Dyslexia: What Brain Research Reveals About Reading
Making a difference today
A staggering 5 to 15 percent of Americans'14.5 to 43.5 million childrenand adults'have dyslexia, a learning disability that makes it difficult toread, write, and spell, no matter how hard the person tries or how intelligenthe or she is. For years'until advances in neuroscience helped reveal a biologicalbasis for the disorder'people with dyslexia were called "dumb" or"lazy." We now know such labels to be cruelly inappropriate. People withdyslexia can be just as bright and motivated as their nondyslexic peers. Theyalso can be found in all economic and ethnic groups.
In a world where reading and writing skills are in increasing demand, theimpact of dyslexia on individuals'and on U.S. society'can be devastating.About 80 percent of learning disabled children eligible for special educationservices have significant reading difficulties, including dyslexia. According tothe National Center for Education Statistics, the high school dropout ratefor students with learning disabilities is more than twice what it is for otherstudents (36 percent compared with 14 percent). One study is currentlytracing individuals from age 5 to their late 20s and will look at the costs ofdyslexia to society as a whole, especially in terms of intervention costs andemployment opportunities.
Research brings greater understanding
During the last two decades, scientists have come to learn that the nature ofdyslexia is very complex. The difficulties observed in reading arise from acore deficit in phonological awareness, a skill that is needed to associate spokenwords with written language. Dyslexics have difficulty sounding outwords as well. Approximately 80 percent of children who have delayed languagedevelopment go on to have reading, writing, and spelling deficits.Research studies also have identified differences in the processing of visualand auditory information in dyslexic readers.
Our understanding of dyslexia exploded in the 1990s after the availability offunctional brain imaging, a technology that allows scientists to observe thebrain at work as a person reads, speaks, or processes phonological features oflanguage. While watching brain images of volunteers as they attempted totranscribe letters into sounds, NIH-funded scientists found conclusive evidencethat the areas in the brain that process written language work differentlyin people with dyslexia. Scientists are now isolating and mapping themany "reading pathways" in the brain involved in dyslexia. The identificationof these pathways may lead to earlier and more effective interventions.Researchers also have uncovered evidence that specific regions of the humangenome are involved in a number of reading-related processes within thebrain. Such findings help to explain why dyslexia tends to run in families.Similarly, family genetic studies show a high concordance between oral andwritten language disorders in affected family members.
Earlier and better interventions
Early intervention is key to helping people with dyslexia learn to read andwrite well. Studies have shown that 74 percent of children who displayreading problems in the third grade will remain poor readers into adulthoodunless they receive special instruction on reading and phonological awareness.Many intervention methods are currently in use, and more studies needto be done to determine which interventions work best. With NIH funding,researchers are examining which methods might help the millions ofAmericans struggling with dyslexia and are using brain imaging technologyto discover the biological mechanisms by which reading gains are achieved.
- A better understanding of the biological and genetic nature of dyslexia.
- Earlier diagnosis of dyslexia and prevention of reading disabilities.
- More effective and precisely targeted intervention treatments.
Making a difference tomorrow
During the past two decades, scientists have made remarkable advances inunderstanding the biological and genetic nature of dyslexia. They have alsogained greater knowledge about the impact of environmental factors'particularlyhow children are taught to read'on the disorder. But myths and misunderstandingsabout dyslexia persist, causing many children'and adults'with this disability to remain undiagnosed and untreated, often with devastatingresults.
- As many as 43.5 million Americans may have dyslexia. Dyslexiaoccurs among people of all economic and ethnic backgrounds.
- About 3.5 percent of American students'slightly more than 2 millionchildren'are receiving special educational services for a readingdisorder.
- Dyslexia is the most common cause of reading, writing, and spellingdifficulties.
- Youth with untreated dyslexia are more likely than their nondyslexicpeers to drop out of high school and become unemployed,underemployed, or incarcerated.
Research equals hope for the future
Now that scientists have established that people with dyslexia have a glitchin their neurological wiring that makes reading extremely difficult for them,they are actively searching for a deeper understanding of how that wiringbecomes disrupted. One line of study is looking at whether immune proteinsin the brain may somehow cause the wiring to go awry. Researchers will alsoneed to examine the role of hormones and neurotransmitters (chemicals thattransport messages between nerve cells) in studies of the reading brain. Inaddition, genetic research into dyslexia continues at an exciting pace.Scientists already have found gene markers for dyslexia on several chromosomes.Knowledge of the genetic and possible biochemical causes of dyslexia willhelp experts more accurately diagnose'and treat'at-risk children.Using brain imaging technologies, researchers also hope to scientificallydetermine which types of reading methods and interventions are most effectivein helping dyslexic children. Some studies suggest that certain types ofintensive reading instruction, if offered early enough, may actually rewire thebrain, causing the neurological factors that trigger dyslexia to be amelioratedor circumvented.
Hope for other disorders
Research into dyslexia could help solve many other neurological puzzles.Studies estimate that between 20 and 40 percent of people with dyslexia alsohave attention deficit/hyperactivity disorder (ADHD). Some dyslexics alsosuffer from poor math skills. Research tools available to neuroscientists studyingdyslexia and its related conditions may also help explain neurodegenerativediseases such as Parkinson's disease and multiple sclerosis. In addition,recent studies demonstrate that scientifically based reading interventions areable to rewire the dyslexic brain, giving scientists valuable insights into howto develop treatments to help the brain relearn tasks after a stroke or otherbrain injury.
Dyslexia is a lifelong reading disorder that can have a disastrous impact on aperson's self-image and ability to live up to his or her potential. With continuedNIH funding for basic and clinical research, the future could bring moreeffective methods of diagnosing and treating dyslexia'and thus hope to millionsof Americans who struggle daily with this disabling learning disorder.
- The discovery of a biological basis for dyslexia.
- The ability of scientists to identify with a high degree of accuracy those childrenwho have dyslexia.
- The development of specialtherapies that can helppeople with dyslexia overcomesome of their readingand writing difficulties.