History of dyslexia research

Main articles: Dyslexia and Dyslexia research

Identified by Oswald Berkhan in 1881,[1] the term 'dyslexia' was later coined in 1887 by Rudolf Berlin,[2] an ophthalmologist practicing in Stuttgart, Germany.[3] He used the term to refer to a case of a young boy who had a severe impairment in learning to read and write in spite of showing typical intellectual and physical abilities in all other respects.

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". This described the case of a 14-year-old boy who had not yet learned to read, yet showed normal intelligence and was generally adept at other activities typical of children of that age.[4]

1900-1950

During the 1890s and early 1900s, James Hinshelwood, a British ophthalmologist, published a series of articles in medical journals describing similar cases of congenital word blindness, which he defined as "a congenital defect occurring in children with otherwise normal and undamaged brains characterised by a difficulty in learning to read." In his 1917 book Congenital Word Blindness, Hinshelwood asserted that the primary disability was in visual memory for words and letters, and described symptoms including letter reversals, and difficulties with spelling and reading comprehension.[5]

In 1925 Samuel T. Orton, a neurologist who worked primarily with stroke victims, met a girl who could not read and who exhibited symptoms similar to stroke victims who had lost the ability to read. Orton began studying reading difficulties and determined that there was a syndrome unrelated to brain damage that made learning to read difficult. Orton called his theory strephosymbolia (meaning 'twisted signs') to describe individuals with dyslexia had difficulty associating the visual forms of words with their spoken forms.[6] Orton observed that reading deficits in dyslexia did not seem to stem from strictly visual deficits.[7] He believed the condition was caused by the failure to establish hemispheric dominance in the brain.[8] He also observed that the children he worked with were disproportionately left- or mixed-handed, although this finding has been difficult to replicate.[9] Influenced by the kinesthetic work of Helen Keller and Grace Fernald, and looking for a way to teach reading using both left and right brain functions,[6] Orton later worked with psychologist and educator Anna Gillingham to develop an educational intervention that pioneered the use of simultaneous multisensory instruction.[10]

In contrast, Dearborn, Gates, Bennet and Blau considered a faulty guidance of the seeing mechanism to be the cause. They sought to discover if a conflict between spontaneous orientation of the scanning action of the eyes from right to left and training aimed at the acquisition of an opposite direction would allow an interpretation of the facts observed in the dyslexic disorder and especially of the ability to mirror-read.

To this end the authors asked four adults to read a text reflected in a mirror for ten minutes a day for five months. In all subjects, the words were not perceived in their globality but required a meticulous analysis of the letters and syllables. They also demonstrated total or partial inversions even sometimes affecting the order of the words in a sentence. They revealed a curious impression of not just horizontal but also vertical inversions. These are errors that exist amongst people with dyslexia and they suffer from the aggravating circumstance inherent in all learning.

1950-2000

1949 research conducted under Clement Launay (thesis G. Mahec Paris 1951) went further. In adult subjects, the reading of a series of 66 tiny lower-case letters, 5 mm high, spaced 5 mm apart, first from left to right, and then from right to left, was more easily and quickly done in the left to right direction. For former dyslexic children, a substantial number read a series of 42 letters with equal speed in both directions, and some (10%) read better from right to left than from left to right. The phenomenon is clearly linked to the dynamics of sight, as it disappears when the space between letters is increased, transforming the reading into spelling. This experience also explains the ability to mirror-read.

In the 1970s, a new hypothesis emerged that dyslexia stems from a deficit in phonological processing, or difficulty in recognizing that spoken words are formed by discrete phonemes, (for example, that the word CAT comes from the sounds [k], [æ], and [t]). As a result, affected individuals have difficulty associating these sounds with the visual letters that make up written words. Key studies of the phonological deficit hypothesis include the finding that the strongest predictor of reading success in school age children is phonological awareness, [11] and that phonological awareness instruction can improve decoding skills for children with reading difficulties.[12]

In 1979 Galaburda and Kemper,[13] and Galaburda et al. 1985,[14] reported observations from the examination of post autopsy brains of people with dyslexia. Observed anatomical differences in the language center in a dyslexic brain, showing microscopic cortical malformations known as ectopias and more rarely vascular micro-malformations and in some instances these cortical malformations appeared as a microgyrus. These studies and those of Cohen et al. 1989,[15] suggested abnormal cortical development which was presumed to occur before or during the sixth month of foetal brain development.[16]

1993 Castles and Coltheart describe developmental dyslexia as two prevalent and distinct varieties using the subtypes of Alexia (acquired dyslexia), Surface and Phonological Dyslexia. Understanding these subtypes is useful in diagnosing learning patterns and developing approaches for overcoming visual perception impairments or speech discrimination deficits. Surface Dyslexia is characterized by subjects who can read known words but who have trouble reading words that are irregular.[17] Phonological Dyslexia is characterized by subjects who can read aloud both regular and irregular words but have difficulties with non-words and with connecting sounds to symbols, or with sounding out words. Phonological processing tasks predict reading accuracy and comprehension.[17] Manis et al. 1996, concluded that there were probably more than two subtypes of dyslexia, which would be related to multiple underlying deficits.[18]

1994 From post autopsy specimens Galaburda et al., reported : Abnormal auditory processing in people with dyslexia suggests that accompanying anatomical abnormalities might be present in the auditory system. They measured cross-sectional neuronal areas in the medial geniculate nuclei (MGNs) of five dyslexic and seven control brains. In contrast to controls, which showed no asymmetry, the left-side medial geniculate nucleus (MGN) neurons were significantly smaller than the right in the dyslexic sample. Also, as compared with controls, there were more small neurons and fewer large neurons in the left dyslexic MGN. These findings are consistent with reported behavioral findings of a left hemisphere-based phonological defect in dyslexic individuals.[19]

The development of Neuroimaging technologies during the 1980s and 1990s enabled dyslexia research to make significant advances. Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies have revealed the neural signature of adult normal reading (e.g.,Bookheimer et al., 1995; Fiez and Petersen, 1998;[20] Price, 1997; Pugh et al., 1996; Turkeltaub et al., 2002)[21] and phonological processing (e.g., Gelfand and Bookheimer, 2003;[22] Poldrack et al., 1999;[23] Price et al., 1997; Rumsey et al., 1997a). Brain imaging studies have also characterized the anomalous patterns of neuronal activation associated with reading and phonological processing in adults with persistent or compensated developmental dyslexia (e.g., Brunswick et al., 1999;[24] Demonet et al., 1992; Flowers et al., 1991; Horwitz et al., 1998;[25] Ingvar et al., 1993; Paulesu et al., 1996; Pugh et al., 2000;[26] Rumsey et al., 1997b; Shaywitz et al., 1998).[27] Employing various experimental approaches and paradigms (e.g., the detection or judgment of rhymes, nonword reading, and implicit reading), these studies have localized dysfunctional phonological processing in dyslexia to left-hemisphere perisylvian regions. Differences in task-related signal change in the left temporoparietal and occipitotemporal cortices have emerged as the most consistent findings in studies of dyslexia in the alphabetic writing system (Paulesu et al., 2001;[28] for review, see Eden and Zeffiro, 1998).[29] However, it has been demonstrated that in nonalphabetic scripts, where reading places less demands on phonemic processing and the integration of visual-orthographic information is crucial, dyslexia is associated with under activity of the left middle frontal gyrus (Siok et al., 2004).[30]

2000s

1999 Wydell and Butterworth reported the case study of an English-Japanese bilingual with monolingual dyslexia.[31] Suggesting that any language where orthography-to-phonology mapping is transparent, or even opaque, or any language whose orthographic unit representing sound is coarse (i.e. at a whole character or word level) should not produce a high incidence of developmental phonological dyslexia, and that orthography can influence dyslexic symptoms

2001 Temple et al. Suggest that dyslexia may be characterized in childhood by disruptions in the neural bases of both phonological and orthographic processes important for reading.[32]

2002 Talcott et al. reported that both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills.[33]

2003 Turkeltaub et al., reported: "The complexities of pediatric brain imaging have precluded studies that trace the neural development of cognitive skills acquired during childhood. Using a task that isolates reading-related brain activity and minimizes confounding performance effects, we carried out a cross-sectional functional magnetic resonance imaging (fMRI) study using subjects whose ages ranged from 6 to 22 years. We found that learning to read is associated with two patterns of change in brain activity: increased activity in left-hemisphere middle temporal and Inferior frontal gyrus and decreased activity in right inferotemporal cortica areas. Activity in the left-posterior superior temporal sulcus of the youngest readers was associated with the maturation of their phonological processing abilities. These findings inform current reading models and provide strong support for Orton's 1925 theory of reading development."[34]

(A guide to the areas of the brain List of regions in the human brain, Cerebral hemisphere. and Cerebral cortex )

2003 Current models of the relation between the brain and dyslexia generally focus on some form of defective or delayed brain maturation. More recently, genetic research has provided increasing evidence supporting a genetic origin of dyslexia.[35]

2004 A University of Hong Kong study argues that dyslexia affects different structural parts of children's brains depending on the language which the children read.[36]

2007 Researchers are searching for a link between the neurological and genetic findings, and the reading disorder. There are many previous and current theories of dyslexia, but one that has much support from research is that, whatever the biological cause, dyslexia is a matter of reduced phonological awareness, the ability to analyze and link the units of spoken and written languages. [37]

2008 S Heim et al. This is one of the first studies not to just compare dyslexics with a non dyslexic control, but to go further and compared the different cognitive sub groups with a non dyslexic control group. Different theories conceptualise dyslexia as either a phonological, attentional, auditory, magnocellular, or automatisation deficit. Such heterogeneity suggests the existence of yet unrecognised subtypes of dyslexics suffering from distinguishable deficits. The purpose of the study was to identify cognitive subtypes of dyslexia. Out of 642 children screened for reading ability 49 dyslexics and 48 controls were tested for phonological awareness, auditory discrimination, motion detection, visual attention, and rhythm imitation. A combined cluster and discriminant analysis approach revealed three clusters of dyslexics with different cognitive deficits. Compared to reading-unimpaired children cluster no. 1 had worse phonological awareness; cluster no. 2 had higher attentional costs; cluster no. 3 performed worse in the phonological, auditory, and magnocellular tasks. These results indicate that dyslexia may result from distinct cognitive impairments. As a consequence, prevention and remediation programmes should be specifically targeted for the individual child's deficit pattern.[38]

Timeline

References

  1. ↑ Berkhan O (1917). "Uber die Wortblindheit, ein Stammeln im Sprechen und Schreiben, ein Fehl im Lesen". Neurologisches Centralblatt 36: 914–927.
  2. ↑ Wagner, Rudolph (January 1973). "Rudolf Berlin: Originator of the term dyslexia". Annals of Dyslexia 23 (1): 57–63. doi:10.1007/BF02653841.
  3. ↑ "Über Dyslexie" [About dyslexia]. Archiv für Psychiatrie 15: 276–278.
  4. ↑ 4.0 4.1 Snowling MJ (November 1996). "Dyslexia: a hundred years on". BMJ 313 (7065): 1096–7. doi:10.1136/bmj.313.7065.1096. PMC 2352421. PMID 8916687.
  5. ↑ 5.0 5.1 Hinshelwood, J. (1917). Congenital Word-blindness. HK Lewis \& Co., ltd.
  6. ↑ 6.0 6.1 6.2 Orton, Samuel (1925). "Word-blindness in school children". Archives of Neurology and Psychiatry 14 (5): 285–516. doi:10.1001/archneurpsyc.1925.02200170002001.
  7. ↑ Henry, MK (1998). "Structured, sequential, multisensory teaching: The Orton legacy". Annals of Dyslexia 48: 1. doi:10.1007/s11881-998-0002-9.
  8. ↑ 8.0 8.1 Orton, S.T. (1928). "Specific reading disability—strephosymbolia". Journal of the American Medical Association 90 (14): 1095–1099. doi:10.1001/jama.1928.02690410007003.
  9. ↑ Geschwind, N (1982). "Biological associations of left-handedness". Annals of Dyslexia 33: 29–40. doi:10.1007/BF02647994.
  10. ↑ Goeke, Jennifer; Kristen D. Ritchey (2006). "Orton-Gillingham and Orton-Gillingham-based reading instruction: a review of the literature". Journal of Special Education 40 (3): 171. doi:10.1177/00224669060400030501.
  11. ↑ Bradley, L; Bryant, PE (1983). "Categorizing sounds and learning to read: A Causal connection". Nature 30 (2): 419–421. doi:10.1038/301419a0.
  12. ↑ Alexander, A; Anderson, H; Heilman, P; Voeller, K; Torgesen, J (1991). "Phonological awareness training and the remediation of analytic decoding deficits in a group of severe dyslexics". Annals of Dyslexia 41: 193–206. doi:10.1007/BF02648086.
  13. ↑ 13.0 13.1 Galaburda, Albert M.; Thomas L. Kemper (1979-02-27). "Cytoarchitectonic Abnormalities in Developmental Dyslexia: A Case Study". Annals of Neurology 6 (2): 94–100. doi:10.1002/ana.410060203. PMID 496415.
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  15. ↑ Cohen M, Campbell R, Yaghmai F (June 1989). "Neuropathological abnormalities in developmental dysphasia". Annals of Neurology 25 (6): 567–70. doi:10.1002/ana.410250607. PMID 2472772.
  16. ↑ 16.0 16.1 Habib M (December 2000). "The neurological basis of developmental dyslexia: an overview and working hypothesis". Brain 123 (12): 2373–99. doi:10.1093/brain/123.12.2373. PMID 11099442.
  17. ↑ 17.0 17.1 17.2 Castles A, Coltheart M (May 1993). "Varieties of developmental dyslexia". Cognition 47 (2): 149–80. doi:10.1016/0010-0277(93)90003-E. PMID 8324999.
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  19. ↑ 19.0 19.1 Galaburda AM, Menard MT, Rosen GD (August 1994). "Evidence for aberrant auditory anatomy in developmental dyslexia". Proceedings of the National Academy of Sciences of the United States of America 91 (17): 8010–3. doi:10.1073/pnas.91.17.8010. PMC 44534. PMID 8058748.
  20. ↑ Fiez JA, Petersen SE (February 1998). "Neuroimaging studies of word reading". Proceedings of the National Academy of Sciences of the United States of America 95 (3): 914–21. doi:10.1073/pnas.95.3.914. PMC 33816. PMID 9448259.
  21. ↑ 21.0 21.1 Turkeltaub PE, Eden GF, Jones KM, Zeffiro TA (July 2002). "Meta-analysis of the functional neuroanatomy of single-word reading: method and validation". NeuroImage 16 (3 Pt 1): 765–80. doi:10.1006/nimg.2002.1131. PMID 12169260.
  22. ↑ Gelfand JR, Bookheimer SY (June 2003). "Dissociating neural mechanisms of temporal sequencing and processing phonemes". Neuron 38 (5): 831–42. doi:10.1016/S0896-6273(03)00285-X. PMID 12797966.
  23. ↑ Poldrack RA, Wagner AD, Prull MW, Desmond JE, Glover GH, Gabrieli JD (July 1999). "Functional specialization for semantic and phonological processing in the left inferior prefrontal cortex". NeuroImage 10 (1): 15–35. doi:10.1006/nimg.1999.0441. PMID 10385578.
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  37. ↑ 37.0 37.1 Lyytinen, Heikki, Erskine, Jane, Aro, Mikko, Richardson, Ulla (2007). "Reading and reading disorders". In Hoff, Erika. Blackwell Handbook of Language Development. Blackwell. pp. 454–474. ISBN 978-1-4051-3253-4.
  38. ↑ 38.0 38.1 Heim S, Tschierse J, Amunts K et al. (2008). "Cognitive subtypes of dyslexia". Acta Neurobiologiae Experimentalis 68 (1): 73–82. PMID 18389017.
  39. ↑ Berkhan O (1917). Neur. Zent 28. Missing or empty |title= (help)
  40. ↑ Wagner, Rudolph (January 1973). "Rudolf Berlin: Originator of the term dyslexia". Annals of Dyslexia 23 (1): 57–63. doi:10.1007/BF02653841.
  41. ↑ "Uber Dyslexie". Archiv fur Psychiatrie 15: 276–278.
  42. ↑ δυσ-, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  43. ↑ λέξις, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  44. ↑ dyslexia, Online Etymology Dictionary
  45. ↑ Henry, Marcia K. (December 1998). "Structured, sequential, multisensory teaching: The Orton legacy". Annals of Dyslexia 48 (1): 1–26. doi:10.1007/s11881-998-0002-9.
  46. ↑ Goeke, Jennifer; Goeke, J. L. (2006). "Orton-Gillingham and Orton-Gillingham-based reading instruction: a review of the literature". Journal of Special Education 40 (3): 171–183. doi:10.1177/00224669060400030501.
  47. ↑ Makita, K. (1968). "The rarity of reading disability in Japanese children". American Journal of Orthopsychiatry 38 (4): 599–614. doi:10.1111/j.1939-0025.1968.tb02428.x. PMID 5661541.
  48. ↑ "Reading disabilities in modern Japanese children. Takehiko Hirose. 2005; Journal of Research in Reading – Wiley InterScience". Retrieved 2013-09-18.
  49. ↑ Bradley, L; Bryant, P. E. (1983). "Categorizing sounds and learning to read—a causal connection". Nature 30 (2): 419–421. doi:10.1038/301419a0.
  50. ↑ Galaburda AM, Sherman GF, Rosen GD, Aboitiz F, Geschwind N (August 1985). "Developmental dyslexia: four consecutive patients with cortical anomalies". Annals of Neurology 18 (2): 222–33. doi:10.1002/ana.410180210. PMID 4037763.
  51. ↑ Cohen M, Campbell R, Yaghmai F (June 1989). "Neuropathological abnormalities in developmental dysphasia". Annals of Neurology 25 (6): 567–70. doi:10.1002/ana.410250607. PMID 2472772. Retrieved 2013-09-18.
  52. ↑ Cestnick Laurie, Coltheart M, (March 1999). "The Relationship Between Language-Processing and Visual-Processing Deficits in Developmental Dyslexia". Cognition 71 (3): 231–55. doi:10.1016/S0010-0277(99)00023-2. PMID 10476605.
  53. ↑ Cestnick Laurie, Jerger James, (October 2000). "Auditory temporal processing and lexical/nonlexical reading in developmental dyslexics.". Journal of American Academy of Audiology 11 (9): 501–513. PMID 11057735.
  54. ↑ Cestnick Laurie (August 2001). "Cross-modality temporal processing deficits in developmental phonological dyslexics.". Brain and Cognition 46 (3): 319–325. doi:10.1006/brcg.2000.1273. PMID 11487282.
  55. ↑ Fiez JA, Petersen SE (February 1998). "Neuroimaging studies of word reading". Proc. Natl. Acad. Sci. U.S.A. 95 (3): 914–21. doi:10.1073/pnas.95.3.914. PMC 33816. PMID 9448259.
  56. ↑ Gelfand JR, Bookheimer SY (June 2003). "Dissociating neural mechanisms of temporal sequencing and processing phonemes". Neuron 38 (5): 831–42. doi:10.1016/S0896-6273(03)00285-X. PMID 12797966.
  57. ↑ Poldrack RA, Wagner AD, Prull MW, Desmond JE, Glover GH, Gabrieli JD (July 1999). "Functional specialization for semantic and phonological processing in the left inferior prefrontal cortex". NeuroImage 10 (1): 15–35. doi:10.1006/nimg.1999.0441. PMID 10385578.
  58. ↑ Ziegler JC, Perry C, Ma-Wyatt A, Ladner D, Schulte-Körne G (November 2003). "Developmental dyslexia in different languages: language-specific or universal?". J Exp Child Psychol 86 (3): 169–93. doi:10.1016/S0022-0965(03)00139-5. PMID 14559203.
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