WHAT IS DYSLEXIA? From Wikipedia, the free encyclopedia This article is about developmental dyslexia. For acquired dyslexia, see Alexia (condition) Credentials . Dyslexia, or developmental reading disorder, [1] is characterized by difficulty with learning to read fluently and with accurate comprehension despite normal intelligence. [2][3][4] This includes difficulty with phonological awareness, phonological decoding, processing speed, orthographic coding, auditory short-term memory, language skills/verbal comprehension, and/or rapid naming. [5][6][7] Dyslexia is the most common learning difficulty. [8] Dyslexia is the most recognized of reading disorders. There are other reading difficulties that are unrelated to dyslexia. Some see dyslexia as distinct from reading difficulties resulting from other causes, such as a non-neurological deficiency with vision or hearing, or poor or inadequate reading instruction. [9][10] There are three proposed cognitive subtypes of dyslexia (auditory, visual and attentional), although individual cases of dyslexia are better explained by specific underlying neuropsychological deficits and co-occurring learning difficulties(e.g. an auditory processing disorder, an attention deficit hyperactivity disorder, a visual processing disorder) and co-occurring learning difficulties (e.g. dyscalculia and dysgraphia). [11][12][13][14][15][16] Although it is considered to be a receptive language-based learning disability in the research literature, dyslexia also affects one's expressive language skills. [17] Researchers at MIT found that people with dyslexia exhibited impaired voice-recognition abilities. [18] Interestingly, a study published online (and in the July issue of the American Journal of Human Genetics), reported a genetic origin to the disorder, and other learning disabilities, that could help lead to earlier diagnoses and more successful interventions. [19] Contents 1 Classification 2 Signs and symptoms o 2.1 Language o 2.2 Associated conditions 3 Causes o 3.1 Neuroanatomy o 3.2 Genetics o 3.3 Gene-environment interaction 4 Management 5 Epidemiology 6 History 7 Research 8 Society and culture 9 See also 10 References 11 External links Classification Internationally, dyslexia has no single definition; more than 70 names are used to describe its manifestations, characterizations or causes. [20]:7–8 The World Federation of Neurology defines dyslexia as "a disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity". [21] The National Institute of Neurological Disorders and Stroke definition also adds, "difficulty with spelling, phonological processing (the manipulation of sounds), and/or rapid visual-verbal responding." [3] Many published definitions from researchers and organizations around the world are purely descriptive or embody causal theories. These definitions for the disorder, defined as dyslexia, encompass a number of reading skills, deficits and difficulties with a number of causes rather than a single condition. [22][23] Dyslexia can also be acquired following brain damage; commonly called alexia, it includes surface dyslexia, semantic dyslexia, phonological dyslexia, and deep dyslexia. [24][25] Acquired surface dyslexia arises after brain damage in a previously literate person and results in pronunciation errors that indicate impairment of the lexical route. [26][27] Numerous symptom-based definitions of dyslexia suggest neurological approaches. The dual-route hypothesis to reading aloud proposes an answer for disordered reading, including both developmental dyslexica and alexica. [28][29] Signs and symptoms See also: Characteristics of dyslexia In early childhood, early symptoms that correlate with a later diagnosis of dyslexia include delays in speech, [30] letter reversal or mirror writing, [31][32] and being easily distracted by background noise. [33] This pattern of early distractibility is partially explained by the co-occurrence of dyslexia and attention-deficit/hyperactivity disorder. Although each disorder occurs in approximately 5% of children, 25-40% of children with either dyslexia or ADHD meet criteria for the other disorder. [34][35] Dyslexic children of school age can have various symptoms; including difficulty identifying or generating rhyming words, or counting syllables in words (phonological awareness), [36] a difficulty segmenting words into individual sounds, or blending sounds to make words, [37] a difficulty with word retrieval or naming problems (see anomic aphasia), [38][39][40] commonly very poor spelling, [41] which has been called dysorthographia or dysgraphia (orthographic coding), whole-word guesses, and tendencies to omit or add letters or words when writing and reading are considered classic signs. Signs persist into adolescence and adulthood with trouble with summarizing a story, memorizing, reading aloud, and learning a foreign language. [42] Adult dyslexics can read with good comprehension, although they tend to read more slowly than non- dyslexics and perform more poorly at spelling and nonsense word reading, a measure of phonological awareness. [43][44] A common misconception about dyslexia is that dyslexic readers write words backwards or move letters around when reading – this only occurs in a very small population of dyslexic readers. [45] Individuals with dyslexia are better identified by reading accuracy, fluency, and writing skills that do not seem to match their level of intelligence from prior observations. Language Main article: Orthographies and dyslexia The complexity of a language's orthography (i.e., its conventional spelling system, see orthographic depth) has a direct impact upon how difficult it is to learn to read that language. English has a comparatively deep orthography within the Latin alphabet writing system, with a complex orthographic structure that employs spelling patterns at several levels: principally, letter-sound correspondences, syllables, and morphemes. Other languages, such as Spanish, have mostly alphabetic orthographies that employ letter-sound correspondences, so-called shallow orthographies. It is relatively easy to learn to read languages like Spanish; it is much more difficult to learn to read languages with more complex orthographies such as English. [46] Logographic writing systems, notably Japanese and Chinese characters, have graphemes that are not linked directly to their pronunciation, which pose a different type [specify] of dyslexic difficulty. [16][47][48][49] From a neurological perspective, different types of writing systems (e.g., alphabetic as compared to logographic writing systems) require different neurological pathways in order to read, write, and spell. Because different writing systems require
© Robert D. Smith, PhD
Robert D. Smith, PhD Diagnosis of Dyslexia, ADD & Learning Disorders Children & Adults