Dyslexia -- difficulty with language/verbal comprehension -- is a connectivity problem with the relay signals in the brain's white matter, U.S. researchers say.
Bart Boets, a clinical psychologist at Catholic University in Leuven, Belgium, and colleagues used functional magnetic resonance imaging to scan the brains of 45 adults -- 23 with dyslexia and 22 without -- while they distinguished among a variety of sounds, some of which differed in subtle ways. The researchers then built a sophisticated correlational map, the Tribune newspapers reported.
The study, published in the journal Science, found both groups were able to distinguish those sounds accurately, though the dyslexic group did so more slowly, and both groups also showed consistent neuron firing patterns as they sorted the sounds.
"Quite to our surprise, we found that the phonetic representations are perfectly intact in dyslexics," Boets, the lead author, said.
The researchers then examined 13 areas of the brain known to communicate with one another -- 12 involved with language and speech; one control area involved with vision.
For both groups, those signals suggested functional connectivity was normal between hemispheres of the auditory cortex, the area associated with phoneme -- the building blocks of language -- recognition.
However, the white matter tracts connecting the phoneme area to the Broca's area, which regulates the conversion of language to speech, was weaker for the dyslexics as a group, Boets said.
