How We Read
Reading is a complicated chain of events coordinated in the brain. Imagine a busy, computerized railroad yard: trains pull in on hundreds of tracks from all directions. The cargo of each train is documented in a central tower, then matched with a destination and assigned to one of dozens of tracks. Some trains may be sent to a holding area until their cargo is needed; others may be routed so they can make multiple stops. The computer system must analyze hundreds of pieces of information for each train pulling in, each train pulling out—so even a brief power failure can clog the railroad yard with thousands of trains, blocked from reaching their destination.
Scientists suspect a similar power failure in the brain is the cause of dyslexia. In normal reading, the eye sends pictures of abstract images (the printed word) to the brain. Each symbol is routed to various portions of the brain for processing or storage, symbols are interpreted and combined in combinations that make sense, then transferred to other portions of the brain that recognize the importance of the messages. Sometimes the messages are relayed to the lips, tongue, and jaw—reading aloud—or the fingers and hands—writing.
Investigators have identified three major "tracks" for sending written messages to the brain for interpretation. The phonic route recognizes individual letters and, over time, builds a list of groups of letters that generally appear together. The direct route is a "mental dictionary" of whole words recognized as a unit; the lexical route breaks strings of letters into a base word, prefixes, and suffixes. The lexical route might, for example, break the word "together" into "to-get-her." The areas of the brain responsible for channeling words along these different routes, processing them, then moving them along as a message that makes sense, coordinate thousands of pieces of information in normal reading. These bits of information are moved through the brain over neurons, the roadways of the nervous system, on neurotransmitters, naturally occurring chemicals that make it possible for messages to travel from one nerve cell to the next. In dyslexia, something jams the signals in the brain and interferes with the interpretation of the written word.