Reading Part II
Let us follow up on last weeks newsletter on reading as a cultural advantage and a human need in truth. What do we know about the neuroscience of reading dysfunction or weakened ability to achieve the goal of reading proficiency? What is the frequency of concern?
Depending on the study, 5-10% of children have reading issues like dyslexia. This has profound lifelong consequences if these issues are not dealt with in the early years of education.
Let us start again by looking at the neuroanatomy of the human reading interface. The first point of human involvement in reading is visual acceptance of the written word on page. In order to complete this task one must be able to see the word clearly in the order that it is displayed on the page and then send the neuroception to the brain via the optic nerve to the visual cortex. Then the angular gyrus interprets the words leaving the frontal lobes to engage in decoding and comprehending the information. This intricate interplay of neural networks not only facilitates the understanding of written language but also strengthens cognitive functions such as memory in the hippocampus, attention in the prefrontal cortex, and critical thinking in the neocortex.
The eyes must track the word across the page in sequence leading to meaningful information transmitted down the neural network. If there is a concern of binocular tracking or presbyopia/farsightedness, the neural transmission will a garbled set of 1's and 0's for our computer. The output is broken before the game even begins. So, in truth, knowing that a child sees the words clearly and is able to track the syntax across the page should be the first evaluation in the sleuthing experience of reading concerns. I will be releasing an interview with Dr. Phillip Bugaiski in the coming weeks to discuss this very topic. Stay tuned.
Okay, let us say that the words are read and then transmitted down the optic nerve and to the visual cortex. Then what? It is incredibly complex as stated here by Dr. Stein: "Yet, if we understood the specific neural pathways that underlie failure to acquire phonological skills specifically in people with dyslexia, we should be able to develop reliable means of identifying it. An important, though not the only, cause in people with dyslexia is impaired development of the brain’s rapid visual temporal processing systems; these are required for sequencing the order of the letters in a word accurately. Such temporal, “transient,” processing is carried out primarily by a distinct set of “magnocellular” (M-) neurones in the visual system; and the development of these has been found to be impaired in many people with dyslexia. Likewise, auditory sequencing of the sounds in a word is mediated by the auditory temporal processing system whose development is impaired in many dyslexics. Together these two deficits can therefore explain their problems with acquiring the phonological principle." (Stein J. 2022)
Neuroimaging studies, particularly functional magnetic resonance imaging (fMRI) have attempted to give us insights into the neural pathways involved in reading and their disruption in dyslexia. This truth remains elusive according to the literature. (Ramus et. al. 2018)
There is a phonological pathway that involves the connection between the inferior frontal gyrus and the superior temporal gyrus. Dyslexic individuals often exhibit reduced connectivity in this pathway, impairing their ability to process phonemes (distinct sounds that make up speech) and assemble them into words .
There is also an orthographic pathway that links the visually processing occipital lobe to the angular gyrus and the inferior frontal gyrus. Abnormalities in this pathway are associated with difficulties in recognizing written words and matching them to their phonological counterparts .
Developmental abnormalities in these and other pathways will then lead to the phenotype of a dyslexic child or a child with reading struggles.
What about the timing of dyslexia onset? This section from the Journal Translational Pediatrics is very illustrative of the typical timing of dyslexia: "The typical progression for acquisition of reading skills is important to understand in order to serve as a comparison for the delays that may occur in individuals with dyslexia. In the toddler years, vocabulary and syntax development (forming sentences) often exist in the context of language exposure in the early environment and sensitive, responsive caregiving. Therefore, in the toddler years, there are typically few differences in vocabulary gains between children with dyslexia and those without dyslexia. However, this starts to change in the preschool years even before children develop reading skills. One of the first prospective studies of children with positive family history for dyslexia found that at 30 months, children who later developed dyslexia had no differences in vocabulary, compared with controls without dyslexia who were matched for age and socioeconomic status. Yet, starting around 36 and 42 months, children who later developed dyslexia had more challenges in vocabulary and syntax compared to these controls. These children at 5 years of age had more apparent problems with letter knowledge, phonological awareness, and expressive vocabulary than their counterparts without dyslexia. To summarize, subtle differences in vocabulary and syntax in children, even starting in the preschool years, especially accompanied by a family history of reading challenges, may be a risk factor for dyslexia and may precede reading difficulties and a diagnosis of dyslexia in school-age. Therefore, when evaluating preschoolers with language delays, clinicians should refer to speech-language pathology for evaluation and intervention, assist families in navigating request for school services, and obtain a family history for dyslexia or reading difficulties. Additionally, clinicians should provide families anticipatory guidance to monitor and report on these children having difficulties with reading at school-age" (Munzer et. al. 2020)
Once the issues are identified, then specialists are enlisted to help unwind the concerns. Reading educators and specialists note that reading disorders can also involve problems with specific skills:
- Word decoding. This is the process whereby a person reads a word or letter and is able to ascribe a sound to it and makes a recurrent match of sound to letter/word. If one has difficulty sounding out written words, they will struggle to match letters to their proper sounds.
- The speed and accuracy of a person reading text. Often easily noted when a person reads aloud.
- Reading comprehension. The ability to accurately take in written word, understand the meaning and utilize the information for thought, retrieval and verbal or written action. (NIH) Watching a child read and comprehend is usually a good starting place for this deficit.
These are the soft early signs that clue us in to risk and intervention needs.
Strategies to mitigate and resolve the issue must be implemented. The earlier the intervention the better. Beyond, vision therapy for tracking defects, phonics instruction can be regarded as the gold standard in reading intervention programs. The best interventions are aimed at teaching 1) letter-speech sound correspondences, 2) decoding strategies that involve blending or segmenting individual letters, and 3) dividing spoken or written words into syllables. (Braid et. al. 2022)
This article is by no means a comprehensive look at this topic, but it is a good launching point.
Dr. M
