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Neuroscientists have used fMRI to identify three areas of the left side of the brain that play key roles in reading. Scientifically, these are known as the left inferior frontal gyrus, the left parieto-temporal area and the left occipito-temporal area. But for our purposes, it's more helpful to think of them as the "phoneme producer," the "word analyzer" and the "automatic detector." We'll describe these regions in the order in which they are activated, but you'll get closer to the truth if you think of them as working simultaneously, like the sections of an orchestra playing a symphony.
Using fMRI, scientists have determined that beginning readers rely most heavily on the phoneme producer and the word analyzer. The first of these helps a person say things--silently or out loud--and does some analysis of the phonemes found in words. The second analyzes words more thoroughly, pulling them apart into their constituent syllables and phonemes and linking the letters to their sounds.
As readers become skilled, something interesting happens: the third section--the automatic detector--becomes more active. Its function is to build a permanent repertoire that enables readers to recognize familiar words on sight. As readers progress, the balance of the symphony shifts and the automatic detector begins to dominate. If all goes well, reading eventually becomes effortless.
In addition to the proper neurological wiring, reading requires good instruction. In a study published in the current issue of Biological Psychiatry, Shaywitz and colleagues identified a group of poor readers who were not classically dyslexic, as their phoneme producers, word analyzers and automatic detectors were all active. But the three regions were linked more strongly to the brain's memory processors than to its language centers, as if the children had spent more time memorizing words than understanding them.
The situation is different for children with dyslexia. Brain scans suggest that a glitch in their brain prevents them from easily gaining access to the word analyzer and the automatic detector. In the past year, several fMRI studies have shown that dyslexics tend to compensate for the problem by overactivating the phoneme producer.
Here at last is physical evidence that the central weakness in dyslexia is twofold. First, as many dyslexia experts have long suspected, there is an inherent difficulty in deriving sense from phonemes. Second, because recognizing words doesn't become automatic, reading is slow and labored. This second aspect, the lack of fluency, has for the most part not been widely appreciated outside the research community.
Imagine having to deal with each word you see as if you had never come across it before, and you will start to get the idea. That's exactly what Abbe Winn of Atlanta realized her daughter Kate, now 9, was doing in kindergarten. "I noticed that when her teacher sent home a list of spelling words, she had a real hard time," Abbe says. "We'd get to the word the and come back five minutes later, and she had no idea what it was."