The current study investigated which time components of rapid automatized naming (RAN) predict group differences between dyslexic and non-dyslexic readers (matched for age and reading level), and how these components relate to different reading measures. Subjects performed two RAN tasks (letters and objects), and data were analyzed through a response time analysis. Our results demonstrated that impaired RAN performance in dyslexic readers mainly stem from enhanced inter-item pause times and not from difficulties at the level of post-access motor production (expressed as articulation rates). Moreover, inter-item pause times account for a significant proportion of variance in reading ability in addition to the effect of phonological awareness in the dyslexic group. This suggests that non-phonological factors may lie at the root of the association between RAN inter-item pauses and reading ability. In normal readers, RAN performance was associated with reading ability only at early ages (i.e. in the reading-matched controls), and again it was the RAN inter-item pause times that explain the association. Copyright © 2011 John Wiley & Sons, Ltd.
Eliciting Dyslexic Symptoms in Proficient Readers by Simulating Deficits in Grapheme-to-Phoneme Conversion and Visuo-Magnocellular Processing
Among the cognitive causes of dyslexia, phonological and magnocellular deficits have attracted a substantial amount of research. Their role and their exact impact on reading ability are still a matter of debate, partly also because large samples of dyslexics are hard to recruit. Here, we report a new technique to simulate dyslexic symptoms in normal readers in two ways. Although difficulties in grapheme-to-phoneme conversion were elicited by manipulating the identifiability of written letters, visual-magnocellular processing deficits were generated by presenting letters moving dynamically on the screen. Both factors were embedded into a lexical word–pseudoword decision task with proficient German readers. Although both experimental variations systematically increased lexical decision times, they did not interact. Subjects successfully performed word–pseudoword distinctions at all levels of simulation, with consistently longer reaction times for pseudowords than for words. Interestingly, detecting a pseudoword was more difficult in the grapheme-to-phoneme conversion simulation as indicated by a significant interaction of word type and letter shape. These behavioural effects are consistent with those observed in ‘real’ dyslexics in the literature. The paradigm is thus a potential means of generating novel hypotheses about dyslexia, which can easily be tested with normal readers before screening and recruiting real dyslexics. Copyright © 2011 John Wiley & Sons, Ltd.
This study focused on predicting dyslexia in children ahead of formal literacy training. Because dyslexia is a constitutional impairment, risk factors should be seen in preschool. It was hypothesized that data gathered at age 5 using questions targeting the dyslexia endophenotype should be reliable and valid predictors of dyslexia at age 11. A questionnaire was given to caretakers of 120 5-year-old children, and a risk index score was calculated based on questions regarding health, laterality, motor skills, language, special needs education and heredity. An at-risk group (n = 25) and matched controls (n = 24) were followed until age 11, when a similar questionnaire and literacy tests were administered to the children who participated in the follow-up study (22 at risk and 20 control). Half of the at-risk children and two of the control children at age 5 were identified as having dyslexia at age 11 (8 girls and 5 boys). It is concluded that it is possible to identify children at the age of 5 who will have dyslexia at the age of 11 through a questionnaire approach. Copyright © 2011 John Wiley & Sons, Ltd.
Studies of interventions for dyslexia have focused entirely on outcomes related to literacy. In this study, we considered a broader picture assessing improved quality of life compared with costs. A model served as a tool to compare costs and effects of treatment according to a new protocol and care as usual. Quality of life was measured and valued by proxies using a general quality-of-life instrument (EQ-5D). We considered medical cost and non-medical cost (e.g. remedial teaching). The model computed cost per successful treatment and cost per quality adjusted life year (QALY) in time. About 75% of the total costs was related to diagnostic tests to distinguish between children with severe dyslexia and children who have reading difficulties for other reasons. The costs per successful treatment of severe dyslexia were €36 366. Successful treatment showed a quality-of-life gain of about 11%. At primary school, the average cost per QALY for severe dyslexia amounted to €58 647. In the long term, the cost per QALY decreased to €26 386 at secondary school and €17 663 thereafter. The results of this study provide evidence that treatment of severe dyslexia is cost-effective when the investigated protocol is followed. Copyright © 2011 John Wiley & Sons, Ltd.
The etiology of developmental dyslexia remains widely debated. An appealing theory postulates that the reading and spelling problems in individuals with dyslexia originate from reduced sensitivity to slow-rate dynamic auditory cues. This low-level auditory deficit is thought to provoke a cascade of effects, including inaccurate speech perception and eventually unspecified phoneme representations. The present study investigated sensitivity to frequency modulation and amplitude rise time, speech-in-noise perception and phonological awareness in 11-year-old children with dyslexia and a matched normal-reading control children. Group comparisons demonstrated that children with dyslexia were less sensitive than normal-reading children to slow-rate dynamic auditory processing, speech-in-noise perception, phonological awareness and literacy abilities. Correlations were found between slow-rate dynamic auditory processing and phonological awareness, and speech-in-noise perception and reading. Yet, no significant correlation between slow-rate dynamic auditory processing and speech-in-noise perception was obtained. Together, these results indicate that children with dyslexia have difficulties with slow-rate dynamic auditory processing and speech-in-noise perception and that these problems persist until sixth grade.
The effect of cognitive training on recall range and speed of information processing in the working memory of dyslexic and skilled readers
Research indicates that impairment of working memory may be one of the factors that impede the ability to read fluently and accurately. Although the capacity of working memory is traditionally considered to be constant, recent data point to a certain plasticity in the neural system that underlies working memory, which can be improved by training. We examined whether dyslexic readers’ recall span and speed of processing in working memory can be increased, enhancing the quality of their reading. Thirty five skilled readers and twenty six dyslexic readers were trained in working memory tasks and compared to control groups of fifteen skilled and fifteen dyslexic readers who complete a self-paced reading training regime. All subjects were trained over a six-week period. Reading and working memory indicators were collected before and after the two trainings. Brain activity using measures of event-related potential (ERP) were collected for the working memory training groups by using a working memory task (Sternberg task). Result indicated after working memory training the ability to store verbal and visual-spatial information in working memory increased, and decoding, reading rate and comprehension scores improved in both groups, although the gap between the dyslexic and the control groups in reading and working memory scores remained constant. The latency of the P300 component decreased and the amplitude increased in all participants following training. No training effect in any parameter was obtained in the self-paced reading training groups. These findings support the notion of plasticity in the neural system underlying working memory and point to the relationships between larger working memory capacity and enhancement of reading skills.
from the Journal of Neurolinguistics
N1, P2 and T-complex of the auditory brain event-related potentials to tones with varying rise times in adults with and without dyslexia
Dyslexia is a learning difficulty affecting the acquisition of fluent reading and spelling skills due to poor phonological processing. Underlying deficits in processing sound rise time have also been found in children and adults with dyslexia. However, the neural basis for these deficits is unknown. In the present study event-related potentials were used to index neural processing and examine the effect of rise time manipulation on the obligatory N1, T-complex and P2 responses in English speaking adults with and without dyslexia. The Tb wave of the T-complex showed differences between groups, with the amplitudes for Tb becoming less negative with increased rise time for the participants with dyslexia only. Frontocentral N1 and P2 did not show group effects. Enhanced Tb amplitude that is modulated by rise time could indicate altered neural networks at the lateral surface of the superior temporal gyrus in adults with dyslexia.
Music, rhythm, rise time perception and developmental dyslexia: Perception of musical meter predicts reading and phonology
The accurate perception of metrical structure may be critical for phonological development and consequently for the development of literacy. Difficulties in metrical processing are associated with basic auditory rise time processing difficulties, suggesting a primary sensory impairment in developmental dyslexia in tracking the lower-frequency modulations in the speech envelope.
The aim of this study was to investigate the Chinese handwriting performance of typical children and children with dyslexia, and to examine whether speed and accuracy of handwriting could reliably discriminate these two groups of children. One hundred and thirty-seven children with dyslexia and 756 typical children were recruited from main stream primary schools for the study. They were requested to copy 90 Chinese characters using the Chinese Handwriting Assessment Tool (CHAT) jointly developed by a project team from two universities in Hong Kong. The process of handwriting was recorded and the stroke errors in writing were analyzed using the CHAT system. Results indicated that children with dyslexia wrote significantly slower, with greater average character size and variation in size (p < .05) than the typical children of same age group. They also wrote with significantly lower accuracy (p < .05). Commonly observed writing errors among the Dyslexic group were missing strokes and concatenated strokes. From the discriminant analysis, it was found that writing speed and accuracy were satisfactory discriminators that could discriminate students into the two groups, with reasonably good classification accuracy of over 70% for every grade. The results were discussed with theoretical implications in relation to fine motor skills, kinesthetic abilities, visual perceptual skills, and the demand of written tasks in school.
Postural control and automaticity in dyslexic children: The relationship between visual information and body sway
Difficulty with literacy acquisition is only one of the symptoms of developmental dyslexia. Dyslexic children also show poor motor coordination and postural control. Those problems could be associated with automaticity, i.e., difficulty in performing a task without dispending a fair amount of conscious efforts. If this is the case, dyslexic children would show difficulties in using “unperceived” sensory cues to control body sway. Therefore, the aim of the study was to examine postural control performance and the coupling between visual information and body sway in dyslexic children. Ten dyslexic children and 10 non-dyslexic children stood upright inside a moving room that remained stationary or oscillated back and forward at frequencies of 0.2 or 0.5 Hz. Body sway magnitude and the relationship between the room’s movement and body sway were examined. The results indicated that dyslexic children oscillated more than non-dyslexic children in both stationary and oscillating conditions. Visual manipulation induced body sway in all children but the coupling between visual information and body sway was weaker and more variable in dyslexic children. Based upon these results, we can suggest that dyslexic children use visual information to postural control with the same underlying processes as non-dyslexic children; however, dyslexic children show poorer performance and more variability while relating visual information and motor action even in a task that does not require an active cognitive and conscious motor involvement, which may be a further evidence of automaticity problem.
Music, rhythm, rise time perception and developmental dyslexia: Perception of musical meter predicts reading and phonology
Rhythm organises musical events into patterns and forms, and rhythm perception in music is usually studied by using metrical tasks. Metrical structure also plays an organisational function in the phonology of language, via speech prosody, and there is evidence for rhythmic perceptual difficulties in developmental dyslexia. Here we investigate the hypothesis that the accurate perception of musical metrical structure is related to basic auditory perception of rise time, and also to phonological and literacy development in children.
This review focuses on phonological awareness (PA) skills and their key role both in literacy acquisition and development and in explaining reading and writing difficulties; in particular, we focus on phonemic awareness, which implies awareness of the smallest speech units. Several questions about PA are addressed; we discuss major research findings over the past few decades both in typically developing children and children with dyslexia, mainly carried out in Spanish. We also discuss the development of PA and how children’s implicit knowledge of speech sounds progresses into explicit knowledge through kindergarten games and other experiences with oral language and, especially, when children start to learn how to read and write. This process is not free of difficulties, given the phenomenon of coarticulation. This step signifies the development of distinct levels of PA skills, which predict reading and writing acquisition. Additionally, the difficulties of dyslexic children in PA tasks are discussed; these difficulties are more evident in speed processing than in accuracy. Finally, the present article reviews issues that should be taken into account when PA tasks are designed both for assessment and intervention. Practical implications for effective intervention for the development and enhancement of PA skills are discussed.
Fluency parameters and types of errors in the reading of students with signs of reading and writing difficulties
CONCLUSION: The students with signs of reading and writing difficulties had worse reading fluency performance, and higher number of errors in all the grades studied. The correlations found evidenced the influence of the type of error on reading fluency, according to different patterns for each group.