The theory that Cerebellar Developmental Delay (CDD) is responsible for the reading and other, related, difficulties typically experienced by dyslexics. Symptoms of Dyslexia spring from "an under-functioning cerebellum, the part of the brain which plays a key role in cognitive skills, concentration, and balance"(Dyslexia treatments). According to the Dore Achievement Center the individualized exercises offered by the center to stimulate and enhance cerebellar function have also resulted, among successfully treated patients, in "improved reading, comprehension, memory, and general mental processing." The DORE Achievement Centers also report a greater degree of self-confidence; higher self-esteem, and a more positive mental attitude and outlook, overall, among the adult dyslexics that the center has successfully treated. Another treatment available for dyslexic adults, through the National Reading Styles Institute, Inc., involves the use of colored overlays:

Nothing cures dyslexia absolutely, but... Colored overlays have made a tremendous difference in the lives of dyslexics. For some people, looking at black letters on white paper causes headaches and eye fatigue, or words may seem to shake, move, or reverse. The correct colored overlay often dramatically reduces visual distortions or discomfort, and improves reading and learning ability.

According to NSRI (2005), colored overlays may help dyslexic adults (and children) with eliminating, or at least lessening: letter or word reversals; eye strain; headaches; problems with tracking words or numbers on a page; problems with copying; difficulties with reading for long periods of time; reading speed slowness, and reading comprehension difficulties.

Additionally, according to the literature, various other theories currently exist about how to best treat and educate dyslexic individuals, both children and adults. Most of these recommend various method(s) of exercising, stimulating, or otherwise strengthening areas of the brain responsible for processing auditory messages. A few others (these mostly for Irlen Syndrome (IS), a condition often co-existing with Dyslexia, in which written letters and symbols appear blurred or otherwise distorted) use eye patches; coloured overlays; specially designed and coloured computer screen backgrounds (EasiReader, 2005), or coloured or tinted glasses or contact lenses.

Additional available descriptive; informational; diagnostic, and academic literature. Much descriptive and diagnostic literature on various aspects of Dyslexia is available online from university; research based, and other websites. Much of that is informational, e.g., articles or links like "What is Dyslexia" or "The Nature of Dyslexia." Other available online information is self-diagnostic, e.g., "How Do I Know If I Have Dyslexia."

Available research findings on Dyslexia include work of top theorists John Stein and Uta Frith. Available articles by Stein, the pioneer of magnocellular theory, and some other magnocellular theorists, include The physiological basis of perceptual confusion in dyslexic children (Steinlab 2005); Neurophysiological bases of Dyslexia (Oxford Dyslexia unit, 2002); To see but not to read; the magnocellular theory of Dyslexia (Stein & Walsh, 1997); Impaired neuronal timing in Developmental Dyslexia -- the magnocellular hypothesis (Stein & Talcott, 1999); and Visual magnocellular impairment in adult developmental dyslexics (Talcott et al., 1998).

Uta Frith, Professor of Cognitive Neuroscience at University College, London, has extensively researched multiple causes of Dyslexia and connections between Dyslexia and other neurobiological disorders, including Autism; Attention Deficit Disorder (ADD), and Asperger's Syndrome. In Paradoxes in the definition of dyslexia (1999), suggests that Dyslexia is a complicated syndrome, springing from an intricate mixture of co-existing biological; cognitive; behavioural, and environmental factors. Therefore, Frith suggests, the syndrome of Dyslexia cannot, nor should it, be pidgeon-holed into one or the other theory, such as magnocellular, cerebellar, double-defict, etc. Rather, the root cause of Dyslexia is more likely to be a combination of those factors, plus environmental factors and other (often elusive) variables. These factors and variables are different in the case of every dyslexic, as well as across languages and cultures. Other, related articles by Frith and others include: Beneath the surface of developmental dyslexia (1985), and Why specific developmental disorders are not specific -- online and developmental effects in autism and dyslexia (Frith & Happe, 1998).

Other articles by Bradford (2005); Frith (1999); Stein (1999); Stein & Walsh (1997); Young (2002); Tallal (1980); Gorman (2003), suggest that among dyslexics, it is currently believed that there is an actual neurobiological difference in the "wiring" of the brain, one that in fact makes auditory-phonetic connections especially difficult to make, thus the (often severe) reading, writing, spelling, and other language learning and retention problems found typically among dyslexics). Within the available literature, it has been currently estimated that approximately one in 10 children is born with Dyslexia (Gorman, 2003). Males with Dyslexia are believed by some...

Other current available research, however, suggests that boys and girls may actually have Dyslexia in more or less equal numbers, but that Dyslexia in boys is more likely to be noticed by teachers, due to boys' typically more boisterous, verbal, or disruptive behaviour in class; Dyslexic girls tend to be quieter and less apt to "act out" as a result of their reading, spelling, and other difficulties, and try to privately compensate for them (Gorman 2003).
Additional articles by Butterworth (2004); Randerson (2001), and Gorman (2003) point out that European nations, including Great Britain; France, and Germany, are just now catching up to the United States in realizing that Dyslexia is indeed a specific neurobiological syndrome that causes learning disabilities, not simply a manifestation of slowness, laziness, or, (perhaps most dangerous, since the child then may not receive help for the condition) a phase of childhood (Gorman, 2003). Moreover, according to another articles ("Dyslexia Poses Bigger Challenge for English Speakers" (2005) and processes of learning to read and write in certain phonetically complex languages (like English), numerous silent letters and words not spelled as they sound (e.g., "island' "colonel"), like English, may actually produce more dyslexic symptoms than other, phonetically simpler, languages, like Italian. Similarly, (Paulescu et al., (1996), suggests that symptoms typical of Dyslexia, i.e., difficulties with reading, writing, spelling, and other uses of (particularly written) language, spring from a combination of biological and cultural factors.

Four Main Theories of Dyslexia

Numerous theories have long co-existed about the root causes of Dyslexia; the four best-known among these are: (1) the phonological deficit theory; (2) the magnocellular theory; (3) the cerebellar theory; and (4) the double deficit theory. Other theories suggest combination causes, including the juxtaposition of, and interplay between, various biological, cognitive, environmental, and other (sometimes shifting) variables (Frith, 1999).

Phonological deficit theory

The phonological deficit theory of Dyslexia is the oldest and most longstanding of the key theories to be found within Dyslexia research. It was pioneered by Pringle-Morgan, who is considered the "father of Dyslexia research," in 1893 (Coleman, 2003). This theory holds that dyslexic readers, due to "phonological deficits" (Coleman, p. 1), have difficulties with "phonemic representation" (Coleman), that is, "mapping sounds into letters in the brain, and with phonemic recall" (pp. 1-2).

In other words, translating auditory sounds (speech) into phonemic representations (the small units of which all written language consists) in order to read the language fluently presents enormous difficulties for individuals with Dyslexia. The phonological deficit theory of Dyslexia is the cornerstone theory, upon which all other, later, theories of Dyslexia causes (e.g., magnocellular; cerebellar; double deficit, and others) have been formulated. This theory was responsible for suggesting that from which all other, more recent, Dyslexia theories derive: that dyslexic individuals have great difficulties with learning to read, and with reading comprehension due to the phonetic nature of language, as opposed to the non-phonetic nature of speech. Learning to speak is a 30,000-year-old evolutionary process. However, reading and writing have only existed for about the last 5,000 years. Therefore, according to some (Frith (1999); Stein, (1999); Gorman (2003);

And under phonological deficit theory in general, there is a "disconnect" between the learning of the speaking, reading, and writing processes of dyslexic, based on phonological deficits. Further, the International Dyslexia Association (2002) concurs, that a glitch indeed exists within the brain wiring of dyslexics, which makes language acquisition and usages, especially as it relates to reading, particularly difficult.

Magnocellular theory

The magnocellular theory of Dyslexia was pioneered by physiologist John Stein at the University of Oxford. Stein, a leading researcher, for over twenty-five years, of the causes and manifestations of Dyslexia, pioneered the theory of magnocellular deficits within the brain as the major cause of Dyslexia, and (by association) Irlen Syndrome (IS) (Professor John Stein, 2005). A fellow of Magdalen College, Stein explains:

I am... interested in the auditory and visual impairments suffered by dyslexic children... responsible for their auditory/phonological and visual/orthographic reading problems. My work... suggests... dyslexic children have impaired auditory and visual temporal processing which explains why they have difficulty acquiring the phonological and orthographic skills required for reading. Understanding these mechanisms has helped to explain why such seemingly bizarre treatments such as occluding one eye, wearing coloured spectacles, playing music into the right ear, and eating fish oils, may help some dyslexic children to overcome their problems.

Magnocellular theory suggests…