History of dyslexia research
[7][8] 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.
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.
This led Morgan to conclude the etiology of reading disability to be congenital and attributed it to defective development of the left angular gyrus of the brain.
[9] Additionally, another British physician, CJ Thomas, provided a summary of congenital word blindness based on 100 cases at special schools in England.
Thomas recommended that children with this disability be taught on a one-to-one bases and initially teach the alphabet be accomplished through touch by encouraging the child to handle large wooden letters.
[14] Orton's 1937 book, hinged around the treatment of specific reading disabilities 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.
[18] In 1975, the passage of the Education for All Handicapped Children Act of 1975 (PL 94–142) defined learning disability as a "disorder in one or more of the basic psychological processes involved in understanding or in using spoken or written language, which may manifest itself in an imperfect ability to listen, think, speak, write, spell or to do mathematical calculations.
[23] Understanding these subtypes is useful in diagnosing learning patterns and developing approaches for overcoming visual perception impairments or speech discrimination deficits.
Cestnick and Coltheart (1999) demonstrated what these underlying deficits are in part, through unveiling different profiles of phonological versus surface dyslexics.
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.
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;[33] Demonet et al., 1992; Flowers et al., 1991; Horwitz et al., 1998;[34] Ingvar et al., 1993; Paulesu et al., 1996; Pugh et al., 2000;[35] Rumsey et al., 1997b; Shaywitz et al., 1998).
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;[37] for review, see Eden and Zeffiro, 1998).
[38] 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).
Suggest that dyslexia may be characterized in childhood by disruptions in the neural bases of both phonological and orthographic processes important for reading.
[42] In 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.
Activity in the left-posterior superior temporal sulcus of the youngest readers was associated with the maturation of their phonological processing abilities.
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.
[48] Also in 2008, Wai Ting Siok et al. describe how dyslexia is language dependent, and especially between alphabetic and non-alphabetic writing systems.
