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Deconstructing Dyslexia

Adults with dyslexia may have trouble reading because of a dysfunctional connection between language-processing areas of their brains.

By | December 5, 2013

The functional and structural connection (blue arrow) between frontal and temporal language areas of the brain is impaired in individuals with dyslexia.BART BOETSScanning the brains of adults with dyslexia and normal readers, scientists found no differences in phonetic representations—the brain’s interpretations of human speech sounds. Rather, adults with dyslexia may have difficulty processing speech sounds because of a dysfunctional connection between frontal and temporal language areas of the brain that impairs access to otherwise intact phonetic representations.

The findings, published today (December 5) in Science, came as quite a surprise to the research team. “The main aim of the study was to finally objectively demonstrate that the quality of phonetic representations is impaired in individuals with dyslexia,” said Katholieke Universiteit Leuven’s Bart Boets, who led the work. But that’s not at all what they found. “Even while scanning throughout the whole brain for local regions where the representations may be impaired . . . we could not find a single region with inferior phonetic representations in dyslexics as compared to typical readers,” Boets explained in an e-mail.

“This is the first paper that really went head on in trying to answer this question, surprisingly,” child and adolescent psychiatrist Fumiko Hoeft from the University of California, San Francisco, told The Scientist in an e-mail. “If true . . . this has tremendous implications for thinking about the cause of the disorder and also the treatment.”

The team first used functional magnetic resonance imaging (fMRI) and an approach called multi-voxel activity analysis (MVPA) to generate whole-brain visualizations from 23 adults diagnosed with dyslexia and 22 adult controls listening to different speech sounds. Finding similarly intact phonetic representations in both groups, the team considered alternate hypotheses, assessing the structural and functional connectivity in participants’ brains. The researchers found that dyslexic individuals showed decreased connectivity between the superior temporal regions that were found to support intact phonetic representations in the initial analysis and the left inferior frontal regions that are known to be involved in more complex phonological processing.

“There have been different opinions in the field about whether dyslexia has something to do with a broken down signal early on in the auditory system, or whether it’s elsewhere, higher up in the brain area,” said Guinevere Eden, who directs the Center for the Study of Learning at Georgetown University, and was not involved in the work.

Advances in neuroimaging techniques like fMRI have been a boon for the field when it comes to “understanding the brain and behavioral relationships in dyslexia,” Washington University radiologist Todd Richards told The Scientist in an e-mail. Boet’s team, in particular, “has capitalized on the use of the advanced brain imaging techniques,” Richards noted, though he added that there are higher resolution technologies out there that, when used in combination, could help improve “our understanding of phonological processing and its connections.”

“For complex disorders like dyslexia . . . fMRI results have to be seen as part of a broader consensus, alongside other tools such as EEG, MEG, electrophysiology and model systems research,” agreed Mike Tyszka from the Caltech Brain Imaging Center, who was not involved in the work. “So perhaps the greatest challenge is how to integrate all these disparate data into a consistent and rigorously validated picture of brain function.”

Boets and his colleagues suggest that their work could have therapeutic implications. Specifically, the realization that a dysfunctional connection within the brain may be to blame could lead to new strategies for helping people with dyslexia learn to read more fluently. “I think, for instance, about innovative, noninvasive brain stimulation techniques—like paired-associative transcranial magnetic stimulation—that might be used for this aim,” said Boets.

“This paper, by telling us more about at what level in the brain things break down, can help in directing interventions,” Eden said.

B. Boets et al., “Intact but less accessible phonetic representations in adults with dyslexia,” Science, 342: 1251-54, 2013.

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Avatar of: r34498

r34498

Posts: 1

December 6, 2013

Okay, so we know by the end result of reading attempts that dyslexics have some problems with phonetic processing. This study offers evidence that the sound representations are functioning in adult dyslexics, but that it is the decreased connectivity between the superior temporal regions (that were found to support intact phonetic representations in the initial analysis) and the left inferior frontal regions that are known to be involved in more complex phonological processing.

I wish the article elaborated on the specific phonological processing performed by the left inferior frontal regions. Also, a 2008 study found that children with dyslexia had greater functional connectivity from the left inferior frontal gyrus to the right inferior frontal gyrus than did the children without dyslexia. Compared to adults (with and without dyslexia) who differed in bilateral connectivity from left inferior frontal gyrus on the same task, the children with and without dyslexia differed in left side connectivity from left inferior frontal gyrus.

The children with dyslexia, then participated in an instructional program that provided explicit instruction in linguistic awareness, alphabetic principle,  decoding and spelling, and a writers' workshop. Follow up scans showed that the children no longer differed from the children without dyslexia in any of the clusters in the group difference map identifying differences between dyslexics and good readers, showing that functional connectivity (and not just regions of interest) may normalize following instructional treatment.

I wonder if a similar result would be found if the adult dyslexics are offered similar intervention? Were these dyslexic adults matched for level of reading interventions they received as a child, or as an adult? As these differneces only there for adults who received little to no intense intervention?

I would like to see a study that provides intervention, rescans and then waits a period of time (a year?) and then rescans again. Does functional connectivity improve in the short term? If so, does it regress without continued "use" so to speak with ongoing interventional exercises? I have the same questions, of course, for children fighting dyslexia. 

Avatar of: BarbD

BarbD

Posts: 1

December 6, 2013

I have a friend appx. 42 years old who is extremely dyslexic, never graduated highschool and even attempted taking tests to get his GED 4 times, which he tried to pass about 8 years ago but faild each time even with tutoring help, yet he is an absolutely unbelievable artist.  He is so talented I think he should be in Hollywood assisting on set decoration, graphic design and the like.  He was taught to be a master mold maker years ago, is an amazing sketch artist, oil/acrylic painter, has painted some beautiful murals on buildings around town and hand makes medieval body armor (seen wearing his art here http://nimg.sulekha.com/entertainment/original700/olatunji-dickson-2010-7-22-17-41-53.jpg ) and took to graphic computer art like nobody's business years ago having never taken a single class.  We urged him to get his GED so he could enroll in graphic art classes to further his skils and so he would have something to put on a resume.  We had him all signed up and paid for graphic art program but failing the GED they would never accept him. The graphic art images he has created could easily be used in hollywood action films. He doesn't post any of his work online for fear of theft.  Silly, but that's how it is.  

And so, he continues working menial jobs in construction, always struggling to get by, to buy art supplies.  Such a waste of talent.  Wish I could help him benefit from his gift.  How would you explain this dyslexic yet exremely artisitc phenomenon?  Sadly he will be one of those artist who becomes famous only after he dies.  I hope that is not the case.

Avatar of: omaha

omaha

Posts: 1

February 9, 2014

This is after the developmental process in adults. Still does not answer, what is happening from birth until age 5 in the developmental process. This is critical to understanding way 27% of the population is dyslexic. Figure this out and I want that market share!

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