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Learning Disabilities

The term learning disability is commonly used to describe individuals who experience difficulties in learning. In 2014 -15, the number of children and youth ages 3 -21 receiving special education services was 6.6 million, or 13% of all U. S. public school students. Specific terms are used for different types of learning disabilities. Dyslexia is a language-based disability affecting reading, writing, and spelling skills. A disability affecting handwriting skills is termed dysgraphia. Dyscalculia is a disability affecting math concepts and problem-solving skills.

Terms used for different types of learning disabilities seem distinct, but individuals can have more than one type of learning disability. Researchers have reported that high co-occurrence rates are due to sharing a common disability base; co-occurrence of dyslexia and dysgraphia is related to their common underlying language base. Learning disabilities also can co-occur with other problems that interfere with learning, such as attention-deficit/hyperactivity disorder, autism, and visual and auditory processing disorders. Estimates of the co-occurrence rate of dyslexia and attention-deficit/hyperactivity disorder are as high as 46%.

Learning disabilities are not due to level of intelligence and motivation. Children can have learning disabilities despite exposure to adequate instruction. Learning disabilities are not outgrown. Indeed, learning disabilities are lifelong disabilities that can be identified in early childhood. However, children and adults with learning disabilities can benefit from effective instructional practices, inclusive as well as individualized instruction in areas of learning needs and from changes in intervention approaches in response to improvements in skills and maturation.

This entry presents information on the neurological bases for three learning disabilities (dyslexia, dysgraphia, and dyscalculia) and information on how intervention changes neurological functioning, using reading intervention as an example.

The Basis of Learning Disabilities

Learning disabilities are neurological disorders in which the brain’s information intake, processing, and responding are adversely affected. Advances in techniques by which brain structure and function can be visualized and measured have enabled researchers to study differences and similarities between the brains of individuals with learning disabilities and those without. These techniques include magnetic resonance imaging to obtain pictures of brain structures, functional magnetic resonance imaging of brain activity as measured by blood flow to different brain areas, and electroencephalography and event-related potentials to measure the electrical activity in different brain regions.

Dyslexia

Three core deficits have been identified in individuals with dyslexia: the ability to hear, identify, and manipulate individual sounds within words (termed phonemic awareness); the ability to detect and discriminate different word sounds (phonological processing); and difficulties in accurate and fluent word reading and spelling. These deficits influence reading abilities by affecting the accurate reading of individual words, the fast and expressive reading of words in sentences, and understanding the meaning of what was read. Imaging techniques have been used to identify regions of the brain that are structurally and functionally different in individuals with dyslexia compared to typically developing individuals. Specific areas in the left parietotemporal region and the left occipitotemporal region have been implicated in dyslexia. Brain structure differences in the left parietotemporal region include less gray matter (less brain tissue consisting of nerve cell bodies and dendrites) and less white matter (nerve fibers with myelin coating). Functional differences in brain processing have been found in the left occipitotemporal and left parietotemporal region. It has been argued that because there are functional disruptions in left occipitotemporal areas during the processing of text, the brains of individuals with dyslexia may try to compensate by using right parietotemporal areas, but these areas are less efficient, leading to slow and effortful reading skills.

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