Dyslexia

{{Main|Pure alexia}}

Dyslexia is divided into developmental and acquired forms.Oxford English Dictionary. 3rd ed. "[https://oed.com/view/Entry/331223 dyslexia, n]. Oxford, UK: Oxford University Press, 2012 ("a learning disability specifically affecting the attainment of literacy, with difficulty esp. in word recognition, spelling, and the conversion of letters to sounds, occurring in a child with otherwise normal development, and now usually regarded as a neurodevelopmental disorder with a genetic component.") Acquired dyslexia occurs subsequent to neurological insult, such as traumatic brain injury or stroke. People with acquired dyslexia exhibit some of the signs or symptoms of the developmental disorder, but require different assessment strategies and treatment approaches.{{cite journal|last=Woollams|first=Anna M.|date=19 January 2014|title=Connectionist neuropsychology: uncovering ultimate causes of acquired dyslexia|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|language=en|volume=369|issue=1634|pages=20120398|doi=10.1098/rstb.2012.0398|issn=0962-8436|pmc=3866427|pmid=24324241}} Pure alexia, also known as agnosic alexia or pure word blindness, is one form of alexia which makes up "the peripheral dyslexia" group.{{cite journal |author=Coslett HB |title=Acquired dyslexia |journal=Semin Neurol |volume=20 |issue=4 |pages=419–26 |year=2000 |pmid=11149697 |doi=10.1055/s-2000-13174 |s2cid=36969285 }}

{{See also|Characteristics of dyslexia}}

In early childhood, symptoms that correlate with a later diagnosis of dyslexia include delayed onset of speech and a lack of phonological awareness. A common myth closely associates dyslexia with mirror writing and reading letters or words backwards.{{cite book|url=https://books.google.com/books?id=8DlS0gfO_QUC&pg=PT88|title=50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior|last2=Lynn|first2=Steven Jay|last3=Ruscio|first3=John|last4=Beyerstein|first4=Barry L.|date=15 September 2011|publisher=John Wiley & Sons|isbn=978-1-4443-6074-5|pages=88–89|last1=Lilienfeld|first1=Scott O.|author-link1=Scott Lilienfeld|author-link4=Barry Beyerstein|access-date=19 May 2016|url-status=live|archive-url=https://web.archive.org/web/20170109130327/https://books.google.com/books?id=8DlS0gfO_QUC&pg=PT88|archive-date=9 January 2017}} These behaviors are seen in many children as they learn to read and write, and are not considered to be defining characteristics of dyslexia.

School-age children with dyslexia may exhibit signs of difficulty in identifying or generating rhyming words, or counting the number of syllables in words—both of which depend on phonological awareness.{{cite web |title=Dyslexia and Related Disorders |date=January 2003 |website=Alabama Dyslexia Association |publisher=International Dyslexia Association |access-date=29 April 2015 |url=http://idaalabama.org/Facts/Dyslexia_and_Related.pdf |url-status=live |archive-url=https://web.archive.org/web/20160304124053/http://idaalabama.org/Facts/Dyslexia_and_Related.pdf |archive-date=4 March 2016 }} They may also show difficulty in segmenting words into individual sounds (such as sounding out the three sounds of k, a, and t in cat) or may struggle to blend sounds, indicating reduced phonemic awareness.{{cite book |last1=Peer |first1=Lindsay |last2=Reid |first2=Gavin |title=Multilingualism, Literacy and Dyslexia |url=https://books.google.com/books?id=-aoABAAAQBAJ&pg=PA219 |year=2014 |publisher=Routledge |isbn=978-1-136-60899-5 |page=219 |url-status=live |archive-url=https://web.archive.org/web/20170109204808/https://books.google.com/books?id=-aoABAAAQBAJ&pg=PA219 |archive-date=9 January 2017 }}

Difficulties with word retrieval or naming things is also associated with dyslexia.{{cite book|author1=Shaywitz, Sally E.|author2=Shaywitz, Bennett A.|chapter=Chapter 34 Making a Hidden Disability Visible: What Has Been Learned from Neurobiological Studies of Dyslexia|editor1=Swanson, H. Lee|editor2=Harris, Karen R.|editor3=Graham, Steve|title=Handbook of Learning Disabilities|chapter-url=https://books.google.com/books?id=oakQfUuutVwC&pg=PA647|edition=2|year=2013|publisher=Guilford Press|isbn=978-1-4625-0856-3|url-status=live|archive-url=https://web.archive.org/web/20170109143943/https://books.google.com/books?id=oakQfUuutVwC&pg=PA647|archive-date=9 January 2017}}{{rp|647}} People with dyslexia are commonly poor spellers, a feature sometimes called dysorthographia or dysgraphia, which depends on the skill of orthographic coding.

Problems persist into adolescence and adulthood and may include difficulties with summarizing stories, memorization, reading aloud, or learning foreign languages. Adults with dyslexia can often read with good comprehension, though they tend to read more slowly than others without a learning difficulty and perform worse in spelling tests or when reading nonsense words—a measure of phonological awareness.{{cite journal|last1=Jarrad|first1=Lum|title=Procedural learning is impaired in dyslexia: evidence from a meta-analysis of serial reaction time studies|journal=Research in Developmental Disabilities|date=October 2013|pages=3460–76|pmid=23920029|pmc=3784964|doi=10.1016/j.ridd.2013.07.017|volume=34|issue=10}}

Dyslexia often co-occurs with other learning disorders, but the reasons for this comorbidity have not been clearly identified.{{cite journal |title=Dyslexia, dysgraphia, procedural learning and the cerebellum |journal=Cortex |volume=47 |issue=1 |pages=117–27 |date=September 2009|pmid=19818437 |doi=10.1016/j.cortex.2009.08.016|last1=Nicolson |first1=R. I. |last2=Fawcett |first2=A. J.|s2cid=32228208 }} These associated disabilities include:

; Dysgraphia: A disorder involving difficulties with writing or typing, sometimes due to problems with eye–hand coordination; it also can impede direction- or sequence-oriented processes, such as tying knots or carrying out repetitive tasks.{{cite book |last1=Reynolds |first1=Cecil R. |last2=Fletcher-Janzen |first2=Elaine |title=Encyclopedia of Special Education |date=2 January 2007 |publisher=John Wiley & Sons |isbn=978-0-471-67798-7 |page=[https://books.google.com/books?id=wdNpBchvdvQC&pg=PA771 771] }} In dyslexia, dysgraphia is often multifactorial, due to impaired letter-writing automaticity, organizational and elaborative difficulties, and impaired visual word forming, which makes it more difficult to retrieve the visual picture of words required for spelling.

; Attention deficit hyperactivity disorder (ADHD): A disorder characterized by problems sustaining attention, hyperactivity, or acting impulsively.{{cite web|url=http://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtml|title=Attention Deficit Hyperactivity Disorder|date=March 2016|publisher=NIH: National Institute of Mental Health|access-date=26 July 2016|url-status=live|archive-url=https://web.archive.org/web/20160723192735/http://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtml|archive-date=23 July 2016}} Dyslexia and ADHD commonly occur together.{{cite book|url=https://books.google.com/books?id=ySIc1BcPJu8C&pg=RA1-PA233|title=Psychology Around Us|date=2011|publisher=RR Donnelley|isbn=978-0-471-38519-6|page=1|author1=Comer, Ronald|url-status=live|archive-url=https://web.archive.org/web/20160604000711/https://books.google.com/books?id=ySIc1BcPJu8C&pg=RA1-PA233|archive-date=4 June 2016}}{{cite journal|last2=Gagliano|first2=A|last3=Curatolo|first3=P|year=2010|title=Comorbidity of ADHD and Dyslexia|url=http://pdfserve.informaworld.com/260009__925867416.pdf |archive-url=https://web.archive.org/web/20110810101321/http://pdfserve.informaworld.com/260009__925867416.pdf |archive-date=2011-08-10 |url-status=live|journal=Developmental Neuropsychology|volume=35|issue=5|pages=475–493|doi=10.1080/87565641.2010.494748|pmid=20721770|last1=Germanò|first1=E|s2cid=42046958}} Approximately 15% or 12–24% of people with dyslexia have ADHD;{{cite book|url=https://books.google.com/books?id=RJOy1vy2RKQC&pg=PA308|title=The Medical Basis of Psychiatry|publisher=Springer Science & Business Media|year=2008|isbn=978-1-59745-252-6|edition=3rd |page=308|author1=Fatemi, S. Hossein|author2=Sartorius, Norman|author3=Clayton, Paula J.|author3-link=Paula Clayton|url-status=live|archive-url=https://web.archive.org/web/20170109101234/https://books.google.com/books?id=RJOy1vy2RKQC&pg=PA308|archive-date=9 January 2017}} and up to 35% of people with ADHD have dyslexia.

; Auditory processing disorder: A listening disorder that affects the ability to process auditory information.{{cite book|author=Capellini, Simone Aparecida|title=Neuropsycholinguistic Perspectives on Dyslexia and Other Learning Disabilities|url=https://books.google.com/books?id=uiEaMQVwyzYC&pg=PA94|year=2007|publisher=Nova Publishers|isbn=978-1-60021-537-7|page=94|url-status=live|archive-url=https://web.archive.org/web/20170109113545/https://books.google.com/books?id=uiEaMQVwyzYC&pg=PA94|archive-date=9 January 2017}}{{cite journal |title=The diagnosis and management of auditory processing disorder|journal= Language, Speech, and Hearing Services in Schools|volume=42 |issue=3 |pages=303–8 |date=July 2011 |pmid=21757566 |doi=10.1044/0161-1461(2011/10-0032)|last1=Moore |first1=D. R.}} This can lead to problems with auditory memory and auditory sequencing. Many people with dyslexia have auditory processing problems, and may develop their own logographic cues to compensate for this type of deficit. Some research suggests that auditory processing skills could be the primary shortfall in dyslexia.{{cite journal|last1=Pammer|first1=Kristen|title=Brain mechanisms and reading remediation: more questions than answers.|journal=Scientifica|date=January 2014|pmid=24527259|pmc=3913493|doi=10.1155/2014/802741|volume=2014|pages=802741|doi-access=free}}{{cite journal|last1=Law|first1=J|title=relationship of phonological ability, speech perception, and auditory perception in adults with dyslexia|journal=Frontiers in Human Neuroscience|date=2014|pmid=25071512|pmc=4078926|doi=10.3389/fnhum.2014.00482|volume=8|pages=482|doi-access=free}}

; Developmental coordination disorder: A neurological condition characterized by difficulty in carrying out routine tasks involving balance, fine-motor control and kinesthetic coordination; difficulty in the use of speech sounds; and problems with short-term memory and organization.{{cite book|author=Susan J. Pickering|chapter=Chapter 2. Working Memory in Dyslexia|editor1=Alloway, Tracy Packiam|editor2=Gathercole, Susan E.|title=Working Memory and Neurodevelopmental Disorders|chapter-url=https://books.google.com/books?id=IoXidOBdNpMC&pg=PA29|year=2012|publisher=Psychology Press|isbn=978-1-135-42134-2|url-status=live|archive-url=https://web.archive.org/web/20170109194637/https://books.google.com/books?id=IoXidOBdNpMC&pg=PA29|archive-date=9 January 2017}}

File:Inferior parietal lobule - superior view animation.gif

Researchers have been trying to find the neurobiological basis of dyslexia since the condition was first identified in 1881.{{cite book|author1=Reid, Gavin|author2=Fawcett, Angela|author3=Manis, Frank|author4=Siegel, Linda|title=The SAGE Handbook of Dyslexia|url=https://books.google.com/books?id=937rqz4Ryc8C&pg=PA127|year=2008|publisher=SAGE Publications|isbn=978-1-84860-037-9|page=127|url-status=live|archive-url=https://web.archive.org/web/20170109200307/https://books.google.com/books?id=937rqz4Ryc8C&pg=PA127|archive-date=9 January 2017}} For example, some have tried to associate the common problem among people with dyslexia of not being able to see letters clearly to abnormal development of their visual nerve cells.{{cite journal |first1=John |last1=Stein |year=2014 |title=Dyslexia: the Role of Vision and Visual Attention |journal=Current Developmental Disorders Reports |volume=1 |issue=4 |pages=267–80 |pmid=25346883 |pmc=4203994 |doi=10.1007/s40474-014-0030-6}}

Neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), have shown a correlation between both functional and structural differences in the brains of children with reading difficulties.{{cite book|author=Whitaker, Harry A.|title=Concise Encyclopedia of Brain and Language|url=https://books.google.com/books?id=GNcDiRV2jJQC&pg=PA180|year=2010|publisher=Elsevier|isbn=978-0-08-096499-7|page=180|url-status=live|archive-url=https://web.archive.org/web/20170109173223/https://books.google.com/books?id=GNcDiRV2jJQC&pg=PA180|archive-date=9 January 2017}} Some people with dyslexia show less activation in parts of the left hemisphere of the brain involved with reading, such as the inferior frontal gyrus, inferior parietal lobule, and the middle and ventral temporal cortex. Over the past decade, brain activation studies using PET to study language have produced a breakthrough in the understanding of the neural basis of language. Neural bases for the visual lexicon and for auditory verbal short-term memory components have been proposed,{{cite journal|last1=Price|first1=cathy|title=A Review and Synthesis of the first 20 years of Pet and fMRI studies of heard Speech, Spoken Language and Reading|journal=NeuroImage|date=16 August 2012|volume=62 |issue=2|pages=816–847|doi=10.1016/j.neuroimage.2012.04.062|pmid=22584224|pmc=3398395}} with some implication that the observed neural manifestation of developmental dyslexia is task-specific (i.e., functional rather than structural). fMRIs of people with dyslexia indicate an interactive role of the cerebellum and cerebral cortex as well as other brain structures in reading.{{cite journal|last1=Sharifi|first1=S|title=Neuroimaging essentials in essential tremor: a systematic review.|journal=NeuroImage: Clinical|date=May 2014|pages=217–231|pmid=25068111|pmc=4110352|doi=10.1016/j.nicl.2014.05.003|volume=5}}{{cite journal|last1=Brandler|first1=William|title=The genetic relationship between handedness and neurodevelopmental disorders|journal=Trends in Molecular Medicine|date=February 2014|pages=83–90|pmid=24275328|pmc=3969300|doi=10.1016/j.molmed.2013.10.008|volume=20|issue=2}}

The cerebellar theory of dyslexia proposes that impairment of cerebellum-controlled muscle movement affects the formation of words by the tongue and facial muscles, resulting in the fluency problems that some people with dyslexia experience. The cerebellum is also involved in the automatization of some tasks, such as reading.{{cite book|last1=Cain|first1=Kate|title=Reading development and difficulties|date=2010|publisher=TJ International|page=134|edition=1st|url=https://books.google.com/books?id=FT6RALjOr9QC&q=cerebellar+theory+of+dyslexia&pg=PA134|access-date=21 March 2015|isbn=9781405151559}} The fact that some children with dyslexia have motor task and balance impairments could be consistent with a cerebellar role in their reading difficulties. However, the cerebellar theory has not been supported by controlled research studies.{{cite book|last1=Levav|first1=Itzhak|title=Psychiatric and Behavioral Disorders in Israel: From Epidemiology to Mental health|date=2009|publisher=Green Publishing|page=52|url=https://books.google.com/books?id=W2RzffMnpg8C&q=cerebellar+theory+of+dyslexia&pg=PA52|access-date=21 March 2015|isbn=9789652294685}}

Research into potential genetic causes of dyslexia has its roots in post-autopsy examination of the brains of people with dyslexia. Observed anatomical differences in the language centers of such brains include microscopic cortical malformations known as ectopias, and more rarely, vascular micro-malformations, and microgyrus—a smaller than usual size for the gyrus.{{cite book|author=Faust, Miriam|title=The Handbook of the Neuropsychology of Language|url=https://books.google.com/books?id=UEWVqdNFL4cC&pg=PA941|year=2012|publisher=John Wiley & Sons|isbn=978-1-4443-3040-3|pages=941–43|url-status=live|archive-url=https://web.archive.org/web/20170109200538/https://books.google.com/books?id=UEWVqdNFL4cC&pg=PA941|archive-date=9 January 2017}} The previously cited studies and others{{cite journal|last1=Benitez|first1=A|title=Neurobiology and neurogenetics of dyslexia|journal=Neurology (In Spanish)|date=November 2010|pmid=21093706|doi=10.1016/j.nrl.2009.12.010|volume=25|issue=9|pages=563–81|doi-access=|hdl=10651/6364|hdl-access=free}} suggest that abnormal cortical development, presumed to occur before or during the sixth month of fetal brain development, may have caused the abnormalities. Abnormal cell formations in people with dyslexia have also been reported in non-language cerebral and subcortical brain structures.{{cite journal|last1=Kere|first1=Julia|title=The molecular genetics and neurobiology of developmental dyslexia as model of a complex phenotype|journal=Biochemical and Biophysical Research Communications|date=September 2014|pages=236–43|doi=10.1016/j.bbrc.2014.07.102|pmid=25078623|volume=452|issue=2|doi-access=free}} Several genes have been associated with dyslexia, including DCDC2{{cite book|author=Marshall, Chloë R.|title=Current Issues in Developmental Disorders|url=https://books.google.com/books?id=jHqYP39rI40C&pg=PA53|year=2012|publisher=Psychology Press|isbn=978-1-136-23067-7|pages=53–56|url-status=live|archive-url=https://web.archive.org/web/20170109103320/https://books.google.com/books?id=jHqYP39rI40C&pg=PA53|archive-date=9 January 2017}} and KIAA0319{{cite journal |vauthors=Paracchini S, Thomas A, Castro S, Lai C, Paramasivam M, Wang Y, Keating BJ, Taylor JM, Hacking DF, Scerri T, Francks C, Richardson AJ, Wade-Martins R, Stein JF, Knight JC, Copp AJ, LoTurco J, Monaco AP |title=The chromosome 6p22 haplotype associated with dyslexia reduces the expression of KIAA0319, a novel gene involved in neuronal migration|journal=Human Molecular Genetics|volume=15|issue=10|date=15 May 2006|pages=1659–1666|doi=10.1093/hmg/ddl089|pmid=16600991|doi-access=free|hdl=11858/00-001M-0000-0012-C979-F|hdl-access=free}} on chromosome 6, and DYX1C1 on chromosome 15.{{cite book|author=Rosen, Glenn D.|title=The Dyslexic Brain: New Pathways in Neuroscience Discovery|url=https://books.google.com/books?id=ZHBxBEekGSkC&pg=PA342|year=2013|publisher=Psychology Press|isbn=978-1-134-81550-0|page=342|url-status=live|archive-url=https://web.archive.org/web/20170109143349/https://books.google.com/books?id=ZHBxBEekGSkC&pg=PA342|archive-date=9 January 2017}}

The contribution of gene–environment interaction to reading disability, which estimates the proportion of variance associated with a person's environment and the proportion associated with their genes, has been intensely studied using twin studies. Both environmental and genetic factors appear to contribute to reading development. Studies examining the influence of environmental factors such as parental education{{cite journal |title=Parental Education Moderates Genetic Influences on Reading Disability |journal=Psychol. Sci. |volume=19 |issue=11 |pages=1124–30 |date=November 2008 |pmid=19076484 |pmc=2605635 |doi=10.1111/j.1467-9280.2008.02213.x |last1=Friend |first1=A |last2=Defries |first2=J. C. |last3=Olson |first3=R. K.}} and teaching quality{{cite journal |bibcode=2010Sci...328..512T|title=Teacher Quality Moderates the Genetic Effects on Early Reading|journal=Science|volume=328|issue=5977|pages=512–4|last1=Taylor|first1=J.|last2=Roehrig|first2=A. D.|last3=Hensler|first3=B. Soden|last4=Connor|first4=C. M.|last5=Schatschneider|first5=C.|year=2010|doi=10.1126/science.1186149|pmid=20413504|pmc=2905841}} have determined that genetics have greater influence in supportive, rather than less optimal, environments.{{cite journal |last1=Pennington |first1=Bruce F. |last2=McGrath |first2=Lauren M. |last3=Rosenberg |first3=Jenni |last4=Barnard |first4=Holly |last5=Smith |first5=Shelley D. |last6=Willcutt |first6=Erik G. |last7=Friend |first7=Angela |last8=Defries |first8=John C. |last9=Olson |first9=Richard K. |date=January 2009 |title=Gene × Environment Interactions in Reading Disability and Attention-Deficit/Hyperactivity Disorder |journal=Developmental Psychology |volume=45 |issue=1 |pages=77–89 |doi=10.1037/a0014549 |pmid=19209992 |pmc=2743891}} However, more optimal conditions may just allow those genetic risk factors to account for more of the variance in outcome because the environmental risk factors have been minimized.

As environment plays a large role in learning and memory, it is likely that epigenetic modifications play an important role in reading ability. Measures of gene expression, histone modifications, and methylation in the human periphery are used to study epigenetic processes; however, all of these have limitations in the extrapolation of results for application to the human brain.{{cite journal |last1=Roth |first1=Tania L. |last2=Roth |first2=Eric D. |last3=Sweatt |first3=J. David |s2cid=23229766 |date=September 2010 |title=Epigenetic regulation of genes in learning and memory |journal=Essays in Biochemistry |volume=48 |issue=1 |pages=263–74 |pmid=20822498 |doi=10.1042/bse0480263}}{{cite journal |last1=Smith |first1=Shelley D. |title=Approach to epigenetic analysis in language disorders |journal=Journal of Neurodevelopmental Disorders |date=December 2011 |volume=3 |issue=4 |pages=356–364 |doi=10.1007/s11689-011-9099-y |pmid=22113455 |pmc=3261263 |issn=1866-1947}}

The orthographic complexity of a language directly affects how difficult it is to learn to read it.

Paulesu, Eraldo; Brunswick, Nicola and Paganelli, Federica (2010). "Cross-cultural differences in unimpaired and dyslexic reading: Behavioral and functional anatomical observations in readers of regular and irregular orthographies. Chapter 12 in [https://books.google.com/books?id=0vJ5AgAAQBAJ&pg=PA266 Reading and Dyslexia in Different Orthographies] {{webarchive|url=https://web.archive.org/web/20170109135414/https://books.google.com/books?id=0vJ5AgAAQBAJ&pg=PA266 |date=9 January 2017 }}. Eds. Nicola Brunswick, Siné McDougall, and Paul de Mornay Davies. Psychology Press. {{ISBN|9781135167813}}{{rp|266}} English and French have comparatively "deep" phonemic orthographies within the Latin alphabet writing system, with complex structures employing spelling patterns on several levels: letter-sound correspondence, syllables, and morphemes.{{cite book|author=Juel, Connie|chapter=The Impact of Early School Experiences on Initial Reading|editor1=David K. Dickinson|editor2=Susan B. Neuman|title=Handbook of Early Literacy Research|chapter-url=https://books.google.com/books?id=_chXAQAAQBAJ&pg=PA421|year=2013|publisher=Guilford Publications|isbn=978-1-4625-1470-0|url-status=live|archive-url=https://web.archive.org/web/20170109162332/https://books.google.com/books?id=_chXAQAAQBAJ&pg=PA421|archive-date=9 January 2017|df=dmy-all}}{{rp|421}} Languages such as Spanish, Italian and Finnish primarily employ letter-sound correspondence—so-called "shallow" orthographies—which makes them easier to learn for people with dyslexia.{{rp|266}} Logographic writing systems, such as Chinese characters, have extensive symbol use, and these also pose problems for dyslexic learners.{{cite journal|title = Annual Research Review: The nature and classification of reading disorders – a commentary on proposals for DSM-5|journal = Journal of Child Psychology and Psychiatry, and Allied Disciplines|date = 1 May 2012|pmc = 3492851|pmid = 22141434|pages = 593–607|volume = 53|issue = 5|doi = 10.1111/j.1469-7610.2011.02495.x|first1 = Margaret J|last1 = Snowling|first2 = Charles|last2 = Hulme}}

File:Gray733.png

For most people who are right-hand dominant, the left hemisphere of their brain is more specialized for language processing. With regard to the mechanism of dyslexia, fMRI studies suggest that this specialization is less pronounced or absent in people with dyslexia. In other studies, dyslexia is correlated with anatomical differences in the corpus callosum, the bundle of nerve fibers that connects the left and right hemispheres.{{cite book |last1=Habib |first1=Michael |title=Pediatric Neurology Part I |volume=111 |chapter=Dyslexia |date=2013 |pages=229–235 |chapter-url=https://www.sciencedirect.com/science/article/pii/B9780444528919000233 |access-date=19 December 2018 |language=en|doi=10.1016/B978-0-444-52891-9.00023-3 |pmid=23622168 |series=Handbook of Clinical Neurology |isbn=9780444528919 }}

Data via diffusion tensor MRI indicate changes in connectivity or in gray matter density in areas related to reading and language. Finally, the left inferior frontal gyrus has shown differences in phonological processing in people with dyslexia. Neurophysiological and imaging procedures are being used to ascertain phenotypic characteristics in people with dyslexia, thus identifying the effects of dyslexia-related genes.{{cite journal|title = Genetics of dyslexia: the evolving landscape|journal = Journal of Medical Genetics|date = 2007|pmc = 2597981|pmid = 17307837|pages = 289–297|volume = 44|issue = 5|doi = 10.1136/jmg.2006.046516|first1 = Johannes|last1 = Schumacher|first2 = Per|last2 = Hoffmann|first3 = Christine|last3 = Schmäl|first4 = Gerd|last4 = Schulte-Körne|first5 = Markus M|last5 = Nöthen}}

The dual-route theory of reading aloud was first described in the early 1970s.{{cite journal |author=Pritchard SC, Coltheart M, Palethorpe S, Castles A |title=Nonword reading: comparing dual-route cascaded and connectionist dual-process models with human data |journal=J Exp Psychol Hum Percept Perform |volume=38 |issue=5 |pages=1268–88 |date=October 2012 |pmid=22309087 |doi=10.1037/a0026703|last2=Coltheart |last3=Palethorpe |last4=Castles}} This theory suggests that two separate mental mechanisms, or cognitive routes, are involved in reading aloud.{{cite book|author1=Eysenck, Michael|author2=Keane, Mark T.|title=Cognitive Psychology 6e|url=https://books.google.com/books?id=U-IF8PAa_jIC&pg=PA373|year=2013|publisher=Psychology Press|isbn=978-1-134-44046-7|page=373|url-status=live|archive-url=https://web.archive.org/web/20170109123837/https://books.google.com/books?id=U-IF8PAa_jIC&pg=PA373|archive-date=9 January 2017}} One mechanism is the lexical route, which is the process whereby skilled readers can recognize known words by sight alone, through a "dictionary" lookup procedure.{{cite book|author1=Eysenck, Michael|author2=Keane, Mark T.|title=Cognitive Psychology 6e|url=https://books.google.com/books?id=U-IF8PAa_jIC&pg=PA450|year=2013|publisher=Psychology Press|isbn=978-1-134-44046-7|page=450|url-status=live|archive-url=https://web.archive.org/web/20170109170422/https://books.google.com/books?id=U-IF8PAa_jIC&pg=PA450|archive-date=9 January 2017}} The other mechanism is the nonlexical or sublexical route, which is the process whereby the reader can "sound out" a written word.{{cite book |last1=Hulme |first1=Charles |last2=Joshi |first2=R. Malatesha |last3=Snowling |first3=Margaret J. |title=Reading and Spelling: Development and Disorders |url=https://books.google.com/books?id=MumCCKK4JR8C&pg=PT151 |year=2012 |publisher=Routledge |isbn=978-1-136-49807-7 |page=151 |url-status=live |archive-url=https://web.archive.org/web/20170109141419/https://books.google.com/books?id=MumCCKK4JR8C&pg=PT151 |archive-date=9 January 2017 }} This is done by identifying the word's constituent parts (letters, phonemes, graphemes) and applying knowledge of how these parts are associated with each {{nowrap|other{{hsp}}{{mdash}}{{hsp}}}}for example, how a string of neighboring letters sound together. The dual-route system could explain the different rates of dyslexia occurrence between different languages (e.g., the consistency of phonological rules in the Spanish language could account for the fact that Spanish-speaking children show a higher level of performance in non-word reading, when compared to English-speakers).{{cite journal|last1=Sprenger-Charolles|first1=Liliane|title=Prevalence and Reliability of Phonological, Surface, and Mixed Profiles in Dyslexia: A Review of Studies Conducted in Languages Varying in Orthographic Depth|journal=Scientific Studies of Reading|date=2011|pages=498–521|doi=10.1080/10888438.2010.524463|volume=15|issue=6|s2cid=15227374|url=https://hal.archives-ouvertes.fr/hal-00733553|url-status=live|archive-url=https://web.archive.org/web/20170830150246/https://hal.archives-ouvertes.fr/hal-00733553|archive-date=30 August 2017}}

Dyslexia is a heterogeneous, dimensional learning disorder that impairs accurate and fluent word reading and spelling.{{cite journal|last1=Boada|first1=Richard|last2=Willcutt|first2=Erik G.|last3=Pennington|first3=Bruce F.|s2cid=43200465|date=2012|title=Understanding the Comorbidity Between Dyslexia and Attention-Deficit/Hyperactivity Disorder|journal=Topics in Language Disorders|quote=... Pennington proposed a multiple deficit model for complex disorders like dyslexia, hypothesizing that such complex disorders are heterogeneous conditions that arise from the additive and interactive effects of multiple genetic and environmental risk factors, which then lead to weaknesses in multiple cognitive domains.|volume=32|issue=3|page=270|doi=10.1097/tld.0b013e31826203ac}}{{cite journal|last=Pennington|first=B|date=September 2006|title=From single to multiple deficit models of developmental disorders|journal=Cognition|volume=101|issue=2|pages=385–413|doi=10.1016/j.cognition.2006.04.008|pmid=16844106|s2cid=7433822}} Typical—but not universal—features include difficulties with phonological awareness, inefficient and often inaccurate processing of sounds in oral language (phonological processing), and verbal working memory deficits.{{cite journal|last1=Peterson|first1=Robin L.|last2=Pennington|first2=Bruce F.|date=28 March 2015|title=Developmental Dyslexia|journal=Annual Review of Clinical Psychology|volume=11|issue=1|pages=283–307|doi=10.1146/annurev-clinpsy-032814-112842|pmid=25594880|ssrn=2588407}}Snowling, Margaret J. Dyslexia: A Very Short Introduction. Oxford University Press, 2019. {{ISBN|9780192550422}}

Dyslexia is a neurodevelopmental disorder, subcategorized in diagnostic guides as a learning disorder with impairment in reading (ICD-11 prefixes "developmental" to "learning disorder"; DSM-5 uses "specific").{{cite web|url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/1008636089|title=6A03.0 Developmental learning disorder with impairment in reading|work=International Classification of Diseases and Related Health Problems, 11th rev. (ICD-11) (Mortality and Morbidity Statistics)|publisher=World Health Organization|access-date=7 October 2019}}{{cite book|title=Diagnostic and statistical manual of mental disorders : DSM-5.|date=2013|publisher=American Psychiatric Association|others=DSM-5 Task Force.|quote=Specific Learning Disorder with impairment in reading ... Dyslexia is an alternative term used to refer to a pattern of learning difficulties characterized by problems with accurate or fluent word recognition, poor decoding, and poor spelling abilities.|isbn=9780890425541|edition=5th|location=Arlington, VA|oclc=830807378|url-access=registration|url=https://archive.org/details/diagnosticstatis0005unse}}{{cite journal|last1=FragaGonzález|first1=Gorka|last2=Karipidis|first2=Iliana|last3=Tijms|first3=Jurgen|date=19 October 2018|title=Dyslexia as a Neurodevelopmental Disorder and What Makes It Different from a Chess Disorder|journal=Brain Sciences|volume=8|issue=10|pages=189|doi=10.3390/brainsci8100189|issn=2076-3425|pmc=6209961|pmid=30347764|doi-access=free}} Dyslexia is not a problem with intelligence. Emotional problems often arise secondary to learning difficulties.{{cite book|last1=Campbell|first1=Robert Jean|title=Campbell's Psychiatric Dictionary|url=https://books.google.com/books?id=kpIs03n1hxkC&pg=PA310|year=2009|publisher=Oxford University Press|isbn=978-0-19-534159-1|pages=310–312|url-status=live|archive-url=https://web.archive.org/web/20170109101113/https://books.google.com/books?id=kpIs03n1hxkC&pg=PA310|archive-date=9 January 2017}} The National Institute of Neurological Disorders and Stroke describes dyslexia as "difficulty with phonological processing (the manipulation of sounds), spelling, and/or rapid visual-verbal responding".

The British Dyslexia Association defines dyslexia as "a learning difficulty that primarily affects the skills involved in accurate and fluent word reading and spelling" and is characterized by "difficulties in phonological awareness, verbal memory and verbal processing speed".{{cite book|author1=Phillips, Sylvia|author2=Kelly, Kathleen|author3=Symes, Liz|title=Assessment of Learners with Dyslexic-Type Difficulties|url=https://books.google.com/books?id=7ZDCAQAAQBAJ&pg=PA7|year=2013|publisher=SAGE|isbn=978-1-4462-8704-0|page=7|url-status=live|archive-url=https://web.archive.org/web/20170109093024/https://books.google.com/books?id=7ZDCAQAAQBAJ&pg=PA7|archive-date=9 January 2017}} Phonological awareness enables one to identify, discriminate, remember (working memory), and mentally manipulate the sound structures of language—phonemes, onsite-rime segments, syllables, and words.{{cite journal |last1=Stahl |first1=Steven A. |last2=Murray |first2=Bruce A. |title=Defining phonological awareness and its relationship to early reading. |journal=Journal of Educational Psychology |volume=86 |issue=2 |pages=221–234 |doi=10.1037/0022-0663.86.2.221 |date=1994}}{{cite journal |title=Phonological Awareness and Phonemic Perception in 4-Year-Old Children With Delayed Expressive Phonology Skills |journal=American Journal of Speech-Language Pathology |date=1 November 2003 |volume=12 |issue=4 |pages=463–471 |doi=10.1044/1058-0360(2003/092) |pmid=14658998 |last1=Rvachew |first1=Susan |last2=Ohberg |first2=Alyssa |last3=Grawburg |first3=Meghann |last4=Heyding |first4=Joan |s2cid=16983189 }}

The following can be done to assess for dyslexia:

Apply a multidisciplinary team approach involving the child's parent(s) and teacher(s), school psychologist, pediatrician, and, as appropriate, speech and language pathologist (speech therapist), and occupational therapist.Catherine Christo, John M. Davis, and Stephen E. Brock, Identifying, Assessing, and Treating Dyslexia at School (New York: Springer Science+Business Media, 2009), 59.

Gain familiarity with typical ages children reach various general developmental milestones, and domain-specific milestones, such as phonological awareness (recognizing rhyming words; identifying the initial sounds in words).Mather, Nancy and Barbara J. Wendling. Essentials of Dyslexia Assessment and Intervention. Hoboken, NJ: John Wiley & Sons, 2012.

Do not rely on tests exclusively. Careful observation of the child in the school and home environments, and sensitive, comprehensive parental interviews are just as important as tests.Reid, Gavin and Jennie Guise. The Dyslexia Assessment. London: Bloomsbury, 2017 ("... assessment for dyslexia includes more than tests; it involves comprehensive insights into the student's learning. This requires a full and comprehensive individual assessment as well as consideration of the environment and contextual factors.").M. S. Thambirajah, Developmental Assessment of the School-Aged Child with Developmental Disabilities: A Clinician's Guide (London: Jessica Kingsley, 2011), 74.

Look at the empirically supported response to intervention (RTI) approach,Jimerson, Shane R., Matthew K. Burns, and Amanda M. VanDerHeyden. Handbook of Response to Intervention: The Science and Practice of Multi-Tiered Systems of Support. 2nd ed. New York: Springer Science+Business Media, 2016. which "... involves monitoring the progress of a group of children through a programme of intervention rather than undertaking a static assessment of their current skills. Children with the most need are those who fail to respond to effective teaching, and they are readily identified using this approach."{{cite journal | author = Snowling Margaret J | year = 2013| title = Early Identification and Interventions for Dyslexia: A Contemporary View | journal = Journal of Research in Special Educational Needs | volume = 13 | issue = 1| pages = 7–14 | doi = 10.1111/j.1471-3802.2012.01262.x | pmid = 26290655| pmc = 4538781}}

There is a wide range of tests that are used in clinical and educational settings to evaluate the possibility of dyslexia.{{cite web|url=http://dyslexiahelp.umich.edu/dyslexics/learn-about-dyslexia/dyslexia-testing/tests|title=Tests for Dyslexia and Learning Disabilities|publisher=University of Michigan|access-date=15 March 2015|url-status=live|archive-url=https://web.archive.org/web/20150313000802/http://dyslexiahelp.umich.edu/dyslexics/learn-about-dyslexia/dyslexia-testing/tests|archive-date=13 March 2015}} If initial testing suggests that a person might have dyslexia, such tests are often followed up with a full diagnostic assessment to determine the extent and nature of the disorder.{{cite book|author1=Peer, Lindsay|author2=Reid, Gavin|title=Introduction to Dyslexia|url=https://books.google.com/books?id=OTiAAAAAQBAJ&pg=PT35|year=2013|publisher=Taylor & Francis|isbn=978-1-135-37290-3|pages=35–40|url-status=live|archive-url=https://web.archive.org/web/20170109134343/https://books.google.com/books?id=OTiAAAAAQBAJ&pg=PT35|archive-date=9 January 2017}} Some tests can be administered by a teacher or computer; others require specialized training and are given by psychologists. Some test results indicate how to carry out teaching strategies.{{cite web|title=Screening and assessment|url=http://www.bdadyslexia.org.uk/educator/screening-and-assessment|website=British Dyslexia Association|access-date=11 March 2015|url-status=live|archive-url=https://web.archive.org/web/20150330101403/http://www.bdadyslexia.org.uk/educator/screening-and-assessment|archive-date=30 March 2015}} Because a variety of different cognitive, behavioral, emotional, and environmental factors all could contribute to difficulty learning to read, a comprehensive evaluation should consider these different possibilities. These tests and observations can include:{{cite journal |last1=Schulte-Körne |first1=Gerd |title=The Prevention, Diagnosis, and Treatment of Dyslexia |journal=Deutsches Ärzteblatt International |date=October 2010 |volume=107 |issue=41 |pages=718–727 |doi=10.3238/arztebl.2010.0718 |pmid=21046003 |pmc=2967798 |issn=1866-0452}}

• General measures of cognitive ability, such as the Wechsler Intelligence Scale for Children, Woodcock-Johnson Tests of Cognitive Abilities, or Stanford-Binet Intelligence Scales. Low general cognitive ability would make reading more difficult. Cognitive ability measures also often try to measure different cognitive processes, such as verbal ability, nonverbal and spatial reasoning, working memory, and processing speed. There are different versions of these tests for different age groups. Almost all of these require additional training to give and score correctly, and are done by psychologists. According to Mather and Schneider (2015), a confirmatory profile and/or pattern of scores on cognitive tests confirming or ruling-out reading disorder has not yet been identified.Mather, N., & Schneider, D. The use of intelligence tests in the diagnosis of specific reading disability.{{cite book|url=https://books.google.com/books?id=ylzEBQAAQBAJ&q=Handbook+of+Intelligence:+Evolutionary+theory,+historical+perspective,+and+current+concepts|title=Handbook of Intelligence: Evolutionary Theory, Historical Perspective, and Current Concepts|last1=Goldstein|first1=Sam|last2=Princiotta|first2=Dana|last3=Naglieri|first3=Jack A.|date=2014|publisher=Springer|isbn=9781493915620|pages=415–434|language=en|access-date=10 January 2019}}
• Screening or evaluation for mental health conditions: Parents and teachers can complete rating scales or behavior checklists to gather information about emotional and behavioral functioning for younger people. Many checklists have similar versions for parents, teachers, and younger people old enough to read reasonably well (often 11 years and older) to complete. Examples include the Behavioral Assessment System for Children, and the Strengths and Difficulties Questionnaire. All of these have nationally representative norms, making it possible to compare the level of symptoms to what would be typical for the younger person's age and biological sex. Other checklists link more specifically to psychiatric diagnoses, such as the Vanderbilt ADHD Rating Scales or the Screen for Child Anxiety Related Emotional Disorders (SCARED). Screening uses brief tools that are designed to catch cases with a disorder, but they often get false positive scores for people who do not have the disorder. Screeners should be followed up by a more accurate test or diagnostic interview as a result. Depressive disorders and anxiety disorders are two-three times higher in people with dyslexia, and attention-deficit/hyperactivity disorder is more common, as well.{{cite journal |last1=Collett |first1=Brent R. |last2=Ohan |first2=Jeneva L. |last3=Myers |first3=Kathleen M. |title=Ten-Year Review of Rating Scales. V: Scales Assessing Attention-Deficit/Hyperactivity Disorder |journal=Journal of the American Academy of Child & Adolescent Psychiatry |date=1 September 2003 |volume=42 |issue=9 |pages=1015–1037 |doi=10.1097/01.CHI.0000070245.24125.B6 |pmid=12960702 |url=https://jaacap.org/article/S0890-8567(09)60999-0/fulltext |access-date=3 October 2019 |language=en |issn=0890-8567|url-access=subscription }}{{cite journal |last1=Stone |first1=Lisanne L |last2=Janssens |first2=Jan M A M |last3=Vermulst |first3=Ad A |last4=Van Der Maten |first4=Marloes |last5=Engels |first5=Rutger C M E |last6=Otten |first6=Roy |title=The Strengths and Difficulties Questionnaire: psychometric properties of the parent and teacher version in children aged 4–7 |journal=BMC Psychology |date=20 February 2015 |volume=3 |issue=1 |pages=4 |doi=10.1186/s40359-015-0061-8 |pmid=25815194 |pmc=4364334 |issn=2050-7283 |doi-access=free }}{{cite journal |last1=Swart |first1=G. T. |title=The Clinician's Guide to the Behavior Assessment System For Children |journal=The Canadian Child and Adolescent Psychiatry Review |volume=14 |issue=3 |pages=90 |issn=1716-9119|pmc=2542918 |year=2005 }}{{cite journal |last1=Birmaher |first1=B. |last2=Khetarpal |first2=S. |last3=Brent |first3=D. |last4=Cully |first4=M. |last5=Balach |first5=L. |last6=Kaufman |first6=J. |last7=Neer |first7=S. M. |title=The Screen for Child Anxiety Related Emotional Disorders (SCARED): scale construction and psychometric characteristics |journal=Journal of the American Academy of Child and Adolescent Psychiatry |volume=36 |issue=4 |pages=545–553 |doi=10.1097/00004583-199704000-00018 |pmid=9100430 |issn=0890-8567|year=1997 }}
• Review of academic achievement and skills: Average spelling/reading ability for a dyslexic is a percentage ranking <16, well below normal. In addition to reviewing grades and teacher notes, standardized test results are helpful in evaluating progress. These include group administered tests, such as the Iowa Tests of Educational Development, that a teacher may give to a group or whole classroom of younger people at the same time. They also could include individually administered tests of achievement, such as the Wide Range Achievement Test, or the Woodcock-Johnson (which also includes a set of achievement tests). The individually administered tests again require more specialized training.{{cite book |last1=Lindquist |first1=E. F. |title=The Iowa tests of educational development: how to use the test results; a manual for teachers and counselors |date=1953 |publisher=Science Research Associates |url=https://books.google.com/books?id=yOc9AAAAYAAJ&q=Iowa+Tests+of+Educational+Development |access-date=3 October 2019 |language=en}}{{cite journal |last1=Dell |first1=Cindy Ann |last2=Harrold |first2=Barbara |last3=Dell |first3=Thomas |title=Test Review: Wilkinson, G. S., & Robertson, G. J. (2006). Wide Range Achievement Test—Fourth Edition. Lutz, FL: Psychological Assessment Resources. WRAT4 Introductory Kit (includes manual, 25 test/response forms [blue and green], and accompanying test materials): $243.00 |journal=Rehabilitation Counseling Bulletin |date=1 October 2008 |volume=52 |issue=1 |pages=57–60 |doi=10.1177/0034355208320076 |s2cid=145644409 |language=en |issn=0034-3552}}{{cite book |last1=Semrud-Clikeman |first1=Margaret |last2=Ellison |first2=Phyllis Anne Teeter |title=Child Neuropsychology: Assessment and Interventions for Neurodevelopmental Disorders, 2nd Edition |date=2009 |publisher=Springer Science & Business Media |isbn=9780387889634 |page=119 |url=https://books.google.com/books?id=NBGSF9Jyg6AC&pg=PT119 |access-date=3 October 2019 |language=en}}

Screening procedures seek to identify children who show signs of possible dyslexia. In the preschool years, a family history of dyslexia, particularly in biological parents and siblings, predicts an eventual dyslexia diagnosis better than any test.Catherine Christo, John M. Davis, and Stephen E. Brock, Identifying, Assessing, and Treating Dyslexia at School (New York: Springer Science+Business Media, 2009), 56. {{ISBN|9780387885995}} In primary school (ages 5–7), the ideal screening procedure consists of training primary school teachers to carefully observe and record their pupils' progress through the phonics curriculum, and thereby identify children progressing slowly.Margaret J. Snowling, Dyslexia: A Very Short Introduction (Oxford, UK: Oxford University Press, 2019), 93–94.[https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/190599/Letters_and_Sounds_-_DFES-00281-2007.pdf Letters and Sounds: Principles and Practice of High Quality Phonics], Ref: DFES-00281-2007 (00281-2007BKT-EN), Primary National Strategy, Department for Education and Skills (United Kingdom), 2007. When teachers identify such students they can supplement their observations with screening tests such as the Phonics screening check{{cite web|url=https://www.gov.uk/government/publications/phonics-screening-check-2019-materials|title=Phonics screening check: 2019 materials|work=United Kingdom Department for Education, Standards and Testing Agency|access-date=14 October 2019}} used by United Kingdom schools during Year one.

In the medical setting, child and adolescent psychiatrist M. S. Thambirajah emphasizes that {{nowrap|"[g]iven}} the high prevalence of developmental disorders in school-aged children, all children seen in clinics should be systematically screened for developmental disorders irrespective of the presenting problem/s." Thambirajah recommends screening for developmental disorders, including dyslexia, by conducting a brief developmental history, a preliminary psychosocial developmental examination, and obtaining a school report regarding academic and social functioning.{{cite book|title=Developmental assessment of the school-aged child with developmental disabilities : a clinician's guide|last=Thambirajah, M. S.|date=2011|publisher=Jessica Kingsley Publishers|isbn=9780857003256|location=London|oclc=747410566}}

{{Main|Management of dyslexia}}

Through the use of compensation strategies, therapy and educational support, individuals with dyslexia can learn to read and write.{{cite journal|last1=Bogon|first1=Johana|title=TVA based assessment of visual attention functions in developmental dyslexia|journal=Frontiers in Psychology|date=October 2014|pmc=4199262|pmid=25360129|doi=10.3389/fpsyg.2014.01172|volume=5|pages=1172|doi-access=free}} There are techniques and technical aids that help to manage or conceal symptoms of the disorder.{{cite book|author=Brunswick, Nicola|title=Supporting Dyslexic Adults in Higher Education and the Workplace|url=https://books.google.com/books?id=suc1o0hueowC&pg=PA115|access-date=10 April 2012|date=10 April 2012|publisher=John Wiley & Sons|isbn=978-0-470-97479-7|pages=115–|url-status=live|archive-url=https://web.archive.org/web/20131231081312/http://books.google.com/books?id=suc1o0hueowC&pg=PA115|archive-date=31 December 2013}} Reducing stress and anxiety can sometimes improve written comprehension.{{cite journal|last1=Schulte-Körne|first1=G|title=The prevention, diagnosis, and treatment of dyslexia|journal=Deutsches Ärzteblatt International|date=October 2010|pages=718–26|pmc=2967798|pmid=21046003|doi=10.3238/arztebl.2010.0718|volume=107|issue=41}} For dyslexia intervention with alphabet-writing systems, the fundamental aim is to increase a child's awareness of correspondences between graphemes (letters) and phonemes (sounds), and to relate these to reading and spelling by teaching how sounds blend into words. Reinforced collateral training focused on reading and spelling may yield longer-lasting gains than oral phonological training alone.{{cite book |author=Lyytinen, Heikki; Erskine, Jane; Aro, Mikko and Richardson, Ulla |url=https://books.google.com/books?id=PCy6c9hIL5YC&pg=PA454 |contribution=Reading and reading disorders |editor-last=Hoff |editor-first=Erika |title=Blackwell Handbook of Language Development |pages=454–474 |publisher=Blackwell |year=2009 |isbn=978-1-4051-9459-4 |url-status=live |archive-url=https://web.archive.org/web/20170109204820/https://books.google.com/books?id=PCy6c9hIL5YC&pg=PA454 |archive-date=9 January 2017 }} Early intervention can be successful in reducing reading failure.{{cite journal|last1=van der Leij|first1=Aryan|title=Dyslexia and early intervention: what did we learn from the Dutch Dyslexia Programme?|journal=Dyslexia|date=1 November 2013|volume=19|issue=4|pages=241–255|doi=10.1002/dys.1466|pmid=24133037|issn=1099-0909}}

Research does not suggest that specially-tailored fonts (such as Dyslexie and OpenDyslexic) help with reading.{{cite journal|last1=Kuster|first1=Sanne M.|last2=van Weerdenburg|first2=Marjolijn|last3=Gompel|first3=Marjolein|last4=Bosman|first4=Anna M. T.|date=April 2018|title=Dyslexie font does not benefit reading in children with or without dyslexia|journal=Annals of Dyslexia|language=en|volume=68|issue=1|pages=25–42|doi=10.1007/s11881-017-0154-6|issn=0736-9387|pmc=5934461|pmid=29204931}} Children with dyslexia read text set in a regular font such as Times New Roman and Arial just as quickly, and they show a preference for regular fonts over specially-tailored fonts. Some research has pointed to increased letter-spacing being beneficial.{{Contradictory inline|date=March 2025|reason=The most obvious characteristic of the 'Dyslexie' font mentioned at the start of this paragraph is in fact that it has considerably increased letter spacing, yet the font is mentioned in a sentence that states that research suggests that such special fonts do NOT help dyslexics with reading.}}

There is currently no evidence showing that music education significantly improves the reading skills of adolescents with dyslexia.{{cite journal|title=Music education for improving reading skills in children and adolescents with dyslexia|journal=Cochrane Database of Systematic Reviews|issue=8|last1=Cogo-Moreira|first1=Hugo|last2=Andriolo|first2=Régis B|last3=Yazigi|first3=Latife|last4=Ploubidis|first4=George B|last5=Brandão de Ávila|first5=Clara Regina|last6=Mari|first6=Jair J|date=15 August 2012|pages=CD009133|doi=10.1002/14651858.cd009133.pub2|pmid=22895983|pmc=11801330 |url=https://researchonline.lshtm.ac.uk/246986/1/CD009133.pdf |archive-url=https://web.archive.org/web/20170830053651/http://researchonline.lshtm.ac.uk/246986/1/CD009133.pdf |archive-date=2017-08-30 |url-status=live}}

Dyslexic children require special instruction for word analysis and spelling from an early age.{{cite journal|last1=O'Hare|first1=Anne|title=Dyslexia: what do paediatricians need to know?|journal= Paediatrics and Child Health|date=2010|pages=338–343|doi=10.1016/j.paed.2010.04.004|volume=20|issue=7}} The prognosis, generally speaking, is positive for individuals who are identified in childhood and receive support from friends and family. The New York educational system (NYED) indicates "a daily uninterrupted 90-minute block of instruction in reading" and "instruction in phonemic awareness, phonics, vocabulary development, reading fluency" so as to improve the individual's reading ability.{{cite web |title=Response to Intervention Guidance – Minimum Requirements of a Response to Intervention Program (RtI) – Instruction Matched to Student Need: Special Education : P12 : NYSED |url=http://www.p12.nysed.gov/specialed/RTI/guidance/instruction.htm |website=p12.nysed.gov |access-date=10 January 2019 |archive-date=8 August 2018 |archive-url=https://web.archive.org/web/20180808183234/http://www.p12.nysed.gov/specialed/RTI/guidance/instruction.htm |url-status=dead }}

The prevalence of dyslexia is unknown, but it has been estimated to be as low as 5% and as high as 17% of the population.{{cite book|title = Psychiatry, 2 Volume Set|url = https://books.google.com/books?id=6Rp0BgAAQBAJ|publisher = John Wiley & Sons|date = 29 January 2015|isbn = 9781118845493|first1 = Allan|last1 = Tasman|first2 = Jerald|last2 = Kay|first3 = Jeffrey A.|last3 = Lieberman|first4 = Michael B.|last4 = First|first5 = Michelle|last5 = Riba|url-status=live|archive-url = https://web.archive.org/web/20150906081853/https://books.google.com/books?id=6Rp0BgAAQBAJ|archive-date = 6 September 2015|df = dmy-all}} Dyslexia is diagnosed more often in males.

There are different definitions of dyslexia used throughout the world. Further, differences in writing systems may affect development of written language ability due to the interplay between auditory and written representations of phonemes.{{cite journal|last1=Protopapas|first1=Athanassios|title=From temporal processing to developmental language disorders: mind the gap|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|date=2013|pmid=24324245|doi=10.1098/rstb.2013.0090|pmc=3866431|volume=369|issue=1634|pages=20130090}} Dyslexia is not limited to difficulty in converting letters to sounds, and Chinese people with dyslexia may have difficulty converting Chinese characters into their meanings.{{cite journal|last1=Zhao|first1=Jing|title=The visual magnocellular-dorsal dysfunction in Chinese children with developmental dyslexia impedes Chinese character recognition.|journal=Scientific Reports|date=November 2014|pmc=4238300|pmid=25412386|doi=10.1038/srep07068|volume=4|pages=7068|bibcode = 2014NatSR...4.7068Z }}{{cite book|author=Marshall, Chloe|title=Current Issues in Developmental Disorders|url=https://books.google.com/books?id=5VK_TWsQ3N4C&pg=PA152|year=2012|publisher=Psychology Press|isbn=978-1-84872-084-8|page=152|url-status=live|archive-url=https://web.archive.org/web/20170109144200/https://books.google.com/books?id=5VK_TWsQ3N4C&pg=PA152|archive-date=9 January 2017}} The Chinese vocabulary uses logographic, monographic, non-alphabet writing where one character can represent an individual phoneme.{{cite book|title = Brain, Mind, and Developmental Psychopathology in Childhood|url = https://books.google.com/books?id=5ujeVaMa9U0C&pg=PA177|publisher = Jason Aronson|date = 16 January 2012|isbn = 9780765708663|first1 = Elena|last1 = Garralda|first2 = Jean-Philippe|last2 = Raynaud}}

The phonological-processing hypothesis attempts to explain why dyslexia occurs in a wide variety of languages. Furthermore, the relationship between phonological capacity and reading appears to be influenced by orthography.{{cite journal|title = Phonological processing deficits as a universal model for dyslexia: evidence from different orthographies|journal = CoDAS|pages = 509–519|volume = 26|issue = 6|doi = 10.1590/2317-1782/20142014135|pmid = 25590915|first1 = Ana Luiza Gomes Pinto|last1 = Navas|first2 = Érica de Cássia|last2 = Ferraz|first3 = Juliana Postigo Amorina|last3 = Borges|first4 = Ana Luiza Gomes Pinto|last4 = Navas|first5 = Érica de Cássia|last5 = Ferraz|first6 = Juliana Postigo Amorina|last6 = Borges|year = 2014|df = dmy-all|doi-access = free}}

{{Main|History of dyslexia research}}

Dyslexia was clinically described by Oswald Berkhan in 1881,{{cite journal |author=Berkhan O |year=1917 |title=Über die Wortblindheit, ein Stammeln im Sprechen und Schreiben, ein Fehl im Lesen |trans-title=About word blindness, adyslalia of speech and writing, a weakness in reading |language=de |journal=Neurologisches Centralblatt |volume=36 |pages=914–27 |url=https://books.google.com/books?id=DmEsAQAAIAAJ&q=Wortblindheit}} but the term dyslexia was coined in 1883 by Rudolf Berlin, an ophthalmologist in Stuttgart.Berlin, Rudolf. [No title.] Medicinisches Correspondenzblatt des Württembergischen Ärztlichen Landesvereins [Correspondence Sheet of the Württemberg Medical Association] 53 (1883): 209.Webster's Third New International Dictionary. "History and Etymology for dyslexia", s.v. "dyslexia, noun". Springfield, MA: Merriam-Webster, 1961, rev. 2016.{{cite journal |title=Über Dyslexie |trans-title=About dyslexia |year=1884 |journal=Archiv für Psychiatrie |volume=15 |pages=276–278}} He used the term to refer to the case of a young boy who had severe difficulty learning to read and write, despite showing typical intelligence and physical abilities in all other respects.{{cite book|title=Annual of the Universal Medical Sciences and Analytical Index: A Yearly Report of the Progress of the General Sanitary Sciences Throughout the World|url=https://books.google.com/books?id=5_IhAQAAMAAJ&pg=PA39|year=1888|publisher=F. A. Davis Company|page=39|url-status=live|archive-url=https://web.archive.org/web/20170109200623/https://books.google.com/books?id=5_IhAQAAMAAJ&pg=PA39|archive-date=9 January 2017}} In 1896, W. Pringle Morgan, a British physician from Seaford, East Sussex, published a description of a reading-specific learning disorder in a report to the British Medical Journal titled "Congenital Word Blindness".{{cite book|last1=Brooks|first1=Patricia|title=Encyclopedia of language development|date=2014|publisher=SAGE|page=30|url=https://books.google.com/books?id=mvfSAwAAQBAJ&pg=PR30|isbn=9781483346434}} The distinction between phonological versus surface types of dyslexia is only descriptive, and without any etiological assumption as to the underlying brain mechanisms. However, studies have alluded to potential differences due to variation in performance.{{cite journal|last1=Mishra|first1=Srikanta K.|title=Medial efferent mechanisms in children with auditory processing disorders.|journal=Frontiers in Human Neuroscience|date=October 2014|pmid=25386132|doi=10.3389/fnhum.2014.00860|pmc=4209830|volume=8|pages=860|doi-access=free}} Over time, the consensus has changed from an intelligence-based model to an age-based model for dyslexia .{{cite journal |last1=Al-Shidhani |first1=Thuraya Ahmed |last2=Arora |first2=Vinita |title=Understanding Dyslexia in Children through Human Development Theories |journal=Sultan Qaboos University Medical Journal |date=2012 |volume=12 |issue=3 |pages=286–294 |doi=10.12816/0003141 |pmid=23269949 |pmc=3529662 |issn=2075-051X}}{{cite journal |last1=FLETCHER |first1=JACK M. |title=Dyslexia: The evolution of a scientific concept |journal=Journal of the International Neuropsychological Society |date=2009 |volume=15 |issue=4 |pages=501–508 |doi=10.1017/S1355617709090900 |pmid=19573267 |pmc=3079378 |issn=1355-6177}}

{{See also|List of artistic depictions of dyslexia}}

As is the case with any disorder, society often makes an assessment based on incomplete information. Before the 1980s, dyslexia was thought to be a consequence of education, rather than a neurological disability. As a result, society often misjudges those with the disorder. There is also sometimes a workplace stigma and negative attitude towards those with dyslexia.{{cite journal|last1=de Berr|first1=J|title=Factors influencing work participation of adults with developmental dyslexia|journal=BMC Public Health|date=2014|pmc=3913008|pmid=24460949|doi=10.1186/1471-2458-14-77|volume=14|pages=77|doi-access=free}} If the instructors of a person with dyslexia lack the necessary training to support a child with the condition, there is often a negative effect on the student's learning participation.{{cite journal|title = The Inclusion of Students with Dyslexia in Higher Education: A Systematic Review Using Narrative Synthesis|journal = Dyslexia (Chichester, England)|date = 1 November 2014|pmc = 4253321|pmid = 25293652|pages = 346–369|volume = 20|issue = 4|doi = 10.1002/dys.1484|first1 = Marco|last1 = Pino|first2 = Luigina|last2 = Mortari}}

Since at least the 1960s in the UK, the children diagnosed with developmental dyslexia have consistently been from privileged families.{{cite web|last=Kale|first=Sirin|date=17 September 2020|title=The Battle over Dyslexia|url=http://www.theguardian.com/news/2020/sep/17/battle-over-dyslexia-warwickshire-staffordshire|access-date=28 September 2020|website=The Guardian|language=en}} Although half of prisoners in the UK have significant reading difficulties, very few have ever been evaluated for dyslexia. Access to some special educational resources and funding is contingent upon having a diagnosis of dyslexia. As a result, when Staffordshire and Warwickshire proposed in 2018 to teach reading to all children with reading difficulties, using techniques proven to be successful for most children with a diagnosis of dyslexia, without first requiring the families to obtain an official diagnosis, dyslexia advocates and parents of children with dyslexia were fearful that they were losing a privileged status.

{{see also|List of people with dyslexia}}

Due to the various cognitive processes that dyslexia affects and the overwhelming societal stigma around the disability, individuals with dyslexia often employ behaviors of self-stigma and perfectionistic self-presentation in order to cope with their disability.{{cite journal |last1=Stoeber |first1=Joachim |last2=Rountree |first2=Margaret L. |title=Perfectionism, self-stigma, and coping in students with dyslexia: The central role of perfectionistic self-presentation |journal=Dyslexia (Chichester, England) |date=February 2021 |volume=27 |issue=1 |pages=62–78 |doi=10.1002/dys.1666 |pmid=32803909 |s2cid=221144226 |issn=1099-0909|doi-access=free }} The perfectionist self-presentation is when an individual attempts to present themselves as the perfect ideal image and hides any imperfections. This behavior presents serious risk as it often results in mental health issues and refusal to seek help for their disability.

{{Further|Dyslexia research}}

File:Writing Systems Template Image.svg

Most dyslexia research relates to alphabetic writing systems, and especially to European languages.{{cite book|last1=Reid|first1=Gavin|title=The Routledge Companion to Dyslexia|url=https://books.google.com/books?id=QrBQAmfXYooC&pg=PA16|year=2012|publisher=Routledge|isbn=978-1-136-61710-2|page=16|url-status=live|archive-url=https://web.archive.org/web/20170109205019/https://books.google.com/books?id=QrBQAmfXYooC&pg=PA16|archive-date=9 January 2017}} However, substantial research is also available regarding people with dyslexia who speak Arabic, Chinese, Hebrew, or other languages.{{cite journal|last1=Richlan|first1=Fabio|title=Functional neuroanatomy of developmental dyslexia; the role of orthographic depth|journal=Frontiers in Human Neuroscience|date=May 2014|pmid=24904383|doi=10.3389/fnhum.2014.00347|pmc=4033006|volume=8|pages=347|doi-access=free}} The outward expression of individuals with reading disability, and regular poor readers, is the same in some respects.{{cite web |title=Reading Difficulty and Disability |url=https://report.nih.gov/NIHfactsheets/Pdfs/ReadingDifficultyandDisability(NICHD).pdf |website=report.nih.gov |publisher=NIH |access-date=10 January 2019 |archive-url=https://web.archive.org/web/20190211145918/https://report.nih.gov/nihfactsheets/Pdfs/ReadingDifficultyandDisability(NICHD).pdf |archive-date=11 February 2019 |url-status=dead }}

• Dyscalculia, difficulty comprehending numbers and math
• Learning to read
• Orton-Gillingham
• List of people with dyslexia

{{Reflist}}

{{Academic peer reviewed|Q=Q73053061|doi-access=free}}

{{refbegin|30em}}

• {{cite journal | vauthors = Ramus F, Altarelli I, Jednoróg K, Zhao J, Scotto di Covella L | title = Neuroanatomy of developmental dyslexia: Pitfalls and promise | journal = Neuroscience and Biobehavioral Reviews | volume = 84 | pages = 434–452 | date = January 2018 | pmid = 28797557 | doi = 10.1016/j.neubiorev.2017.08.001 | s2cid = 33176236 }}
• {{cite book|url=https://books.google.com/books?id=wMR4AgAAQBAJ&pg=PP1|title=Dyslexia, Reading and the Brain: A Sourcebook of Psychological and Biological Research|first = Alan | last = Beaton |date=14 October 2004|publisher=Psychology Press|isbn=978-1-135-42275-2}}
• {{cite book|url=https://books.google.com/books?id=8OywcklCBPkC&pg=PP1|title=Fifty Years in Dyslexia Research| first = Thomas Richard | last = Miles |date=4 August 2006|publisher=Wiley|isbn=978-0-470-02747-9|author-link=Thomas Richard Miles}}
• {{cite book|url=https://books.google.com/books?id=szJZ1LDQv7YC&pg=PP1|title=Dyslexia in Context: Research, Policy and Practice| vauthors = Reid G, Fawcett A |date=12 May 2008|publisher=John Wiley & Sons|isbn=978-0-470-77801-2}}
• {{cite book|url=https://books.google.com/books?id=7Jbvue2kNdYC&pg=PP1|title=The Psychology of Dyslexia: A Handbook for Teachers with Case Studies|first = Michael | last = Thomson |date=18 March 2009|publisher=John Wiley & Sons|isbn=978-0-470-74197-9}}
• {{cite book|url=https://books.google.com/books?id=EFh4kCrMbK4C&pg=PP1|title=Dyslexia| first = Gavin | last = Reid |date=17 March 2011|publisher=A&C Black|isbn=978-1-4411-6585-5|edition=3}}
• {{cite book|url=https://books.google.com/books?id=K2xdsMJ1MWgC&pg=PP1|title=Dyslexia and Other Learning Difficulties| first = Mark | last = Selikowitz |date=2 July 2012|publisher=Oxford University Press|isbn=978-0-19-969177-7}}
• {{cite book|url=https://books.google.com/books?id=EgXsAgAAQBAJ&pg=PP1|title=Reading, Writing and Dyslexia: A Cognitive Analysis| first = Andrew W. | last = Ellis |date=25 February 2014|publisher=Psychology Press|isbn=978-1-317-71630-3}}
• {{cite book|url=https://books.google.com/books?id=4lz2AgAAQBAJ&pg=PP1|title=The Dyslexia Debate| vauthors = Elliott JG, Grigorenko EL |date=24 March 2014|publisher=Cambridge University Press|isbn=978-0-521-11986-3|author-link=Julian Elliott}}
• {{cite book|url=https://books.google.com/books?id=oXe6BAAAQBAJ&pg=PP1|title=Dyslexia and Us: A collection of personal stories|last1=Agnew|first1=Susie|last2=Stewart|first2=Jackie|last3=Redgrave|first3=Steve|date=8 October 2014|publisher=Andrews UK Limited|isbn=978-1-78333-250-2 }}
• {{cite journal | vauthors = Norton ES, Beach SD, Gabrieli JD | title = Neurobiology of dyslexia | journal = Current Opinion in Neurobiology | volume = 30 | pages = 73–8 | date = February 2015 | pmid = 25290881 | pmc = 4293303 | doi = 10.1016/j.conb.2014.09.007 | hdl = 1721.1/102416 }}
• {{cite journal | vauthors = Serrallach B, Groß C, Bernhofs V, Engelmann D, Benner J, Gündert N, Blatow M, Wengenroth M, Seitz A, Brunner M, Seither S, Parncutt R, Schneider P, Seither-Preisler A | title = Neural Biomarkers for Dyslexia, ADHD, and ADD in the Auditory Cortex of Children | journal = Frontiers in Neuroscience | volume = 10 | pages = 324 | year = 2016 | pmid = 27471442 | doi = 10.3389/fnins.2016.00324 | pmc = 4945653 | doi-access = free }}
• {{cite journal | vauthors = Shao S, Niu Y, Zhang X, Kong R, Wang J, Liu L, Luo X, Zhang J, Song R | title = Opposite Associations between Individual KIAA0319 Polymorphisms and Developmental Dyslexia Risk across Populations: A Stratified Meta-Analysis by the Study Population | journal = Scientific Reports | volume = 6 | pages = 30454 | date = July 2016 | pmid = 27464509 | pmc = 4964335 | doi = 10.1038/srep30454 | bibcode = 2016NatSR...630454S }}
• {{cite journal | vauthors = Brewer CC, Zalewski CK, King KA, Zobay O, Riley A, Ferguson MA, Bird JE, McCabe MM, Hood LJ, Drayna D, Griffith AJ, Morell RJ, Friedman TB, Moore DR | title = Heritability of non-speech auditory processing skills | journal = European Journal of Human Genetics | volume = 24 | issue = 8 | pages = 1137–44 | date = August 2016 | pmid = 26883091 | pmc = 4872837 | doi = 10.1038/ejhg.2015.277 }}
• {{cite journal | vauthors = Mascheretti S, De Luca A, Trezzi V, Peruzzo D, Nordio A, Marino C, Arrigoni F | title = Neurogenetics of developmental dyslexia: from genes to behavior through brain neuroimaging and cognitive and sensorial mechanisms | journal = Translational Psychiatry | volume = 7 | issue = 1 | pages = e987 | date = January 2017 | pmid = 28045463 | pmc = 5545717 | doi = 10.1038/tp.2016.240 }}
• {{cite journal | vauthors = Fraga González G, Žarić G, Tijms J, Bonte M, van der Molen MW | title = Contributions of Letter-Speech Sound Learning and Visual Print Tuning to Reading Improvement: Evidence from Brain Potential and Dyslexia Training Studies | journal = Brain Sciences | volume = 7 | issue = 1 | pages = 10 | date = January 2017 | pmid = 28106790 | pmc = 5297299 | doi = 10.3390/brainsci7010010 | doi-access = free }}
• {{cite journal | vauthors = Rudov A, Rocchi MB, Accorsi A, Spada G, Procopio AD, Olivieri F, Rippo MR, Albertini MC | title = Putative miRNAs for the diagnosis of dyslexia, dyspraxia, and specific language impairment | journal = Epigenetics | volume = 8 | issue = 10 | pages = 1023–9 | date = October 2013 | pmid = 23949389 | pmc = 3891682 | doi = 10.4161/epi.26026 }}
• {{cite journal | vauthors = Vágvölgyi R, Coldea A, Dresler T, Schrader J, Nuerk HC | title = A Review about Functional Illiteracy: Definition, Cognitive, Linguistic, and Numerical Aspects | journal = Frontiers in Psychology | volume = 7 | pages = 1617 | year = 2016 | pmid = 27891100 | pmc = 5102880 | doi = 10.3389/fpsyg.2016.01617 | doi-access = free }}

{{refend}}

{{Spoken Wikipedia|date=2022-09-02|En-Dyslexia-article.ogg}}

{{Scholia|topic}}

{{Library resources box|by=no|onlinebooks=no|about=yes|lcheading=dyslexia}}

{{Medical resources

| DiseasesDB = 4016

| ICD11 = {{ICD11|6A03.0}} (developmental), {{ICD11|MB4B.0}}

| ICD10 = {{ICD10|F81.0}} (developmental), {{ICD10|R48.0}}

| ICD9 = {{ICD9|315.02}}

| ICDO =

| OMIM = 127700

| MedlinePlus = 001406

| eMedicineSubj = article

| eMedicineTopic = 1835801

| MeshID = D004410

| Scholia = Q132971

}}

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