Developmental Dyslexia: Theories and Experimental Approaches

A special issue of Brain Sciences (ISSN 2076-3425). This special issue belongs to the section "Neurolinguistics".

Deadline for manuscript submissions: closed (9 January 2023) | Viewed by 24183

Special Issue Editor


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Guest Editor
Institute for Social Pediatrics and Adolescent Medicine, University of Munich, Haydnstrasse 5, D-80336 Munich, Germany
Interests: dyslexia; visual system; neurobiology of consciousness; philosophy of science

Special Issue Information

Dear Colleagues,

In recent years, experimental approaches have been undertaken to examine the psychological and linguistic aspects of developmental dyslexia, and to clarify its neuroanatomical and neurophysiological bases. Sensory and behavioral abnormalities have been demonstrated that are more common in dyslexic readers than in normal readers, and brain structures that exhibit symptoms of unusual processing and anatomical abnormalities were discovered in dyslexic individuals, but a causal relationship has not been demonstrated. Theories have been proposed to provide explanations for the nature of developmental dyslexia, and these have stimulated therapeutic interventions. However, these theories cannot sufficiently explain what causes developmental dyslexia, in what way altered neurobiological processing leads to developmental dyslexia, and which therapeutic interventions are appropriate to eliminate or compensate for the impairments that lead to developmental dyslexia. The aim of this Special Issue is to present experimental approaches and theories that contribute to the understanding of developmental dyslexia and its causal relationships, and lead to new therapeutic approaches.

Prof. Dr. Reinhard Werth
Guest Editor

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Keywords

  • developmental dyslexia
  • magnocells
  • parvocells
  • dorsal stream
  • ventral stream
  • eye movements

Published Papers (9 papers)

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Research

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30 pages, 3085 KiB  
Article
Letter Migrations between Words in Reading Aloud Can Result either from an Impairment in Orthographic Input or in Phonological Output
by Liora Toledano and Naama Friedmann
Brain Sci. 2023, 13(4), 588; https://doi.org/10.3390/brainsci13040588 - 30 Mar 2023
Viewed by 1564
Abstract
Letter migrations between words in reading aloud (e.g., reading “cane love” as “lane love” or “lane cove”) are known to result from a deficit in the visual-orthographic analysis and characterize attentional dyslexia. In spontaneous speech, individuals with impairment in the phonological output buffer [...] Read more.
Letter migrations between words in reading aloud (e.g., reading “cane love” as “lane love” or “lane cove”) are known to result from a deficit in the visual-orthographic analysis and characterize attentional dyslexia. In spontaneous speech, individuals with impairment in the phonological output buffer may show migrations of phonemes between words. The purpose of this study was to examine whether migrations between words in reading aloud can also result from a deficit in the phonological output buffer, to explore the characteristics of migrations resulting from orthographic input and from phonological output deficits, and to examine methods to distinguish these two sources. Using tasks of reading aloud of lists of 92–182 word pairs, we identified 18 adults and adolescents with developmental dyslexia who made between-word letter migrations in reading aloud, significantly more than age-matched controls (372 adults, 26 7th-graders and 44 4th–5th-graders). To distinguish between the orthographic input and phonological output sources for these migrations, we administered a test assessing orthographic input without spoken output (written semantic decision on 140 migratable word pairs) and a repetition test of 36 auditorily presented migratable word pairs, assessing spoken output without orthographic input (as well as nonword repetition and 3 span tests). These tests indicated that the migrations in reading aloud of 10 of the participants with dyslexia resulted from an orthographic input deficit—they made migrations not only in reading aloud but also in written word pair comprehension, but not in word pair repetition. For the other 8 participants, the migrations resulted from a phonological output deficit: they made migrations in reading aloud and in word pair repetition, but not in comprehension, and had limited spans and made errors in nonword repetition. We identified several differences between the two types of between-word errors: first, the individuals with attentional dyslexia made omissions of a letter that appeared in the same position in the two words, but the phonological output buffer group did not make such omissions. Second, the groups differed in the origin of migration: orthographic input migrations involve letters that are orthographically adjacent, whereas phonological output migrations involve phonologically adjacent phonemes: phonemes that have just been spoken or that are prepared together in the phonological buffer for production. Migrations from the line below and from 2 lines above the target occurred only in the orthographic input group. This study thus indicates that between-word migrations in reading aloud can result not only from attentional dyslexia, but also from a phonological output buffer deficit, and offers ways to distinguish between the two. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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24 pages, 3003 KiB  
Article
French Students with Dyslexia Facing the Punctuation System: Insecurity, Inventory Use, and Error Studies
by Audrey Mazur and Matthieu Quignard
Brain Sci. 2023, 13(4), 532; https://doi.org/10.3390/brainsci13040532 - 23 Mar 2023
Viewed by 1170
Abstract
Punctuation strongly contributes to the cohesion of the text. Despite this relevant role in written activity, this linguistic paradigm is too rarely observed. Moreover, it is all the more important to analyze its management as it is one of the difficulties declared by [...] Read more.
Punctuation strongly contributes to the cohesion of the text. Despite this relevant role in written activity, this linguistic paradigm is too rarely observed. Moreover, it is all the more important to analyze its management as it is one of the difficulties declared by students with dyslexia. In that sense, the purpose of this paper is to analyze punctuation management during written text production by students with dyslexia, compared to matched control students. Previous English and Dutch studies confirm this feeling and reveal that students with dyslexia make many punctuation errors. That being said, there is no consensus; other studies do not reach this conclusion. For this present study, students with dyslexia and control students matched in age, university level, and gender were asked to produce spontaneous written and spoken narrative and expository texts. The written texts (N = 86) were collected using Eye and Pen© software with digitizing tablets. Results reveal that if students with dyslexia use the same inventory of punctuation marks as control students, they use fewer punctuation marks and make more errors than control students. These results are discussed and highlighted by the literature dealing with written production as a complex cognitive activity. They reveal that punctuation management is deficient for students with dyslexia, suggesting that the cohesion system can be impacted by dyslexia. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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13 pages, 2107 KiB  
Article
Accessible Dyslexia Detection with Real-Time Reading Feedback through Robust Interpretable Eye-Tracking Features
by Ivan Vajs, Tamara Papić, Vanja Ković, Andrej M. Savić and Milica M. Janković
Brain Sci. 2023, 13(3), 405; https://doi.org/10.3390/brainsci13030405 - 26 Feb 2023
Cited by 5 | Viewed by 1990
Abstract
Developing reliable, quantifiable, and accessible metrics for dyslexia diagnosis and tracking represents an important goal, considering the widespread nature of dyslexia and its negative impact on education and quality of life. In this study, we observe eye-tracking data from 15 dyslexic and 15 [...] Read more.
Developing reliable, quantifiable, and accessible metrics for dyslexia diagnosis and tracking represents an important goal, considering the widespread nature of dyslexia and its negative impact on education and quality of life. In this study, we observe eye-tracking data from 15 dyslexic and 15 neurotypical Serbian school-age children who read text segments presented on different color configurations. Two new eye-tracking features were introduced that quantify the amount of spatial complexity of the subject’s gaze through time and inherently provide information regarding the locations in the text in which the subject struggled the most. The features were extracted from the raw eye-tracking data (x, y coordinates), from the original data gathered at 60 Hz, and from the downsampled data at 30 Hz, examining the compatibility of features with low-cost or custom-made eye-trackers. The features were used as inputs to machine learning algorithms, and the best-obtained accuracy was 88.9% for 60 Hz and 87.8% for 30 Hz. The features were also used to analyze the influence of background/overlay color on the quality of reading, and it was shown that the introduced features separate the dyslexic and control groups regardless of the background/overlay color. The colors can, however, influence each subject differently, which implies that an individualistic approach would be necessary to obtain the best therapeutic results. The performed study shows promise in dyslexia detection and evaluation, as the proposed features can be implemented in real time as feedback during reading and show effectiveness at detecting dyslexia with data obtained using a lower sampling rate. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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21 pages, 1181 KiB  
Article
Revisiting Multifactor Models of Dyslexia: Do They Fit Empirical Data and What Are Their Implications for Intervention?
by Maria Luisa Lorusso and Alessio Toraldo
Brain Sci. 2023, 13(2), 328; https://doi.org/10.3390/brainsci13020328 - 14 Feb 2023
Cited by 4 | Viewed by 1973
Abstract
Developmental dyslexia can be viewed as the result of the effects of single deficits or multiple deficits. This study presents a test of the applicability of a multifactor-interactive model (MFi-M) with a preliminary set of five variables corresponding to different neuropsychological functions involved [...] Read more.
Developmental dyslexia can be viewed as the result of the effects of single deficits or multiple deficits. This study presents a test of the applicability of a multifactor-interactive model (MFi-M) with a preliminary set of five variables corresponding to different neuropsychological functions involved in the reading process. The model has been tested on a sample of 55 school-age children with developmental dyslexia. The results show that the data fit a model in which each variable contributes to the reading ability in a non-additive but rather interactive way. These findings constitute a preliminary validation of the plausibility of the MFi-M, and encourage further research to add relevant factors and specify their relative weights. It is further discussed how subtype-based intervention approaches can be a suitable and advantageous framework for clinical intervention in a MFi-M perspective. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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22 pages, 4564 KiB  
Article
Multiple Case Studies in German Children with Dyslexia: Characterization of Phonological, Auditory, Visual, and Cerebellar Processing on the Group and Individual Levels
by Carolin Ligges and Thomas Lehmann
Brain Sci. 2022, 12(10), 1292; https://doi.org/10.3390/brainsci12101292 - 25 Sep 2022
Cited by 2 | Viewed by 1679
Abstract
Background: The underlying mechanisms of dyslexia are still debated. The question remains as to whether there is evidence of a predominant type of deficit or whether it is a multideficit disorder with individual profiles. The assumptions of which mechanism causes the disorder influences [...] Read more.
Background: The underlying mechanisms of dyslexia are still debated. The question remains as to whether there is evidence of a predominant type of deficit or whether it is a multideficit disorder with individual profiles. The assumptions of which mechanism causes the disorder influences the selection of the training approach. Methods: A sample of German neurotypical reading children (NT) and children with dyslexia (DYSL) was investigated with a comprehensive behavioral test battery assessing phonological, auditory, visual, and cerebellar performance, thus addressing performance described in three major theories in dyslexia. Results: In the present sample using the test battery of the present study, DYSL had the strongest impairment in phonological and auditory processing, accompanied by individual processing deficits in cerebellar performance, but only a few in the investigated visual domains. Phonological awareness and auditory performance were the only significant predictors for reading ability. Conclusion: These findings point out that those reading difficulties were associated with phonological as well as auditory processing deficits in the present sample. Future research should investigate individual deficit profiles longitudinally, with studies starting before literacy acquisition at as many processing domains as possible. These individual deficit profiles should then be used to select appropriate interventions to promote reading and spelling. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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Review

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22 pages, 647 KiB  
Review
Dyslexia: Causes and Concomitant Impairments
by Reinhard Werth
Brain Sci. 2023, 13(3), 472; https://doi.org/10.3390/brainsci13030472 - 10 Mar 2023
Cited by 3 | Viewed by 3064
Abstract
In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The [...] Read more.
In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of letters. When these impairments are compensated by a new reading strategy, reading ability improves immediately. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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12 pages, 277 KiB  
Review
Theories about Developmental Dyslexia
by John Stein
Brain Sci. 2023, 13(2), 208; https://doi.org/10.3390/brainsci13020208 - 26 Jan 2023
Cited by 7 | Viewed by 6253
Abstract
Despite proving its usefulness for over a century, the concept of developmental dyslexia (DD) is currently in severe disarray because of the recent introduction of the phonological theory of its causation. Since mastering the phonological principle is essential for all reading, failure to [...] Read more.
Despite proving its usefulness for over a century, the concept of developmental dyslexia (DD) is currently in severe disarray because of the recent introduction of the phonological theory of its causation. Since mastering the phonological principle is essential for all reading, failure to do so cannot be used to distinguish DD from the many other causes of such failure. To overcome this problem, many new psychological, signal detection, and neurological theories have been introduced recently. All these new theories converge on the idea that DD is fundamentally caused by impaired signalling of the timing of the visual and auditory cues that are essential for reading. These are provided by large ‘magnocellular’ neurones which respond rapidly to sensory transients. The evidence for this conclusion is overwhelming. Especially convincing are intervention studies that have shown that improving magnocellular function improves dyslexic children’s reading, together with cohort studies that have demonstrated that the magnocellular timing deficit is present in infants who later become dyslexic, long before they begin learning to read. The converse of the magnocellular deficit in dyslexics may be that they gain parvocellular abundance. This may often impart the exceptional ‘holistic’ talents that have been ascribed to them and that society needs to nurture. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
17 pages, 1476 KiB  
Review
Trends in Dyslexia Research during the Period 1950 to 2020—Theories, Definitions, and Publications
by Turid Helland
Brain Sci. 2022, 12(10), 1323; https://doi.org/10.3390/brainsci12101323 - 29 Sep 2022
Cited by 5 | Viewed by 3156
Abstract
Introduction. The focus of the present paper is on (1) how dyslexia research and hence definitions have developed during the period 1950–2020 and includes (2) a database search of scientific publications on dyslexia during the same period. The focus is on the definitions [...] Read more.
Introduction. The focus of the present paper is on (1) how dyslexia research and hence definitions have developed during the period 1950–2020 and includes (2) a database search of scientific publications on dyslexia during the same period. The focus is on the definitions of dyslexia and the organization of the network search based on the causal four-level model by Morton and Frith. Method. (1) The definitions are presented in accordance with a historic review of dyslexia research from 1950 to 2020 and based on (2) Google Scholar counts of publications on dyslexia, on defining dyslexia, on dyslexia at the four levels (symptomatic, cognitive, biological, environmental), and by areas (sensorimotor, comorbidity). Finally, a percentage calculation shows the relative development within each level and area by decennium (1950–1960, 1960–1970, 1970–1980, 1990–2000, 2002–2010, 2010–2020). Results. (1) Of the seven definitions presented, only the definition by the BDA 2007 included the four levels of the causal model. (2) The number of publications increased substantially over the period. However, relatively few publications have defined dyslexia. An increase in publications from 1950 to 2020 was seen across the four levels and two areas—however, with an alteration in the thematic focus over this time span. Summary. Defining dyslexia has still not reached a consensus. This uncertainty may explain why only one of the seven definitions proved satisfactory according to the four-level model. Along with the general increase in research, publications on dyslexia have increased accordingly during the period 1950 to 2020. Although the symptomatic level has played a dominant role over the whole period, thematic shifts have been seen over these 70 years. In particular, a substantial thematic shift was seen by the turn of the millennium. There has been a relative increase in the focus on literacy at the symptomatic level, on phonological awareness at the cognitive level, in gender at the biological level, and second language learning as comorbidities. However, increases in counts are not alone a valid indication of scientific progress. In particular, the lack of definitional criteria as a basis for participant and method selection should attract much more focus in future studies. The present study underlines the multifactorial nature of dyslexia, as evidenced by a substantial increase in the number of publications on the subject. It is a challenge for future research to continuously use and possibly redefine dyslexia definitions in line with such standards. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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Other

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20 pages, 741 KiB  
Systematic Review
ERP Indicators of Phonological Awareness Development in Children: A Systematic Review
by Katarina Stekić, Olivera Ilić, Vanja Ković and Andrej M. Savić
Brain Sci. 2023, 13(2), 290; https://doi.org/10.3390/brainsci13020290 - 08 Feb 2023
Cited by 2 | Viewed by 2051
Abstract
Phonological awareness is the ability to correctly recognize and manipulate phonological structures. The role of phonological awareness in reading development has become evident in behavioral research showing that it is inherently tied to measures of phonological processing and reading ability. This has also [...] Read more.
Phonological awareness is the ability to correctly recognize and manipulate phonological structures. The role of phonological awareness in reading development has become evident in behavioral research showing that it is inherently tied to measures of phonological processing and reading ability. This has also been shown with ERP research that examined how phonological processing training can benefit reading skills. However, there have not been many attempts to systematically review how phonological awareness itself is developed neurocognitively. In the present review, we screened 224 papers and systematically reviewed 40 papers that have explored phonological awareness and phonological processing using ERP methodology with both typically developing and children with reading problems. This review highlights ERP components that can be used as neurocognitive predictors of early developmental dyslexia and reading disorders in young children. Additionally, we have presented how phonological processing is developed neurocognitively throughout childhood, as well as which phonological tasks can be used to predict the development of phonological awareness prior to developing reading skills. Neurocognitive measures of early phonological processing can serve as supplemental diagnostic sources to behavioral measures of reading abilities because they show different aspects of phonological sensitivity when compared to behavioral measures. Full article
(This article belongs to the Special Issue Developmental Dyslexia: Theories and Experimental Approaches)
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