Visual versus phonological abilities in Spanish dyslexic boys and girls

Phonological and visual theories propose different primary deficits as part of the explanation for dyslexia. Both theories were put to test in a sample of Spanish dyslexic readers. Twenty-one dyslexic and 22 typically-developing children matched on chronological age were administered phonological discrimination and awareness tasks and coherent motion perception tasks. No differences were found between groups on the coherent motion tasks, whereas dyslexic readers were impaired relative to controls on phonological discrimination tasks. Gender differences followed the opposite pattern, with no differences on phonological tasks, and dyslexic girls performing significantly worse than dyslexic boys in coherent motion perception. These results point to the importance of phonological deficits related to speech perception in Spanish, and to possible gender differences in the neurobiological bases for dyslexia.     

Are there different patterns of cerebral asymmetry between dyslexic subtypes?

The purpose of this research has been to analyze the cerebral asymmetry in dyslexic children and, specifically for demonstrating whether there are different patterns of cerebral asymmetry among subtypes of dyslexia. We used a sample of 89 dyslexic children divided into subtypes obtained from the Jimenez and Ramirez (2002) study. The dual-task method was used to assess hemispheric specialization. The data were compared with that obtained from a control group of normal readers of same age (CA; N= 37) and with a younger reading level control group (RL; N= 40). We found that in the dyslexic group, similarly to the younger reading level group, a high percentage of children showed convergence in the left hemisphere of both linguistic and spatial functions. This pattern was also found in the RL control group. On the other hand, we did not find different patterns of cerebral asymmetry between dyslexic subtypes.     

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。     

Attention Processes in Children with Movement Difficulties, Reading Difficulties or Both

Reading difficulties (RD) and movement difficulties (MD) co-occur more often in clinical populations than expected for independent disorders. In this study, we investigated the pattern of association between attentional processes, RD and MD in a population of 9 year old school children. Children were screened to identify index groups with RD, MD or both, plus a control group. These groups were then tested on a battery of cognitive attention assessments (TEA-Ch). Results confirmed that the occurrence of RD and MD was greater than would be predicted for independent disorders. Additionally, children with MD, whether or not combined with RD, had poor performance on all attention measures when compared with typically developing children. Children with RD only, were no poorer on measures of attention than typical children. The results are discussed with respect to approaches proposed to account for the co-occurrence of disorders.     

The Nature of the Automatization Deficit in Chinese Children with Dyslexia

Clarifying whether automatization deficits constitute the primary causes or symptoms of developmental dyslexia, we focused on three critical issues of the dyslexic automatization deficit, namely universality, domain specificity, and severity. Thirty Chinese dyslexic children (mean age 10 years and 5 months), 30 chronological-age-, and 30 reading-level-matched children were tested in 4 areas of automaticity: motor, visual search, Stroop facilitation effects, and automatic word recognition. The results showed that the dyslexic children performed significantly worse than the CA-controls but not the RL-controls in all the tasks except for Stroop congruent-color words, on which they performed worse than children in both control groups. The deficits reflect a lag in reading experiences rather than a persistent cognitive deficit.     

Effects of Tradislexia videogame on phonological awareness and word recognition in dyslexic children

The purpose of this research was to analyze the effects of multimedia training on phonological awareness and word recognition in dyslexic children. We used a control pretest-posttest design, and a sample of 62 children (26 male, 36 female) was selected from Primary Education. Children were selected and classified into two different groups: (1) an experimental group (N=32), and (2) a control group (N=30). The average range age was 9 and 12 years (M=126.7, SD=11.7). We administered phonological awareness tasks, which include different types of syllabic structure from the Sicole-R Multimedia Battery for assessment of cognitive processes in reading. We analyzed whether the Tradislexia videogame affected phonological awareness, considering separately the complexity of syllable structure and type of phonological awareness task. We also analyzed whether the gains in phonological processes were related to training based on type of task or type of syllable structure. The results showed that when we controlled the position of phoneme, the multimedia treatment in segmentation and blending with words that include CV syllables is a better predictor to explain improvement of word decoding processes.     

Dynamic visual perception of dyslexic children

This study describes the capacity of children to detect fast changes of a small visual pattern. Three visual detection tasks for a group of normally reading (N = 140) and another group of dyslexic children (N = 366) in the age range of 7 to 16 years have been used. All three tasks require the detection of the fast changing orientation of a small pattern before it disappears. In one task, stationary fixation was required, because the orientation changes took place always at the same location. In the saccade condition, the pattern was displaced suddenly to one or the other side and a saccade was required to detect the orientation. In a third condition, a distractor was presented at one side shortly before the oriented pattern appeared at the opposite side. In this case, an antisaccade with respect to the distractor was required. In all three conditions, the dyslexic group as a whole performed significantly below the level of the control group. The performance improved with age in both groups. The differences between the test and control group were largest in the distractor condition. When compared with eye-movement performance in an antisaccade task, a parallel development of the performance of both tasks was observed in both groups. The study shows that a certain percentage of dyslexic children has difficulties in the perception of fast changing stimuli, a task presumably challenging the magnocellular system.     

Phonological similarity neighborhoods and children’s short-term memory: Typical development and dyslexia

In this article, we explore whether structural characteristics of the phonological lexicon affect serial recall in typically developing and dyslexic children. Recent work has emphasized the importance of long-term phonological representations in supporting short-term memory performance. This occurs via redintegration (reconstruction) processes, which show significant neighborhood density effects in adults. We assessed whether serial recall in children was affected by neighborhood density in word and nonword tasks. Furthermore, we compared dyslexic children with typically developing children of the same age or reading level. Dyslexic children are held to have impaired phonological representations of lexical items. These impaired representations may impair or prevent the use of long-term phonological representations to redintegrate short-term memory traces. We report significant rime neighborhood density effects for serial recall of both words and nonwords, for both dyslexic and typically developing children.     

Residual differences in language processing in compensated dyslexics revealed in simple word reading tasks

Using regional cerebral blood flow as an index of cerebral activity we studied dyslexic and control subjects during simple word reading tasks. The groups were pre-tested for reading skill and the dyslexic group had a lower reading performance but could read and comprehend standard texts. The aim was to elucidate differences in the cerebral activation pattern during reading. The tasks were simple enough that performance differences between the groups could be excluded. We found specific differences between the two groups that were dependent on the language task. When the visual route for language information was used, minor qualitative differences were found between the groups pertaining to the dominant hemisphere. Increasing the complexity of the task by using pseudowords activated the left frontal region more in the dyslexic group than in the control group. A similar effect was seen in a minor region in extrastriate lateral occipital cortex (BA 19). This finding indicates that the dyslexics used areas in these regions that the controls did not. On the other hand, the dyslexics activated less in the right angular gyrus, right dorsolateral prefrontal cortex, and in the right pallidum. Reading skill correlated with the level of activity in the right frontal cortex. We conclude, that cerebral activation pattern elicited by reading is different in dyslexics compared to controls in spite of an almost complete functional compensation.     

Comparing children with and without dyslexia on the Movement Assessment Battery for Children and the Test of Gross Motor Development

Dyslexia is the most commonly occurring learning disability in the United States, characterized by difficulties with word recognition, spelling, and decoding. A growing body of literature suggests that deficits in motor skill performance exist in the dyslexic population. This study compared the performance of children with and without dyslexia on different subtests of the Test of Gross Motor Development and Movement Assessment Battery for Children and assessed whether there were developmental changes in the scores of the dyslexic group. Participants included 26 dyslexic children (19 boys and 7 girls; 9.5 yr. old, SD = 1.7) and 23 age- and sex-matched typically developing (17 boys and 6 girls; 9.9 yr. old, SD = 1.3) children as a control group. Mann-Whitney U tests indicated that the dyslexic group performed significantly lower than the control group only on the Total Balance subtest of the Movement Assessment Battery for Children. Additionally, the young dyslexic group performed significantly better on the Total Balance subtest, compared to the older dyslexic group. These results suggest that cerebellar dysfunction may account for differences in performance.     

Saccadic reaction times of dyslexic and age-matched normal subjects

Saccadic reaction times (SRT) were measured in a simple task: subjects had to make saccades from a central fixation point to peripheral targets, which appeared randomly 4 deg to the left or to the right. In the first test the fixation point went off before the target appeared (gap trials); in the second test it remained on the screen (overlap trials). The distribution of SRTs for trained normal adults (N = 4), untrained normal adults (N = 11), untrained normal children (aged 9-11 years, N = 9), untrained normal teenagers (aged 15-17 years, N = 8), dyslexic children (aged 9-11 years, N = 15), and dyslexic teenagers (aged 15-17 years, N = 5) were compared, with special emphasis on the number of express saccades, ie saccades with extremely short reaction times (100-120 ms, under the present conditions). In normal adults with the gap paradigm, the distribution of reaction times typically exhibits two or three modes (express saccades, fast regular saccades, and very few slow regular saccades), whereas in the overlap paradigm only one or two modes (few fast regular saccades and many slow regular saccades) are obtained. On average, normal children produce more express saccades than naive normal adults. Dyslexic children produce more express saccades than the normal age-matched controls. Among the dyslexic children, four different types of abnormalities in their reaction times were encountered. The group of dyslexic teenagers was characterized by a larger number of express saccades at the expense of fast regular saccades in gap trials and by fewer express saccades and fewer fast regular saccades in overlap trials when compared to the age-matched control group. It is concluded that the abnormal patterns of saccadic reaction times reflect defects in the system of visual attention and/or in its control over the oculomotor system, rather than indicating a defect in the oculomotor system itself. In this context, symptoms of dyslexia appear as a combination of attentional deficits and irregular timing of saccadic eye movements.     

Abnormalities of visual evoked potentials by checkerboards in children with specific reading disability

Visual evoked potentials by checkerboards of varying check sizes were recorded in the two hemispheres of 16 specific reading disabled and 8 normal children. In most of the disabled subjects a gross hemisphere asymmetry was assessed, while in the control group the usual evoked potential symmetry was observed. In some disabled subjects the evoked potentials had a larger amplitude in the right hemisphere, while in others the amplitude was larger in the left hemisphere. In a small subgroup the evoked potentials were symmetrical, but they had a smaller amplitude than in the control subjects. The results, giving evidence of a dysfunction in basic visual processing, are discussed in the context of current literature on clinical subgroups and the interhemispheric relationship in the dyslexic syndrome.     

Voluntary saccadic control in dyslexia

The role of eye-movement control in dyslexia is still unclear. Recent studies, however, confirmed that dyslexics show poor saccadic control in single and sequential target tasks. In the present study we investigated whether dyslexic subjects are impaired on an antisaccade task requiring saccades against the direction of a stimulus. Altogether, 620 subjects between the ages of 7 and 17 years were classified as dyslexics (N = 506) or control subjects (N = 114) on the grounds of the discrepancy between their intellectual abilities and reading/spelling achievements. All subjects performed an overlap prosaccade and a gap antisaccade task with 100 trials to each side of stimulation in random order. Variables analysed were the overall saccadic reaction time of both tasks; and from the antisaccade task the number of errors (prosaccades), the number of corrected errors, and the number of trials in which the subjects still failed to reach the side opposite the stimulus even after two saccades. An analysis of variance was carried out taking into account the development of saccadic behaviour with age and the differences between the groups. The results confirm development of saccade control with age, especially in the voluntary component (a frontal-lobe function) for both groups, but indicate that the antisaccade task performance, as measured by the error and the correction rate, is significantly worse in the dyslexic group at ages above 8 years. Up to 50% of the dyslexics performed the antisaccade task 1.5 standard deviations below the mean of the controls.     

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。     

Speed of phonological and orthographic processing as factors in dyslexia: electrophysiological evidence

The author investigated the hypothesis that speed of processing in the phonological and orthographic systems is one of the underlying variables of word-reading effectiveness. Speed of processing was assessed using measures of behavioral reaction time and electrophysiological latencies during phonological and orthographic task performance. Participants were 20 dyslexic and 20 normal-reading, male college students. An electrophysiological component complex (N1-P2-N2), as well as 2 other components (P3 and N4), was identified in both groups on each of the experimental tasks. Significant group differences were obtained only on the phonological tasks. Speed of processing during phonological judgment tasks was significantly prolonged among the dyslexic readers compared with the controls as reflected by P2, P3, and N4 latencies and reaction time. Between-task comparisons revealed significantly prolonged P2, P3, and N4 latencies on phonological compared with orthographic tasks in both dyslexic and normal readers, indicating that phonological classification of words may demand more time than orthographic classification. However, the gap score between speed of processing on the phonological and orthographic tasks was larger among the dyslexic readers and was observed mainly in P3 latency and reaction time. The highest correlation between word-reading accuracy score and the experimental measures was obtained in the dyslexic group with P3 latency gap score and in the control group with P2 latency gap score. The author proposes that slow phonological processing may cause "asynchrony" between the processing speeds within and between phonological and orthographic systems and may lead to a lack of efficient integration among the various subprocesses activated in reading, may slow down reading rate, and may impair word-reading effectiveness.     

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.     

Automaticity: a new framework for dyslexia research?

The performance of a group of 23 13-year-old dyslexic children was compared with that of same-age controls on a battery of tests of motor balance. A dual-task paradigm was used--subjects performed each test twice, once as a single task, and once as a dual task concurrently with a secondary task. Two alternative secondary tasks were used, the classic counting-backwards task and an auditory choice reaction task. Both secondary tasks were calibrated for each subject to ensure that their performance on the secondary task alone fell between pre-specified performance criteria. In all single-task conditions there was no difference between the performance of the two groups. By contrast, in 19 out of the 20 tests performed under dual-task conditions, the dyslexic group were significantly impaired, whereas the controls showed no impairment, thus resulting in significantly better performance by the control group than the dyslexic group. The sole exception was that the dyslexic children were not impaired on the easiest balance condition with the choice reaction task. Under the dual-task conditions the dyslexic children also performed worse than the controls on the secondary task. It is very hard to accommodate the findings within the traditional framework of a deficit specific to lexical skills. One plausible explanation of the results is that, unlike the controls, the dyslexic children need to invest significant conscious resources for monitoring balance, and thus their performance is adversely affected by any secondary task which serves to distract attention from the primary task. This need for "conscious compensation" suggests that for dyslexic children the skill of motor balance is poorly automatized. It is possible, therefore, that many of the reading deficits of dyslexic children are merely symptoms of a more general learning deficit--the failure to fully automatize skills.     

A comparison of word recognition processes in dyslexic and normal readers at two reading-age levels

This study addressed the question of whether dyslexic children use qualitatively different word identification processes as compared to normal readers at the same stage of reading acquisition. Fifty-two dyslexic children and reading-age matched normal readers were required to pronounce words and pseudowords designed to tap several word recognition and decoding processes. Performance profiles were compared for the two reading groups at two reading ages. Although an invariant acquisition sequence was observed across reading groups, differences in level of performance between dyslexics and reading-age controls varied as a function of reading age. The performance of the more advanced dyslexics was virtually indistinguishable from normal readers on all measures. In contrast, the younger reading age dyslexics differed from normal readers on several measures of spelling-sound correspondences. However, no reading group differences were observed on measures of word recognition. The results indicated that dyslexics and normal readers at the same reading age use essentially the same processes to recognize words, but may differ in knowledge of correspondence rules.     

A developmental, interactive activation model of the word superiority effect

Parallel distributed processing (PDP) models of reading developed out of an appreciation of the role that context plays in letter and word perception. Adult readers can more accurately identify letters in a word than alone or in other random display contexts, a phenomenon known as the Word Superiority Effect (WSE). We examined the effects of orthographic context on the letter recognition skills of dyslexic children, comparing their performance to adults, and chronological- and reading-age matched groups. Consistent with previous studies, results showed adults better able to identify letters in the context of words and pseudowords than in random letter strings. Young normal readers demonstrated the WSE, but their pseudoword advantage was less than adults. The dyslexic children showed no WSE at all. PDP computer simulations for the experimental data using the Interactive Activation model (IA) suggested that the orthographic components of the lexical system of normal children are interactive and distributed as they are in adults but provide less bottom-up activation. In addition, top-down processing increases with age and reading skill, but may be absent for dyslexic readers.     

Visual form-processing deficits in autism

People with autism have a number of reported deficits in object recognition and global processing. Is there a low-level spatial integration deficit associated with this? We measured spatial-form-coherence detection thresholds using a Glass stimulus in a field of random dots, and compared performance to a similar motion-coherence task. A coherent visual patch was depicted by dots separated by a rotational transformation in space (form) or space-time (motion). To measure parallel visual integration, stimuli were presented for only 250 ms. We compared detection thresholds for children with autism, children with Asperger syndrome, and a matched control group. Children with autism showed a significant form-coherence deficit and a significant motion-coherence deficit, while the performance of the children with Asperger syndrome did not differ significantly from that of controls on either task.