Read all about it: kids take different neural paths to reach print mastery.
Ethan's romance with print blossomed with trine. At age 1, he scrutinized each license plate in the supermarket parking lot. At 2 1/2, he placed letter-emblazoned blocks in alphabetic order and corrected his mother, by moving her hand, when she pointed to the wrong line of text while reading to him. However, the boy was 3 before he uttered his first spoken word.
Now nearly 11 years old and attending fourth grade in a public school, Ethan reads words and spells as well as most high school seniors do, although his comprehension of written passages is only average for his age. He's also learning to read Hebrew. Ethan talks to other children awkwardly and has difficulty, maintaining conversations.
Scientists refer to Ethan's unusual condition, which afflicts roughly 1 in 5,000 people, as hyperlexia. Initially described in 1967, hyperlexia combines autismlike speech and social problems with a jump-start on reading. As the first precocious reader of this kind to submit to a brain-imaging analysis, Ethan stands at the forefront of scientific efforts to understand how the brain underwrites reading. In a report last year, a team at Georgetown University Medical Center in Washington, D.C., outlined the neural structures that foster Ethan's advanced grasp of printed words.
Since then, these and other researchers have accumulated evidence on neural regions that contribute to skilled reading of both Western-style alphabetic text and non-alphabetic systems, such as Chinese writing. These findings are beginning to show how learning to read triggers certain universal brain accommodations, no matter what the language. At the same time, other brain responses critical for effective reading vary with the nature of one's writing system.
Increased understanding of the neural building blocks of successful reading may inspire improved forms of reading instruction. For now, brain research on Ethan and normal readers underscores the resilience and adaptability of each person's brain, so that there's more than one way to become a good reader, says G. Reid Lyon of the National Institute of Child Health and Human Development in Bethesda, Md.
SKILLED BRAINS When Ethan piqued the interest of Georgetown's Guinevere Eden, her team had already made headway in identifying how the brain develops in healthy kids who read well. Like professional musicians, Eden says, good readers learn a complex skill through nearly lifelong practice. At some point, playing musical notes or reading script becomes effortless, injecting newfound joy into the enterprise.
The brain makes accommodations to achieve such expertise. For instance, one research team has reported that in brain areas devoted to seeing, hearing, and coordinating muscle movements, professional musicians possess more neurons than either amateur musicians or nonmusicians do.
Reading invokes activity in a unique set of brain regions, according to Eden's group. The team used functional magnetic resonance imaging (fMRI) to measure the rate of blood flow, a marker of cell activity, in the brains of 41 young people, ages 6 to 22, who read well for their ages.
Reading skill in these people displayed a critical link to activity in a brain region known as the superior temporal cortex, which is located above the left ear. Rapid word reading ignited neural responses in this area for study participants of all ages.
In the fMRI test, each participant used handheld buttons to indicate whether a word briefly flashed on a computer screen contained a tall letter or not. The word sauce, for instance, contains no tall letter, but alarm has the tall letter l. Earlier studies had indicated that volunteers automatically read each word as they searched for tall letters.
The superior temporal cortex brokers an essential element of reading alphabetic text, Eden proposes. It assists in matching appropriate sounds to printed letters, so that words can be sounded out. "One could envision this area as a dial that predicts a child's aptitude for reading," she remarks.
At 9 years old, Ethan exhibited unusually intense activity in this brain region, even when compared with older children who read as well as he did.
Word reading also galvanizes two related parts of the frontal left brain, but only in experienced readers, Eden's team finds. Adults who performed particularly well on two phonies-related tests--using different-colored blocks to represent specific speech sounds and naming printed letters as fast as possible--exhibited the most activity in these neural locales while reading words.
In these frontal regions, Ethan displayed activity similar to that of adults. Eden suggests that these frontal-brain responses reflect an experienced reader's accumulated knowledge of spelling regularities and of the many exceptions to those rules.
Conversely, in budding readers, word reading evokes strong activity in right brain areas, at least for a few years. These regions, which exhibit much weaker activity in adult readers, were previously implicated in identifying objects by sight. Children often use visual patterns and cues in the early stages of learning to read, as in recognizing dog as a small word with a tail on its last letter, just as a real-life dog sports a tail on its end.
Intriguingly, Ethan displayed more such right brain activity than did the older volunteers who read at his level or children of his age who read at their age-appropriate levels. Right brain mechanisms may contribute to Ethan's intense focus on words, Eden says.
WORD HUB Neither Ethan nor the other good readers studied by Eden's team exhibited much activity in a brain area that receives considerable attention from other neuroseientists who study reading. Some argue that this small structure, situated at the back and bottom of the left brain, gradually specializes to recognize words instantly. Others suspect that this clump of tissue aids recognition of all sorts of objects, not just printed words.
Activity rises in this brain structure, called the left fusiform gyrus, as children become better readers, according to a group led by Sally Shaywitz and Bennett Shaywitz, both of Yale University School of Medicine. The team's findings suggest that the area specializes in identifying frequently encountered printed words, proposes Bruce D. MeCandliss of Weill Medical College of Cornell University in New York City.
Cathy J. Price of University College London disagrees. People who suffer damage to the left fusiform gyrus experience difficulties in naming pictures of objects as well as in reading, she argues. Recent evidence suggests that this brain structure contributes to the identification of any item in the center of one's visual field, which includes a word being read, Price says.
This area was inactive in Eden's fMRI studies of young readers. However, her simple tests may not have called upon it. Conscious consideration of a word's spelling or pronunciation may rev up the left fusiform gyrus.
That and several other left brain areas respond to spelling and rhyming tasks with increasing vigor as good readers get older, according to James R. Booth of Northwestern University in Evanston, Ill. In the August 2004 Journal of Cognitive Neuroscience, he and his coworkers reported results of an fMRI study of 15 kids, ages 9 to 12, and 15 adults, ages 20 to 35.
In one series of trials, volunteers alternately read or listened to two words, such as hold and plant, and then indicated which word resembled the spelling of a third word, such as cold. In other tasks, participants read or heard two words, such as myth and home, and determined which one rhymed with a third word, such as foam.
Both the spelling task and the rhyming task evoked left fusiform gyrus activity in adults and children, Booth says. However, only adults exhibited strong responses in another left-brain structure, the angular gyrus. This tissue may foster experienced readers' ability to ladle out a stream of words from a stew of spelling regularities and exceptions, Booth proposes.
CHINESE UNIVERSALS Just as the precocious Ethan offers an intriguing perspective on the brain's role in reading, so does a huge group of print consumers that has received surprisingly little scientific attention--the Chinese.
Recent investigations of Chinese readers suggest that people everywhere invoke core neural responses in order to read, but other types of brain activity are necessary to attain mastery of alphabetic or non-alphabetic writing systems, psycholinguist Charles A. Perfetti of the University of Pittsburgh explained last February in Washington, D.C., at the annual meeting of the American Association for the Advancement of Science.
Many investigators have assumed that, unlike alphabetic systems, written Chinese employs drawings that symbolize whole words.
Even if that were the ease with ancient Chinese pictographic symbols, those characters have transformed into much more abstract shapes that induce sounds of spoken syllables in modern readers' minds, Perfetti says. Chinese characters thus represent bigger chunks of spoken words than alphabetic letters do.
"All writing systems represent spoken language, but they have different design principles," Perfetti asserts.
Consider Mandarin Chinese. It currently includes 420 syllables. These syllables correspond to nearly 4,600 written characters, so an average of about 11 characters share a single pronunciation, which can be modified by using any of four tones.
In spoken Chinese, the meaning of the many different words that sound alike becomes apparent only in the context of conversation. People listening to English sometimes discern word meanings in this way--consider the words guise and guys--but need to do so much less often than Chinese listeners do.
Many Mandarin Chinese words consist of only one syllable, Perfetti adds. That has encouraged the false impression, at least among Westerners, that the language's written characters represent only words, he says.
Experiments show that Mandarin Chinese characters correspond to spoken Chinese rather than to the idea that the word represents, Perfetti says. For instance, if shown the written character for the word red printed in blue ink, volunteers name the ink color more slowly than if the same character is printed in red ink. Analogous results have been noted among English readers, whose writing system inarguably represents spoken sounds.
Response times for Chinese readers turn almost as sluggish if a different character with same pronunciation and tone as red, such as the character for flood, appears in blue ink. This effect indicates that written characters correspond to sounds in spoken Chinese, not to specific words. The pronunciation of flood calls to mind red and slows naming of the clashing ink color, Perfetti says. If the characters represented specific words, instead of sounds, this delay would not occur.
A smaller but still notable slowdown occurs when a character with the same pronunciation as red but a different vocal tone, such as character for boom, appears in blue ink. Again, the common pronunciation calls to mind red, causing readers to take a little longer to identify the different ink color.
Studies of blood flow and electric responses indicate that Chinese readers activate many of the same left brain areas that English readers do, Perfetti adds. Right brain regions involved in vision also contribute to reading Chinese but not to reading English. This finding is consistent with the possibility that learning to read Chinese stimulates spatial perception (SN: 2/12/05, p. 99).
Such results suggest that different neural disruptions may underlie severe problems in reading, depending on the writing system. For example, despite sharing some facets of disturbed brain function, kids with dyslexia in China and the United States display low activity in different parts of the frontal brain (SN: 9/4/04, p. 148). "The brain basis of dyslexia might not be universal," Perfetti says.
The neural roots of hyperlexia may also vary from one writing system to another. Someday, Ethan may pick up a magazine and read about how his brain compares with that of a precocious reader living halfway around the world.
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|Article Type:||Cover Story|
|Date:||Apr 30, 2005|
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