Clinical Research

Dyslexia

Anatomical correlates of dyslexia: frontal and cerebellar findings

Brain, Vol. 126, No. 2, 482-494, February 2003 © 2003 Guarantors of Brain

Mark A. Eckert¹, Christiana M. Leonard¹, Todd L. Richards², Elizabeth H. Aylward², Jennifer Thomson³ and Virginia W. Berninger³

¹Department of Neuroscience, McKnight Brain Institute of the University of Florida, Gainesville, FL | ² Departments of Radiology | ³ Education, University of Washington, Seattle, WA, USA

Correspondence with Mark Eckert, PO Box 100244, Department of Neuroscience, University of Florida McKnight Brain Institute, Gainesville, FL 32610

In this study, we examined the neuroanatomy of dyslexic (14 males, four females) and control (19 males, 13 females) children in grades 4–6 from a family genetics study. The dyslexics had specific deficits in word reading relative to the population mean and verbal IQ, but did not have primary language or motor deficits. Measurements of the posterior temporal lobe, inferior frontal gyrus, cerebellum and whole brain were collected from MRI scans. The dyslexics exhibited significantly smaller right anterior lobes of the cerebellum, pars triangularis bilaterally, and brain volume. Measures of the right cerebellar anterior lobe and the left and right pars triangularis correctly classified 72% of the dyslexic subjects (94% of whom had a rapid automatic naming deficit) and 88% of the controls. The cerebellar anterior lobe and pars triangularis made significant contributions to the classification of subjects after controlling for brain volume. Correlational analyses showed that these neuroanatomical measurements were also significantly correlated with reading, spelling and language measures related to dyslexia. Age was not related to any anatomical variable. Results for the dyslexic children from the family genetics study are discussed with reference to dyslexic adults from a prior study, who were ascertained on the basis of a discrepancy between phonological coding and reading comprehension. The volume of the right anterior lobe of the cerebellum distinguished dyslexic from control participants in both studies. The cerebellum is one of the most consistent locations for structural differences between dyslexic and control participants in imaging studies. This study may be the first to show that anomalies in a cerebellar-frontal circuit are associated with rapid automatic naming and the double-deficit subtype of dyslexia.

Brain abnormalities underlying altered activation in dyslexia: a voxel based morphometry study

Brain Advance Access originally published online on June 23, 2005 © The Author (2005). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.

G. Silani¹, U. Frith², J.-F. Demonet³, F. Fazio^4,5,6, D. Perani⁷, C. Price⁸, C. D. Frith⁸ and E. Paulesu¹

¹Psychology Department, University Milano-Bicocca, Milan, Italy | ²Institute of Cognitive Neuroscience, University College London, London, UK | ³INSERM U455, Hòpital Purpan, Toulouse, France | ⁴Neuroscience and Biomedical Technologies Department, University Milano-Bicocca, Milan, Italy | ⁵CNR—Istituto di Bioimmagini e Fisiologia Molecolare (IBFM), Milan, Italy | ⁶Nuclear Medicine Department, San Raffaele Hospital, Milan, Italy | ⁷Neuroscience Department, University Vita Salute San Raffaele, Milan, Italy | ⁸Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, UK

Correspondence with Prof. Eraldo Paulesu, Psychology Department, University Milano-Bicocca, Piazza dell' Ateneo Nuovo 1, 20126 Milan, Italy

Voxel-based morphometry (VBM) was used to assess the consistency among functional imaging and brain morphometry data in developmental dyslexia. Subjects, from three different cultural contexts (UK, France and Italy), were the same as those described in a previous PET activation paper, which revealed a common pattern of reduced activation during reading tasks in the left temporal and occipital lobes. We provide evidence that altered activation observed within the reading system is associated with altered density of grey and white matter of specific brain regions, such as the left middle and inferior temporal gyri and the left arcuate fasciculus. This supports the view that dyslexia is associated with both local grey matter dysfunction and with altered connectivity among phonological/reading areas. The differences were replicable across samples confirming that the neurological disorder underlying dyslexia is the same across the cultures investigated in the study.

Received October 17, 2004. Revised May 20, 2005. Accepted May 24, 2005.

Is developmental dyslexia a disconnection syndrome?

Evidence from PET scanning

Brain, Vol. 119, No. 1, 143-157, 1996 © 1996 Oxford University Press

Eraldo Paulesu^1,5, Uta Frith^2,3, Margaret Snowling⁴, Alison Gallagher², John Morton^2,3, Richard S. J. Frackowiak¹ and Christopher D. Frith^1,3.

¹Wellcome Department of Cognitive Neurology, Institute of Neurology UK | ²Medical Research Council Cognitive Development Unit UK | ³Psychology Department, University College London UK | ⁴Department of Psychology, University of York UK | ⁵INB-CNR Istituto Scientifico, H. San Raffaele, Università di Milano Milano, Italy.

Correspondence with Professor Uta Frith, MRC Cognitive Development Unit, 4 Taviton Street, London WIH OBT, UK.

A rhyming and a short-term memory task with visually presented letters were used to study brain activity in five compensated adult developmental dyslexics. Their only cognitive difficulty was in phonological processing, manifest in a wide range of tasks including spoonerisms, phonemic fluency and digit naming speed. PET scans showed that for the dyslexics, a subset only of the brain regions normally involved in phonological processing was activated: Broca's area during the rhyming task, temporo-parietal cortex during the short-term memory task. In contrast to normal controls these areas were not activated in concert. Furthermore the left insula was never activated. We propose that the defective phonological system of these dyslexics is due to weak connectivity between anterior and posterior language areas. This could be due to a dysfunctional left insula which may normally act as an anatomical bridge between Broca's area, superior temporal and inferior parietal cortex. The independent activation of the posterior and anterior speech areas in dyslexics supports the notion that representations of unsegmented and segmented phonology are functionally and anatomically separate.

Received April 24, 1995. Revised June 17, 1995. Accepted September 21, 1995.

Auditory processing disorder in children with reading disabilities: effect of audiovisual training

Brain Advance Access originally published online on October 5, 2007 Brain 2007 © The Author (2007). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.

Evelyne Veuillet¹, Annie Magnan², Jean Ecalle², Hung Thai-Van¹ and Lionel Collet¹

¹Université de Lyon, Lyon, F-69003, France, Université Lyon 1, CNRS, UMR 5020, Lyon, F-60007, France, Hôpital Edouard Herriot, Pavillon U, Service d'Audiologie et d'Explorations Orofaciales, F-69003 Lyon, France, IFNL, Lyon, F-60003, France and 2Université de Lyon, Bron, F-69676, France, université Lyon 2, CNRS, EA 3082, Laboratoire EMC, Bron, F-69676, France

Correspondence with Evelyne Veuillet, Hôpital Edouard Herriot, Pavillon U, Service d’Audiologie et d’Explorations Orofaciales, Place d’Arsonval, 69437 Lyon Cedex 03, France.

Reading disability is associated with phonological problems which might originate in auditory processing disorders. The aim of the present study was 2-fold: first, the perceptual skills of average-reading children and children with dyslexia were compared in a categorical perception task assessing the processing of a phonemic contrast based on voice onset time (VOT). The medial olivocochlear (MOC) system, an inhibitory pathway functioning under central control, was also explored. Secondly, we investigated whether audiovisual training focusing on voicing contrast could modify VOT sensitivity and, in parallel, induce MOC system plasticity. The results showed an altered voicing sensitivity in some children with dyslexia, and that the most severely impaired children presented the most severe reading difficulties. These deficits in VOT perception were sometimes accompanied by MOC function abnormalities, in particular a reduction in or even absence of the asymmetry in favour of the right ear found in average-reading children. Audiovisual training significantly improved reading and shifted the categorical perception curve of certain children with dyslexia towards the average-reading children's pattern of voicing sensitivity. Likewise, in certain children MOC functioning showed increased asymmetry in favour of the right ear following audiovisual training. The training-related improvements in reading score were greatest in children presenting the greatest changes in MOC lateralization. Taken together, these results confirm the notion that some auditory system processing mechanisms are impaired in children with dyslexia and that audiovisual training can diminish these deficits.

Received April 12, 2007. Revised September 4, 2007. Accepted September 5, 2007.