Dyslexia is a term that many people have heard before, but there are many misconceptions and misunderstandings about what it means. This post is part one of a three-part series on dyslexia, and it focuses on what dyslexia is.
WHAT IS DYSLEXIA?
In general, dyslexia is a term that is used to describe problems in reading that are characterized by difficulties with accurate or quick word recognition, poor decoding (ability to sound out unfamiliar words), and poor spelling abilities. Learning disabilities are unique, and there are many characteristics that might or might not apply to any single person diagnosed with a learning disability, but most researchers agree:
Learning disabilities are the results of difficulties with cognitive abilities--the way the brain processes certain types of information.
The cognitive processing deficits associated with learning disabilities are generally not related to visual-perceptual difficulties (e.g., the way that the student sees words) but rather related to language processing, such as vocabulary, the ability to retrieve information from memory, or the ability to recognize and process sounds and match them to letters or symbols.
Some learning disabilities might be related to genetics or inherited within families.
Reading disabilities are much more common than disabilities in math or writing.
Learning disabilities fall within a spectrum of severity.
Effective instruction, supports, and accommodations can offset the impact of a learning disability within a classroom.
Learning disabilities often co-occur with other types of difficulties, such as attention-deficit/hyperactivity disorder (ADHD), communication disorders, developmental coordination disorder, autism, or other disorders. This makes differential diagnosis that much more complicated.
What are signs of dyslexia?
Language delays (e.g., trouble with vocabulary, word finding, imprecise language, etc.)
Difficulties with rhyming or other tasks that involve playing with sounds within words
Difficulties with alphabetic knowledge, including recognizing letters or identifying letter sounds
Trouble sounding out even simple words, like cat, top, or bat
Slow, unsteady reading (i.e., dysfluent reading)
Poor spelling
Avoiding reading
Trouble finishing classwork or homework in a reasonable period of time
What about reading backwards or right to left? What about backwards letters? Aren’t those types of reading behaviors associated with dyslexia?
Trouble with reading from right to left and from top to bottom is likely more a symptom of reading difficulties rather than a cause of dyslexia, per sé. Jumping around on the page could occur when the child is having difficulty reading words in order, so they skip ahead to words that they recognize. Alternatively, the student may need additional training in print conventions and directionality of text, because this is not a habit that has been solidified in his or her reading behaviors. In general, there is limited evidence to suggest that eye movement abnormalities better explain dyslexia rather than difficulties with word recognition and language processing.
Reversing letters while writing is considered age-appropriate through about age seven or second grade. These types of errors are often more related to difficulties with phonics and inexperience and difficulty reading rather than seeing the letters backwards. After the end of second grade, reversing letters is often a sign that further evaluation might be needed, but this is all dependent upon information from a variety of sources. Just because a child is in the second grade or below does not mean that he or she would not benefit from practice writing letters the correct way. Working on letters one at a time in isolation and incorporating multi-sensory techniques might help a child who is struggling to remember letter orientation to catch on a bit quicker.
Brain processes related to reading development and dyslexia
As brain imaging science has become more advanced, some studies have been conducted to look at the brain pathways that are associated with both efficient and inefficient reading. There is not space here to provide an in depth discussion of what research suggests about reading development and brain pathways. However, there are some general trends from research in this area that might be of interest here.
Functional brain imaging studies (i.e., fMRI) have been used to provide information about the neural pathways related to efficient reading. Three main pathways have been identified:
The parieto-temporal system is essential for phonetic decoding in reading: that is, looking at the letters within a word, associating those letters with sounds, determining the sound units within the words, and then ultimately identifying the word itself. Children who are learning to read rely initially on the parieto-temporal system almost exclusively.
As readers develop more skill, a different pathway in the brain becomes more active: the occipito-temporal pathway. The occipito-temporal pathway is more related to whole-word reading--that is, the whole word is recognized automatically, rather than being broken down into phonetic parts, as it is in the parieto-temporal system. This neural activation related to whole word recognition allows the reader to access each word more quickly, allowing for more fluent reading, rather than relying on the slower, phonetic decoding of each word within the text.
There is a third area associated with phonetic decoding that has also been identified, and that area lies within the frontal lobe in Broca’s area. Again, this neural pathway for reading is not as efficient as the occipito-temporal pathway.
Brain imaging studies have suggested differences in activation between these neural pathways with more efficient readers and readers who have been identified with dyslexia.
Good readers have been shown to have more consistently rely upon the occipito-temporal pathway, with less activation in the other two, front pathways.
Children with dyslexia have shown the opposite pattern, with two distinct patterns:
Children with dyslexia often can activate all three brain pathways individually but have trouble with activating them simultaneously.
There is often an overactivation of the third pathway associated with Broca’s area, which appears to be the endpoint for the brain’s articulation system.
Using these two systems, children with dyslexia are often able to break apart the sound structures within words and pronounce the sounds within their head, but because they have trouble activating the more efficient system, their reading is less fluent and less automatic than a child without dyslexia.
Effective intervention systems have been shown to help children with dyslexia develop the posterior, automatic system and improve fluency.
As a wrap up, brain imaging studies seem to suggest real differences in the neural pathways that are activated during reading when skilled readers are compared to children with dyslexia, which supports a biological basis for dyslexia. However, imaging studies have also shown that effective intervention can strengthen more efficient neural pathways even in children diagnosed with dyslexia.
Terminology in schools versus other settings
Dyslexia is a term that has traditionally been used more by researchers and within medical settings than in schools. Its counterparts in other areas of learning include dysgraphia (learning disability in writing) and dyscalculia (learning disability in mathematics).
In schools, terminology is often driven by laws and procedural guidelines from the federal and state departments of education, and the current federal guidelines provide a classification called specific learning disability which includes several different categories within that broad classification (e.g., specific learning disability in basic reading skills). The federal guidelines specifically reference dyslexia as a possible diagnosis that would fall under the educational classification of specific learning disability.
Sources:
Lichtenstein, R. (2010). Learning disabilities identification: A primer for parents from Helping Children at Home and School III from the National Association of School Psychologists.
Miller, D. C. (2013). Essentials of School Neuropsychological Assessment, Second Edition.