Genes, language development, and language disorders

Genetic factors are important contributors to language and learning disorders, and discovery of the underlying genes can help delineate the basic neurological pathways that are involved. This information, in turn, can help define disorders and their perceptual and processing deficits. Initial molecular genetic studies of dyslexia, for example, appear to converge on defects in neuronal and axonal migration. Further study of individuals with abnormalities of these genes may lead to the recognition of characteristic cognitive deficits attributable to the neurological dysfunction. Such abnormalities may affect other disorders as well, and studies of co-morbidity of dyslexia with attention deficit disorder and speech sound disorder are helping to define the scope of these genes and show the etiological and cognitive commonalities between these conditions. The genetic contributions to specific language impairment (SLI) are not as well defined at this time, but similar molecular approaches are being applied to identify genes that influence SLI and comorbid disorders. While there is co-morbidity of SLI with dyslexia, it appears that most of the common genetic effects may be with the language characteristics of autism spectrum disorders rather than with dyslexia and related disorders. Identification of these genes and their neurological and cognitive effects should lay out a functional network of interacting genes and pathways that subserve language development. Understanding these processes can form the basis for refined procedures for diagnosis and treatment.     

An Examination of Lexical and Sublexical Reading Skills in Children with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is an inherited neurocutaneous disorder associated with a high frequency of cognitive and learning difficulties. Based on discrepancies between IQ and academic achievement, approximately 17% of children with NF1 have been classified as having reading impairments. In this study, the lexical and sublexical reading skills of children with NF1 (n = 30) were examined using the Castles' Word/Non-Word Test (modified version), together with measures of neuropsychological functioning and academic achievement. Twenty children (67%) demonstrated deficits in one or more reading subskills, with 75% of these meeting criteria for phonological dyslexia and 20% classified with mixed dyslexia. These findings indicate that a large proportion of children with NF1 may be characterized by a specific difficulty with the sublexical procedure, suggesting a difficulty employing spelling-to-sound rules to assemble a pronunciation when reading. In line with previous studies, the present findings also suggest that discrepancy-based methods may not be sufficiently sensitive to identify children who experience reading difficulties.     

阅读障碍儿童的形音捆绑缺陷及其脑神经机制

形音捆绑缺陷研究是国内外阅读障碍研究领域的一个新方向。本文阐述了形音捆绑加工的理论与定义,综述了国内外研究者经常采用的三种形音捆绑的研究范式:配对联想学习、变化检测范式和线索回忆任务,介绍并分析了各研究范式的优缺点、适用范围及主要研究发现。同时,综述与评价了国内外有关阅读障碍形音捆绑缺陷的脑机制研究的主要结论及不足。最后,本文讨论了现有研究在实验设计和理论上的贡献与不足,提出了今后的研究方向和改进建议。     

基于PASS模型的汉语阅读障碍认知加工特点的实验研究

研究以智力的PASS认知模型为基础,考察了3-5年级阅读障碍组和正常对照组的PASS认知加工特点,探究汉语阅读障碍儿童的PASS认知缺陷模式,为后期的干预提供理论上的支持和帮助。结果发现,PASS四个认知加工均存在明显的年级差异,低年级儿童的PASS认知加工能力明显不如中高年级儿童。汉语阅读障碍儿童在DN: CAS 12项分任务上的成绩均低于正常对照组儿童。同时,大多数汉语阅读障碍儿童存在不止一种的PASS认知加工缺陷,即汉语发展性阅读障碍内部是一个异质群体;阅读障碍儿童在继时性加工上存在的问题最为严重,存在缺陷的人数也最多。     

汉语发展性阅读障碍亚类型的初步探讨

以阅读水平匹配组为参照对29名汉语发展性阅读障碍儿童的认知缺陷模式进行了分析,并考察了不同亚类型阅读障碍儿童的汉字识别模式。结果表明汉语发展性阅读障碍存在不同的亚类型,以语音缺陷型、快速命名缺陷型及两者结合的双重缺陷型为主,与英语国家研究中的双重缺陷假设一致。语音缺陷型儿童汉字识别时有更多的语义错误,对声旁中的部分语音线索不敏感;快速命名缺陷型儿童汉字识别时依赖声旁语音线索,表现出阅读发展的一般延迟;双重或多重认知缺陷型是阅读损伤最严重的亚类型     

发展性阅读障碍与小脑异常：小脑的功能和两者的因果关系

发展性阅读障碍(下文简称为"阅读障碍")不仅会影响个人的终身发展,还会对社会造成沉重的经济负担,深入探讨相关的神经机制,对实现阅读障碍的早期预测和干预十分重要。以往关于阅读障碍神经机制的模型多集中于大脑,近些年的研究发现,阅读障碍也与小脑异常有关,但到目前为止我们仍不清楚两者的关系。通过总结最新的研究进展,我们发现小脑在阅读障碍中可能发挥着多种功能,且小脑异常与阅读障碍可能互为因果。在此基础之上,我们提出了"阅读中小脑与大脑的功能映射假说",旨在从一个全新的角度揭示小脑与阅读的关系,以及两者与大脑的关系。相关内容对全面揭示阅读障碍的神经机制,以及小脑在高级认知加工中的作用,具有重要的启示意义。     

Dorsal stream deficits suggest hidden dyslexia among deaf poor readers: correlated evidence from reduced perceptual speed and elevated coherent motion detection thresholds

Prelingual deafness and developmental dyslexia have confounding developmental effects on reading acquisition. Therefore, standard reading assessment methods for diagnosing dyslexia in hearing people are ineffective for use with deaf people. Recently, Samar, Parasnis, and Berent (2002) reported visual evoked potential evidence that deaf poor readers, compared to deaf good readers, have dorsal stream visual system deficits like those previously found for hearing dyslexics. Here, we report new psychometric and psychophysical evidence that deficits in dorsal stream function, likely involving extrastriate area MT, are associated with relatively poor reading comprehension in deaf adults. Poorer reading comprehension within a group of 23 prelingually deaf adults was associated with lower scores on the Symbol Digit Modality Test, a perceptual speed test commonly used to help identify dyslexia in hearing people. Furthermore, coherent dot motion detection thresholds, which reflect the functional status of area MT, correlated negatively with reading scores in each visual quadrant. Elevated motion thresholds for deaf poor readers were not due to general cognitive differences in IQ but were specifically correlated with poor perceptual speed. With IQ controlled, a highly reliable right visual field advantage for coherent motion detection was found. Additional analyses suggested that the functional status of dorsal stream motion detection mechanisms in deaf people is related to reading comprehension, but the direction and strength of lateralization of those mechanisms is independent of reading comprehension. Our results generally imply that dyslexia is a hidden contributor to relatively poor reading skill within the deaf population and that assessment of dorsal stream function may provide a diagnostic biological marker for dyslexia in deaf people.     

A study of hyperlexia

Twelve children with early intense reading and superior word recognition skills coupled with disordered language and cognitive behavior are described. Cognitive, linguistic, and reading measures evidenced a generalized cognitive deficit in forming superordinate schemata which was not specific to visual or auditory modalities. Positive family histories for reading problems were present for 11 of the 12 children, suggesting a relationship between hyperlexia and dyslexia.     

Visual rapid naming and phonological abilities: different subtypes in dyslexic children

One implication of the double-deficit hypothesis for dyslexia is that there should be subtypes of dyslexic readers that exhibit rapid naming deficits with or without concomitant phonological processing problems. In the current study, we investigated the validity of this hypothesis for Portuguese orthography, which is more consistent than English orthography, by exploring different cognitive profiles in a sample of dyslexic children. In particular, we were interested in identifying readers characterized by a pure rapid automatized naming deficit. We also examined whether rapid naming and phonological awareness independently account for individual differences in reading performance. We characterized the performance of dyslexic readers and a control group of normal readers matched for age on reading, visual rapid naming and phonological processing tasks. Our results suggest that there is a subgroup of dyslexic readers with intact phonological processing capacity (in terms of both accuracy and speed measures) but poor rapid naming skills. We also provide evidence for an independent association between rapid naming and reading competence in the dyslexic sample, when the effect of phonological skills was controlled. Altogether, the results are more consistent with the view that rapid naming problems in dyslexia represent a second core deficit rather than an exclusive phonological explanation for the rapid naming deficits. Furthermore, additional non-phonological processes, which subserve rapid naming performance, contribute independently to reading development.     

Paired associate learning in Chinese children with dyslexia

A total of 82 Chinese 11- and 12-year-olds with and without dyslexia were tested on four paired associate learning (PAL) tasks, phonological awareness, morphological awareness, rapid naming, and verbal short-term memory in three different experiments. Experiment 1 demonstrated that children with dyslexia were significantly poorer in visual-verbal PAL than nondyslexic children but that these groups did not differ in visual-visual PAL performance. In Experiment 2, children with dyslexia had more difficulties in transferring rules to new stimuli in a rule-based visual-verbal PAL task as compared with children without dyslexia. Long-term retention of PAL was not impaired in dyslexic children across either experiment. In Experiment 3, rates of visual-verbal PAL deficits among children with dyslexia were all at or above 39%, the highest among all cognitive deficits tested. Moreover, rule-based visual-verbal PAL, in addition to morphological awareness and rapid naming ability, uniquely distinguished children with and without dyslexia even with other metalinguistic skills statistically controlled. Results underscore the importance of visual-verbal PAL for understanding reading impairment in Chinese children.     

中文阅读障碍儿童的时间加工缺陷:来自知觉学习干预研究的证据

前人研究指出,阅读障碍群体具有听觉通道内的时间加工缺陷,但截止目前为止,该缺陷的非模态性、跨语言一般性、干预前景及具体机制尚不明确。本文通过综述三项在中文阅读障碍儿童中开展的听觉、视觉时间加工知觉训练,以及它们对阅读成绩的迁移效应,对时间加工技能与阅读障碍的关系,及其影响阅读发展的认知机制进行了探讨和分析,并在此基础上,提出了未来的研究构想,以充实该领域的理论建构。     

The Effect of Parents’ Literacy Skills and Children’s Preliteracy Skills on the Risk of Dyslexia

The combination of investigating child and family characteristics sheds light on the constellation of risk factors that can ultimately lead to dyslexia. This family-risk study examines plausible preschool risk factors and their specificity. Participants (N?=?196, 42 % girls) included familial risk (FR) children with and without dyslexia in Grade 3 and controls. First, we found impairments in phonological awareness, rapid naming, and letter knowledge in FR kindergartners with later dyslexia, and mild phonological-awareness deficits in FR kindergartners without subsequent dyslexia. These skills were better predictors of reading than arithmetic, except for rapid naming. Second, the literacy environment at home was comparable among groups. Third, having a dyslexic parent and literacy abilities of the non-dyslexic parent related to offspring risk of dyslexia. Parental literacy abilities might be viewed as indicators of offspring’s liability for literacy difficulties, since parents provide offspring with genetic and environmental endowment. We propose an intergenerational multiple deficit model in which both parents confer cognitive risks.     

Speed of processing and reading disability: a cross-linguistic investigation of dyslexia and borderline intellectual functioning

English and Italian children with dyslexia were compared with children with reading difficulties associated with low-IQ on tests of simple and choice RT, and in number and symbol scanning tasks. On all four speed-of-processing tasks, children with low-IQ responded more slowly than children with dyslexia and age-controls. In the choice RT task, the performance of children with low-IQ was also less accurate than that of children of normal IQ, consistent with theories linking processing speed limitations with low-IQ. These findings support the hypothesis that dyslexia is a specific cognitive deficit that can arise in the context of normal IQ and normal speed of processing. The same cognitive phenotype was observed in readers of a deep (English) and a shallow (Italian) orthography.     

发展性阅读障碍的视听时间敏感性缺陷及其脑神经机制

阅读是一个视听加工过程,阅读障碍的产生可能是过程中视听时间敏感性缺陷的结果。视听时间敏感性指个体对视觉和听觉刺激出现时间的感知能力,可通过同时性判断、时间顺序判断和视听整合考察。研究发现,阅读障碍者在这一能力上表现出行为和脑层面异常。而这些研究多是拼音文字背景,汉语文字下该领域研究相当少。未来需要丰富实验设计,扩大对汉语背景下视听时间敏感性研究,并以此开发干预手段,为阅读障碍的机制和治疗提供借鉴。     

Dyslexia and dyscalculia: Two learning disorders with different cognitive profiles

This study tests the hypothesis that dyslexia and dyscalculia are associated with two largely independent cognitive deficits, namely a phonological deficit in the case of dyslexia and a deficit in the number module in the case of dyscalculia. In four groups of 8- to 10-year-olds (42 control, 21 dyslexic, 20 dyscalculic, and 26 dyslexic/dyscalculic), phonological awareness, phonological and visual-spatial short-term and working memory, naming speed, and basic number processing skills were assessed. A phonological deficit was found for both dyslexic groups, irrespective of additional arithmetic deficits, but not for the dyscalculia-only group. In contrast, deficits in processing of symbolic and nonsymbolic magnitudes were observed in both groups of dyscalculic children, irrespective of additional reading difficulties, but not in the dyslexia-only group. Cognitive deficits in the comorbid dyslexia/dyscalculia group were additive; that is, they resulted from the combination of two learning disorders. These findings suggest that dyslexia and dyscalculia have separable cognitive profiles, namely a phonological deficit in the case of dyslexia and a deficient number module in the case of dyscalculia.     

获得性阅读障碍的“主要系统”假说

认知神经心理学为阅读机制的探讨提供了大量的证据,认为不同阅读障碍是不同加工通道选择性受损的结果。近年来,基于联结主义的三角模型理论,研究者提出了主要系统假说（primary system hypothesis）,认为阅读障碍是主要的认知系统（如视觉、语义和语音系统）受损导致的：表层障碍是因为语义系统受损导致的阅读困难,语音和深层障碍是语音和语义系统同时受损时综合症状的连续体。该理论认为各主要系统可能同时是多个认知活动的加工成分,一个系统的受损会影响所有与之相关的认知过程,从而把阅读障碍与其它认知功能障碍联系起来。统一的主要系统受损下对各种获得性阅读障碍形成机制在文中得到详细的解释     

发展性阅读障碍亚类型研究进展

发展性阅读障碍是一种特殊的学习障碍,伴有多种认知缺陷并且存在不同的亚类型。依据相关的阅读模型理论,阅读障碍可划分为语音型和表层型。从认知缺陷角度出发,语音加工缺陷是主要的缺陷表现,以此为特征形成一种主要的阅读障碍的亚类型,同时还有以正字法加工缺陷和快速命名缺陷为主的其他亚类型。而以基本感知觉缺陷为标准,主要有以视觉加工缺陷和以听觉加工缺陷为主的两种亚类型。在汉语条件下,依据同样的阅读模型理论,语音型阅读障碍亚类型比例明显低于拼音文字条件下的。汉语阅读障碍也具有分别以语音加工缺陷、快速命名缺陷和正字法加工缺陷为主要认知缺陷的亚类型。未来有必要从神经机制角度进一步明确不同亚类型的神经基础。     

Generalist genes: implications for the cognitive sciences

In the 'generalist genes' hypothesis, it is suggested that the same genes affect most cognitive abilities and disabilities. This recently proposed hypothesis is based on considerable multivariate genetic research showing that there is substantial genetic overlap between such broad areas of cognition as language, reading, mathematics and general cognitive ability. We assume that the hypothesis is correct and consider here its implications for cognitive neuroscience. In our opinion, the two key genetic concepts of pleiotropy (in which one gene affects many traits) and polygenicity (in which many genes affect a trait) that underlie the generalist genes hypothesis imply a 'generalist brain'. That is, the genetic input into brain structure and function is general not specific.     

Right-hemisphere reading in a case of developmental deep dyslexia

The right-hemisphere hypothesis of deep dyslexia has received support from functional imaging studies of acquired deep dyslexia following damage to the left cerebral hemisphere, but no imaging studies of cases of developmental deep dyslexia, in which brain damage is not suspected, have been reported. In this paper, we report the first evidence of right hyperactivation in an adult case of developmental deep dyslexia. Hyperactivation was observed in the right inferior frontal cortex during functional magnetic resonance imaging (fMRI) of the oral reading of imageable content words and nonwords to which imageable lexical responses were frequently made. No evidence of right hyperactivation was observed in the oral reading of function words, nor during the naming of imageable words in response to pictured objects. The results reveal strategic and selective use of right-hemisphere functions for particular types of written stimuli. We propose that children with developmental deep dyslexia compensate for their lack of phonological skills by accessing right-hemisphere imageable associations that provide a mnemonic for linking written forms to spoken names.