Structural imaging in dyslexia: the planum temporale

The search for a neurobiological substrate for dyslexia has focused on anomalous planum symmetry. The results of imaging studies of the planum have been inconsistent, perhaps due to diagnostic uncertainty, technical differences in measurement criteria, and inadequate control of handedness, sex, and cognitive ability. Although structural imaging studies have not clarified the neurobiology of reading disability, converging evidence suggests that variation in asymmetry of the planum temporale does have functional significance. Studies in a variety of populations have shown a significant association between planar asymmetry, the strength of hand preference, and general verbal skills such as vocabulary and comprehension. Future structural imaging studies of dyslexia should match participants on hand preference and general verbal ability in order to determine the relationship between brain structure and written and oral language.     

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.     

Auditory processing in developmental dyslexia: An exploratory study of an auditory and visual matching training program with Swedish children with developmental dyslexia

This study examined whether training using a nonverbal auditory-visual matching task had a remedial effect on reading skills in developmental dyslexia. The pretest/post-test design was used with Swedish children ( N = 41), between the ages of 7 and 12. Training comprised twice-weekly sessions of 15 minutes, over eight weeks. There was an improvement in auditory-visual matching during the training period. There were also improvements in some reading test scores, especially in reading nonsense words and in reading speed. These improvements in tasks which are thought to rely on phonological processing suggest that such reading difficulties in dyslexia may stem in part from more basic perceptual difficulties, including those required to manage the visual and auditory components of the decoding task. The utility of the concept of auditory structuring is discussed in relation to auditory and phonological processing skills when a child learns to read.     

Global and local pitch perception in children with developmental dyslexia

This study investigated global versus local pitch pattern perception in children with dyslexia aged between 8 and 11 years. Children listened to two consecutive 4-tone pitch sequences while performing a same/different task. On the different trials, sequences either preserved the contour (local condition) or they violated the contour (global condition). Compared to normally developing children, dyslexics showed robust pitch perception deficits in the local but not the global condition. This finding was replicated in a simple pitch direction task, which minimizes sequencing and short term memory. Results are consistent with a left-hemisphere deficit in dyslexia because local pitch changes are supposedly processed by the left hemisphere, whereas global pitch changes are processed by the right hemisphere. The present data suggest a link between impaired pitch processing and abnormal phonological development in children with dyslexia, which makes pitch pattern processing a potent tool for early diagnosis and remediation of dyslexia.     

Accuracy and speed of orthographic processing in persons with developmental dyslexia

A group of 39 persons (20 male and 19 female, 11.0 to 32.5 yr.) with developmental dyslexia and 42 controls (21 male and 21 female, 11.2 to 32.3 years) were compared on computerized tests of sight word reading, nonword decoding, and spelling recognition. The subjects with developmental dyslexia performed significantly slower and less accurately than controls on all tasks. Further, the effect size of the group differences was larger for the older group. Within-group analyses showed a significant difference by age group on accuracy. Only the control group showed a significant age difference between groups on response time. Mean accuracy and response times for the reading-disabled subjects resembled shifted versions of the control group means. These results agree with previous reports that phonological deficits persist for reading-disabled adults and suggest a test of whether the discrepancy between reading-disabled and typically achieving readers may actually increase across age groups.     

Coherence of hemispheric function in developmental dyslexia

Left parieto-occipital EEG leads record a frequency spectrum in dyslexics that is consistently different from the spectrum obtained from normals. It is suggested that these effects represent significant differences in the functional organization of these areas. EEG coherence values indicate that normals have significantly greater sharing between hemispheres at symmetrical locations. Dyslexics demonstrate significantly greater sharing within hemisphere than do normals. The data supports developmental dyslexia being a functional hemispheric disconnection syndrome.     

Rate variables and automatized naming in developmental dyslexia

The rate variable in rapid automatized naming (RAN) was investigated in 50 adolescent and 40 adult students with developmental dyslexia, in matched normal controls, and in learning-disabled students without reading difficulties. Visual stimuli depicting familiar colors and common objects were presented in isolation at three film speeds and three exposure times. Film speed and exposure time contributed as independent variables to error rate; and dyslexic subjects of both age groups made significantly more naming errors than controls. Dyslexic subjects also responded with longer naming latencies than controls when the same RAN stimuli were presented in a continuous sequential mode as a matrix of rows and columns. Naming latencies in the sequential presentation were highly correlated with naming errors in the film version. The implications of reduced naming rates for nongraphological stimuli in developmental dyslexia are discussed.     

Separating global and specific factors in developmental dyslexia

The general goal of the study was to identify global and specific components in developmental dyslexia using various manipulations based on the rapid automatization paradigm (RAN). In two experiments, we used both factor analysis and the Rate-and-Amount Model to verify if one (or more) global factor(s) and a variety of specific effects contribute to the naming (and visual search) deficits in children with dyslexia.

Results of Experiment 1 indicated the presence of three global components: pictorial naming, detailed orthographic analysis, and visual search. Pictorial naming is predicated by typical RAN tasks (such as naming colors or objects), independent of set size, but also from a variety of other tasks including Stroop interference conditions. The detailed orthographic analysis factor accounts for naming of orthographic stimuli at high set size. Visual search marked tasks requiring the scanning of visual targets.

Results of Experiment 2 confirmed the separation between the pictorial naming and detailed orthographic analysis factors both in the original sample and in a new group of children. Furthermore, specific effects of frequency, lexicality, and length were shown to contribute to the reading deficit.

Overall, it is proposed that focusing on the profile of both global and specific effects provides a more effective and, at the same time, simpler account of the dyslexics' impairment.     

Separating global and specific factors in developmental dyslexia

The general goal of the study was to identify global and specific components in developmental dyslexia using various manipulations based on the rapid automatization paradigm (RAN). In two experiments, we used both factor analysis and the Rate-and-Amount Model to verify if one (or more) global factor(s) and a variety of specific effects contribute to the naming (and visual search) deficits in children with dyslexia. Results of Experiment 1 indicated the presence of three global components: pictorial naming, detailed orthographic analysis, and visual search. Pictorial naming is predicated by typical RAN tasks (such as naming colors or objects), independent of set size, but also from a variety of other tasks including Stroop interference conditions. The detailed orthographic analysis factor accounts for naming of orthographic stimuli at high set size. Visual search marked tasks requiring the scanning of visual targets. Results of Experiment 2 confirmed the separation between the pictorial naming and detailed orthographic analysis factors both in the original sample and in a new group of children. Furthermore, specific effects of frequency, lexicality, and length were shown to contribute to the reading deficit. Overall, it is proposed that focusing on the profile of both global and specific effects provides a more effective and, at the same time, simpler account of the dyslexics' impairment.     

Procedural learning and automatization process in children with developmental coordination disorder and/or developmental dyslexia

ObjectiveThere is increasing evidence to suggest that developmental dyslexia (DD) and developmental coordination disorder (DCD) actually form part of a broader disorder. Their frequent association could be justified by a deficit of the procedural memory system, that subtends many of the cognitive, motor and linguistic abilities that are impaired in both DD and DCD. However, studies of procedural learning in these two disorders have yielded divergent results, and in any case no studies have so far addressed the issue of automatization (dual-task paradigm).MethodsWe administered a finger tapping task to participants aged 8–12 years (19 DCD, 18 DD, and 22 with both DD and DCD) to explore procedural learning and automatic movements in these three groups of children, comparing motor performances at the prelearning stage, after 2 weeks of training, and in a post-training dual-task condition.ResultsFirst, results indicated that all the children were able to learn a sequence of movements and even automatize their movements. Second, they revealed between-groups differences in procedural/automatization learning abilities, setting the DCD group apart from the other two. Third, contrary to our expectations concerning comorbidity, they suggested that the DD + DCD association does not have an additional impact on behavioral performances.     

Atypical cognitive disorders in a man with developmental surface dyslexia

The neuropsychological profile of a man with a developmental surface dyslexia is presented here. This case study is of interest because J.C. exhibited a pattern of cognitive disorders rarely documented in previous data. Results showed that JC's difficulties in reading comprehension were closely related to complex memory disorders and were also associated with cognitive slowness. The present observations do not support the visual memory failure hypothesis. The data rather suggest that the core difficulty primarily lies with the nonautomatization of grapheme-phoneme correspondence rules, which in turn dramatically contributed to lexicon weaknesses. The hypothesis of a timing mechanism in reading disorders is discussed.     

Naming difficulties in adolescents with dyslexia: application of the tip-of-the-tongue paradigm

The present study used the "tip-of-the-tongue" (TOT) experimental paradigm in a picture-naming task to explore the naming deficits of adolescents with dyslexia. As compared with a control group of typically developing readers, the adolescents with dyslexia had fewer correct responses and more TOT responses. When they failed to retrieve a target word, the adolescents with dyslexia had more phonological substitutions and benefited less from a phonological cue. However, both groups did not differ in the amount of semantic substitutions and supplied the same amount and kind of partial semantic information on the missing target word. These findings suggest that adolescents with dyslexia have significant naming difficulties that seem to arise because of difficulty in accessing the phonological word forms after the corresponding abstract lexical representation has been successfully accessed.     

Mental rotation of letters and shapes in developmental dyslexia

Extending the work of Corballis et al (1985, Cortex 21 225-236), we investigated mental rotation of letters (experiment 1), and of letters and shapes (experiment 2) in normal readers and developmental dyslexics. Whereas the overall response times were equal for shapes in both groups, for letters they were slower in dyslexics. For letters as well as for shapes, however, the same mental-rotation effects were obtained between the groups. The results are interpreted as support for the notion of developmental dyslexia as a deficit in functional coordination between graphemic and phonological letter representations.     

发展性阅读障碍的视觉注意广度技能

发展性阅读障碍在许多任务中都出现同时性加工多个视觉刺激的困难, 即视觉注意广度缺陷.本文分别综述了国内外探查阅读障碍视觉注意广度的研究.目前, 相关研究结果仍存争议, 这可能与背景语言的正字法深度以及被试年龄发展差异有关.未来研究还需利用干预,跨语言比较等方法进一步探讨阅读障碍与视觉注意广度之间的关系, 并结合脑电,脑成像技术探究汉语阅读障碍视觉注意广度的内在神经机制.     

The processing of rhythmic structures in music and prosody by children with developmental dyslexia and developmental language disorder

Rhythm perception seems to be crucial to language development. Many studies have shown that children with developmental dyslexia and developmental language disorder have difficulties in processing rhythmic structures. In this study, we investigated the relationships between prosody and musical processing in Italian children with typical and atypical development. The tasks aimed to reproduce linguistic prosodic structures through musical sequences, offering a direct comparison between the two domains without violating the specificities of each one. About 16 Typically Developing children, 16 children with a diagnosis of Developmental Dyslexia, and 16 with a diagnosis of developmental language disorder (age 10–13 years) participated in the experimental study. Three tasks were administered: an association task between a sentence and its humming version, a stress discrimination task (between couples of sounds reproducing the intonation of Italian trisyllabic words), and an association task between trisyllabic nonwords with different stress position and three‐notes musical sequences with different musical stress. Children with developmental language disorder perform significantly lower than Typically Developing children on the humming test. By contrast, children with developmental dyslexia are significantly slower than TD in associating nonwords with musical sequences. Accuracy and speed in the experimental tests correlate with metaphonological, language, and word reading scores. Theoretical and clinical implications are discussed within a multidimensional model of neurodevelopmental disorders including prosodic and rhythmic skills at word and sentence level.     

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。     

Writing problems in developmental dyslexia: under-recognized and under-treated

The International Dyslexia Association defines dyslexia as unexpected problems of neurobiological origin in accuracy and rate of oral reading of single real words, single pseudowords, or text or of written spelling. However, prior research has focused more on the reading than the spelling problems of students with dyslexia. A test battery was administered to 122 children who met the inclusion criteria for dyslexia and qualified their families for participation in a family genetics study that has been ongoing for over a decade. Their parents completed the same test battery. Although a past structural equation modeling study of typically developing children identified a significant path from handwriting to composition quality, the current structural equation modeling study identified a significant path from spelling to composition for children and their parents with dyslexia. Grapho-motor planning did not contribute uniquely to their composition, showing that writing is not just a motor skill. Students with dyslexia do have a problem in automatic letter writing and naming, which was related to impaired inhibition and verbal fluency and may explain their spelling problems. Results are discussed in reference to the importance of providing explicit instruction in the phonological, orthographic, and morphological processes of spelling and in composition to students with dyslexia and not only offering accommodation for their writing problems.     

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.     

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.