Comparing and Contrasting the Phonological and Cerebellar Theories of Dyslexia

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Comparing and Contrasting the Phonological and Cerebellar Theories of Dyslexia

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By definition, developmental dyslexia is a "discrepancy between the reading ability and intelligence in children receiving adequate reading tuition" (Ramus et al, 2002). There has been substantial empirical evidence lending support to genetic causes of the condition. It is characterized as chronic, with deficiencies in reading being only one of the symptoms. While there has been progress in dyslexia research, there is still contention on the genetic and cognitive roots of dyslexia (Ramus et al, 2002). There is marked contention on the origins of dyslexia among psychologists. The distinguishing traits of the condition include reading and writing difficulties. It is surmised that it spawns from sensory dysfunctions, and these have been thoroughly backed up by empirical research. However, the definitive cause of the condition is yet to be determined (Coleman, 2002). The disorder has frequently been hypothesized to be the result of various sensory malfunctions.

This essay aims to compare the two theories of dyslexia at the biological, cognitive and behavioral levels.
In addition, at the cognitive level, the phonological deficit theory represents the condition as a deficiency in the coding of data.
Simos et al (2002) has utilized magnetoencephalography (MEG) to examine 10 pediatric dyslexics and 8 control subjects on a visual reading task
Still on the biological aspect of the magnocellular theory, Nicolson, Fawcett, & Dean (2001) have found that the issues confronting pediatric dyslexics are not constrained only to reading and spelling difficulties.
There is also no definitive number as to dyslexics that exhibit motor difficulties, and a number of studies have only found a limited percentage of dyslexics who have exhibited such difficulties
The lack of agreement on the core features of dyslexia may be one reason for the difficulty in defining inclusion criteria for research and its current variability.

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[...] Ramus, F. (2001). Talk of two theories. Retrieved on July from http://cogprints.org/1764/00/nature01.html Ramus, F. Rosen, S. Dakin, S., Day, B., Castellote, J., & White, S.(2002). Theories of developmental dyslexia: insights from a multiple case study of dyslexic adults. Shaywitz, S. & Shaywitz, B. (2001). The neurobiology of reading and dyslexia. Focus on the Basics A. Retrieved on July from http://www.ncsall.net/?id=278 Simos, P.G., Fletcher, J.M., Bergman, E., et al. (2002). Dyslexia-specific brain activation profile becomes normal following successful remedial training. Neurology [...]

[...] Critique of the Two Theories One of the weaknesses of the phonological theory is its failure to explain the rationale behind the sensory and motor difficulties among those afflicted with the condition. Those who advocate the phonological theory reason out that these facets are not central to dyslexia (Ramus et al, 2002; Snowling, 2001). On the other hand, the cerebellar theory has its own share of criticisms, including its inability to explain sensory difficulties; however, its advocates are considering the possibility of different cerebellar and magnocellular dyslexia subtypes (Fawcett and Nicolson, 2001). [...]

[...] Liberman, A. & Mattingly, J. (1985). The motor theory of speech perception revised. Cognition 1-36. Nicolson, R. et al. (1999) Motor learning difficulties and abnormal cerebellar activation in dyslexic adults. Lancet 43–7. Nicolson, R., Fawcett, A., & Dean, P. (2001). Developmental dyslexia: the cerebellar deficit hypothesis. Trends in Neurosciences 508-511. Nicolson, R.I. & Fawcett, A. (1999). Developmental dyslexia: The role of the cerebellum. Dyslexia, vol no Paulesu, E., Frith, U. et al (1996). Developmental dyslexia: a disconnection syndrome? Brain 143-157. [...]

[...] That is, in contrast with the cerebellar theory that has auditory and visual deficits as requisites to dyslexia, the study points out that the presence of a phonological deficit alone defines the condition. The presence of auditory deficits only worsens the condition, but are not necessarily required for having dyslexia. These deficits result in “literacy impairments.” Moreover, the study did not reinforce that motor deficiencies are rooted on the cerebellum (Ramus et al, 2002). At the biological and cognitive levels, the phonological deficit theory asserts that those afflicted with dyslexia are deficient in the “representation, storage, and retrieval of speech sounds.” (Ramus et al, 2002). [...]

[...] Annals of the New York Academy of Science 70–82. Georgiewa, P., Rzannyb, R., Gaserc, C., Gerharda, U., Viewega, U., Freesmeyera, D. et al (2002). Phonological processing in dyslexic children: a study combining functional imaging and event related potentials. Sciencedirect. Grigorenko, E.L., Wood, F.B., Meyer, M.S., & Pauls, D.L. (2000). Chromosome 6p influences on different dyslexia-related cognitive processes: further confirmation. American Journal of Human Genetics 715–23 Knopik, V.S., Smith, S.D., Cardon, L., et al. (2002). Differential genetic etiology of reading component processes as a function of IQ. [...]

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