Phonemic deficits in developmental dyslexia

Summary The present study explored a possible relationship between reading difficulties and speech difficulties. Dyslexic and normal readers, matched for Reading Age, were compared first on a reading task and secondly on a speaking task.In the first experiment, the two groups were asked to read nonsense words aloud. Both groups were able to read one-syllable nonwords equally well but the dyslexics had more difficulty than the normal readers when asked to read two-syllable nonwords. Moreover, they found two-syllable nonwords containing consonant clusters particularly difficult. The probability of their making an error increased with the number of consonant clusters.In the second experiment, the subjects were required to repeat real words and nonsense words of two, three, or four syllables. Both groups found nonsense words more difficult to repeat than real words. However, the relative difficulty of nonsense words over real words was greater for the dyslexic group. Their difficulty was especially marked when they had to repeat four-syllable nonsense words.Thus, in both experiments the dyslexic readers were more affected by the phonological complexity of the stimuli than the normal readers were. Hence, it was suggested that the dyslexic readers tested were subject to a general phonemic deficit which affected their ability to process both written and spoken words.     

发展性阅读障碍的听觉时间加工缺陷

发展性阅读障碍是指个体在智力正常并且不缺乏学校教育的情况下, 仍无法获得与年龄相匹配的阅读技能的一种学习障碍, 其缺陷的本质一直是研究者争论的焦点。大量研究显示, 阅读障碍者常表现出听觉时间加工损伤。在行为层面, 阅读障碍者难以辨别快速、连续呈现刺激的顺序以及刺激本身的动态时间特征。在神经层面, 阅读障碍者诱发的失匹配负波更弱且具有异常的神经同步加工。这些损伤同时存在于对言语和非言语刺激的加工中, 表明听觉时间加工缺陷非言语加工所特有。未来的研究还需阐明以下几个问题：1)阅读障碍的听觉时间加工缺陷发生在哪些时间窗口, 随年龄增长如何变化; 2)阅读障碍听觉时间加工缺陷在神经层面的时间进程是怎样的; 3)听觉时间加工缺陷是否为阅读障碍的核心缺陷。     

Picture naming deficits in developmental dyslexia in German

Recent research with English developmental dyslexics comparing the picture naming performance of these children to the picture naming performance of non-dyslexic (‘garden variety’) poor readers, reading age matched controls and chronological age matched controls has suggested that a selective difficulty in retrieving the phonological codes of known names on demand underlies the picture naming deficit found in developmental dyslexia (Swan & Goswami, Picture naming deficits in developmental dyslexia: the phonological representations hypothesis, Brain and Language, 56 (1997), 334–353). If the underlying causal factors in dyslexia are independent of the orthography that the child is learning to read, then a difficulty in retrieving the phonological codes of known names on demand should also be found in developmental dyslexics who are learning to read other languages. We therefore set out to replicate Swan and Goswami’s study with a group of German developmental dyslexics. We were interested to see whether a phonological deficit is characteristic of dyslexia in all orthographies, even those, such as German, in which high orthographic transparency means that dyslexic children read with considerable accuracy.     

M-stream deficits and reading-related visual processes in developmental dyslexia

Some visual processing deficits in developmental dyslexia have been attributed to abnormalities in the subcortical M stream and/or the cortical dorsal stream of the visual pathways. The nature of the relationship between these visual deficits and reading is unknown. The purpose of the present article was to characterize reading-related perceptual processes that may link the visual deficits to reading problems. We identified contrast sensitivity, position encoding, oculomotor control, visual attention, parafoveal/foveal interactions, and saccadic suppression as potential reading-related dorsal stream processes. We then evaluated the role of each process in reading and the status of each process in dyslexia. In theory, a number of dorsal stream processes (e.g., oculomotor control and visual attention) might contribute to reading problems in developmental dyslexia. More work is needed to demonstrate the connection empirically.     

发展性阅读障碍书写加工缺陷及其神经机制

发展性阅读障碍是学习障碍的主要类型之一, 严重影响个体认知、情感与社会适应性的发展。书写与阅读关系密切, 阅读障碍者常常表现出书写加工缺陷。在行为层面, 阅读障碍者书写缺陷表现在书写质量差、速度慢和停顿多等多个方面。在脑机制层面, 脑成像研究发现, 阅读障碍者书写加工缺陷与字形加工脑区活动, 以及字形与运动区脑功能与结构连接异常有关。总体而言, 阅读障碍者书写过程中的字形通达缺陷的证据比较充分, 但字形与运动编码的衔接以及运动执行是否存在困难, 尚缺乏研究证据。相对于字母语言, 书写与阅读的关系在汉语中更为紧密, 汉语阅读障碍的书写研究将为开发汉语特色的诊治方案提供重要指导。     

Action representation deficits in adolescents with developmental dyslexia

Developmental dyslexia (DD), a severe and frequent disorder of reading acquisition, is characterized by a diversity of cognitive and motor deficits whose interactions still remain under debate. Although deficits in the automatization of sensorimotor control have been highlighted, internal action representation allowing prediction has never before been investigated. In this study, we considered action representation of 18 adolescents with pure DD and 18 age-matched typical readers. Participants actually and mentally performed a visually guided pointing task involving strong spatiotemporal constraints (speed/accuracy trade-off paradigm). While actual and mental movement times of typical readers were isochronous and both conformed to Fitts’ law, the movement times of dyslexics differed between conditions, and only the actual movement times conformed to Fitts’ law. Furthermore, the quality of motor imagery correlated with word reading abilities. This suggests that the process of action representation is impaired in pure DD and supports the sensorimotor perspective of DD. Theoretical implications are discussed.     

Heterogeneity of deficits in developmental dyslexia and implications for methodology

Most of the studies overviewed by Farmer and Klein (1995) in their review of temporal processing disorders in developmental dyslexia have taken a group study approach in which a group of dyslexic readers is compared with a group of normal readers on some task thought to be relevant to the reading disorder. Because of the acknowledged heterogeneity of deficits among developmental dyslexics, this group study methodology is inappropriate and is likely to lead to findings in one lab that cannot be replicated in another. The single case study methodology, which has been used successfully in the study of adult neuropsychological impairments, should be adopted in the study of developmental impairments as well. In the case study approach, each individual is studied thoroughly with tasks designed to tap the various components of the cognitive domain under study in order to determine which components are spared and which impaired. Data are not averaged, but reported separately for each case. Some recent findings from case studies on developmental dyslexia are reviewed and suggestions are made as to how the case study approach could be used in analyzing whether a temporal processing disorder, or any other hypothesized factor, is causal to the reading disorder.     

Early naming deficits, developmental dyslexia, and a specific deficit hypothesis.

The present research represents the final 2 years of a 5-year longitudinal investigation of (a) confrontation-based, word-retrieval deficits in dyslexic children; (b) the role of vocabulary development in these deficits; (c) the relationship between confrontation naming performance and three carefully defined aspects of reading performance in the general population and in eight dyslexic case studies; and (d) the possible specificity of word-retrieval deficits in dyslexia. Results indicate enduring problems in word-retrieval processes for dyslexic children across the primary grades and into middle childhood. Second, these deficits cannot be explained by simple vocabulary deficits. Third, these results in conjunction with our earlier data consolidate a pattern of differential relationships between specific reading and confrontation naming skills that are based on development and on the level of processes involved. Trends within case studies suggest the more pronounced the retrieval deficit, the more global the reading impairment. And fourth, there appear to be some specific differences in the basis of word-retrieval problems between dyslexic and garden-variety or lower achieving readers. Results are discussed within a speculative framework that implicates problems in timing as a possible predetermining condition in the dyslexias.     

发展性阅读障碍的噪音抑制缺陷

发展性阅读障碍的缺陷本质一直是研究者们关注和争论的焦点。近些年, 有研究者提出了一种新的理论假设——噪音抑制缺陷假设, 并得到了许多研究证据的支持。这种缺陷在视觉和听觉通道中均存在, 说明阅读障碍具有多感觉/一般性噪音抑制缺陷。但也有研究者指出知觉噪音抑制本质上反映了注意的功能, 因而这种缺陷可能是由注意缺陷导致的。目前还缺乏直接证据支持汉语阅读障碍存在噪音抑制缺陷。最后本文对该领域未来的发展方向做出展望。     

Developmental dyslexia and word retrieval deficits

Developmental dyslexics, selected on the basis of very slow naming rates on the Rapid Automatic Naming Tasks (RAN), were compared to normal readers on oral language, picture categorization, and reading tasks. Findings indicated that the dyslexics' word retrieval deficits were one symptom of a more generalized, however subtle, oral language deficit which involved both receptive and expressive oral language functioning. The dyslexics' word retrieval problem also seemed chiefly related to language processing and not to deficits in semantic memory as there were no significant differences between dyslexics and controls on a nonverbal semantic memory task (picture categorization). In naming and identifying printed words, the dyslexics appeared to rely considerably upon the "indirect" or "assembly-of-phonology" route; they were slower in naming irregularly spelled words compared to regularly spelled words and on a lexical decision task, the dyslexics were slower in making negative decisions for "pseudohomophones" (e.g., "braik") than for other matched nonwords. Results are discussed in terms of the logogen model with some consideration of a developmental model as well.     

Flicker masking and developmental dyslexia

Recent studies have provided evidence that dyslexic children tend to show longer visual persistence than control children when presented with low-spatial-frequency grating stimuli. The possibility that this phenomenon might reflect an impairment of inhibitory Y-cell activity in the visual system of dyslexics has been investigated. A flicker masking technique was used to mask Y-cell activity selectively in a group of dyslexic boys and a group of age-matched controls. There were no overall differences in reaction times to the offsets of grating patterns of various spatial frequencies between the groups, and no differences between subgroups defined by age, degree of reading impairment, or any other criterion. The results show no evidence of abnormal Y-cell function in developmental dyslexia.     

Acquired and developmental spelling dyslexia

Two cases of acquired spelling dyslexia and one case of developmental spelling dyslexia are described along with accounts of their performance on various psycholinguistic tasks. It is argued that there is some evidence that spelling dyslexia may exist in developmental form but that parallels are difficult to draw because of the very different histories of child and adult cases. It is also suggested that features of surface dyslexia exist in at least a proportion of spelling dyslexic cases and that this may be influenced by level of premorbid reading skill.     

The developmental relationship between identity and equivalence conservation

Hooper's (1969a) finding that identity conservation develops prior to equivalence conservation was investigated using a more stringent within-subject design. Seventy-two kindergarten, first, and second graders were given three conservation tasks: (1) Identity, (2) Equivalence 1, in which the perceptual cues were comparable to those in Identity, and (3) Equivalence 2, the traditional Piagetian conservation task. Each task was administered under two levels of transformation. No significant differences in performance as a function of level of transformation, type of equivalence task, or sex of S were found, but first and second grade Ss performed better than kindergarten Ss. Eighty-six percent of the sample conserved in an all-or-none fashion, and 7 Ss (10%) passed equivalence while failing identity, thus contradicting the developmental priority of identity conservation.     

The cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia

The present study was conducted to examine the cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia. Thirty Chinese dyslexic children in Hong Kong were compared with 30 average readers of the same chronological age (CA controls) and 30 average readers of the same reading level (RL controls) in a number of rapid naming, visual, phonological, and orthographic tasks. Chinese dyslexic children performed significantly worse than the CA controls but similarly to the RL controls on most of the cognitive tasks. The rapid naming deficit was found to be the most dominant type of cognitive deficit in Chinese dyslexic children. Over half of the dyslexic children exhibited deficits in 3 or more cognitive areas, and there was a significant association between the number of cognitive deficits and the degree of reading and spelling impairment. The present findings support the multiple-deficit hypothesis in Chinese developmental dyslexia.     

Working memory functioning in developmental dyslexia

Working memory impairments in dyslexia are well documented. However, research has mostly been limited to the phonological domain, a modality in which people with dyslexia have a range of problems. In this paper, 22 adult students with dyslexia and 22 age- and IQ-matched controls were presented with both verbal and visuospatial working memory tasks. Performance was compared on measures of simple span, complex span (requiring both storage and processing), and dynamic memory updating in the two domains. The dyslexic group had significantly lower spans than the controls on all the verbal tasks, both simple and complex, and also on the spatial complex span measure. Impairments remained on the complex span measures after controlling statistically for simple span performance, suggesting a central executive impairment in dyslexia. The novelty of task demands on the initial trials of the spatial updating task also proved more problematic for the dyslexic than control participants. The results are interpreted in terms of extant theories of dyslexia. The possibility of a supervisory attentional system deficit in dyslexia is also raised. It seems clear that working memory difficulties in dyslexia extend into adulthood, can affect performance in both the phonological and visuospatial modalities, and implicate central executive dysfunction, in addition to problems with storage.     

发展性阅读障碍儿童阅读中的眼跳定位缺陷：基于新词学习的实验证据

通过与生理年龄匹配儿童比较新词重复学习中眼跳定位模式变化的异同, 探讨发展性阅读障碍儿童在新词学习中的眼跳定位是否存在缺陷。以发展性阅读障碍儿童和生理年龄匹配儿童为被试, 采用重复学习新词范式, 结果发现：(1)与生理年龄匹配组相比, 发展性阅读障碍儿童跳入新词的眼跳距离较短、首次注视落点位置更靠近词首; (2)生理年龄匹配组儿童利用学习次数调节新词眼跳定位模式的能力高于发展性阅读障碍儿童, 即随着新词学习次数的增加, 生理年龄匹配组儿童跳入和跳出新词的眼跳距离随之增长, 首次注视落点位置更靠近词中心; 相比之下, 发展性阅读障碍儿童仅在跳出新词的眼跳距离上有所增长, 但增加幅度也显著小于生理年龄匹配组。结果表明, 发展性阅读障碍儿童在新词学习中的眼跳定位, 及利用学习次数对眼跳定位的调节上均表现出一定缺陷。     

Working memory functioning in developmental dyslexia

Working memory impairments in dyslexia are well documented. However, research has mostly been limited to the phonological domain, a modality in which people with dyslexia have a range of problems. In this paper, 22 adult students with dyslexia and 22 age- and IQ-matched controls were presented with both verbal and visuospatial working memory tasks. Performance was compared on measures of simple span, complex span (requiring both storage and processing), and dynamic memory updating in the two domains. The dyslexic group had significantly lower spans than the controls on all the verbal tasks, both simple and complex, and also on the spatial complex span measure. Impairments remained on the complex span measures after controlling statistically for simple span performance, suggesting a central executive impairment in dyslexia. The novelty of task demands on the initial trials of the spatial updating task also proved more problematic for the dyslexic than control participants. The results are interpreted in terms of extant theories of dyslexia. The possibility of a supervisory attentional system deficit in dyslexia is also raised. It seems clear that working memory difficulties in dyslexia extend into adulthood, can affect performance in both the phonological and visuospatial modalities, and implicate central executive dysfunction, in addition to problems with storage.     

发展性阅读障碍的视觉空间注意加工能力

鉴于阅读起始于基础视觉加工阶段, 越来越多的研究者开始关注阅读障碍者的视觉空间注意加工能力。视觉空间注意是指个体对视觉刺激的空间位置的注意, 可通过线索提示、视觉搜索和视觉注意广度等视觉任务来考察。大量国内外研究发现, 发展性阅读障碍者在视觉空间注意任务下表现出行为和神经活动方面的异常。其中的神经机制问题不仅反映在与视觉空间注意有关的顶叶区域激活异常, 还存在于脑区间功能连接异常(如顶叶区域与字形加工区的功能连接)。未来研究还需利用横断和追踪研究探讨阅读障碍与视觉空间注意能力发展关系的内在机制, 以及探究语言特性对阅读障碍者视觉空间注意缺陷的可能调节作用。     

Why theories about developmental dyslexia require developmental designs

This article examines the importance of developmental designs in dyslexia research using a neuroconstructivist framework. According to neuroconstructivism, the lowest level of impairment should be identified as early as possible, and developmental effects on higher-level cognition examined longitudinally. A number of recent studies proposing candidate low-level impairments have not used such developmental designs. The role of normal variation in postulated causal factors on development is ignored, inadequate control groups are used, and the nature and timing of environmental inputs are not measured, even though reading is taught systematically and both reading acquisition and dyslexia vary with orthography. It is suggested here that only a phonological deficit arising from low-level auditory processing problems meets the criteria for a neuroconstructivist approach.     

Multiple stimulus presentation yields larger deficits in children with developmental dyslexia: A study with reading and RAN-type tasks

In this study, we examined the effect of multiple versus single stimulus presentation in typically developing readers and children with developmental dyslexia. The tasks involved either reading single words or arrays of words or naming single or multiple colors and digits (rapid automatized naming or RAN). To be able to compare these sets of conditions, we recorded total response times (i.e., the time between stimulus onset and the end of the participant’s vocal response) in all cases. The study included 43 typically developing readers and 25 children with dyslexia.

Results indicate that typically developing readers have a clear advantage with multiple over single items on both RAN and reading tasks. The children with dyslexia showed a moderate advantage for multiple stimuli in naming colors and digits but presented the opposite pattern in reading.

With regard to reading, the disproportionate impairment of the children with dyslexia in dealing with multiple arrays suggests difficulty in integrating the multiple subcomponents of the reading task over and above the basic nuclear deficit in decoding words. Regarding the RAN tasks, results confirm that the requirement of integrating multiple subcomponents may be critical in mediating the predictive value of these measures on reading.