New study closes in on cause of dyslexia
By Geoffrey Mohan, Los Angeles Times/MCTLOS ANGELES--A faulty connection between where the brain stores the auditory building blocks of language and where it processes them may be to blame for dyslexia, a new study suggests.
December 8, 2013, 12:01 am TWN
The findings represent the first neuroanatomical evidence that the vexing spelling and reading disorder striking people who otherwise can speak a language fluently lies in a connectivity problem in the brain's white matter, where nerve fibers relay electrochemical signals.
Various degrees of dyslexia strike about one in 10 people, making it difficult for them to analyze and assemble letter combinations and relate them to the auditory packets of learned language, called phonemes.
Scientists have debated whether those with the disorder were accurately forming and storing phonemes, or whether impeded access to them complicated the task of synthesizing sounds with written, visual symbols.
Learning language is innate — babies across cultures, time, language and demographics acquire it at roughly the same age and in the same stages. But reading takes years of conscious, cumulative effort to associate abstract symbols with an acquired database of sounds. Those who fail or struggle with the process often face further cognitive difficulties, emotional problems and sometimes severe social consequences.
A Belgium-based research team delved into the puzzle by mapping the brain activity involved in phoneme sorting. They used functional magnetic resonance imaging machines to scan the brains of 45 college-age adults (23 with dyslexia, 22 without) while they distinguished among a variety of sounds, some of which differed in subtle ways, then built a sophisticated correlational map.