Current Status of Treatments for Dyslexia: Critical Review

Ann W. Alexander, MD; Anne-Marie Slinger-Constant, MD

Disclosures

J Child Neurol. 2004;19(10):744-758. 

In This Article

Components in the Development of Reading

Rumelhart et al. observed that reading can be viewed as an interactive process between information processed from current sensory information (bottom up) and the meaning of what has been read (top down).[67] The connectionist models support this view. Oral reading is the most demanding, and Figure 4 represents the neural components necessary for the development of this skill. A combination and integration of distinct phonologic, morphologic, orthographic, and semantic representations for the decoding of a word are optimal for normal reading development (accurate and automatic decoding) according to Snowling and Nation.[68] Harm and Seidenberg's computer simulations confirm the need for this interplay.[31] Articulatory and prosodic representations are necessary for appropriate oral production but also for enhancement of phonologic, morphologic, and semantic maps. Without efficient phonologic and morphologic decoding ability, the reader must rely on context (semantic and syntactic cues).[69] The transition into fluent reading with comprehension depends on developing orthographic automaticity but also on syntactic competence and semantic strength.

The development of skilled oral reading.a visual schematic illustrating the neural substrates and networks needed for the optimal development of skilled (fluent, with appropriate expression and comprehension) oral reading. The stoplights serve to illustrate whether the neural substrates allow for efficient networking ( green ), as is shown here. They can be used to explain treatment plans, illustrating when substrates are suboptimal, resulting in a "bottleneck" ( yellow ), or are nonexistent, requiring a "detour."

To confound the issue further, an appreciation of the developmental course is essential. Snyder and Downey found that 8- to 9-year-old children's syntactic knowledge, followed by their ability to retell a story and their word retrieval ability on a confrontation naming task, accounted for better reading comprehension.[70] Older children (11–14 years) were found to rely on bottom-up and top-down strategies, depending on the material being read. Bottom-up phonetic processes are used to decode isolated unfamiliar words in less familiar text; more top-down strategies are used when reading stories and text on familiar topics. At this age, their discourse processing skills, followed by their phonologic awareness abilities, accounted for the greater variance in their reading scores. Weak phonemic representations result in weak phonologic representations, thought to be the core deficit in developmental dyslexia.[71] Orthographic representations are acquired more efficiently if there is an appreciation of the phonologic components of the word. Likewise, phonics rules are difficult to apply without a strong phonologic base. Some children might also complain of the words swimming or moving on the page, making it difficult to keep their place and causing fatigue, as well as placing them at risk of orthographic mapping deficits.

Single-word reading is typically more markedly affected in dyslexic individuals owing to the weakness of the phoneme, morpheme, and orthographic representations. However, children with strong cognitive and semantic abilities (lexical-semantic representations) can offset the severity of the decoding deficit in contextualized text reading. They make good use of context for the decoding of unknown words and exhibit greater strength in comprehension than would be expected. Unfortunately, this strategy alone is less efficient than the combination of phonologic decoding and orthographic knowledge because reading material is often on unknown topics (decontextualized).

As content becomes more syntactically complex, the child requires a facility with syntax to be able to read and understand the material, especially if its content is not familiar. Dyslexic individuals often have a history of poor morphosyntactic development. Thus, more ambiguous and abstract language presents obstacles to comprehension. Similarly, the impoverished vocabulary stores of some children seriously impact their reading comprehension; although they might be able to decode the word, they do not know what it means.

If a child presents with a reading disability, consideration of each factor on the schematic might clarify which factors are playing a role and need to be addressed in the treatment plan. Weakness in the representation of articulatory gestures and phonologic representations implicates lower-level sensory processing, as do difficulties with auditory processing. Do the children complain of words moving on the page? Talcott et al. found a unique variance for visual motion sensitivity and orthographic skills and a similar variance for auditory sensitivity to change and phonologic skills in a subset of subjects with dyslexia.[54] Rapid word retrieval is often a factor in inefficient reading and is thought to be the result of deficits in phonologic, morphologic, and semantic processing; attention; executive function; articulatory processing; and/or a weak visual-verbal connection.[22,72] There is presumed to be an interplay between all of these neural components, so that a breakdown in any one could result in problems. Wolf et al. pointed out that these same networks subserve reading and might account for the word retrieval deficits being found in the poorest readers.[22] Children with these retrieval deficits progress more poorly and have significant difficulty with sight word reading, especially with fluency. A poor vocabulary suggests weak semantic representations, creating fewer resources for comprehension. A weak syntactic system would contribute to difficulty with comprehension as well. Impaired attention, working memory, and executive function and intention resources could contribute to inefficient acquisition of reading from both a bottom-up and a top-down approach. Slow temporal processing strains the time-sensitive working memory system too. Interventions designed to address the needs of the individual child should consider all of these factors.

The most prevalent comorbid condition impacting the development of the individual with dyslexia is attention deficit. Optimal attention increases learning. Attention deficit results in inconsistent perception of stimuli hampering the development of strong neural connections and weakens the working memory necessary for processing multiple perceptions. Optimal treatment of the attention deficit is an imperative. The child who is struggling with cognitive and linguistic development places more demand on the attention system when learning, and research has found it to be a deterrent to a good response to intervention.

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