairments or of difficulties in processing basic visual and auditory stimuli. Recent findings suggest that a single type of impairment in the dynamics of perception, which affects the efficiency of short-term memory, might underlie the broad range of difficulties of dyslexics. Experimental findings show that the general population quickly and automatically tunes around incoming stimuli, 'anchors to them' and performs faster and more accurately when these stimuli are subsequently repeated. Dyslexic individuals fail to benefit from stimulus-specific repetitions. This deficit can account for phonological, working memory, visual and auditory difficulties, in addition to the greater sensitivity of dyslexics to external noise.     

Executive Functions in Dyslexia

This study focused on executive functions in dyslexia. A group of 43 heavily-affected young dyslexics, divided into two groups based on the results of a receptive language test, and 20 non-dyslexic controls, were tested with a Dichotic Listening Test, the Stroop Color Word Test and the Wisconsin Card Sorting Test. The dyslexic subjects demonstrated significant impairment on all tasks, but with different patterns of impairment according to the subgrouping. The subgroups were equally impaired on the Dichotic Listening Test, but differed on the Stroop and the Wisconsin Tests. The data support a hypothesis suggesting executive problems in dyslexia, depending on receptive language skills.     

Neural Mechanisms in Dyslexia

ABSTRACT— Within the last two decades, evidence from many laboratories has converged to indicate the cognitive basis for dyslexia: Dyslexia is a disorder within the language system and, more specifically, within a particular subcomponent of that system, phonological processing. Converging evidence from a number of laboratories using functional brain imaging indicates that there is a disruption of left-hemisphere posterior neural systems in child and adult dyslexic readers when they perform reading tasks. The discovery of a disruption in the neural systems serving reading has significant implications for the acceptance of dyslexia as a valid disorder—a necessary condition for its identification and treatment. Brain-imaging findings provide, for the first time, convincing, irrefutable evidence that what has been considered a hidden disability is "real," and these findings have practical implications for the provision of accommodations, a critical component of management for older children and young adults attending postsecondary and graduate programs. The utilization of advances in neuroscience to inform educational policy and practices provides an exciting example of translational science being used for the public good.     

深层失读及其认知神经心理康复

以语义性错读为特征的深层失读症是一类特殊的阅读障碍类型,它的存在提示了人类在口语阅读过程中需要经过语义性通路。深层失读在拼音文字使用者中并不多见,但在汉语使用者中却多有发现,这种差别提示了汉字阅读与拼音文字阅读之间可能存在某种重要区别。该文概要介绍了深层失读的表现,比较了汉语深层失读与拼音文字深层失读的差异,阐述了深层失读的机制,同时介绍了深层失读病人的神经心理康复手段和方法     

听觉、时间加工能力与发展性阅读障碍

近年来阅读障碍者的知觉加工越来越受到重视 ,本文介绍了近期国外关于阅读障碍者的听觉加工能力、时间加工能力的最新研究进展。快速听觉加工能力的缺失在阅读障碍者身上普遍存在 ,并被认为是阅读障碍产生的主要原因 ;有研究者提出“时间控制障碍”假说 ,认为阅读障碍源自一种普遍性的时间知觉障碍 ,不具有通道特异性。除此之外 ,还发现阅读障碍者对声音频率、响度等非时间特征也出现了觉察困难。通过这些研究我们可以看到 ,听觉加工能力、快速时间加工能力与阅读能力之间可能有着密切的关系 ,但这几种能力如何具体作用于阅读发展 ,它们之间如何相互作用、相互影响仍需进一步探讨。     

Differences in brain morphology and working memory capacity across childhood

Working memory (WM) skills are closely associated with learning progress in key areas such as reading and mathematics across childhood. As yet, however, little is known about how the brain systems underpinning WM develop over this critical developmental period. The current study investigated whether and how structural brain correlates of components of the working memory system change over development. Verbal and visuospatial short‐term and working memory were assessed in 153 children between 5.58 and 15.92 years, and latent components of the working memory system were derived. Fractional anisotropy and cortical thickness maps were derived from T1‐weighted and diffusion‐weighted MRI and processed using eigenanatomy decomposition. There was a greater involvement of the corpus callosum and posterior temporal white matter in younger children for performance associated with the executive part of the working memory system. For older children, this was more closely linked with the thickness of the occipitotemporal cortex. These findings suggest that increasing specialization leads to shifts in the contribution of neural substrates over childhood, moving from an early dependence on a distributed system supported by long‐range connections to later reliance on specialized local circuitry. Our findings demonstrate that despite the component factor structure being stable across childhood, the underlying brain systems supporting working memory change. Taking the age of the child into account, and not just their overall score, is likely to be critical for understanding the nature of the limitations on their working memory capacity.     

阅读障碍儿童的技能自动化能力

以自动化缺陷假说为理论背景,采用系列反应时学习任务,探讨了41名五、六年级的汉语发展性阅读障碍儿童和41名正常儿童的技能自动化能力,通过比较对系列刺激和随机刺激的反应时差异,发现障碍组儿童的反应时虽然普遍长于正常组,但两组儿童都表现出了相同模式的系列学习效应,不支持发展性阅读障碍的技能自动化缺陷假说.     

Dyslexia: saccadic eye movements

This paper describes an extensive study of the parameters of saccadic eye movement in a group of 28 poor-reading children and a comparative normally reading group of 31 children. Ages ranged from 6.0 to 16.9 yr. Poor readers had normal intelligence but were lagging by at least two years in reading ability as compared to their peer age group. Parameters studied in refixation eye movements included saccadic latency, accuracy, velocity, and acceleration, as well as differences in latency for abduct and adduct movements. Shapes of saccades were also studied. It was shown that eye-movement performance in simple saccadic refixation was not distinguishably different for poor readers and normal readers, even though in reading, which requires higher processing, eye-movement characteristics are quite different. Maturational changes for various saccadic eye-movement parameters were also examined for the normal and poor reading groups.     

Morphological Processing in Adult Dyslexia

This study employed the masked-priming paradigm [Forster and Davis (J Exp Psychol bearn Mem Cogn 10: 680–698, 1984).], along with traditional methods of evaluation of morphological awareness and phonological processing, to obtain a finer-grained picture of the relationship between morphological abilities and reading in adult dyslexic readers. Participants were 21 dyslexic and 21 normally reading native Hebrew-speaking male college students. The results with masked priming demonstrated almost normal status of morphological knowledge in adult dyslexic readers with the presence of characteristic processing slowness. Phonological processing and morphological awareness were also shown to contribute primarily to word decoding in the regular and dyslexic group alike. At the same time, the contribution of different phonological skills to morphological priming effects (for pattern and root) dropped to zero. The findings demonstrated that weakness of dyslexic readers in morphological awareness tasks cannot be explained either by hypotheses on the structural deficit of morphological knowledge in dyslexia or by phonological deficit hypotheses. The explanation for this phenomenon seems to lie in the specific deficit of morphological processing, or even, more generally, in metalinguistic processing deficiency in dyslexia.     

Morphological Knowledge in Children with Dyslexia

The phonological skills are not the only linguistic abilities which are observed to have some influence on reading achievement in dyslexics. In addition to phonological skills, morphological skills should be also taken in consideration. The aim of this study is to extend investigation the linguistic abilities of children with dyslexia to the morphological level through examination whether there is a lack of morphological knowledge in children with dyslexia for Bosnian language with transparent orthography. Testing sample included 45 children with dyslexia that are compared with chronological age and reading level controls. The dyslexic children performed significantly worse than same age controls on all forms of word and the most complex word formation tasks. Based on the examination of standardized discriminant function coefficients the variable with the highest weight in defining the first discriminant function was the suffixal formation, declination of personal pronouns, changing gender of adjectives with regard to the gender of a noun, and changing of gender of cardinal numbers with regard to the gender of a noun best differentiates groups. Results of multivariate analyses of variance also showed that chronological age and reading level groups outperformed dyslexics on all these tasks. Our results suggest that dyslexics have problems with morphological knowledge which indicate that certain actions regarding the development of morphological abilities in dyslexics should be taken in the elementary grades.     

4～6年级小学生发展性阅读障碍的异质性研究

通过比较阅读障碍儿童和正常儿童在语音意识、语素意识、语音通达(语音判断)和语义通达(语义相关判断)等任务中的表现,考察阅读障碍内部的异质性以及汉语阅读障碍儿童缺陷的主要类型。结果表明,影响儿童阅读的因素包括语音、语素和词典通达等。阅读障碍儿童内部存在一定的异质性。而从汉语的本身特点和语素与各测验之间的关系来看,汉语的语素缺陷可能成为阅读困难的重要原因之一。     

Letter Dyslexia in a Letter-by-Letter Reader

We describe a letter-by-letter patient who produced misreading errors in both letters in isolation and in words. All errors were visual in nature. We hypothesized an access deficit to the abstract visual representation of letters that prevents letter identification. This deficit could account for the patient's letter-by-letter behavior, since each letter constituted a potential identification problem. An access deficit, moreover, could also explain the patient's letter visual errors. In access processing, in fact, the letters sharing common structural features in their abstract representations were the ones more frequently mismatched.     

Dyslexia: the articulatory hypothesis revisited

Articulatory disorders have been associated with developmental phonological dyslexia in the literature. However, very few information is available about the articulatory movements involved in speech production in dyslexic children. This study uses aerodynamic/acoustic data to explore how dyslexic children produce bilabial stops in French (/b, p/) within a sentence where they occurred in two positions and in three vowel environments. Average durations of articulatory closure and release were calculated in 10 phonological dyslexic children and two groups of age-matched and reading age-matched controls. Moreover, deviation from a standard pronunciation of the same material was evaluated separately by blind examiners. Our results reveal differences in the timing of the articulatory movements between dyslexics and normal controls, as well as more deviations from the target consonant for the dyslexics than for the controls. These observations are consistent with recent findings pointing to a general deficit in fine motor control in dyslexia.     

中文发展性阅读障碍研究

本文总结了作者有关中文发展性阅读障碍的部分研究成果,探讨了阅读困难儿童词汇加工的特征及其本质,讨论了中文阅读技能与其他认知加工,特别是基本视知觉的关系.文章指出阅读障碍儿童由于词汇识别水平低,他们在汉字识别过程中表现出比同年龄的控制组更大的规则性效应,在语义通达过程中,对语音的依赖较大.阅读障碍儿童不仅在汉字的命名速度上慢于控制组儿童,数字的语音通达速度也慢于控制组儿童.文章还总结了汉字阅读与视知觉的关系,发现视觉加工对字形相似性判断有较大的解释作用.     

Clock drawing performance and brain morphology in mild cognitive impairment and Alzheimer's disease

The Clock Drawing Test (CDT) is a widely used instrument in the neuropsychological assessment of Alzheimer's disease (AD). As CDT performance necessitates several cognitive functions (e.g., visuospatial and constructional abilities, executive functioning), an interaction of multiple brain regions is likely. Fifty-one subjects with mild cognitive impairment, 23 with AD and 15 healthy controls underwent high-resolution magnetic resonance imaging. Optimized voxel-based morphometry (VBM) was performed to investigate the putative association between CDT performance and gray matter (GM) density throughout the entire brain. In the first step of analysis (p<.001, uncorrected), VBM revealed a reduced GM density in numerous cortical (temporal lobe, frontal lobe, parietal lobe, cerebellum) and subcortical (thalamus, basal ganglia) brain regions to be associated with poorer CDT performance. When corrected for multiple comparisons (p<.01), the associations remained significant predominantly in the left temporal and--less pronounced--the right temporal lobe. VBM demonstrated CDT performance to depend on the integrity of widely distributed cortical and subcortical areas in both brain hemispheres with accentuation in the left-sided temporal lobe region.     

Dyslexia and reasoning: The importance of visual processes

Recent research has suggested that individuals with dyslexia rely on explicit visuospatial representations for syllogistic reasoning while most non‐dyslexics opt for an abstract verbal strategy. This paper investigates the role of visual processes in relational reasoning amongst dyslexic reasoners. Expt 1 presents written and verbal protocol evidence to suggest that reasoners with dyslexia generate detailed representations of relational properties and use these to make a visual comparison of objects. Non‐dyslexics use a linear array of objects to make a simple transitive inference. Expt 2 examined evidence for the visual‐impedance effect which suggests that visual information detracts from reasoning leading to longer latencies and reduced accuracy. While non‐dyslexics showed the impedance effects predicted, dyslexics showed only reduced accuracy on problems designed specifically to elicit imagery. Expt 3 presented problems with less semantically and visually rich content. The non‐dyslexic group again showed impedance effects, but dyslexics did not. Furthermore, in both studies, visual memory predicted reasoning accuracy for dyslexic participants, but not for non‐dyslexics, particularly on problems with highly visual content. The findings are discussed in terms of the importance of visual and semantic processes in reasoning for individuals with dyslexia, and we argue that these processes play a compensatory role, offsetting phonological and verbal memory deficits.     

发展性阅读障碍的理论及眼动研究

关于发展性阅读障碍,国外研究者,基于认知和生物因素,先后提出了语音缺陷论、小脑缺陷论、一般性大细胞功能障碍论等对发展性阅读障碍进行解释,并考察了患者的眼动特征,提出了有效的诊治方法。目前,汉语发展性阅读障碍研究主要局限在语音和正字法领域,也涉及局部脑区的功能缺陷,但还未从多角度测查其成因,如眼动。这里,在理论梳理的基础上,系统探讨了发展性阅读障碍者的眼动特征,如注视时间、注视次数、眼跳、回视等,及视觉加工的眼动机制