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Dyslexia and the Brain: What Does Current Research Tell Us?

By: Roxanne F. Hudson, Leslie High, and Stephanie Al Otaiba

The identification of a child with dyslexia is a difficult process, but there are ways that parents and teachers can learn more about the reading difficulty and support the child’s learning.

Almost every teacher in the United States has at least one student who could fit the same description written so many years ago. This situation leads many school personnel to wonder why their articulate, clearly bright student has so many problems with what appears to be a simple task – reading a text that everyone else seems to easily comprehend.

What is dyslexia?

Dyslexia is an often-misunderstood, confusing term for reading problems. The word dyslexia is made up of two different parts: dys meaning not or difficult, and lexia meaning words, reading, or language. So quite literally, dyslexia means difficulty with words (Catts & Kamhi, 2005).

Despite the many confusions and misunderstandings, the term dyslexia is commonly used by medical personnel, researchers, and clinicians. One of the most common misunderstandings about this condition is that dyslexia is a problem of letter or word reversals (b/d, was/saw) or of letters, words, or sentences “dancing around” on the page (Rayner, Foorman, Perfetti, Pesetsky, & Seidenberg, 2001).

Dyslexia is a specific learning disability in reading that often affects spelling as well. In fact, reading disability is the most widely known and most carefully studied of the learning disabilities, affecting 80% of all those designated as learning disabled. Because of this, we will use the terms dyslexia and reading disabilities (RD) interchangeably in this article to describe the students of interest.

It is neurobiological in origin, meaning that the problem is located physically in the brain. Dyslexia is not caused by poverty, developmental delay, speech or hearing impairments, or learning a second language, although those conditions may put a child more at risk for developing a reading disability (Snow, Burns, & Griffin, 1998).

Children with dyslexia will often show two obvious difficulties when asked to read text at their grade level. First, they will not be able to read as many of the words in a text by sight as average readers. There will be many words on which they stumble, guess at, or attempt to “sound out.” This is the problem with “fluent word recognition” identified in the previous definition.

Second, they will often show decoding difficulties, meaning that their attempts to identify words they do not know will produce many errors. They will not be very accurate in using letter-sound relationships in combination with context to identify unknown words.

Studies of structural differences in the brains of people of all ages show differences between people with and without reading disabilities.

The brain is chiefly made up of two types of material: gray matter and white matter. Gray matter is what we see when we look at a brain and is mostly composed of nerve cells. Its primary function is processing information.

White matter is found within the deeper parts of the brain, and is composed of connective fibers covered in myelin, the coating designed to facilitate communication between nerves. White matter is primarily responsible for information transfer around the brain.

Booth and Burman (2001) found that people with dyslexia have less gray matter in the left parietotemporal area (Area A in Figure 2) than nondyslexic individuals. Having less gray matter in this region of the brain could lead to problems processing the sound structure of language (phonological awareness).

Many people with dyslexia also have less white matter in this same area than average readers, which is important because more white matter is correlated with increased reading skill (Deutsch, Dougherty, Bammer, Siok, Gabrieli, & Wandell, 2005). Having less white matter could lessen the ability or efficiency of the regions of the brain to communicate with one another.

Can dyslexia be cured?

In a word, no. Dyslexia is a lifelong condition that affects people into old age. However, that does not mean that instruction cannot remediate some of the difficulties people with dyslexia have with written language. A large body of evidence shows what types of instruction struggling readers need to be successful (e.g., National Institute of Child Health and Human Development, 2000; Snow et al., 1998; Torgesen, 2000).