neural signature for dyslexia

Dyslexia, Language Processing Problems, & Reading (2 of 4)

neural signature for dyslexia

Highlights of Recent Research

In the past decade, much research on dyslexia has been conducted, and the most revealing of this research has focused on the use of functional magnetic resonance imaging (fMRI) which has proven the existence of dyslexia.  This research has shown that the brain is wired differently in those individuals with dyslexia.  Rather than using the left hemisphere where the processing of language occurs, people with dyslexia use an inefficient pathway and rely more on the right hemisphere and the frontal lobe when reading.  Research is also proving that with specific instruction, the brain can be “rewired” to use the more efficient pathways that those without dyslexia use when reading.


Dr. Kenneth Pugh

Dr. Kenneth R. Pugh, President and Director of Research, Haskins Laboratories, was the keynote for the Northern Ohio Branch of the International Dyslexia Association (NOBIDA) 2014 conference.  The most interesting take away for me was his statement that Orton-Gillingham (OG) results are now confirmed by neuroscience.  Dr. Pugh explained that the left hand posterior system appears to be unstable but trainable in young at risk readers, and there is now evidence that appropriate training has a normalizing effect on the neurobiological trajectory in emergent “at risk” readers.  This appropriate training, or treatment protocol, is a 5 step plan (unscripted) and individualized to include:

  • letter-sound associations
  • phoneme manipulation
  • reading words
  • reading text
  • assessment


Dr. Maryanne Wolf

Dr. Maryanne Wolf theorized in the book, The Proust and the Squid, that there are 3 subtypes of dyslexia. The most common of these subtypes is a deficit in phonological processing and this impacts the ability to decode words. This is the basis for the IDA’s definition of dyslexia.  People with this subtype of dyslexia simply have a harder time processing the individual sounds that make up spoken words and they have a harder time mapping the sound (phoneme) to the written letter(s) (grapheme).

To put it simply, people with a deficit in phonological processing do not have an ear for the sounds of speech and have difficulty distinguishing the sounds of speech, especially similar sounds.  People without dyslexia are more attuned to the sounds of speech and can be compared to the ability of musicians to identify by sound the musical notes that are played and to identify when a wrong note has been played.

The 2nd subtype of dyslexia she theorized is a deficit in rapid naming. People with this subtype of dyslexia will have normal phonological processing, but their fluency and comprehension will be affected by the retrieval of language based information. These are the people that will have problems with word recall, either by saying the wrong word or the word is “on the tip of their tongue”. This affects fluency because it takes longer to retrieve language information. This also impacts comprehension because sometimes the retrieved language information is wrong, such as either retrieving the wrong definition or wrong word, either of which can change meaning.

The 3rd subtype of dyslexia is double deficit: deficits in both phonological processing and rapid naming. This subtype is the least common and the hardest to remediate.

Research from neuroscientists at MIT and Stanford/UCSF now supports Dr. Maryanne Wolf’s theory on the 3 subtypes of dyslexia by showing different patterns of brain activation when reading and rhyming words.  Children with a deficit in phonological awareness only, rapid naming only, or difficulty in both areas each showed different patterns of brain activation and connectivity as revealed by MRI.  (Source:  Functional neuroanatomical evidence for the double-deficit hypothesis of developmental dyslexia, 2014.  Elizabeth S. Norton, Jessica M. Black, Leanne M. Stanley, Hiroko Tanaka, John D.E. Gabrieli, Carolyn Sawyer, Fumiko Hoeft.)


Dr. Louisa Moats

Dr. Louisa Moats, in the webinar Wanted: Teachers with Knowledge of Language (Upper Midwest Branch of the International Dyslexia Association, February 18, 2014; Education Week, March 26, 2014) stated:

“One of the key aspects of the definition of dyslexia that we commonly use are that poor readers with the symptoms of dyslexia are typically, and notice that word typically, are not wired for phonological processing and/or automatic word recognition. And why do we use the word typically? Because there are students who experience reading difficulties that don’t necessarily involve overt problems with phonology, but that involve fluency in text reading and/or that involve access to critical language constructs that enable them to comprehend, so reading difficulties are not simple, and they tend to be more complex than we want them to be. (minute mark 6:55-7:58)

Reading difficulties should be differentiated. Dyslexia often is associated with problems with phonologically based word recognition, but the reality is that dyslexia also includes a subgroup of fluency based problems and problems with memory for words so that words are not recognized quickly and words are not recalled accurately for spelling.  And we have underestimated both the prevalence of that subtype and the difference in methodologies that are required for that subtype. And then language comprehension problems overlap with these so that many students who deserve the label of dyslexia often have co-existing problems with language comprehension, with language processing, with language expression and that is why the word dyslexia is such a good word because it means difficulty with language. So if what we are talking about, whether it is in more specific terms or more general terms, pertaining to all of the kids who struggle with reading, and that is a very large proportion, at least 1/3, it is much more than the 5-10% as ever getting the label dyslexia. If we, as professionals, are going to be ready to really teach this population in a way that they can learn and we can move them ahead and facilitate their progress with this otherwise difficult thing, we need to be prepared to help all of these subgroups and identify all of these subgroups.”  (minute mark 19:05-21:00)


Continue Reading: