In Dyslexia Study, a Child’s Reading Is Written on Brain

For those who struggle with dyslexia, a reading problem that confounds 1 in every 5 Americans, the written word is a misfire in the mind.

Indeed, a lifetime of reading problems can be traced to a distinctive flaw in the brain that makes the mind strain and stumble over written words. That telltale signature of dyslexia now can be detected reliably in brain scans of children as young as 7, researchers discovered.

In the largest brain imaging study so far of children with reading problems, Yale University researchers determined that the act of reading prompted different patterns of mental effort in children with dyslexia, compared to those who read more easily.

By monitoring so many children while they read, the Yale researchers also were able to see how these growing minds learned to compensate for their own imperfections by relying more heavily on parts of the brain not normally associated with fluent reading.

Their work is the latest study to reveal that reading challenges the brain in subtle and disconcerting ways, all involving a complex network of neural circuits called into action every time the mind encounters a word on the page.

The scans showed that people with dyslexia have a much lower level of activity in areas at the back of the brain thought to be responsible for quickly matching words, sounds and meaning, compared to normal readers.

Moreover, the pattern of activity in neural circuits that handle the written word was the same as previously detected in adults with dyslexia, who have wrestled with the written word for a lifetime.

“We know now that this disruption is not due simply to a lifetime of poor reading because we see it in children as young as age 7,” said Dr. Sally Shaywitz, director of the Yale University Center for Learning and Attention and a co-author of the study published this month in the research journal Biological Psychiatry.

“The disruption is right there from the time they are beginning to read,” she said.

The results are noteworthy, several reading experts said, because they encompass so many children.

The brain imaging technique, called functional magnetic resonance imaging, or fMRI, used by the Yale team, allows researchers to watch the living brain at work without risking a child’s health or well being. It is painless, noninvasive and does not use X-rays, radiation or dyes.

Imaging experiments, however, often rely on a handful of volunteers, making it difficult to consider any finding a definitive diagnosis of any brain function. There can be less to their gaudy patterns of brain activation than meets the eye.

“This is the first study, not just in dyslexia but in any cognitive aspect of the brain, that has used a sample so large,” said Guinevere Eden, director of the Georgetown University Center for the Study of Learning in Washington, who uses brain scanning techniques to study reading disorders.

“It is very solid,” said UCLA neuropsychologist Susan Bookheimer, who studies dyslexia and other reading disorders. “In the past this has been done primarily in adults. This is a nice way of getting at the kids.”

USC psychologist Franklin Manis, who is leading a five-year, $1.8-million study of reading problems and the brain involving several hundred children, called the findings “striking.” They offer confirmation of evidence that reading disorders such as dyslexia, which affect as many as 8 million children ages 4 to 13, are caused by subtle problems in brain cells and synapses, not by any lack of intellectual ability or motivation.

Even so, they do little to dispel the mystery of the cause and effect of the many reading problems gathered together under the single diagnosis of dyslexia, Manis said.

In a real way, dyslexia is less a learning disorder than a symptom of a society increasingly dependent on reading.

“In a world in which print is everywhere, dyslexia becomes a more salient problem,” Manis said.

Nature long ago crafted sophisticated neural networks for the brain to almost instantly understand speech.

But the written word is a wholly artificial creation that relies on parts of the brain designed for other tasks.

“Language comes naturally to us, but reading is a skill we have to learn,” Eden said. “There is no single neural infrastructure for reading.”

Instead, “there are a lot of neural areas that are moonlighting for reading.”

Most people with the disorder have trouble associating written words and letters with the sounds they represent.

Some troubled readers cannot mentally resolve the pattern of the characters of the alphabet fast enough. Others stumble because they cannot properly sound out the phonemes, the sounds that make up words.

Many of those with dyslexia simply cannot process such distinctions fast enough to keep up with the fluent flow of text.

To read well, the brain has only a few thousandths of a second to translate the symbols into sound and meaning. Most children can process such sounds in less than 40 milliseconds, researchers at Rutgers University in New Jersey have shown.

Children who have reading problems may need as much as 500 milliseconds.

But experts at the Cognitive Neurosciences Institute at University College in London argue that dyslexia may be caused by a fundamental difficulty in perceiving speech rhythms.

In research made public last week in the Proceedings of the National Academy of Sciences, cognitive psychologist Usha Goswami and her colleagues found that dyslexic children could not track the beat in speech.

These children were significantly less sensitive than normal readers to rhythmic beats in nonsense sounds.

The ability to keep a beat seemed to follow skilled reading and spelling ability, not only in dyslexic children but also in normal readers and a small group of precocious readers.

Goswami suggested that the ability to adeptly detect a beat matters when the brain is trying to process syllables.

While most researchers concentrate on flaws in brain circuits directly involved in language, some scientists have found evidence that people with dyslexia appear to have flaws in the brain’s visual system that makes it hard for them to track movement.

Stanford University researchers have found other evidence that reading problems are tied to a specific defect in the brain’s white matter, which plays a key role in transmitting information between different brain regions involved in language comprehension.

Genes could also play a role in dyslexia. So could family reading habits. Even the educational system and the nature of the written language can contribute. For example, the reading disorder is twice as prevalent in the U.S. than in Italy, where the written word more consistently matches its spoken word.

In the end, it will take more than evidence of brain imaging alone to understand dyslexia, reading experts said.

“There are a lot of very fundamental questions to which we don’t have the answer: When we see a pattern in the brain, is it a consequence of dyslexia or a cause? Does it tell us the underlying problem or what to do about it?” UCLA’s Bookheimer said. “What we know is that there is an area of the brain that doesn’t light up. We have a lot to learn.”

Eventually, the brain scanning techniques could help detect such reading problems earlier, when teachers could better help overcome the difficulty, perhaps even before a child first picks up an alphabet primer.

Already, they can help researchers better understand which kinds of reading instruction work best.

But the scanning is much too primitive--and the technology still too expensive--to be a tool for screening individual children for the disorder.