More evidence shows that children's brains with dyslexia respond abnormally to language stimuli

October 26, 2003

WASHINGTON -- Researchers have additional evidence that reading problems are linked to abnormal sound processing, thanks to high-precision pictures of the brain at work. In a recent study, when children without reading problems tried to distinguish between similar spoken syllables, speech areas in the left brain worked much harder than corresponding areas in the right brain, whose function is still unknown. But when children with dyslexia made the same attempt, those right-brain areas actually worked harder, going into overdrive after a brief delay. These findings appear in the October issue of Neuropsychology, which is published by the American Psychological Association (APA).

Psychologists at The University of Texas Health Science Center at Houston targeted the suspect brain areas by isolating speech-processing sites from sites involved with other aspects of language, such as memory and meaning. As a result, they believe their research contributes to the identification of a central marker of the deficit that makes it hard for people with dyslexia to process similar but different sounds -- in both spoken and written form. The results parallel prior evidence gathered by the Houston team that brains of children with dyslexia also respond abnormally during reading.

The researchers studied the brain activity of 12 children with and 11 children without dyslexia during a simple speech perception task. The children were eight to 12 years old. Magnetoencephalography (MEG), a non-invasive, high-resolution form of functional imaging, highlighted precise activity in participants' left and right temporoparietal (TP) language areas while the children discriminated between spoken pairs of syllables, such as /ga/ and /ka/. This kind of task, known as phonological processing, is fundamental to acquiring reading skill. The temporoparietal areas are on the surface in the back of the brain.

While distinguishing between sounds, the non-impaired readers showed more relative activity in the speech part of the left TP area. During the same task, after a slight delay, impaired readers showed a sharp peak of relative activation in corresponding (but functionally mysterious) areas on the right side. The poorer the child's performance in phonological processing, the more their right brains "lit up" during that task.

The results, says co-author Joshua Breier, Ph.D., suggest that children with dyslexia "may lack the predominant involvement of left-hemisphere auditory association cortices" shown by children and adults without reading problems.

Dyslexia may affect up to 17 percent of the school-age population and can continue into adulthood. Reading experts have long suspected that many reading problems, especially in decoding letter sounds, are rooted in the brain and have more to do with sound than sight. Brain imaging studies have confirmed that suspicion and helped to put to rest any notion that dyslexia, although it can make a child feel "stupid" and be a problem in school, reflects visual problems or a lower overall intelligence.

"The neurological deficit appears to be specific to very restricted areas of the brain," says Breier, "and can occur in children with a wide range of general intellectual function."

Such findings are helping to shape national education policy. In fact, co-author Jack Fletcher, Ph.D., points out that most states, following federal guidelines, have for decades used a discrepancy between IQ and reading tests to determine eligibility for special education in the learning disability category, which accounts for more than half of all students in special education. However, several national bodies have, in the past year, proposed allowing states to use alternative means of establishing eligibility. Legislation is in progress. Breier explains that given the research, "The use of IQ in reading disability definitions, at least for these children, is not appropriate." Adds Fletcher, "It's poor reading that's important."

And, poor reading can improve. "The present study shows that reliable brain correlates can be identified in individual children," Breier points out. Given that effective teaching changes brain activation patterns, he says, "the brain in people with reading difficulties is responsive to intense intervention."

Further research will gauge the reliability of the findings, which were established with a participant number typical of a brain-imaging study, using high-precision measurements. In addition, the Houston researchers hope to determine under which treatment conditions MEG brain imaging might be associated with how well a child with dyslexia responds to intervention.
-end-
Article: "Abnormal Activation of Temporoparietal Language Areas During Phonetic Analysis in Children with Dyslexia," by Joshua I. Breier, Ph.D.; Panagiotis G. Simos, Ph.D.; Jack M. Fletcher, Ph.D.; Eduardo M. Castillo, Ph.D.; Wenbo Zhang, Ph.D.; and Andrew C. Papanicolaou, Ph.D.; The University of Texas Health Science Center at Houston; Neuropsychology, Vol. 17, No. 4.

(Full text of the article is available from the APA Public Affairs Office and at http://www.apa.org/releases/dyslexia_article.pdf)

Joshua Breier can be reached in Houston at The Institute for Rehabilitation and Research by email at Joshua.i.breier@uth.tmc.edu or by phone at 713-797-7570. His secretary is Michelle O'Neal.

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 150,000 researchers, educators, clinicians, consultants and students. Through its divisions in 53 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

American Psychological Association

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.