Deficits In Developmental Dyslexia Research Articles

Unilateral implicit motor learning deficit in developmental dyslexia

It has been suggested that developmental dyslexia involves various literacy, sensory, motor skill, and processing speed deficits. Some recent studies have shown that individuals with developmental dyslexia exhibit implicit motor learning deficits, which may be related to cerebellar functioning. However, previous studies on implicit motor learning in developmental dyslexics have produced conflicting results. Findings from cerebellar lesion patients have shown that patients' implicit motor learning performance varied when different hands were used to complete tasks. This suggests that dyslexia may have different effects on implicit motor learning between the two hands if cerebellar dysfunction is involved. To specify this question, we used a one-handed version of a serial reaction time task to compare the performance of 27 Chinese children with developmental dyslexics with another 27 age-matched children without reading difficulties. All the subjects were students from two primary schools, Grades 4 to 6. The results showed that children with developmental dyslexic responded more slowly than nondyslexic children, and exhibited no implicit motor learning in the condition of left-hand response. In contrast, there was no significant difference in reaction time between two groups of children when they used the right hand to respond. This finding indicates that children with developmental dyslexia exhibited normal motor skill and implicit motor learning ability provided the right hand was used. Taken together, these results suggested that Chinese children with developmental dyslexia exhibit unilateral deficits in motor skill and implicit motor learning in the left hand. Our findings lend partial support to the cerebellar deficit theory of developmental dyslexia.

Is the ‘naming’ deficit in dyslexia a misnomer?

We report a study that investigated the widely held belief that naming-speed deficits in developmental dyslexia reflect impaired access to lexical-phonological codes. To investigate this issue, we compared adult dyslexic and adult non-dyslexic readers’ performance when naming and semantically categorizing arrays of objects. Dyslexic readers yielded slower response latencies than non-dyslexic readers when naming objects, but a subsequent comparison of object-naming and object-categorization tasks showed that the apparent ‘naming’ deficit could be attributed to a more general difficulty in retrieving information – either phonological or semantic – from the visual stimulus. Our findings suggest that although visual–phonological connections may be crucial in explaining naming-speed performance they do not fully characterise dyslexic readers’ naming-speed impairments.

Fractionating the multi-character processing deficit in developmental dyslexia: Evidence from two case studies

While there is growing evidence that some dyslexic children suffer from a deficit in simultaneously processing multiple visually displayed elements, the precise nature of the deficit remains largely unclear. The aim of the present study is to investigate possible cognitive impairments at the source of this deficit in dyslexic children. The visual processing of simultaneously presented letters was thus thoroughly assessed in two dyslexic children by means of a task that requires the report of briefly presented multi-letters arrays. A computational model of the attentional involvement in multi-object recognition (Bundesen, 1990, 1998) served as framework for analysing the data. By combining psychophysical measurements with computational modelling, we demonstrated that the visual processing deficit of simultaneously displayed letters, observed in the two dyslexic individuals reported in the current study, stems from at least two distinct cognitive sources: a reduction of the rate of—letter—information uptake, and a limitation of the maximal number of elements extracted from a brief visual display and stored in visual short-term memory. Possible relations between these impairments and learning to read proficiently are discussed.

Face processing in developmental dyslexia

Event Abstract Back to Event Face processing in developmental dyslexia István Kóbor1*, Éva Bankó2, József Takács3, Ágnes Lukács4, Viktor Gál3 and Zoltán Vidnyánszky3 1 Semmelweis University, MR Research Center, Szentágothai J. Knowledge Center, Hungary 2 Pázmány Péter Catholic University, Faculty of Information Technology, Hungary 3 Pázmány Péter Catholic University - Semmelweis University, Neurobionics Research Group, Hungarian Academy of Sciences, Hungary 4 Social Sciences Department of Cognitive Science, Budapest University of Technology and Economics Faculty of Economics , Hungary The existance and nature of visual processing deficits in developmental dyslexia has been debated for a long time. Recently, it has been proposed that visual object processing might be impaired in dyslexia and that dyslexics’ deficits are especially pronounced when the images are noisy. In the present study we aimed at invstigating the face discrimination performance and the electrophysiological correlates of face processing in adult dyslexics, including in case of noisy (phase-randomized) face images. We measured ERP responses (with 64 channel EEG) while participants (16 dyslexic and 16 control subjects) performed a face gender discrimination task. Our results revealed that dyslexics can discriminate face gender just as efficiently as the control subjects both in the presence and absence of noise: as shown by the lack of significant differences between the two groups’ performance and reaction times. In accordance with this, we found no significant difference in the early components (P1, N170) of ERP responses to the face stimuli between the dyslexic and control subjects. Furthermore, our result also revealed similar increase of the noise-sensitive P2 component in the case of noisy face stimuli in the dyslexic and control subjects. However, in agreement with previous findings, we found significant differences in the ERP responses over the occipito-temporal electrodes between the two groups in a later time window, peaking around 270 ms. Taken together, these results provide evidence that face processing is normal in developmental dyslexia as well as show that – in contrary to earlier suggestions - there is no general impairment of noise exclusion processes in dyslexics. Conference: IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010. Presentation Type: Poster Presentation Topic: Disorders of the nervous system Citation: Kóbor I, Bankó É, Takács J, Lukács Á, Gál V and Vidnyánszky Z (2010). Face processing in developmental dyslexia. Front. Neurosci. Conference Abstract: IBRO International Workshop 2010. doi: 10.3389/conf.fnins.2010.10.00038 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 Apr 2010; Published Online: 20 Apr 2010. * Correspondence: István Kóbor, Semmelweis University, MR Research Center, Szentágothai J. Knowledge Center, Budapest, Hungary, ikobor@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers István Kóbor Éva Bankó József Takács Ágnes Lukács Viktor Gál Zoltán Vidnyánszky Google István Kóbor Éva Bankó József Takács Ágnes Lukács Viktor Gál Zoltán Vidnyánszky Google Scholar István Kóbor Éva Bankó József Takács Ágnes Lukács Viktor Gál Zoltán Vidnyánszky PubMed István Kóbor Éva Bankó József Takács Ágnes Lukács Viktor Gál Zoltán Vidnyánszky Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Different underlying neurocognitive deficits in developmental dyslexia: A comparative study

The aim of this study was to investigate the role of several specific neurocognitive functions in developmental dyslexia (DD). The performances of 60 dyslexic children and 65 age-matched normally reading children were compared on tests of phonological abilities, visual processing, selective and sustained attention, implicit learning, and executive functions. Results documented deficits in dyslexics on both phonological and non-phonological tasks. More stringently, in dyslexic children individual differences in non-phonological abilities accounted for 23.3% of unique variance in word reading and for 19.3% in non-word reading after controlling for age, IQ and phonological skills. These findings are in accordance with the hypothesis that DD is a multifactorial deficit and suggest that neurocognitive developmental dysfunctions in DD may not be limited to the linguistic brain area, but may involve a more multifocal cortical system.

Intact first- and second-order implicit sequence learning in secondary-school-aged children with developmental dyslexia

We examined the influence of task complexity on implicit sequence learning in secondary-school-aged children with developmental dyslexia (DD). This was done to determine whether automatization problems in reading extend to the automatization of all skill and depend on the complexity of the to-be-learned skill. A total of 28 dyslexic children between 12 and 15 years and 28 matched control children carried out two serial reaction time tasks using a first-order conditional (FOC) and second-order conditional (SOC) sequence. In both tasks, children incidentally learned a sequence of hidden target positions, but whereas FOC sequence learning could be based on knowledge about the immediate preceding position, SOC sequence learning required more complex knowledge about the previous two positions. The results demonstrated that sequence learning was highly comparable in dyslexic and control children, regardless of the sequence complexity. This shows that implicit sequence learning, as manifested in the present study, is maintained in DD and is unrelated to task complexity. We suggest that previous reports of sequence-learning deficits in DD can be accounted for by attenuated explicit sequence learning, possibly related to malfunctions in prefrontal processing. The present findings indicate that deficits in skill learning and automatization in DD are not general in nature, but task dependent.

Speech‐perception‐in‐noise deficits in dyslexia

Speech perception deficits in developmental dyslexia were investigated in quiet and various noise conditions. Dyslexics exhibited clear speech perception deficits in noise but not in silence. Place-of-articulation was more affected than voicing or manner-of-articulation. Speech-perception-in-noise deficits persisted when performance of dyslexics was compared to that of much younger children matched on reading age, underscoring the fundamental nature of speech-perception-in-noise deficits. The deficits were not due to poor spectral or temporal resolution because dyslexics exhibited normal 'masking release' effects (i.e. better performance in fluctuating than in stationary noise). Moreover, speech-perception-in-noise predicted significant unique variance in reading even after controlling for low-level auditory, attentional, speech output, short-term memory and phonological awareness processes. Finally, the presence of external noise did not seem to be a necessary condition for speech perception deficits to occur because similar deficits were obtained when speech was degraded by eliminating temporal fine-structure cues without using external noise. In conclusion, the core deficit of dyslexics seems to be a lack of speech robustness in the presence of external or internal noise.

Differences in effective connectivity between dyslexic children and normal readers during a pseudoword reading task: An fMRI study

This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task. The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas of the left hemisphere. The results revealed differences in connectivity patterns. In dyslexic patients, in contrast with chronological age- and reading level-matched groups, no causal relationship was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading level-matched group. These findings were interpreted as evidence for a phonological deficit in developmental dyslexia.

What Phonological Deficit?

We review a series of experiments aimed at understanding the nature of the phonological deficit in developmental dyslexia. These experiments investigate input and output phonological representations, phonological grammar, foreign speech perception and production, and unconscious speech processing and lexical access. Our results converge on the observation that the phonological representations of people with dyslexia may be intact, and that the phonological deficit surfaces only as a function of certain task requirements, notably short-term memory, conscious awareness, and time constraints. In an attempt to reformulate those task requirements more economically, we propose that individuals with dyslexia have a deficit in access to phonological representations. We discuss the explanatory power of this concept and we speculate that a similar notion might also adequately describe the nature of other associated cognitive deficits when present.

Visual deficits in developmental dyslexia: relationships between non‐linguistic visual tasks and their contribution to components of reading

Developmental dyslexia is often characterized by a visual deficit, but the nature of this impairment and how it relates to reading ability is disputed (Brain 2003; 126: 841-865). In order to investigate this issue, we compared groups of adults with and without dyslexia on the Ternus, visual-search and symbols tasks. Dyslexic readers yielded more errors on the visual-search and symbols tasks compared with non-dyslexic readers. A positive correlation between visual-search and symbols task performance suggests a common mechanism shared by these tasks. Performance on the visual-search and symbols tasks also correlated with non-word reading and rapid automatized naming measures, and visual search contributed independent variance to non-word reading. The Ternus task did not discriminate reading groups nor contributed significant variance to reading measures. We consider how visual-attention processes might underlie specific component reading measures.

Reading ability and phonological awareness in Japanese children with dyslexia

In alphabetic languages, the deficit of the phonological awareness is considered as the core deficit in developmental dyslexia. However, the role of phonological awareness in the acquisition of reading Japanese kana, the transparent, mora-based phonogram, has not been understood completely. We examine the abilities of Japanese dyslexic children on different types of Japanese phonological tasks, and discussed which tasks significantly account for each aspect of reading ability. Methods: Fifteen dyslexic children (9.53 ± 1.52 years old), and 15 children with normal reading ability (9.17 ± 0.90 years old) participated in this study. They performed three types of phonological awareness tasks. The mora counting task and the mora reversal task of words require phonological awareness at the mora level. The letter rhyming task, which resembles the task in English language, requires phonological awareness at the phoneme level. We evaluated the reading ability by the reading speed, the reading errors, and the number of pauses while reading sentences aloud. Results: The task performances of the dyslexic group on all three phonological awareness tasks were significantly lower than those of the control group. Stepwise multiple regression analysis revealed that the mora counting task and the rhyming letter task most significantly explained the reading speed and number of reading pauses. The mora reversal task of words, together with the antegraded digit span, significantly explained the reading errors. Conclusions: Japanese dyslexics showed deficits of phonological awareness both at the mora and the phoneme levels. Phonological awareness must be crucial for acquiring the ability of decoding phonograms, including Japanese kana.

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.

Reading-related cognitive deficits in developmental dyslexia, attention-deficit/hyperactivity disorder, and developmental coordination disorder among Chinese children

Reading-related cognitive deficits in developmental dyslexia, attention-deficit/hyperactivity disorder, and developmental coordination disorder among Chinese children

Phonological oddballs in the focus of attention elicit a normal P3b in dyslexic adults

Difficulties in phonological processing have been proposed to be the core symptom of developmental dyslexia. Phoneme awareness tasks have been shown to both index and predict individual reading ability. In a previous experiment, we observed that dyslexic adults fail to display a P3a modulation for phonological deviants within an alliterated word stream when concentrating primarily on a lexical decision task [Fosker and Thierry, 2004, Neurosci. Lett. 357, 171–174]. Here we recorded the P3b oddball response elicited by initial phonemes within streams of alliterated words and pseudo-words when participants focussed directly on detecting the oddball phonemes. Despite significant verbal screening test differences between dyslexic adults and controls, the error rates, reactions times, and main components (P2, N2, P3a, and P3b) were indistinguishable across groups. The only difference between groups was found in the N1 range, where dyslexic participants failed to show the modulations induced by phonological pairings (/b/–/p/ versus /r/–/g/) in controls. In light of previous P3a differences, these results suggest an important role for attention allocation in the manifestation of phonological deficits in developmental dyslexia.

Picture naming and developmental reading disorders

One of the most frequently cited papers from the twenty‐five years of the Journal of Research in Reading is ‘Object‐naming deficits in developmental dyslexia’ by Maggie Snowling, Bente van Wagtendonk and Carolyn Stafford, published in 1988. Looking back at the paper some sixteen years after its publication, it is striking to note how topical some of the issues discussed by Snowling and colleagues remain. This commentary revisits some of these issues and examines how subsequent research has consolidated and extended Snowling et al.'s findings and conclusions.

More than words: a common neural basis for reading and naming deficits in developmental dyslexia?

Dyslexic individuals show subtle impairments in naming pictures of objects in addition to their difficulties with reading. The present study investigated whether word reading and picture naming deficits in developmental dyslexia can be reduced to a common neurological impairment. Eight dyslexic subjects, impaired on measures of reading, spelling and naming speed, were matched for age and general ability with 10 control subjects. Participants were scanned using PET during two experimental conditions: reading words and naming pictures in the form of corresponding line drawings. In addition, two high-level baseline conditions were used to control for visual and articulatory processes. Relative to the control group, the dyslexic participants showed reduced activation in a left occipitotemporal area during both word reading and picture naming. This was the case even in the context of intact behavioural performance during scanning. Abnormal activation in this region, as reported previously for reading, is therefore not specific to orthographic decoding but may reflect a more general impairment in integrating phonology and visual information. Our investigation points to a common neurological basis for deficits in word reading and picture naming in developmental dyslexia.

The cognitive deficits responsible for developmental dyslexia: Review of evidence for a selective visual attentional disorder

There is strong converging evidence suggesting that developmental dyslexia stems from a phonological processing deficit. However, this hypothesis has been challenged by the widely admitted heterogeneity of the dyslexic population, and by several reports of dyslexic individuals with no apparent phonological deficit. In this paper, we discuss the hypothesis that a phonological deficit may not be the only core deficit in developmental dyslexia and critically examine several alternative proposals. To establish that a given cognitive deficit is causally related to dyslexia, at least two conditions need to be fulfilled. First, the hypothesized deficit needs to be associated with developmental dyslexia independently of additional phonological deficits. Second, the hypothesized deficit must predict reading ability, on both empirical and theoretical grounds. While most current hypotheses fail to fulfil these criteria, we argue that the visual attentional deficit hypothesis does. Recent studies providing evidence for the independence of phonological and visual attentional deficits in developmental dyslexia are reviewed together with empirical data showing that phonological and visual attentional processing skills contribute independently to reading performance. A theoretical model of reading is outlined in support of a causal link between a visual attentional disorder and a failure in reading acquisition.

Two visual motion processing deficits in developmental dyslexia associated with different reading skills deficits.

Developmental dyslexia is associated with deficits in the processing of visual motion stimuli, and some evidence suggests that these motion processing deficits are related to various reading subskills deficits. However, little is known about the mechanisms underlying such associations. This study lays a richer groundwork for exploration of such mechanisms by more comprehensively and rigorously characterizing the relationship between motion processing deficits and reading subskills deficits. Thirty-six adult participants, 19 of whom had a history of developmental dyslexia, completed a battery of visual, cognitive, and reading tests. This battery combined motion processing and reading subskills measures used across previous studies and added carefully matched visual processing control tasks. Results suggest that there are in fact two distinct motion processing deficits in developmental dyslexia, rather than one as assumed by previous research, and that each of these deficits is associated with a different type of reading subskills deficit. A deficit in detecting coherent motion is selectively associated with low accuracy on reading subskills tests, and a deficit in discriminating velocities is selectively associated with slow performance on these same tests. In addition, evidence from visual processing control tasks as well as self-reports of ADHD symptoms suggests that these motion processing deficits are specific to the domain of visual motion, and result neither from a broader visual deficit, nor from the sort of generalized attention deficit commonly comorbid with developmental dyslexia. Finally, dissociation between these two motion processing deficits suggests that they may have distinct neural and functional underpinnings. The two distinct patterns of motion processing and reading deficits demonstrated by this study may reflect separable underlying neurocognitive mechanisms of developmental dyslexia.

Auditory and visual automatic attention deficits in developmental dyslexia

Several studies have provided evidence for a phonological deficit in developmental dyslexia. However, recent studies provide evidence for a multimodal temporal processing deficit in dyslexia. In fact, dyslexics show both auditory and visual abnormalities, which could result from a more general problem in the perceptual selection of stimuli. Here we report the results of a behavioral study showing that children with dyslexia have both auditory and visual deficits in the automatic orienting of spatial attention. These findings suggest that a deficit of selective spatial attention may distort the development of phonological and orthographic representations that is essential for learning to read.

Evidence for a domain-specific deficit in developmental dyslexia

Thomas & Karmiloff-Smith (T&K-S) claim that “Residual Normality” is a priori unlikely, that is, that specific cognitive deficits should not exist in developmental disorders. Here I review evidence that a specific cognitive deficit is at the core of developmental dyslexia and I provide a possible neurological account thereof.