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Olivo G, Persson J, Hedenius M. Exploring brain plasticity in developmental dyslexia through implicit sequence learning. NPJ SCIENCE OF LEARNING 2024; 9:37. [PMID: 38802367 PMCID: PMC11130236 DOI: 10.1038/s41539-024-00250-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 05/08/2024] [Indexed: 05/29/2024]
Abstract
Developmental dyslexia (DD) is defined as difficulties in learning to read even with normal intelligence and adequate educational guidance. Deficits in implicit sequence learning (ISL) abilities have been reported in children with DD. We investigated brain plasticity in a group of 17 children with DD, compared with 18 typically developing (TD) children, after two sessions of training on a serial reaction time (SRT) task with a 24-h interval. Our outcome measures for the task were: a sequence-specific implicit learning measure (ISL), entailing implicit recognition and learning of sequential associations; and a general visuomotor skill learning measure (GSL). Gray matter volume (GMV) increased, and white matter volume (WMV) decreased from day 1 to day 2 in cerebellar areas regardless of group. A moderating effect of group was found on the correlation between WMV underlying the left precentral gyrus at day 2 and the change in ISL performance, suggesting the use of different underlying learning mechanisms in DD and TD children during the ISL task. Moreover, DD had larger WMV in the posterior thalamic radiation compared with TD, supporting previous reports of atypical development of this structure in DD. Further studies with larger sample sizes are warranted to validate these results.
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Affiliation(s)
- Gaia Olivo
- University of Gothenburg, Department of Psychology, Haraldsgatan 1, 405 03, Göteborg, Sweden.
- Karolinska Institute, Department of Neurobiology, Care Sciences and Society, Aging Research Center, Tomtebodavägen 18a, SE-171 65, Solna, Sweden.
| | - Jonas Persson
- Karolinska Institute, Department of Neurobiology, Care Sciences and Society, Aging Research Center, Tomtebodavägen 18a, SE-171 65, Solna, Sweden
- Center for Life-span Developmental Research (LEADER), School of Law, Psychology, and Social Work, Örebro University, Örebro, Sweden
| | - Martina Hedenius
- Uppsala University, Department of Public Health and Caring Sciences, Biomedical Center, Husargatan 3, 751 22, Uppsala, Sweden
- Center of Neurodevelopmental Disorders (KIND), Centre for Psychiatry Research; Department of Women's and Children's Health, Karolinska Institutet & Stockholm Health Care Services, Region Stockholm, Gävlegatan 22, 11330, Stockholm, Sweden
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2
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Bhandari R, Phatangare RV, Eckert MA, Vaden KI, Wang JZ. Dyslexia Data Consortium Repository: A Data Sharing and Delivery Platform for Research. BRAIN INFORMATICS : 16TH INTERNATIONAL CONFERENCE, BI 2023, HOBOKEN, NJ, USA, AUGUST 1-3, 2023, PROCEEDINGS. INTERNATIONAL CONFERENCE ON BRAIN INFORMATICS (16TH : 2023 : HOBOKEN, N.J.) 2023; 13974:167-178. [PMID: 38352916 PMCID: PMC10859776 DOI: 10.1007/978-3-031-43075-6_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Specific learning disability of reading, or dyslexia, affects 5-17% of the population in the United States. Research on the neurobiology of dyslexia has included studies with relatively small sample sizes across research sites, thus limiting inference and the application of novel methods, such as deep learning. To address these issues and facilitate open science, we developed an online platform for data-sharing and advanced research programs to enhance opportunities for replication by providing researchers with secondary data that can be used in their research (https://www.dyslexiadata.org). This platform integrates a set of well-designed machine learning algorithms and tools to generate secondary datasets, such as cortical thickness, as well as regional brain volume metrics that have been consistently associated with dyslexia. Researchers can access shared data to address fundamental questions about dyslexia and development, replicate research findings, apply new methods, and educate the next generation of researchers. The overarching goal of this platform is to advance our understanding of a disorder that has significant academic, social, and economic impacts on children, their families, and society.
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Affiliation(s)
| | | | - Mark A Eckert
- Department of Otolaryngology - Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
| | - Kenneth I Vaden
- Department of Otolaryngology - Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
| | - James Z Wang
- School of Computing, Clemson University, Clemson, SC, USA
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3
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Del Mauro G, Del Maschio N, Abutalebi J. The relationship between reading abilities and the left occipitotemporal sulcus: A dual perspective study. BRAIN AND LANGUAGE 2022; 235:105189. [PMID: 36260960 DOI: 10.1016/j.bandl.2022.105189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 10/07/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
Reading activates a region within the left lateral occipitotemporal sulcus (OTS) known as the 'visual word form area' (VWFA). While several studies have investigated the impact of reading on brain structure through neuroplastic mechanisms, it has been recently suggested that individual differences in the pattern of the posterior OTS may predict reading skills in adults. In the present study, we first examined whether the structure and morphology and the anatomical connectivity of the left OTS are associated to reading ability. Second, we explored whether reading skills are predicted by the pattern of the left OTS. We found that reading skills were positively associated with increased connectivity between the left OTS and a network of reading-related regions in the left hemisphere. On the other hand, we did not observe an association between the pattern of the left OTS and reading skills. Finally, we found evidence that the morphology and the connectivity of the left OTS are correlated to its sulcal pattern.
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Affiliation(s)
- Gianpaolo Del Mauro
- Centre for Neurolinguistics and Psycholinguistics (CNPL), Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy
| | - Nicola Del Maschio
- Centre for Neurolinguistics and Psycholinguistics (CNPL), Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy; Facultyof Psychology, Vita-Salute San Raffaele University, Milan, Italy
| | - Jubin Abutalebi
- Centre for Neurolinguistics and Psycholinguistics (CNPL), Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy; Facultyof Psychology, Vita-Salute San Raffaele University, Milan, Italy; TheArctic University of Norway, Tromsø, Norway.
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4
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Hedenius M, Persson J. Neural correlates of sequence learning in children with developmental dyslexia. Hum Brain Mapp 2022; 43:3559-3576. [PMID: 35434881 PMCID: PMC9248315 DOI: 10.1002/hbm.25868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 03/31/2022] [Accepted: 03/31/2022] [Indexed: 12/02/2022] Open
Abstract
Developmental Dyslexia (DD) is a condition in which reading accuracy and/or fluency falls substantially below what is expected based on the individuals age, general level of cognitive ability, and educational opportunities. The procedural circuit deficit hypothesis (PDH) proposes that DD may be largely explained in terms of alterations of the cortico‐basal ganglia procedural memory system (in particular of the striatum) whereas the (hippocampus‐dependent) declarative memory system is intact, and may serve a compensatory role in the condition. The present study was designed to test this hypothesis. Using Magnetic Resonance Imaging, we examined the functional and structural brain correlates of sequence‐specific procedural learning (SL) on the serial reaction time task, in 17 children with DD and 18 typically developing (TD) children. The study was performed over 2 days with a 24‐h interval between sessions. In line with the PDH, the DD group showed less activation of the striatum during the processing of sequential statistical regularities. These alterations predicted the amount of SL at day 2, which in turn explained variance in children's reading fluency. Additionally, reduced hippocampal activation predicted larger SL gains between day 1 and day 2 in the TD group, but not in the DD group. At the structural level, caudate nucleus volume predicted the amount of acquired SL at day 2 in the TD group, but not in the DD group. The findings encourage further research into factors that promote learning in children with DD, including through compensatory mechanisms.
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Affiliation(s)
- Martina Hedenius
- Department of Public Health and Caring Sciences, Speech-Language Pathology, Uppsala University, Uppsala, Sweden.,Center of Neurodevelopmental Disorders (KIND), Centre for Psychiatry Research, Department of Women's and Children's Health, Karolinska Institutet and Child and Adolescent Psychiatry, Stockholm Health Care Services, Region Stockholml, Stockholm County Council, BUP-FOU Centrum, Gävlegatan, Stockholm, Sweden
| | - Jonas Persson
- Aging Research Center (ARC), Karolinska Institutet and Stockholm University, Solna, Sweden.,Center for Lifespan Developmental Research (LEADER), School of Law, Psychology, and Social Work, Örebro University, Örebro, Sweden
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Yan X, Jiang K, Li H, Wang Z, Perkins K, Cao F. Convergent and divergent brain structural and functional abnormalities associated with developmental dyslexia. eLife 2021; 10:e69523. [PMID: 34569931 PMCID: PMC8497057 DOI: 10.7554/elife.69523] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 09/24/2021] [Indexed: 01/18/2023] Open
Abstract
Brain abnormalities in the reading network have been repeatedly reported in individuals with developmental dyslexia (DD); however, it is still not totally understood where the structural and functional abnormalities are consistent/inconsistent across languages. In the current multimodal meta-analysis, we found convergent structural and functional alterations in the left superior temporal gyrus across languages, suggesting a neural signature of DD. We found greater reduction in grey matter volume and brain activation in the left inferior frontal gyrus in morpho-syllabic languages (e.g. Chinese) than in alphabetic languages, and greater reduction in brain activation in the left middle temporal gyrus and fusiform gyrus in alphabetic languages than in morpho-syllabic languages. These language differences are explained as consequences of being DD while learning a specific language. In addition, we also found brain regions that showed increased grey matter volume and brain activation, presumably suggesting compensations and brain regions that showed inconsistent alterations in brain structure and function. Our study provides important insights about the etiology of DD from a cross-linguistic perspective with considerations of consistency/inconsistency between structural and functional alterations.
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Affiliation(s)
- Xiaohui Yan
- Department of Psychology, Sun Yat-Sen UniversityGuangzhouChina
| | - Ke Jiang
- Department of Psychology, Sun Yat-Sen UniversityGuangzhouChina
| | - Hui Li
- Department of Preschool Education, Anyang Preschool Education CollegeAnyangChina
| | - Ziyi Wang
- School of Foreign Language, Jining UniversityJiningChina
| | - Kyle Perkins
- Florida International University (Retired Professor)MiamiUnited States
| | - Fan Cao
- Department of Psychology, Sun Yat-Sen UniversityGuangzhouChina
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Yang Y, Zuo Z, Tam F, Graham SJ, Li J, Ji Y, Meng Z, Gu C, Bi HY, Ou J, Xu M. The brain basis of handwriting deficits in Chinese children with developmental dyslexia. Dev Sci 2021; 25:e13161. [PMID: 34288292 PMCID: PMC9286553 DOI: 10.1111/desc.13161] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 06/15/2021] [Accepted: 07/14/2021] [Indexed: 02/06/2023]
Abstract
Abundant behavioral studies have demonstrated high comorbidity of reading and handwriting difficulties in developmental dyslexia (DD), a neurological condition characterized by unexpectedly low reading ability despite adequate nonverbal intelligence and typical schooling. The neural correlates of handwriting deficits remain largely unknown; however, as well as the extent that handwriting deficits share common neural bases with reading deficits in DD. The present work used functional magnetic resonance imaging to examine brain activity during handwriting and reading tasks in Chinese dyslexic children (n = 18) and age-matched controls (n = 23). Compared to controls, dyslexic children exhibited reduced activation during handwriting tasks in brain regions supporting sensory-motor processing (including supplementary motor area and postcentral gyrus) and visual-orthography processing (including bilateral precuneus and right cuneus). Among these regions, the left supplementary motor area and the right precuneus also showed a trend of reduced activation during reading tasks in dyslexics. Moreover, increased activation was found in the left inferior frontal gyrus and anterior cingulate cortex in dyslexics, which may reflect more efforts of executive control to compensate for the impairments of motor and visual-orthographic processing. Finally, dyslexic children exhibited aberrant functional connectivity among brain areas for cognitive control and sensory-motor processes during handwriting tasks. Together, these findings suggest that handwriting deficits in DD are associated with functional abnormalities of multiple brain regions implicated in motor execution, visual-orthographic processing, and cognitive control, providing important implications for the diagnosis and treatment of dyslexia.
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Affiliation(s)
- Yang Yang
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology,Chinese Academy of Sciences, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Zhentao Zuo
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Fred Tam
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - Simon J Graham
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Junjun Li
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology,Chinese Academy of Sciences, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Yuzhu Ji
- Department of Psychology, College of Education, Zhejiang University of Technology, Hangzhou, China
| | - Zelong Meng
- Department of Psychology, School of Humanities and Social Sciences, Beijing Forestry University, Beijing, China
| | - Chanyuan Gu
- Department of Chinese and Bilingual Studies, Faculty of Humanities, The Hong Kong Polytechnic University, Hong Kong, China
| | - Hong-Yan Bi
- CAS Key Laboratory of Behavioral Science, Center for Brain Science and Learning Difficulties, Institute of Psychology,Chinese Academy of Sciences, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Jian Ou
- Center for Brain Disorders and Cognitive Sciences, Shenzhen University, Shenzhen, China
| | - Min Xu
- Center for Brain Disorders and Cognitive Sciences, Shenzhen University, Shenzhen, China.,Center for Language and Brain, Shenzhen Institute of Neuroscience, Shenzhen, China
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7
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Ota M, Koshibe Y, Higashi S, Nemoto K, Tsukada E, Tamura M, Takahashi T, Arai T. Structural Brain Network Correlated with Reading Impairment in Alzheimer's Disease. Dement Geriatr Cogn Disord 2021; 49:264-269. [PMID: 32810848 DOI: 10.1159/000508406] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 05/04/2020] [Indexed: 12/22/2022] Open
Abstract
AIM Alzheimer's disease (AD) is the most common age-related neurodegenerative disease and leads to dementia. AD is characterized by progressive declines in memory and, as the disease progresses, language dysfunction. Although it has been reported that AD patients show progressive aphasia, no study has examined the relationship between language functions estimated by the Standard Language Test for Aphasia (SLTA) and brain network connectivity in Japanese AD patients. If present, such a relationship would be of particular interest because Japanese speakers are accustomed to mingling ideography and phonography. METHODS 22 Japanese patients with AD who underwent 1.5-tesla MRI scan and SLTA, the scale for speech and reading impairment, participated in this study. We computed brain network connectivity metrics such as degree, betweenness centrality, and clustering coefficient, and estimated their relationships with the subscores of SLTA. RESULTS There was a significant negative correlation between the score for "reading aloud Kanji words" and the clustering coefficient in the left inferior temporal region, bilateral hippocampal regions, and right parietotemporal region. We also found a significant negative correlation between the score for "auditory comprehension of words" and the clustering coefficient in the left prefrontal region. No significant relationship was found between the other SLTA scores and the network metrics. CONCLUSIONS Our data suggest relationships between reading impairments and regional brain network connectivity in Japanese patients with AD. The brain connectome may provide adjunct biological information that could improve our understanding of reading impairment.
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Affiliation(s)
- Miho Ota
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan,
| | - Yuko Koshibe
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Shinji Higashi
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.,Department of Psychiatry, Ibaraki Medical Center, Tokyo Medical University, Ami-machi, Japan
| | - Kiyotaka Nemoto
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Eriko Tsukada
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Masashi Tamura
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Takumi Takahashi
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Tetsuaki Arai
- Department of Psychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
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8
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Torre GAA, Eden GF. Relationships between gray matter volume and reading ability in typically developing children, adolescents, and young adults. Dev Cogn Neurosci 2019; 36:100636. [PMID: 30913497 PMCID: PMC6626657 DOI: 10.1016/j.dcn.2019.100636] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 03/06/2019] [Accepted: 03/08/2019] [Indexed: 01/20/2023] Open
Abstract
Reading is explicitly taught and foreshadows academic and vocational success. Studies comparing typical readers to those with developmental dyslexia have identified anatomical brain differences in bilateral temporo-parietal cortex, left temporo-occipital cortex, and bilateral cerebellum. Yet, it is unclear whether linear relationships exist between these brain structures and single real word reading ability in the general population. If dyslexia represents the lower end of the normal continuum, then relationships between gray matter volume (GMV) and reading ability would exist for all reading levels. Our study examined this question using voxel-based morphometry in a large sample (n = 404) of typically developing participants aged 6-22 derived from the NIH normative database. We tested correlations between individual GMV and single word reading and found none. After dividing this sample into groups based on age and on sex, we only found results in the group aged 15-22: positive correlations between GMV in left fusiform gyrus and reading, driven by females; and in right superior temporal gyrus in males. Multiple regressions also yielded no results, demonstrating that there is no general linear relationship between GMV and single real word reading ability. This provides an important context by which to interpret findings of GMV differences in dyslexia.
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Affiliation(s)
- Gabrielle-Ann A Torre
- Center for the Study of Learning, Department of Pediatrics, Georgetown University Medical Center, Washington, DC, United States
| | - Guinevere F Eden
- Center for the Study of Learning, Department of Pediatrics, Georgetown University Medical Center, Washington, DC, United States.
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9
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Moreau D, Wiebels K, Wilson AJ, Waldie KE. Volumetric and surface characteristics of gray matter in adult dyslexia and dyscalculia. Neuropsychologia 2019; 127:204-210. [PMID: 30738813 DOI: 10.1016/j.neuropsychologia.2019.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 02/04/2019] [Accepted: 02/04/2019] [Indexed: 01/18/2023]
Abstract
Dyslexia, dyscalculia and their comorbid manifestation are prevalent disorders associated with well-documented behavioral manifestations. However, attempts to relate these manifestations to abnormalities in brain structure have yielded mixed results, with no clear consistency across a range of measures. In this study, we used a unique design including adults with dyslexia, dyscalculia, both disorders and controls, to explore differences in gray matter characteristics across groups. Specifically, we examined whether dyslexia, dyscalculia, or their comorbid manifestation could be related to volumetric and surface characteristics of gray matter, using voxel-based and surface-based morphometry. We demonstrate with Bayesian analyses that the present data favor the null model of no differences between groups across the brain, a result that is in line with recent findings in this field of research. Importantly, we provide detailed statistical maps to enable robust assessment of our findings, and to promote cumulative evaluation of the evidence. Together, these findings suggest that gray matter differences associated with dyslexia and dyscalculia might not be as reliable as suggested by previous literature, with important implications for our understanding of these disorders.
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Affiliation(s)
- David Moreau
- School of Psychology and Centre for Brain Research, University of Auckland, New Zealand.
| | - Kristina Wiebels
- School of Psychology and Centre for Brain Research, University of Auckland, New Zealand
| | - Anna J Wilson
- Department of Psychology, University of Canterbury, New Zealand
| | - Karen E Waldie
- School of Psychology and Centre for Brain Research, University of Auckland, New Zealand
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10
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van Oers CAMM, Goldberg N, Fiorin G, van den Heuvel MP, Kappelle LJ, Wijnen FNK. No evidence for cerebellar abnormality in adults with developmental dyslexia. Exp Brain Res 2018; 236:2991-3001. [PMID: 30116863 PMCID: PMC6223834 DOI: 10.1007/s00221-018-5351-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 08/02/2018] [Indexed: 01/18/2023]
Abstract
Developmental dyslexia is commonly believed to result from a deficiency in the recognition and processing of speech sounds. According to the cerebellar deficit hypothesis, this phonological deficit is caused by deficient cerebellar function. In the current study, 26 adults with developmental dyslexia and 25 non-dyslexic participants underwent testing of reading-related skills, cerebellar functions, and MRI scanning of the brain. Anatomical assessment of the cerebellum was conducted with voxel-based morphometry. Behavioural evidence, that was indicative of impaired cerebellar function, was found to co-occur with reading impairments in the dyslexic subjects, but a causal relation between the two was not observed. No differences in local grey matter volume, nor in structure-function relationships within the cerebellum were found between the two groups. Possibly, the observed behavioural pattern is due to aberrant white matter connectivity. In conclusion, no support for the cerebellar deficit hypothesis or the presence of anatomical differences of the cerebellum in adults with developmental dyslexia was found.
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Affiliation(s)
- Casper A M M van Oers
- Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
- Department of Neurology, Amphia Hospital, Breda, The Netherlands.
| | - Nadya Goldberg
- Utrecht institute of Linguistics OTS, Utrecht, The Netherlands
| | - Gaetano Fiorin
- Utrecht institute of Linguistics OTS, Utrecht, The Netherlands
| | - Martijn P van den Heuvel
- Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands
| | - L Jaap Kappelle
- Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands
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11
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Singh S, Walk AM, Conway CM. Atypical predictive processing during visual statistical learning in children with developmental dyslexia: an event-related potential study. ANNALS OF DYSLEXIA 2018; 68:165-179. [PMID: 29907920 PMCID: PMC6390967 DOI: 10.1007/s11881-018-0161-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 06/05/2018] [Indexed: 06/08/2023]
Abstract
Previous research suggests that individuals with developmental dyslexia perform below typical readers on non-linguistic cognitive tasks involving the learning and encoding of statistical-sequential patterns. However, the neural mechanisms underlying such a deficit have not been well examined. The aim of the present study was to investigate the event-related potential (ERP) correlates of sequence processing in a sample of children diagnosed with dyslexia using a non-linguistic visual statistical learning paradigm. Whereas the response time data suggested that both typical and atypical readers learned the statistical patterns embedded in the task, the ERP data suggested otherwise. Specifically, ERPs of the typically developing children (n = 12) showed a P300-like response indicative of learning, whereas the children diagnosed with a reading disorder (n = 8) showed no such ERP effects. These results may be due to intact implicit motor learning in the children with dyslexia but delayed attention-dependent predictive processing. These findings are consistent with other evidence suggesting that differences in statistical learning ability might underlie some of the reading deficits observed in developmental dyslexia.
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Affiliation(s)
- Sonia Singh
- Department of Psychology, Georgia State University, P.O. Box 5010, Atlanta, GA, 30302, USA.
| | - Anne M Walk
- Department of Kinesiology and Community Health, University of Illinois, 405 N. 900 S. Goodwin Ave, Urbana, IL, 61801, USA
| | - Christopher M Conway
- Department of Psychology, Georgia State University, P.O. Box 5010, Atlanta, GA, 30302, USA
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12
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Sawi OM, Rueckl JG. Reading and the Neurocognitive Bases of Statistical Learning 1. SCIENTIFIC STUDIES OF READING : THE OFFICIAL JOURNAL OF THE SOCIETY FOR THE SCIENTIFIC STUDY OF READING 2018; 23:8-23. [PMID: 31105421 PMCID: PMC6521969 DOI: 10.1080/10888438.2018.1457681] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The processes underlying word reading are shaped by statistical properties of the writing system. According to some theoretical perspectives (e.g. Harm & Seidenberg, 2004) reading acquisition should be understood as an exercise in statistical learning. Statistical learning (SL) involves the extraction of organizing principles from a set of inputs. Several lines of research provide convergent evidence supporting the connection between SL and reading acquisition (e.g., Arciuli & Simpson, 2012; Frost et al., 2014; Bogaerts et al., 2015). An obstacle to fully appreciating the theoretical and educational implications of these findings is that SL is itself not well understood. In this paper, we review the current literature on SL with a particular focus on organizing this literature by grounding it in theories of learning and memory more generally. This approach can clarify the nature of SL and provide a framework for understanding its role in reading, reading acquisition, and reading disorders.
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Affiliation(s)
| | - Jay G Rueckl
- University of Connecticut & Haskins Laboratories
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13
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Ramus F, Altarelli I, Jednoróg K, Zhao J, Scotto di Covella L. Neuroanatomy of developmental dyslexia: Pitfalls and promise. Neurosci Biobehav Rev 2017; 84:434-452. [PMID: 28797557 DOI: 10.1016/j.neubiorev.2017.08.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 07/28/2017] [Accepted: 08/02/2017] [Indexed: 01/18/2023]
Abstract
Investigations into the neuroanatomical bases of developmental dyslexia have now spanned more than 40 years, starting with the post-mortem examination of a few individual brains in the 60s and 70s, and exploding in the 90s with the widespread use of MRI. The time is now ripe to reappraise the considerable amount of data gathered with MRI using different types of sequences (T1, diffusion, spectroscopy) and analysed using different methods (manual, voxel-based or surface-based morphometry, fractional anisotropy and tractography, multivariate analyses…). While selective reviews of mostly small-scale studies seem to provide a coherent view of the brain disruptions that are typical of dyslexia, involving left perisylvian and occipito-temporal regions, we argue that this view may be deceptive and that meta-analyses and large-scale studies rather highlight many inconsistencies and limitations. We discuss problems inherent to small sample size as well as methodological difficulties that still undermine the discovery of reliable neuroanatomical bases of dyslexia, and we outline some recommendations to further improve this research area.
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Affiliation(s)
- Franck Ramus
- Laboratoire de sciences cognitives et psycholinguistique (CNRS, ENS, EHESS, PSL Research University), Ecole Normale Supérieure, 29 rue d'Ulm, 75005 Paris, France.
| | - Irene Altarelli
- Brain and Learning Lab, Campus Biotech, University of Geneva, 9 Chemin des Mines, 1205 Geneva, Switzerland
| | - Katarzyna Jednoróg
- Laboratory of Psychophysiology, Department of Neurophysiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur St, 02-093 Warsaw, Poland
| | - Jingjing Zhao
- School of Psychology, Shaanxi Normal University and Key Laboratory for Behavior and Cognitive Neuroscience of Shaanxi Province, Xi'an, Shaanxi, 710062, China
| | - Lou Scotto di Covella
- Laboratoire de sciences cognitives et psycholinguistique (CNRS, ENS, EHESS, PSL Research University), Ecole Normale Supérieure, 29 rue d'Ulm, 75005 Paris, France
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14
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Fernandez VG, Juranek J, Romanowska-Pawliczek A, Stuebing K, Williams VJ, Fletcher JM. White matter integrity of cerebellar-cortical tracts in reading impaired children: A probabilistic tractography study. BRAIN AND LANGUAGE 2016; 161:45-56. [PMID: 26307492 PMCID: PMC4803624 DOI: 10.1016/j.bandl.2015.07.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Revised: 07/01/2015] [Accepted: 07/10/2015] [Indexed: 06/04/2023]
Abstract
Little is known about the white matter integrity of cerebellar-cortical pathways in individuals with dyslexia. Building on previous findings of decreased volume in the anterior lobe of the cerebellum, we utilized novel cerebellar segmentation procedures and probabilistic tractography to examine tracts that connect the anterior lobe of the cerebellum and cortical regions typically associated with reading: the temporoparietal (TP), occipitotemporal (OT), and inferior frontal (IF) regions. The sample included 29 reading impaired children and 27 typical readers. We found greater fractional anisotropy (FA) for the poor readers in tracts connecting the cerebellum with TP and IF regions relative to typical readers. In the OT region, FA was greater for the older poor readers, but smaller for the younger ones. This study provides evidence for discrete, regionally-bound functions of the cerebellum and suggests that projections from the anterior cerebellum appear to have a regulatory effect on cortical pathways important for reading.
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Affiliation(s)
- Vindia G Fernandez
- University of Houston, 4811 Calhoun Rd., 3rd Floor, Houston, TX 77204-6022, United States.
| | - Jenifer Juranek
- University of Texas Health Science Center, 6655 Travis, Houston, TX 77030-1312, United States.
| | | | - Karla Stuebing
- University of Houston, 4811 Calhoun Rd., 3rd Floor, Houston, TX 77204-6022, United States.
| | - Victoria J Williams
- University of Houston, 4811 Calhoun Rd., 3rd Floor, Houston, TX 77204-6022, United States.
| | - Jack M Fletcher
- University of Houston, 4811 Calhoun Rd., 3rd Floor, Houston, TX 77204-6022, United States.
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15
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Skeide MA, Kraft I, Müller B, Schaadt G, Neef NE, Brauer J, Wilcke A, Kirsten H, Boltze J, Friederici AD. NRSN1 associated grey matter volume of the visual word form area reveals dyslexia before school. Brain 2016; 139:2792-2803. [PMID: 27343255 DOI: 10.1093/brain/aww153] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 05/08/2016] [Indexed: 02/02/2023] Open
Abstract
Literacy learning depends on the flexibility of the human brain to reconfigure itself in response to environmental influences. At the same time, literacy and disorders of literacy acquisition are heritable and thus to some degree genetically predetermined. Here we used a multivariate non-parametric genetic model to relate literacy-associated genetic variants to grey and white matter volumes derived by voxel-based morphometry in a cohort of 141 children. Subsequently, a sample of 34 children attending grades 4 to 8, and another sample of 20 children, longitudinally followed from kindergarten to first grade, were classified as dyslexics and controls using linear binary support vector machines. The NRSN1-associated grey matter volume of the 'visual word form area' achieved a classification accuracy of ~ 73% in literacy-experienced students and distinguished between later dyslexic individuals and controls with an accuracy of 75% at kindergarten age. These findings suggest that the cortical plasticity of a region vital for literacy might be genetically modulated, thereby potentially preconstraining literacy outcome. Accordingly, these results could pave the way for identifying and treating the most common learning disorder before it manifests itself in school.
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Affiliation(s)
- Michael A Skeide
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany
| | - Indra Kraft
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany
| | - Bent Müller
- 2 Cognitive Genetics Unit, Department of Cell Therapy, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - Gesa Schaadt
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany 3 Department of Psychology, Humboldt-Universität zu Berlin, Rudower Chaussee 18, 12489 Berlin, Germany
| | - Nicole E Neef
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany
| | - Jens Brauer
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany
| | - Arndt Wilcke
- 2 Cognitive Genetics Unit, Department of Cell Therapy, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - Holger Kirsten
- 2 Cognitive Genetics Unit, Department of Cell Therapy, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany 4 Institute for Medical Informatics, Statistics and Epidemiology, Universität Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany 5 LIFE - Leipzig Research Center for Civilization Diseases, Universität Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany
| | - Johannes Boltze
- 2 Cognitive Genetics Unit, Department of Cell Therapy, Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany 6 Fraunhofer Research Institution for Marine Biotechnology, Department of Medical Cell Technology, and Institute for Medical and Marine Biotechnology, University of Lübeck, Mönkhofer Weg 239a, 23562 Lübeck, Germany
| | - Angela D Friederici
- 1 Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103 Leipzig, Germany
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16
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Gray Matter Features of Reading Disability: A Combined Meta-Analytic and Direct Analysis Approach(1,2,3,4). eNeuro 2016; 3:eN-CFN-0103-15. [PMID: 26835509 PMCID: PMC4724065 DOI: 10.1523/eneuro.0103-15.2015] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 12/21/2015] [Accepted: 12/25/2015] [Indexed: 01/18/2023] Open
Abstract
Meta-analysis of voxel-based morphometry dyslexia studies and direct analysis of 293 reading disability and control cases from six different research sites were performed to characterize defining gray matter features of reading disability. These analyses demonstrated consistently lower gray matter volume in left posterior superior temporal sulcus/middle temporal gyrus regions and left orbitofrontal gyrus/pars orbitalis regions. Gray matter volume within both of these regions significantly predicted individual variation in reading comprehension after correcting for multiple comparisons. These regional gray matter differences were observed across published studies and in the multisite dataset after controlling for potential age and gender effects, and despite increased anatomical variance in the reading disability group, but were not significant after controlling for total gray matter volume. Thus, the orbitofrontal and posterior superior temporal sulcus gray matter findings are relatively reliable effects that appear to be dependent on cases with low total gray matter volume. The results are considered in the context of genetics studies linking orbitofrontal and superior temporal sulcus regions to alleles that confer risk for reading disability.
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17
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Tamboer P, Scholte HS, Vorst HCM. Dyslexia and voxel-based morphometry: correlations between five behavioural measures of dyslexia and gray and white matter volumes. ANNALS OF DYSLEXIA 2015; 65:121-141. [PMID: 25908528 PMCID: PMC4565889 DOI: 10.1007/s11881-015-0102-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 03/04/2015] [Indexed: 05/29/2023]
Abstract
In voxel-based morphometry studies of dyslexia, the relation between causal theories of dyslexia and gray matter (GM) and white matter (WM) volume alterations is still under debate. Some alterations are consistently reported, but others failed to reach significance. We investigated GM alterations in a large sample of Dutch students (37 dyslexics and 57 non-dyslexics) with two analyses: group differences in local GM and total GM and WM volume and correlations between GM and WM volumes and five behavioural measures. We found no significant group differences after corrections for multiple comparisons although total WM volume was lower in the group of dyslexics when age was partialled out. We presented an overview of uncorrected clusters of voxels (p < 0.05, cluster size k > 200) with reduced or increased GM volume. We found four significant correlations between factors of dyslexia representing various behavioural measures and the clusters found in the first analysis. In the whole sample, a factor related to performances in spelling correlated negatively with GM volume in the left posterior cerebellum. Within the group of dyslexics, a factor related to performances in Dutch-English rhyme words correlated positively with GM volume in the left and right caudate nucleus and negatively with increased total WM volume. Most of our findings were in accordance with previous reports. A relatively new finding was the involvement of the caudate nucleus. We confirmed the multiple cognitive nature of dyslexia and suggested that experience greatly influences anatomical alterations depending on various subtypes of dyslexia, especially in a student sample.
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Affiliation(s)
- Peter Tamboer
- Department of Psychology, Faculty of Social and Behavioural Sciences, University of Amsterdam, Amsterdam, The Netherlands.
- , Weesperplein 4, Room 218, 1018XA, Amsterdam, The Netherlands.
- , Overtoom 247B, 1054HW, Amsterdam, The Netherlands.
| | - H Steven Scholte
- Department of Psychology, Faculty of Social and Behavioural Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Harrie C M Vorst
- Department of Psychology, Faculty of Social and Behavioural Sciences, University of Amsterdam, Amsterdam, The Netherlands
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18
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Jednoróg K, Marchewka A, Altarelli I, Monzalvo Lopez AK, van Ermingen‐Marbach M, Grande M, Grabowska A, Heim S, Ramus F. How reliable are gray matter disruptions in specific reading disability across multiple countries and languages? Insights from a large-scale voxel-based morphometry study. Hum Brain Mapp 2015; 36:1741-54. [PMID: 25598483 PMCID: PMC6869714 DOI: 10.1002/hbm.22734] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 12/14/2014] [Accepted: 01/06/2015] [Indexed: 01/18/2023] Open
Abstract
The neural basis of specific reading disability (SRD) remains only partly understood. A dozen studies have used voxel-based morphometry (VBM) to investigate gray matter volume (GMV) differences between SRD and control children, however, recent meta-analyses suggest that few regions are consistent across studies. We used data collected across three countries (France, Poland, and Germany) with the aim of both increasing sample size (236 SRD and controls) to obtain a clearer picture of group differences, and of further assessing the consistency of the findings across languages. VBM analysis reveals a significant group difference in a single cluster in the left thalamus. Furthermore, we observe correlations between reading accuracy and GMV in the left supramarginal gyrus and in the left cerebellum, in controls only. Most strikingly, we fail to replicate all the group differences in GMV reported in previous studies, despite the superior statistical power. The main limitation of this study is the heterogeneity of the sample drawn from different countries (i.e., speaking languages with varying orthographic transparencies) and selected based on different assessment batteries. Nevertheless, analyses within each country support the conclusions of the cross-linguistic analysis. Explanations for the discrepancy between the present and previous studies may include: (1) the limited suitability of VBM to reveal the subtle brain disruptions underlying SRD; (2) insufficient correction for multiple statistical tests and flexibility in data analysis, and (3) publication bias in favor of positive results. Thus the study echoes widespread concerns about the risk of false-positive results inherent to small-scale VBM studies.
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Affiliation(s)
- Katarzyna Jednoróg
- Laboratory of PsychophysiologyDepartment of NeurophysiologyNencki Institute of Experimental BiologyWarsawPoland
| | - Artur Marchewka
- Laboratory of Brain ImagingNeurobiology Center, Nencki Institute of Experimental BiologyWarsawPoland
| | - Irene Altarelli
- Laboratoire de Sciences Cognitives et PsycholinguistiqueDépartement d'Etudes CognitivesEcole Normale Supérieure, EHESS, CNRS, PSL Research UniversityParisFrance
- Brain and Learning Laboratory, FPSE, University of GenevaGenevaSwitzerland
| | - Ana Karla Monzalvo Lopez
- INSERM, Cognitive Neuroimaging UnitGif sur Yvette91191France
- Commissariat ´ l'Energie Atomique, Division of Life Sciences, Institute of BioImaging, Neurospin centerGif sur Yvette91191France
- University Paris 11OrsayFrance
| | - Muna van Ermingen‐Marbach
- Department of PsychiatryPsychotherapy, and Psychosomatics, Medical Faculty, RWTH AachenGermany
- SRH University of Applied Sciences for Health Gera GmbHGeraGermany
| | - Marion Grande
- Section Clinical and Cognitive NeurosciencesDepartment of NeurologyUniklinik RWTH AachenGermany
| | - Anna Grabowska
- Laboratory of PsychophysiologyDepartment of NeurophysiologyNencki Institute of Experimental BiologyWarsawPoland
- University of Social Sciences and HumanitiesWarsawPoland
| | - Stefan Heim
- Department of PsychiatryPsychotherapy, and Psychosomatics, Medical Faculty, RWTH AachenGermany
- Research Centre Jülich, Institute of Neuroscience and Medicine [INM‐1]JülichGermany
| | - Franck Ramus
- Laboratoire de Sciences Cognitives et PsycholinguistiqueDépartement d'Etudes CognitivesEcole Normale Supérieure, EHESS, CNRS, PSL Research UniversityParisFrance
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19
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Truong DT, Rendall AR, Rosen GD, Fitch RH. Morphometric changes in subcortical structures of the central auditory pathway in mice with bilateral nodular heterotopia. Behav Brain Res 2014; 282:61-9. [PMID: 25549859 DOI: 10.1016/j.bbr.2014.12.046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 12/17/2014] [Accepted: 12/21/2014] [Indexed: 02/09/2023]
Abstract
Malformations of cortical development (MCD) have been observed in human reading and language impaired populations. Injury-induced MCD in rodent models of reading disability show morphological changes in the auditory thalamic nucleus (medial geniculate nucleus; MGN) and auditory processing impairments, thus suggesting a link between MCD, MGN, and auditory processing behavior. Previous neuroanatomical examination of a BXD29 recombinant inbred strain (BXD29-Tlr4(lps-2J)/J) revealed MCD consisting of bilateral subcortical nodular heterotopia with partial callosal agenesis. Subsequent behavioral characterization showed a severe impairment in auditory processing-a deficient behavioral phenotype seen across both male and female BXD29-Tlr4(lps-2J)/J mice. In the present study we expanded upon the neuroanatomical findings in the BXD29-Tlr4(lps-2J)/J mutant mouse by investigating whether subcortical changes in cellular morphology are present in neural structures critical to central auditory processing (MGN, and the ventral and dorsal subdivisions of the cochlear nucleus; VCN and DCN, respectively). Stereological assessment of brain tissue of male and female BXD29-Tlr4(lps-2J)/J mice previously tested on an auditory processing battery revealed overall smaller neurons in the MGN of BXD29-Tlr4(lps-2J)/J mutant mice in comparison to BXD29/Ty coisogenic controls, regardless of sex. Interestingly, examination of the VCN and DCN revealed sexually dimorphic changes in neuronal size, with a distribution shift toward larger neurons in female BXD29-Tlr4(lps-2J)/J brains. These effects were not seen in males. Together, the combined data set supports and further expands the observed co-occurrence of MCD, auditory processing impairments, and changes in subcortical anatomy of the central auditory pathway. The current stereological findings also highlight sex differences in neuroanatomical presentation in the presence of a common auditory behavioral phenotype.
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Affiliation(s)
- Dongnhu T Truong
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA
| | - Amanda R Rendall
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA
| | - Glenn D Rosen
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
| | - R Holly Fitch
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA.
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20
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Volumetric analysis of regional variability in the cerebellum of children with dyslexia. THE CEREBELLUM 2014; 12:906-15. [PMID: 23828023 DOI: 10.1007/s12311-013-0504-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cerebellar deficits and subsequent impairment in procedural learning may contribute to both motor difficulties and reading impairment in dyslexia. We used quantitative magnetic resonance imaging to investigate the role of regional variation in cerebellar anatomy in children with single-word decoding impairments (N = 23), children with impairment in fluency alone (N = 8), and typically developing children (N = 16). Children with decoding impairments (dyslexia) demonstrated no statistically significant differences in overall grey and white matter volumes or cerebellar asymmetry; however, reduced volume in the anterior lobe of the cerebellum relative to typically developing children was observed. These results implicate cerebellar involvement in dyslexia and establish an important foundation for future research on the connectivity of the cerebellum and cortical regions typically associated with reading impairment.
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21
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22
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Krafnick AJ, Flowers DL, Luetje MM, Napoliello EM, Eden GF. An investigation into the origin of anatomical differences in dyslexia. J Neurosci 2014; 34:901-8. [PMID: 24431448 PMCID: PMC3891966 DOI: 10.1523/jneurosci.2092-13.2013] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Studies have converged in their findings of relatively less gray matter volume (GMV) in developmental dyslexia in bilateral temporoparietal and left occipitotemporal cortical regions. However, the interpretation of these results has been difficult. The reported neuroanatomical differences in dyslexia may be causal to the reading problems, following from, for example, neural migration errors that occurred during early human development and before learning to read. Alternatively, less GMV may represent the consequence of an impoverished reading experience, akin to the experience-dependent GMV differences attributed to illiterate compared with literate adults. Most likely, a combination of these factors is driving these observations. Here we attempt to disambiguate these influences by using a reading level-matched design, where dyslexic children were contrasted not only with age-matched controls, but also with younger controls who read at the same level as the dyslexics. Consistent with previous reports, dyslexics showed less GMV in multiple left and right hemisphere regions, including left superior temporal sulcus when compared with age-matched controls. However, not all of these differences emerged when dyslexics were compared with controls matched on reading abilities, with only right precentral gyrus GMV surviving this second analysis. When similar analyses were performed for white matter volume, no regions emerged from both comparisons. These results indicate that the GMV differences in dyslexia reported here and in prior studies are in large part the outcome of experience (e.g., disordered reading experience) compared with controls, with only a fraction of the differences being driven by dyslexia per se.
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Affiliation(s)
- Anthony J Krafnick
- Center for the Study of Learning, Georgetown University Medical Center, Washington, DC 20057, and Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina 27157
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23
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Du W, Kelly SW. Implicit sequence learning in dyslexia: a within-sequence comparison of first- and higher-order information. ANNALS OF DYSLEXIA 2013; 63:154-70. [PMID: 22996058 DOI: 10.1007/s11881-012-0077-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 07/12/2012] [Indexed: 05/21/2023]
Abstract
The present study examines implicit sequence learning in adult dyslexics with a focus on comparing sequence transitions with different statistical complexities. Learning of a 12-item deterministic sequence was assessed in 12 dyslexic and 12 non-dyslexic university students. Both groups showed equivalent standard reaction time increments when the sequence was unexpectedly changed, suggesting that learning of the sequence took place. However, a novel analysis comparing transitions of differing complexity within the learning blocks indicated that dyslexic participants were impaired only for higher-order but not first-order sequence learning. No difference was found in the explicit awareness contribution between the two groups and this was found not to correlate with reaction time performance. This result suggests that statistical complexity of the sequence may account for intact and impaired learning performance in dyslexia.
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Affiliation(s)
- Wenchong Du
- The School of Psychological Sciences and Health, University of Strathclyde, Glasgow G1 1QE, UK
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24
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Hedenius M, Ullman MT, Alm P, Jennische M, Persson J. Enhanced recognition memory after incidental encoding in children with developmental dyslexia. PLoS One 2013; 8:e63998. [PMID: 23717524 PMCID: PMC3662708 DOI: 10.1371/journal.pone.0063998] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 04/08/2013] [Indexed: 11/18/2022] Open
Abstract
Developmental dyslexia (DD) has previously been associated with a number of cognitive deficits. Little attention has been directed to cognitive functions that remain intact in the disorder, though the investigation and identification of such strengths might be useful for developing new, and improving current, therapeutical interventions. In this study, an old/new recognition memory paradigm was used to examine previously untested aspects of declarative memory in children with DD and typically developing control children. The DD group was not only not impaired at the task, but actually showed superior recognition memory, as compared to the control children. These findings complement previous reports of enhanced cognition in other domains (e.g., visuo-spatial processing) in DD. Possible underlying mechanisms for the observed DD advantage in declarative memory, and the possibility of compensation by this system for reading deficits in dyslexia, are discussed.
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Affiliation(s)
- Martina Hedenius
- Department of Neuroscience, Uppsala University, Uppsala, Sweden.
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25
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Evans TM, Flowers DL, Napoliello EM, Eden GF. Sex-specific gray matter volume differences in females with developmental dyslexia. Brain Struct Funct 2013; 219:1041-54. [PMID: 23625146 DOI: 10.1007/s00429-013-0552-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 04/09/2013] [Indexed: 01/18/2023]
Abstract
Developmental dyslexia, characterized by unexpected reading difficulty, is associated with anomalous brain anatomy and function. Previous structural neuroimaging studies have converged in reports of less gray matter volume (GMV) in dyslexics within left hemisphere regions known to subserve language. Due to the higher prevalence of dyslexia in males, these studies are heavily weighted towards males, raising the question whether studies of dyslexia in females only and using the same techniques, would generate the same findings. In a replication study of men, we obtained the same findings of less GMV in dyslexics in left middle/inferior temporal gyri and right postcentral/supramarginal gyri as reported in the literature. However, comparisons in women with and without dyslexia did not yield left hemisphere differences, and instead, we found less GMV in right precuneus and paracentral lobule/medial frontal gyrus. In boys, we found less GMV in left inferior parietal cortex (supramarginal/angular gyri), again consistent with previous work, while in girls differences were within right central sulcus, spanning adjacent gyri, and left primary visual cortex. Our investigation into anatomical variants in dyslexia replicates existing studies in males, but at the same time shows that dyslexia in females is not characterized by involvement of left hemisphere language regions but rather early sensory and motor cortices (i.e., motor and premotor cortex, primary visual cortex). Our findings suggest that models on the brain basis of dyslexia, primarily developed through the study of males, may not be appropriate for females and suggest a need for more sex-specific investigations into dyslexia.
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Affiliation(s)
- Tanya M Evans
- Center for the Study of Learning, Department of Pediatrics, Georgetown University Medical Center, BOX 571406, Suite 150, Building D, 4000 Reservoir Road, NW, Washington, DC, 20057, USA
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26
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Szalkowski CE, Booker AB, Truong DT, Threlkeld SW, Rosen GD, Fitch RH. Knockdown of the candidate dyslexia susceptibility gene homolog dyx1c1 in rodents: effects on auditory processing, visual attention, and cortical and thalamic anatomy. Dev Neurosci 2013; 35:50-68. [PMID: 23594585 DOI: 10.1159/000348431] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 01/23/2013] [Indexed: 12/24/2022] Open
Abstract
The current study investigated the behavioral and neuroanatomical effects of embryonic knockdown of the candidate dyslexia susceptibility gene (CDSG) homolog Dyx1c1 through RNA interference (RNAi) in rats. Specifically, we examined long-term effects on visual attention abilities in male rats, in addition to assessing rapid and complex auditory processing abilities in male and, for the first time, female rats. Our results replicated prior evidence of complex acoustic processing deficits in Dyx1c1 male rats and revealed new evidence of comparable deficits in Dyx1c1 female rats. Moreover, we found new evidence that knocking down Dyx1c1 produced orthogonal impairments in visual attention in the male subgroup. Stereological analyses of male brains from prior RNAi studies revealed that, despite consistent visible evidence of disruptions of neuronal migration (i.e., heterotopia), knockdown of Dyx1c1 did not significantly alter the cortical volume, hippocampal volume, or midsagittal area of the corpus callosum (measured in a separate cohort of like-treated Dyx1c1 male rats). Dyx1c1 transfection did, however, lead to significant changes in medial geniculate nucleus (MGN) anatomy, with a significant shift to smaller MGN neurons in Dyx1c1-transfected animals. Combined results provide important information about the impact of Dyx1c1 on behavioral functions that parallel domains known to be affected in language-impaired populations as well as information about widespread changes to the brain following early disruption of this CDSG.
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Affiliation(s)
- Caitlin E Szalkowski
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, Storrs, Conn. 06269, USA.
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27
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Szalkowski CE, Fiondella CF, Truong DT, Rosen GD, LoTurco JJ, Fitch RH. The effects of Kiaa0319 knockdown on cortical and subcortical anatomy in male rats. Int J Dev Neurosci 2013; 31:116-22. [PMID: 23220223 PMCID: PMC3689304 DOI: 10.1016/j.ijdevneu.2012.11.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 11/20/2012] [Accepted: 11/21/2012] [Indexed: 12/13/2022] Open
Abstract
Developmental dyslexia is a disorder characterized by a specific deficit in reading despite adequate overall intelligence and educational resources. The neurological substrate underlying these significant behavioral impairments is not known. Studies of post mortem brain tissue from male and female dyslexic individuals revealed focal disruptions of neuronal migration concentrated in the left hemisphere, along with aberrant symmetry of the right and left the planum temporale, and changes in cell size distribution within the medial geniculate nucleus of the thalamus (Galaburda et al., 1985; Humphreys et al., 1990). More recent neuroimaging studies have identified several changes in the brains of dyslexic individuals, including regional changes in gray matter, changes in white matter, and changes in patterns of functional activation. In a further effort to elucidate the etiology of dyslexia, epidemiological and genetic studies have identified several candidate dyslexia susceptibility genes. Some recent work has investigated associations between some of these genetic variants and structural changes in the brain. Variants of one candidate dyslexia susceptibility gene, KIAA0319, have been linked to morphological changes in the cerebellum and functional activational changes in the superior temporal sulcus (Jamadar et al., 2011; Pinel et al., 2012). Animal models have been used to create a knockdown of Kiaa0319 (the rodent homolog of the human gene) via in utero RNA interference in order to study the gene's effects on brain development and behavior. Studies using this animal model have demonstrated that knocking down the gene leads to focal disruptions of neuronal migration in the form of ectopias and heterotopias, similar to those observed in the brains of human dyslexics. However, further changes to the structure of the brain have not been studied following this genetic disruption. The current study sought to determine the effects of embryonic Kiaa0319 knockdown on volume of the cortex and hippocampus, as well as midsagittal area of the corpus callosum in male rats. Results demonstrate that Kiaa0319 knockdown did not change the volume of the cortex or hippocampus, but did result in a significant reduction in the midsagittal area of the corpus callosum. Taken in the context of previous reports of behavioral deficits following Kiaa0319 knockdown (Szalkowski et al., 2012), and reports that reductions of corpus callosum size are related to processing deficits in humans (Paul, 2011), these results suggest that Kiaa0319 has a specific involvement in neural systems important for temporal processing.
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Affiliation(s)
- Caitlin E Szalkowski
- Department of Psychology/Behavioral Neuroscience, University of Connecticut, Storrs, 06269, United States.
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28
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Sela I, Karni A. Differences in learning volitional (manual) and non-volitional (posture) aspects of a complex motor skill in young adult dyslexic and skilled readers. PLoS One 2012; 7:e43488. [PMID: 23049736 PMCID: PMC3458875 DOI: 10.1371/journal.pone.0043488] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 07/20/2012] [Indexed: 11/18/2022] Open
Abstract
The 'Cerebellar Deficit Theory' of developmental dyslexia proposes that a subtle developmental cerebellar dysfunction leads to deficits in attaining 'automatic' procedures and therefore manifests as subtle motor impairments (e.g., balance control, motor skill learning) in addition to the reading and phonological difficulties. A more recent version of the theory suggests a core deficit in motor skill acquisition. This study was undertaken to compare the time-course and the nature of practice-related changes in volitional (manual) and non-volitional (posture) motor performance in dyslexic and typical readers while learning a new movement sequence. Seventeen dyslexic and 26 skilled young adult readers underwent a three-session training program in which they practiced a novel sequence of manual movements while standing in a quiet stance position. Both groups exhibited robust and well-retained gains in speed, with no loss of accuracy, on the volitional, manual, aspects of the task, with a time-course characteristic of procedural learning. However, the dyslexic readers exhibited a pervasive slowness in the initiation of volitional performance. In addition, while typical readers showed clear and well-retained task-related adaptation of the balance and posture control system, the dyslexic readers had significantly larger sway and variance of sway throughout the three sessions and were less efficient in adapting the posture control system to support the acquisition of the novel movement sequence. These results support the notion of a non-language-related deficit in developmental dyslexia, one related to the recruitment of motor systems for effective task performance rather than to a general motor learning disability.
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Affiliation(s)
- Itamar Sela
- Edmond J. Safra Brain Research Center for the Study of Learning Disabilities, University of Haifa, Haifa, Israel.
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29
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Richlan F, Kronbichler M, Wimmer H. Structural abnormalities in the dyslexic brain: a meta-analysis of voxel-based morphometry studies. Hum Brain Mapp 2012; 34:3055-65. [PMID: 22711189 DOI: 10.1002/hbm.22127] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 04/19/2012] [Accepted: 04/20/2012] [Indexed: 01/18/2023] Open
Abstract
We used coordinate-based meta-analysis in order to objectively quantify gray matter abnormalities reported in nine Voxel-Based Morphometry studies of developmental dyslexia. Consistently across studies, reduced gray matter volume in dyslexic readers was found in the right superior temporal gyrus and left superior temporal sulcus. These results were related to findings from previous meta-analyses on functional brain abnormalities in dyslexic readers. Convergence of gray matter reduction and reading-related underactivation was found for the left superior temporal sulcus. Recent studies point to the presence of both functional and structural abnormalities in left temporal and occipito-temporal brain regions before reading onset.
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Affiliation(s)
- Fabio Richlan
- Department of Psychology and Center for Neurocognitive Research, University of Salzburg, Salzburg, Austria
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30
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Narayana S, Laird AR, Tandon N, Franklin C, Lancaster JL, Fox PT. Electrophysiological and functional connectivity of the human supplementary motor area. Neuroimage 2012; 62:250-65. [PMID: 22569543 DOI: 10.1016/j.neuroimage.2012.04.060] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 04/16/2012] [Accepted: 04/21/2012] [Indexed: 11/26/2022] Open
Abstract
Neuro-imaging methods for detecting functional and structural inter-regional connectivity are in a rapid phase of development. While reports of regional connectivity patterns based on individual methods are becoming common, studies comparing the results of two or more connectivity-mapping methods remain rare. In this study, we applied transcranial magnetic stimulation during PET imaging (TMS/PET), a stimulation-based method, and meta-analytic connectivity modeling (MACM), a task-based method to map the connectivity patterns of the supplementary motor area (SMA). Further, we drew upon the behavioral domain meta-data of the BrainMap® database to characterize the behavioral domain specificity of two maps. Both MACM and TMS/PET detected multi-synaptic connectivity patterns, with the MACM-detected connections being more extensive. Both MACM and TMS/PET detected connections belonging to multiple behavioral domains, including action, cognition and perception. Finally, we show that the two connectivity-mapping methods are complementary in that, the MACM informed on the functional nature of SMA connections, while TMS/PET identified brain areas electrophysiologically connected with the SMA. Thus, we demonstrate that integrating multimodal database and imaging techniques can derive comprehensive connectivity maps of brain areas.
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Affiliation(s)
- Shalini Narayana
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX 78229, USA.
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31
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Krafnick AJ, Flowers DL, Napoliello EM, Eden GF. Gray matter volume changes following reading intervention in dyslexic children. Neuroimage 2010; 57:733-41. [PMID: 21029785 DOI: 10.1016/j.neuroimage.2010.10.062] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 10/18/2010] [Accepted: 10/20/2010] [Indexed: 01/20/2023] Open
Abstract
Studies in children and adults with the reading disability developmental dyslexia have shown behavioral improvements after reading intervention. In another line of work, it has been shown that intensive training in a variety of cognitive and sensorimotor skills can result in changes in gray matter volume (GMV). This study examined changes in GMV following intensive reading intervention in children with dyslexia using voxel-based morphometry (VBM). Eleven dyslexic children underwent an eight week training focused on mental imagery, articulation and tracing of letters, groups of letters and words, which resulted in significant gains in reading skills. This was followed by an eight week null period (control) where no intervention was administered and no further significant gains in reading were observed. Structural scans were obtained before the intervention, after the intervention and after the null period. GMV increases between the first two time points were found in the left anterior fusiform gyrus/hippocampus, left precuneus, right hippocampus and right anterior cerebellum. However these areas did not change between time points two and three (control period), suggesting that the changes were specific to the intervention period. These results demonstrate for the first time that (1) training-induced changes in GMV can be observed in a pediatric sample and (2) reading improvements induced by intervention are accompanied by GMV changes.
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Affiliation(s)
- Anthony J Krafnick
- Center for the Study of Learning, Georgetown University Medical Center, 4000 Reservoir Road, Building D Suite 150, Washington, DC 20057, USA.
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Facoetti A, Trussardi AN, Ruffino M, Lorusso ML, Cattaneo C, Galli R, Molteni M, Zorzi M. Multisensory Spatial Attention Deficits Are Predictive of Phonological Decoding Skills in Developmental Dyslexia. J Cogn Neurosci 2010; 22:1011-25. [PMID: 19366290 DOI: 10.1162/jocn.2009.21232] [Citation(s) in RCA: 182] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Abstract
Although the dominant approach posits that developmental dyslexia arises from deficits in systems that are exclusively linguistic in nature (i.e., phonological deficit theory), dyslexics show a variety of lower level deficits in sensory and attentional processing. Although their link to the reading disorder remains contentious, recent empirical and computational studies suggest that spatial attention plays an important role in phonological decoding. The present behavioral study investigated exogenous spatial attention in dyslexic children and matched controls by measuring RTs to visual and auditory stimuli in cued-detection tasks. Dyslexics with poor nonword decoding accuracy showed a slower time course of visual and auditory (multisensory) spatial attention compared with both chronological age and reading level controls as well as compared with dyslexics with slow but accurate nonword decoding. Individual differences in the time course of multisensory spatial attention accounted for 31% of unique variance in the nonword reading performance of the entire dyslexic sample after controlling for age, IQ, and phonological skills. The present study suggests that multisensory “sluggish attention shifting”—related to a temporoparietal dysfunction—selectively impairs the sublexical mechanisms that are critical for reading development. These findings may offer a new approach for early identification and remediation of developmental dyslexia.
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Affiliation(s)
- Andrea Facoetti
- 1Università di Padova, Italy
- 2Istituto Scientifico “E. Medea” di Bosisio Parini, Lecco, Italy
| | | | - Milena Ruffino
- 1Università di Padova, Italy
- 2Istituto Scientifico “E. Medea” di Bosisio Parini, Lecco, Italy
| | | | - Carmen Cattaneo
- 2Istituto Scientifico “E. Medea” di Bosisio Parini, Lecco, Italy
| | - Raffaella Galli
- 2Istituto Scientifico “E. Medea” di Bosisio Parini, Lecco, Italy
| | - Massimo Molteni
- 2Istituto Scientifico “E. Medea” di Bosisio Parini, Lecco, Italy
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Sun YF, Lee JS, Kirby R. Brain imaging findings in dyslexia. Pediatr Neonatol 2010; 51:89-96. [PMID: 20417459 DOI: 10.1016/s1875-9572(10)60017-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 07/07/2009] [Accepted: 07/28/2009] [Indexed: 01/18/2023] Open
Abstract
Dyslexia is a brain-based disorder that has been intensively studied in the Western world for more than a century because of its social burden. However, affected individuals in Chinese communities are neither recognized nor formally diagnosed. Previous studies have concentrated on the disadvantages of reading deficits, and few have addressed non-linguistic skills, which are included in the symptoms. In addition, certain dyslexics possess visual spatial talents that have usually been ignored. In this review, we discuss the available information regarding brain imaging studies of dyslexia based on studies in Caucasian subjects. Gray matter deficits have been demonstrated in dyslexics using structural magnetic resonance imaging. Reduced neural activities in the left temporal and left parietal cortices, and diffuse widespread activation patterns in the cerebellum could be detected using functional magnetic resonance imaging. Changes in lactate levels, N-acetylaspartate/choline-containing compounds and N-acetylaspartate/creatine ratios, and phosphomonoester peak area were detected in magnetic resonance spectroscopy studies. Lower fractional anisotropy values in bilateral white matter tracts have been demonstrated by diffusion tensor imaging. Abnormal Broca's area activation was found using positron emission tomography imaging. Increased activities in the right frontal and temporal brain regions were detected using electroencephalography. Reduced hemispheric asymmetry and increased left inferior frontal activation were reported following magnetoencephalography. Although these imaging modalities are not currently diagnostic or prognostic, they are able to provide information on the causes of dyslexia beyond what was previously provided by behavioral or cognition studies.
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Affiliation(s)
- Ying-Fang Sun
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.
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Frye RE, Liederman J, Malmberg B, McLean J, Strickland D, Beauchamp MS. Surface area accounts for the relation of gray matter volume to reading-related skills and history of dyslexia. Cereb Cortex 2010; 20:2625-35. [PMID: 20154011 DOI: 10.1093/cercor/bhq010] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
It is unknown whether the abnormalities in brain structure and function observed in dyslexic readers are congenital or arise later in development. Analyzing the 2 components of gray matter volume separately may help in differentiating these possibilities. Gray matter volume is the product of cortical surface area, determined during prenatal brain development, and cortical thickness, determined during postnatal development. For this study, 16 adults with a history of phonological dyslexia and 16 age- and gender-matched controls underwent magnetic resonance imaging and an extensive battery of tests of reading-related skills. Cortical surface area and gray matter volume measures of the whole brain, the inferior frontal gyrus, and the fusiform gyrus were similarly related to phonological skills and a history of dyslexia. There was no relationship between cortical thickness and phonological skills or history of dyslexia. Because cortical surface area reflects cortical folding patterns determined prenatally, this suggests that brain differences in dyslexia are rooted in early cortical development and are not due to compensatory changes that occur during postnatal development and would be expected to influence cortical thickness. This study demonstrates the importance of examining the separate components of gray matter volume when studying developmental abnormalities.
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Affiliation(s)
- Richard E Frye
- Division of Child and Adolescent Neurology, Department of Pediatrics, University of Texas Health Science Center, Houston, TX 77030, USA.
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