To What Extent Are the Deficits Underlying Developmental Dyslexia Specific to Reading - Coursework Example

To what extent are the deficits underlying developmental dyslexia specific to reading? Developmental dyslexia (DD) or reading disability is a disorder in which a person encounters great difficulty in interpreting written language. It affects children who have otherwise normal intelligence. This research paper aims to review contemporary literature to find out the extent to which the deficits underlying DD could be held specific to reading. Abnormal connectivity patterns in parts of the brain responsible for language functions like the left fusiform gyrus which is related to reading lay foundation for DD. Also, other changes in brain activity have been reported in patients with dyslexia which will be explored in the following discussion. This research paper will attempt to prove with the help of evidence that the deficits underlying DD pertain to reading to a great extent. Evidence suggests that there is a definite connection between motion processing deficits and reading deficits in children suffering from DD. It is important to establish what are the deficits underlying DD first to scrutinize if they are related to reading skills deficits or not. DD has a neurological origin (Eide & Eide, 2011, p. 8; 2010, Nicolson & Fawcett, p. 11). Research implies that the processing of visual motion stimuli suffers damage in DD. It is deficits in this processing of visual stimuli that produce deficits in reading subskills as well (Wilmer et al., 2004, p. 528). This relationship between motion processing deficits and reading subskills deficits forms an area of special importance and requires much more research because “little is known about the mechanisms underlying such associations” (Wilmer et al., 2004, p. 528). Despite many years of research, the extent to which the deficits underlying DD could be considered specific to reading is still not established. However, it is assumed that deficits specific to reading do contribute in dyslexia. The study done by Wilmer et al. (2004) is very interesting because it attempts to accomplish the feat of exploring the mechanisms underlying those associations about which little is currently known. The authors of the study rigorously try to properly characterize the relationship between reading deficits and motion processing deficits. All participants were subjected to a series of motion processing, visual, cognitive, and reading tests. Results of the study prove a definite relationship to exist between motion processing deficits and reading subskills deficits. Furthermore, the study also found that each of each of the motion processing deficit in DD was related to a different type of reading subskills deficit. In DD, people cannot detect motion coherently and this deficit in visual processing “is selectively associated with low accuracy on reading subskills tests” (Wilmer et al., 2004, p. 528). This suggests that deficits underlying DD are specific to reading to a significant extent. Its only that reading deficits are just “not nearly as consistent as phonological deficits” (Ramus et al., cited in Bremner et al., 2012, p. 291). This undermines their status as strong contributors of DD. Research stresses that DD is a kind of neurodevelopmental disorder which is prevalent in every culture (Peterson & Pennington, 2012). It occurs in all social classes “irrespective of intelligence” (Dulac et al., 2013, p. 229). The phonological theory remains the most popular and compelling explanation for DD despite the presence of increasingly clear evidence that phonological variations alone do not cause this disorder. Rather, these variations “interact with other cognitive risk factors at a neurobiological level” (Peterson & Pennington, 2012). Still, phonological deficits form “one central difficulty in dyslexia” (Miller et al., 2003, p. 185). But, it should be remembered that not any one type of deficit underlies DD. This opens the possibility of other deficits playing a part in developing DD. Not only deficits in visual motion processing contribute to DD, rather findings of another research study conducted by Menghini et al. (2010) confirm the hypothesis that “DD is a multifactorial deficit” (Menghini et al., 2010, p. 863). All children in this study were subjected to tests of reading abilities, visual processing, phonological abilities, and other certain functions. The interesting part is that results of the study confirmed problems in dyslexic children “on both phonological and non-phonological tasks” (Menghini et al., 2010, p. 863). This suggests that DD does not only occur due to deficits in visual processing, rather it is a multifactorial disorder and deficits in non-phonological tasks also underlie this grave phenomenon. Another study exploring the neurological basis of DD claims that DD or simply dyslexia is a very popular disorder around the globe affecting many school-age children, but its actual underlying mechanisms are still ambiguous. It is due to mysterious nature of these mechanisms that little is known about the extent to which deficits underlying DD could be considered specific to reading. This is why underlying mechanisms of DD form an area of “intense research endeavor” (Habib, 2000). Several neuropsychological studies have provided logical evidence that the main mechanism leading to occurrence of DD in children is phonological in nature (Aaron, 1989, p. 120). Such is the general consensus (Hayes, 2006, p. 48). Phonological changes in the brain form the most widely accepted explanation for DD around the world (Gazzaniga, 2004, p. 819). It is claimed that learning difficulties in children are predominantly caused by “a basic defect in segmenting and manipulating the phoneme constituents of speech” (Habib, 2000). Another report also identifies that the phonological impairment idea forms “the most likely explanation of the brain basis of dyslexic reading and spelling problems” (Eide & Eide, 2011, p. 23). This is also called “phonological core hypothesis” (Davey & Field, 2014, p. 280). It implies that a variation or a change in the phonological processing system in the brain sets off dyslexia in people. This phonological impairment theory has been favored as the sole explanation for dyslexia for the past three decades by major reading specialists (Eide & Eide, 2011, p. 23). Part of this theory’s popularity can be explained by the fact that a majority of dyslexic patients demonstrate problems with phonological processing. This is why phonological deficits are recognized as the primary underlying mechanism of DD (Marschark & Clark, 2014, p. 208). It is only now that more attention has begun to be paid on deficits specific to reading. However, despite more important role played by phonological mechanisms, DD still remains a multifactorial deficit and always relies on non-phonological mechanisms as well. This means that the significance of reading deficits cannot be denied. Research also claims that this popular idea of poor phonological development forming the main cause of DD has become significantly weaker now (Stein & Kapoula, 2012, p. 158). Research labels reading “a possible contributing factor” for causing impairment of visual mechanisms in brain (Habib, 2000). This suggests that many deficits underlying DD are specific to reading. However, it should also be kept in mind that all theories proposed to date about the neurofunctional defects in dyslexic patients “suffer from notable exceptions, where a given effect is sometimes only present in a minority of subjects, obviously limiting the impact of such observations” (Habib, 2000). If phonological and non-phonological mechanisms are considered two different variables contributing in DD, finding a relationship between them in some studies does not absolutely certify this relationship or association. It does not suggest that these two mechanisms underlying DD are strictly associated or tied which means that “any theory based on such observations must remain hypothetical, explaining, at best, only one part of the reality” (Habib, 2000). But, a majority of dyslexic children are affected by problems which cause difficulties in binocular vision and motion perception. These problems can be considered a consequence of reading impairment validating this argument that deficits underlying DD are specific to reading. After all there is a reason why children with DD around the globe “process visual information more slowly than normal readers” (Habib, 2000). Research implies that another reason why a core deficit underlying DD is difficult to identify is because most studies to date “have focused on higher-level arithmetic processes, typically encountered at school level” (Ferrari & Vuletic, 2010, p. 115). This research pattern has served to obscure the developmental root causes of DD. Results obtained from studies based on a limited number of subjects cannot be generalized to a larger population (Reeves, 2008, p. 34). Such ideas criticize this statement that deficits underlying DD are specific to reading to a large extent. The population or samples studied in some of the research studies which cast vote in favor of the reading deficits arguments have also been criticized and their reliability has been questioned. It is claimed that conclusions regarding association between phonological and non-phonological mechanisms differ because of the possibility of researchers promoting different theories and basing “their observations on more or less different populations” (Habib, 2000). This serves to explain why there is so much confusion regarding underlying mechanisms of DD. This is because there is no general consensus for studies based on DD have been criticized for loosely representing the dyslexic population. We cannot say for sure that deficits underlying DD pertain to reading by a large extent because there is lack of valuable information about the neurobiological bases of language learning disorders like DD. Much research has been done to date in search of the neurofunctional defects in DD, but nothing can be said about association between visual processing and reading subskills deficits for sure yet. Results obtained from one study may apply to a minority of dyslexic subjects which limits the validity. However, this much is held absolutely true that in contrast to deficits specific to reading, phonological disorders play a central role in DD (Habib, 2000). The phonological theory is considered one of the most important discoveries made in the area of mechanisms leading to DD. This discovery has been repeatedly made in different studies. The core deficit is considered phonological in nature which is also held responsible for learning impairments in children. Also, this core deficit has more to do with oral language than with visual perception (Habib, 2000). This also undermines the possibility that deficits underlying DD are specific to reading by a significant extent. But, this fact should not be ignored that DD is not a single-deficit disorder. Rather, DD is multi-dimensional. “it arises from a combination of traits” (Coch et al., 2010, p. 119). A single-deficit phonological theory for DD reigned for many years due to lack of knowledge. Even if phonological deficits rule other underlying mechanisms or deficits causing DD, a single phonological deficit cannot cause DD. “A single phonological deficit is likely not necessary and sufficient to cause the disorder” (Peterson & Pennington, 2012). Clearly, a growing body of evidence is found consistent with a multiple deficit account for DD. Imaging technologies also support this idea that certain changes in brain are a cause of dyslexia. Such changes which cause problems in reading should be seen as underlying mechanisms of DD, rather than a result of it. In fact, some studies have even found that infants born in families at risk for dyslexia demonstrate “aberrant neural response to speech sounds from as early as the first week of life” (Peterson & Pennington, 2012). This claim supports the argument that deficits underlying DD happen to be specific to reading by a large extent. A new research from Stanford in Stanford Report suggests that deficits underlying DD are specific to reading. The researchers took 39 children as their research participants and took their brain scans once a year for three years in a row. Like other studies discussed earlier, children in these study were also subjected to standardized tests regarding cognitive, reading, and language functions. The rate of development was assessed on grounds of the white matter region of the brain which is related to reading functions. Test scores for these children were accurately determined this way. Research also supports this by claiming that DD is characterized by “abnormal white matter development” (Peterson & Pennington, 2012). Because deficits in reading skills contribute to development of DD in children, results of this study emphasize on reading lessons for children. This study also emphasizes on early screening because it can help determine which students are at most risk at an early stage in life. It is this age when brain scans turn out to be most helpful as not many ways of helping students are left by the time they reach elementary school level (Carey, 2012). The kind of reading skills a child has at age 7 tell a lot about what kind of reading skills he/she would have “10 years down the road” (Carey, 2012). This is why early screening via reading lessons should be emphasized indefinitely. Also, neural differences in white matter should not be only considered effects of dyslexia. Rather, research accounting for reading experience in dyslexics confirms that “many observed neural differences reflect causes rather than effects of dyslexia” (Peterson & Pennington, 2012). This serves to support the idea that deficits underlying DD are specific to reading. Another report also confirms the validity of brain scans at a young stage in life. Dyslexia was noticed even in pre-school children when they had their brains scanned as part of a study conducted in the US. Among the 40 pre-school children studied, quite a few had shrinkage in the part of the brain called the arcuate fasciculus. This is the part of the brain which is responsible for processing sounds and language. Children who had shrinkage in this region had lower test scores. The volume of this particular part of the brain has a very strong link with poorer pre-reading test results. An important thing worth mentioning here which was something unknown until this study was conducted is that these brain differences, like shrinkage of some particular part like the arcuate fasciculus, “could be a cause rather than a consequence of dyslexia” (Roberts, 2013). This is a very important thing to remember because it emphasizes on the possibility of reading deficits as important mechanism underlying DD. Disability in reading is otherwise considered a secondary consequence of DD (Eide & Eide, 2011, p. 8). But, this report in contrast suggests that brain differences causing reading deficits could be the cause or underlying mechanism of DD. There is much obscurity surrounding underlying mechanisms of DD and this research report is definitely an accomplishment in itself for removing some of that obscurity. A lot of emphasis is also laid on brain imaging by the study. It is claimed that brain imaging should be credited for giving better results regarding “differences between the brains of people with and without dyslexia” (Roberts, 2013). Concluding, the above discussion regarding mechanisms underlying DD suggests that the phonological variations are considered a core deficit in a majority of studies. This is because these variations are demonstrated by nearly everyone with DD. However, more people now consider reading deficits a cause, rather than a consequence of dyslexia. Such studies attach importance to this possibility that deficits underlying DD could be specific to reading by a large percentage. They stress that instead of considering impairments in reading skills one of the many consequences of DD, they should be considered an important cause or underlying mechanism of DD. 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