how the brain reads -- 8/13/20
Today's encore selection - from Overcoming Dyslexia by Sally Shaywitz, M.D. Recent research using magnetic resonance imaging has provided neuroscientists with a clearer picture of which parts of the brain are responsible for reading -- and how the brain develops over time into a sophisticated reading machine:
"Imaging studies have identified at least two neural pathways for reading, one for beginning reading, for slowly sounding out words, and another that is a speedier pathway for skilled reading. ... As they read, good readers activate highly-interconnected neural systems that encompass regions in the back and front of the left side of the brain. Not surprisingly, the reading circuitry includes brain regions dedicated to processing the visual features, that is, the lines and curves that make up letters, and to transforming the letters into the sounds of language and to getting to the meaning of words.
"Most of the reading part of the brain is in the back. Called the posterior reading system ... it is made up of two different pathways for reading words, one sitting somewhat higher in the brain than the other. The upper pathway is located primarily in the middle of the brain (technically, the parieto-temporal region), just above and slightly behind the ear. The lower path runs closer to the bottom of the brain; it is the site where two lobes of the brain -- the occipital and the temporal -- converge (referred to as the occipito-temporal area). This hectic region serves as a hub where incoming information from different sensory systems comes together and where, for example, all the relevant information about a word -- how it looks, how it sounds, and what it means -- is tightly bound together and stored. ...
"The parieto-temporal system works for the novice reader. Slow and analytic, its function seems to be in the early stages of learning to read, that is in initially analyzing a word, pulling it apart, and linking its letters to their sounds. In contrast to the step-by-step parieto-temporal system, the occipito-temporal region is the express pathway to reading and is the one used by skilled readers. The more skilled the reader, the more she activates this region. It responds very rapidly -- in less than 150 milliseconds (less than a heartbeat) -- to seeing a word; instead of analyzing a word, the occipito-temporal area reacts almost instantly to the whole word as a pattern. One brief glance and the word is automatically identified on sight. Not surprisingly, the occipito-temporal region is referred to as the word form area or system.
"Here's how we think the word form system works. After a child has analyzed and correctly read a word several times, he forms an exact neural model of that specific word; the model (word form), reflecting the word's spelling, its pronunciation, and its meaning, is now permanently stored in the occipito-temporal system. Subsequently, just seeing the word in print immediately activates the word form and all the relevant information about that word. It all happens automatically, without conscious thought or effort. As skilled readers speed through the text, the word form area is in full gear, instantly recognizing one word after another. Not surprisingly, the best readers, those with the highest scores on tests of reading, are the ones who show the most activation of the word form region during imaging. ... There are therefore three neural pathways for reading: two slower, analytic ones, the parieto-temporal and frontal, that are used mainly by beginning readers, and an express route, the occipito-temporal, relied on by experienced, skilled readers. ..."