Older news items (pre-2010) brought over from the old website
Unraveling the roots of dyslexia
There is some evidence that dyslexia is distinguished by a basic deficit in phonological processing, characterized by difficulties in segmenting spoken words into their minimally discernable speech segments (speech sounds, or phonemes). A new study investigating brain activity of dyslexics and normal adult readers when presented with letters, speech sounds, or a matching or non-matching combination of the two, has revealed that dyslexic adults showed lower activation of the superior temporal cortex when needing to integrate letter and speech sounds. The findings point to reading failure being caused by a neural deficit in integrating letters with their speech sounds.
Blau, V. et al. 2009. Reduced Neural Integration of Letters and Speech Sounds Links Phonological and Reading Deficits in Adult Dyslexia. Current Biology, 19 (6), 503-508.
http://www.eurekalert.org/pub_releases/2009-03/cp-utr030509.php
Chinese and English dyslexias stem from different brain abnormalities.
Dyslexia involves impairment in connecting the sight and sound of a word. In English, this is commonly seen in transpositions of letters, while in Chinese, the problem can affect how a person converts a symbol into both sound and meaning. Following an earlier study in which the brain areas involved in dyslexia were found to be different for English and Chinese readers, a new technique has confirmed and clarified the results. Chinese children with dyslexia had a significantly smaller left middle frontal gyrus than did Chinese children without the disorder, even though both groups had the same overall volume of gray matter. Intriguingly, this area is not associated with symbol recognition, but with working memory. Earlier research has found English-speaking dyslexics have less gray matter in the left parietal region. The findings also suggest that dyslexics in one language will probably not be dyslexic in the other.
[865] Siok, W T., Niu Z., Jin Z., Perfetti C. A., & Tan L H.
(2008). A structural–functional basis for dyslexia in the cortex of Chinese readers.
Proceedings of the National Academy of Sciences. 105(14), 5561 - 5566.
http://www.nature.com/news/2008/080407/full/news.2008.739.html
http://sciencenow.sciencemag.org/cgi/content/full/2008/408/1?etoc
New evidence for the cause of dyslexia
A new study casts new light on the cause of dyslexia. Recent research has tended to focus on the magnocellular (M) pathway, one of two visual pathways in the brain that processes motion and brightness. The other visual channel, the parvocellular (P) pathway, processes detail and color. Although some studies have implicated an impaired M channel, showing that dyslexic children have trouble seeing rapidly changing or moving stimuli, results have been inconsistent. A new study suggests that the problem is rather a more general problem in basic sensory perception — an inability to shut out “noise”, that is, the sounds and patterns surrounding the target information.
[462] Sperling, A. J., Lu Z-L., Manis F. R., & Seidenberg M. S.
(2005). Deficits in perceptual noise exclusion in developmental dyslexia.
Nat Neurosci. 8(7), 862 - 863.
http://www.eurekalert.org/pub_releases/2005-05/uow-sso052505.php
Dyslexia doesn't have a universal biological cause
While most of the latest research focuses on the biological causes of dyslexia, a new study reveals that the disorder affects the brains of Chinese and English speakers differently, suggesting that the neural basis of reading differs depending on the nature of the writing system. The findings have enormous implications for helping impaired readers in China, where 2% to 7% of children are dyslexic. The study also highlights the importance of paying attention to differences in languages, even languages as similar as English and Italian. It has been shown that the degree of impairment when reading can differ depending on the language.
[1058] Siok, W T., Perfetti C. A., Jin Z., & Tan L H.
(2004). Biological abnormality of impaired reading is constrained by culture.
Nature. 431(7004), 71 - 76.
http://msnbc.msn.com/id/5888011/
Dyslexics have less gray matter in the brain's language centers
A new imaging study involving people with a family history of dyslexia confirms earlier research suggesting dyslexics have a significant reduction of gray matter in centers associated with language processing. The study lends credence to earlier studies that suggested intensive reading therapy activates parts of the brain needed for decoding words.
[1446] Brambati, S. M., Termine C., Ruffino M., Stella G., Fazio F., Cappa S. F., et al.
(2004). Regional reductions of gray matter volume in familial dyslexia.
Neurology. 63(4), 742 - 745.
Brain development and puberty may be key factors in learning disorders
New research suggests that the brains of children with learning problems not only appear to develop more slowly than those of their unaffected counterparts but also actually may stop developing around the time of puberty's onset. In the study, children with impairments started out about three years behind, but their rate of improvement was very similar to that of the children without impairments — until around 10 years, when further development in the children with learning problems stopped. The researchers suggest that delayed brain development and its interaction with puberty may be key factors contributing to language-based learning disabilities such as dyslexia. This hypothesis suggests a completely new approach to the study of learning problems. It also points to the importance of early intervention.
[216] Wright, B. A., & Zecker S. G.
(2004). Learning problems, delayed development, and puberty.
Proceedings of the National Academy of Sciences of the United States of America. 101(26), 9942 - 9946.
http://www.eurekalert.org/pub_releases/2004-06/nu-bda061604.php
Sensory processing different in people with dyslexia
An imaging study of dyslexics has found that dyslexic readers appear to process auditory and visual sensory cues differently than do normal readers. In the study 30 dyslexic readers and 30 normal readers performed three matching tasks — an auditory task, a visual task and a multisensory task — involving consonant-vowel pairs. During the auditory matching task the dyslexic readers showed increased activity in the visual pathway of the brain, while that same region deactivated in the normal readers. The dyslexic readers' increased activation patterns in the visual pathway corresponded to poorer performance on the matching task.
Burdette, J.H., Laurienti, P.J., Flowers, L., Kraft, R., Maldjian, J. & Wood, F.B. 2003. Report presented at the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
http://www.eurekalert.org/pub_releases/2003-12/rson-fdm112403.php
Imaging study confirms theory of dyslexia
Functional magnetic resonance imaging (fMRI) has confirmed part of an eighty-year-old theory on the neurobiological basis of dyslexia. Dr Orton theorized that normally developing readers learn to suppress the visual images reported by the right hemisphere of the brain because these images potentially interfere with input from the left. The imaging study found that children do in fact "turn off" the right side of the visual parts of the brain as they become accomplished readers, and also demonstrated that different phonological skills relate to activity in different parts of the brain when children read. This observation lends support to the theory that there may be several neurobiological profiles that correspond to different subtypes of dyslexia, each associated with varying deficits in one or more of these different phonological skills.
[304] Turkeltaub, P. E., Gareau L., Flowers L. D., Zeffiro T. A., & Eden G. F.
(2003). Development of neural mechanisms for reading.
Nat Neurosci. 6(7), 767 - 773.
http://www.eurekalert.org/pub_releases/2003-05/gumc-wor051603.php