Posts Tagged ‘Brain mapping; complex phenotypes; developmental dyslexia; environment; genetics; reading ability and disability’
he science of reading and developmental dyslexia has experienced spectacular advances during the last few years. Five aspects of this research are discussed in the article. (1) The holistic phenomenon of reading is complex. Many lower-level psychological processes (e.g., phonemic awareness, phonological decoding, ability to process stimuli rapidly and automatize this process, memory, ability to recognize words) contribute to a single act of reading. Conceptualizing the complex process of reading through its partly overlapping but partly independent components—which contribute to, but do not fully explain, the holistic process of reading—provides an excellent model for understanding complex hierarchies of higher mental functions.
Those who master reading skills successfully and those who have difficulties doing so differ in a wide range of reading-related processes. The central deficit experienced by poor readers appears to be related to phonological processing (a complex hierarchy of functions related to processing phonemes), whereas characteristics of automatization processes seem to moderate the reading outcome for people whose phonological skills are weak. (2) There are new data addressing models of dyslexia in languages other than English. The most fascinating finding is that the model implicating phonological deficit as central to dyslexia, and the lack of ability to automatize as leading to troubled reading, appears to be universal, regardless of the specific language.
However, there is an interaction effect between the characteristics of a particular language and the developmental model of dyslexia. In phonologically more difficult languages (e.g., English), the most pronounced weakness appears to occur in phonological processing, whereas in phonologically easier languages (e.g., German), the crucial role in the manifestation of dyslexia is played by the lack of the skills needed to achieve automatization. (3) There is abundant evidence that reading (i.e., any single act of reading as well as reading as a holistic process) is “cooked” by the brain. Although no unified brain map of reading has been developed, some specific areas of the brain have been implicated in different reading-related cognitive processes by different laboratories and on different samples. (4) Indisputable evidence has been accumulated suggesting the involvement of the genome in developmental dyslexia. As of now, specific regions of the genome have been identified as being intimately involved with a number of different reading-related processes.
Today the field of developmental dyslexia is the only area of genetic studies of human abilities and disabilities in which linkages to the genome have been robustly replicated in independent laboratories. (5) Finally, evidence suggests that developmental dyslexia might be only one of the manifestations of a deep, underlying, anatomical syndrome. The comorbidity of developmental dyslexia with both internalizing and externalizing behavioral disturbances, as well as with other learning disabilities, underscores the need for wide-ranging cognitive and behavioral approaches in the remediation programs offered to dyslexic children.
Developmental reading disorder, also called dyslexia, is a reading disability that occurs when the brain does not properly recognize and process certain symbols.
Causes, incidence, and risk factors
Developmental reading disorder (DRD), or dyslexia, occurs when there is a problem in areas of the brain that help interpret language. It is not caused by vision problems. The disorder is a specific information processing problem that does not interfere with one’s ability to think or to understand complex ideas. Most people with DRD have normal intelligence, and many have above-average intelligence.
DRD may appear in combination with developmental writing disorder and developmental arithmetic disorder. All of these involve using symbols to convey information. These conditions may appear alone or in any combination.
DRD often runs in families.
Symptoms
A person with DRD may have trouble rhyming and separating sounds that make up spoken words. These abilities appear to be critical in the process of learning to read. A child’s initial reading skills are based on word recognition, which involves being able to separate out the sounds in words and match them with letters and groups of letters.
Because people with DRD have difficulty connecting the sounds of language to the letters of words, they may have difficulty understanding sentences.
True dyslexia is much broader than simply confusing or transposing letters, for example mistaking ”b” and “d.”.
In general, symptoms of DRD may include:
- Difficulty determining the meaning (idea content) of a simple sentence
- Difficulty learning to recognize written words
- Difficulty rhyming
DRD may occur in combination with writing or math learning problems.
Signs and tests
Other causes of learning disability and, in particular, reading disability, must be ruled out before a diagnosis of DRD can be made. Emotional disorders, mental retardation, diseases of the brain, and certain cultural and education factors can cause learning disabilities.
Before diagnosing DRD, the health care provider will:
- Perform a complete medical exam, including a neurological exam
- Ask questions about the person’s developmental, social, and school performance
- Ask if anyone else in the family has had dyslexia
Psychoeducational testing and psychological assessment may be done.
Treatment
Every person with DRD requires a different strategy. An individual education plan should be created for each child with the condition.
The following may be recommended:
- Extra learning assistance, called remedial instruction
- Private, individual tutoring
- Special day classes
Positive reinforcement is important as many students with learning disabilities have poor self-esteem. Psychological counseling may be helpful.
Expectations (prognosis)
Specialized help (called remedial instruction) can lead to marked improvement in reading and understanding.
Reading difficulties may persist for life.
Complications
DRD may lead to:
- Problems in school, including behavior problems
- Loss of self-esteem
- Reading problems that persist into adulthood, which may affect job performance, particularly if the problem was not addressed early in life
Calling your health care provider
Call your health care provider if your child appears to be having trouble learning to read.
Prevention
Learning disorders, such as DRD, tend to run in families. Affected families should make every effort to recognize existing problems early.
Early intervention will provide the best possible outcome.
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Review Date: 12/10/2010.
Reviewed by: John Goldenring, MD, MPH, JD, Pediatrics, Sharp Rees-Stealy Medical Group, San Diego, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.