Brain Research and Dyslexia
Within the past two decades, scientists have been able to use sophisticated equipment to study the workings of the human brain. With this equipment, scientists can measure electrical impulses, chemical changes, or blood flow through the brain while their research subjects perform specific tasks. This has allowed scientists to look at the mental changes associated with learning to read, and to compare the mental activity of people with dyslexia with that of people who have no reading problems.
One thing that the brain research shows is that each brain is different; not all people with dyslexia process information exactly the same way. However, by studying many individuals, it is possible to generalize and to explore common elements that may contribute to dyslexia.
FACT
Learning new skills can alter brain structure. Researchers recently found that certain areas of the brain grew larger when they taught their subjects to juggle. When the jugglers stopped practicing and their brains were measured again, the brain expansion they had seen earlier was reduced.
Searching for Answers
Good scientific research is limited in scope; scientists are careful to study only one particular theory or question, under controlled conditions. The brain is an extremely complex system, and each research project sheds light on only a small part of the mental processes of learning, reading, and dyslexia. Thus research cannot yet provide all the answers. Instead, each new study provides an intriguing look into another piece of the puzzle. Scientists measure many different responses in children with dyslexia, such as the timing of the brain's response to external stimuli, the way that the brain recognizes letter patterns, and the pattern of activity in the two brain hemispheres associated with different reading tasks.
Speed and Response Time
Scientists have discovered that the brains of children with dyslexia take a fraction of a second longer to respond to certain stimuli than the brains of children who read well; this pattern persists through adulthood. The delayed response time is seen both in tests of listening to the sounds of language and responding to visually presented symbols. These delays could explain why individuals with dyslexia tend to read more slowly.
It is also possible that because of the problem with timing, children with dyslexia may not hear the sounds and rhythms of language in the same way that others do. This may explain why they have difficulty breaking down words into component sounds or blending sounds into words.
Visual Word Form Recognition
Researchers have also discovered that the part of the brain used to quickly recognize letters, letter sequences, and words in most people does not seem to activate in the brains of adults and older children with dyslexia. In most people, an area in the left rear (occipital) of the brain activates almost immediately upon seeing any sequence of letters; the activity is very brief, and ends within about half a second after the word or letter sequence is first seen. Scientists call this part of the brain the visual word form area.
FACT
In skilled readers, most words are recognized by sight even before the person is consciously aware that he is looking at a word. This is why silent reading is faster than oral reading. Sounding out and speaking words is a slower mental process and requires involvement of brain areas involved in speech production.
People with dyslexia simply do not seem to engage this area of the brain when presented with words or letter patterns. Whatever activity takes place is stronger in a corresponding area on the right side of the brain, which is known to be involved in face recognition. Part of the problem may be timing; in most readers, the visual word form area activation is completed in the fraction of a second before the brain begins to activate in research subjects with dyslexia.
The visual word form area may function as an important sorting mechanism, where the brain quickly responds to familiar words and directs unfamiliar words to other left hemispheric areas for further processing. An inability to use this brain area may explain why people with dyslexia have difficulty with remembering and recognizing familiar words.
Right-Brain Activity
Scientists studying the process of learning to read in normal children have observed that the brain changes as children gain reading proficiency. Very young children have high levels of activity in both the right and left brain hemispheres when looking at letters and words. As children gain the ability to recognize familiar words and letter patterns on sight, the right brain activity subsides and a strong pattern of left hemispheric activity is observed.
The left hemisphere is important to reading because it contains pathways and areas in the temporal and occipital regions, near the rear of the brain, which are specialized for attending to and understanding the sounds of language. This is the part of the brain that will become specialized for connecting letters to the sounds they represent, and for connecting and blending the individual sounds in a series of letters to form a word.
Other studies have shown that adults and children with dyslexia have more right brain and frontal brain activity than good readers when performing certain reading tasks. For most people, the left brain hemisphere is also slightly larger than the right. Several studies show that adults with dyslexia tend to have more evenly structured, symmetrical brains, with the right hemisphere being about the same size as the left, and activity less differentiated between left and right hemispheres.
The child or adult who is using right brain processes to try to decipher text is probably getting mixed signals, and will understandably find reading to be a difficult and confusing task. On the other hand, the evidence from these studies helps to explain why the reading problems associated with dyslexia tend to go hand-inhand with creativity, artistic ability, and strong spatial reasoning skills, as these are abilities associated with the right hemisphere.
