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What is Dyslexia?

One of the most common learning disabilities is dyslexia. The word "dyslexia" was first used in 1895 to describe a child with normal intelligence who exhibited difficulty in learning to read. It comes from the Greek meaning "difficulty with words or language."

Dyslexia is believed to have a biological basis, caused by an unusual organization of certain neuronal connections or brain cells, the details of which are under active investigation.

Individuals with dyslexia may have problems in reading, spelling, speaking, listening or writing. These individuals show lower achievement on reading and reading related measures than would be expected given their overall intellectual aptitude. Dyslexia seems to run in families and it is now thought to have a genetic basis. Approximately 4 - 15% of the population may be affected by dyslexia.

Children with dyslexia learn differently. With appropriate intervention, they can perform well in a regular classroom.

Samuel Orton (1879-1948), was a clinician and researcher and was among the first to identify the syndrome of dyslexia and to offer a physiological explanation for its cause. Although the behavioral manifestations of developmental dyslexia have long been known, its neurobiological foundations are still poorly understood. Until recently, many researchers have considered the core deficit in dyslexia to involve dysfunction of language mechanisms, while others have emphasized the possible role of failure of sensory processing mechanisms.

Recent advances in functional neuroimaging techniques provide a way to identify the regional specialization and spatial congruence of the cortical areas engaged in low-level sensory and language processing. These techniques make possible novel investigations of the pathophysiology of the reading disorder developmental dyslexia.

The International Dyslexia Association / NICHD Research Definition of Dyslexia, 2002

Dyslexia is a specific learning disability that is neurological in origin. It is characterized by difficulties with accurate and / or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.

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