In the last 30 years, a tremendous amount of research has been done to demystify dyslexia, and scientists have been successful enough to narrow down the problem to the actual genes responsible for causing dyslexia. However, most teachers, parents, and those who suffer from dyslexia really don’t seem to understand the “why’s” of this disorder.
Dyslexia is a language processing disorder, which means that key areas in the brain that are responsible for language are affected in some way. Using the diagram at the top, I’m going to explain how all this works–and what is comes down to is a disorganized brain–one that is not wired to read. Yet, most people with dyslexia are intelligent, and their brains compensate for the disorder by having other areas of the brain take over in order to learn while the reading areas remain inactive or inefficient. When we say that the area of the brain is inactive that means that it lacks blood flow to that area … this information is obtained from fMRIs–mini MRI’s in a helmet–that allow a person to do an activity while imaging the blood flow to the brain.
There are three key areas for reading: Broca’s area (pink) [refer to diagram at the top], Wernicke’s area (blue), and the occipital lobe (yellow). When a reader is fluent and has no issues with reading, it means that all these areas are working together in harmony and synchronicity; collaborating back and forth to make meaning of words, sentences, and sounds. But when the brain lacks this seamless flow of shared information–that’s what causes dyslexia.
For example, Broca’s area (pink), located on the left side of the brain (supposing the person is right handed–if left handed it’s the exact opposite), is responsible for expressive language–meaning being able to say sounds, write, manipulate sounds, and organize language. Notice that in the dyslexic brain, Broca’s area is enlarged, but that doesn’t mean it works better. It’s just trying to compensate for the lack of teamwork from the other two areas.
The next important brain function is Wernicke’s area (blue), which is located right above the ear on the left side of the brain. Wernicke’s area covers a large area of the brain and is responsible for understanding language and creating a verbal memory. It’s a storehouse of words, patterns, and sounds. In other words, in a non dyslexic brain, this area takes in information and processes it and commits it to a working verbal memory. It can also decode words that it doesn’t understand right away. Being able to decode words means having the ability to break apart a word into chunks, sounds, or use context clues within a sentence to figure out the meaning of words. Notice that in the dyslexic brain, Wernicke’s area is inactive; therefore, it has no large storehouse of memorized words and it doesn’t understand the meaning or structure of those words either.
The last important area for reading is the occipital lobe (yellow), located at the back of the brain. This is the hot spot for all our visual processing and how we “see” and understand what we see. Obviously, this is where the brain recognize letters and words right away, and works with the other two areas to make meaning out of words. Notice once again that this area is inactive in a dyslexic brain. It’s important to note that most dyslexic children do not have anything wrong with their vision. There are cases where students have tracking issues, binocularity, and a slew of other vision related problems which can affect reading. But in a true dyslexic, no amount of vision therapy will help his or her ability to read.
So with that said, let’s watch the chain reaction of events. First the eyes see a word, then the visual reference is zapped all the way back to the occipital lobe where it processes what it sees. The dyslexic brain is not going to see what you and I see because this area is not activated or working properly. Now it shoots the information it has received and processed (incorrectly) to Wernicke’s area to help the brain understand what it has read–but alas Wernicke’s area is not activated either and can’t remember words or letters, so more jumbling and confusion occurs in the brain. At the same time, the incorrect information has been zapped to Broca’s area where it’s trying to sound out the incorrect information. This area is activated, but receives incorrect information from the occipital lobe and has no help from Wernicke’s area (understanding language) in order to decode or sound out the word.
Talk about confusion!! The lack of teamwork makes the poor dyslexic brain go around in circles. No wonder the dyslexic brain struggles with reading. Studies show that in many dyslexics, the right brain lights up with activity instead to compensate for the lack of left brain activity. The right brain is not necessarily wired for reading–the actual neurons and nerve cells are are not formed in a patterned, systematic way as they are in the left brain. So the dyslexic brain uses images or memorizes words to make up for the inability to decode the word and understand the language processes.
Not only does the dyslexic brain suffer from inactivity in the key language areas but it also has a few structural differences as well. First, in some key areas it lacks white and gray brain matter. Gray brain matter processes information and is located more on the surface while white brain matter transfers important information around the brain and is located deeper inside the brain. In many cases, the inactive language areas are also lacking brain matter–which is key in building neurons to learn how to read.
In addition, studies have also shown that a dyslexic brain is symmetrical OR assymetrical with the right brain being larger. Remember, the right brain is not built for language, but it’s overcompensating once again to help out the weak areas on the left brain. A non dyslexic brain is always assymetrical with the left brain being larger–once again because of all the key language and mathematical processing areas are located in this area.
Resources: LD Online:
Dyslexia and the Brain, 2007