Brain Primer

Deciphering Dyslexia

  • Reviewed3 Apr 2023
  • Author Karen Weintraub
  • Source BrainFacts/SfN
Little girl at desk working via Phynart Studio

Imagine every time you read some text, the letters in between words continually scrambled around. For some people with dyslexia, this is what happens each time they read a book or labels at the grocery store.

Dyslexia is the most common and best-studied of learning disabilities, affecting as many as 15-20% of all people in the U.S. People with dyslexia have a pronounced difficulty with reading despite having standard intelligence, education, and motivation.

Symptoms include trouble with pronunciation, lack of fluency, difficulty retrieving words, poor spelling, and hesitancy in speaking. People with dyslexia might need more time to respond orally to a question and might read more slowly than their peers. Dyslexia is usually diagnosed during elementary school years, when a child is slow to read or struggles with reading. Although reading skills and fluency can improve, dyslexia often persists lifelong.

Deciphering printed letters and words, as well as recalling their sounds and meanings, involves many areas of the brain. Brain imaging studies indicate these areas can be less well-connected in people with dyslexia. One of these areas is a region on the left side of the brain called the visual word form area (VWFA), which is involved in the recognition of printed letters and words. People with dyslexia also show less brain activity in the left occipitotemporal cortex, which is considered essential for skilled reading — or fluent execution and coordination of word recognition and text comprehension.

Researchers believe such brain differences are present before the reading and language difficulties become apparent; although another possibility is that people with dyslexia read less and, therefore, their brains develop less in the regions associated with reading. Those with dyslexia also appear to compensate for the reduced activity on the left side of the brain by relying more heavily on the right side.

Genetic analyses have revealed a handful of susceptibility genes, with animal models suggesting these genes affect the migration of brain cells during development, leading to differences in brain circuitry. Dyslexia tends to run in families, with roughly half of those with dyslexia sharing the condition with a close relative. If one twin is diagnosed with dyslexia, the second twin is likely to have the condition 55-70% of the time. But the genetics of dyslexia is complex, and likely involves a wide range of genes and environmental factors.

Treatment for dyslexia involves behavioral and educational intervention, especially exercises like breaking words down into sounds and linking the sounds to specific letter patterns. Some researchers evaluate a child’s ability to name things rapidly and automatically as an early indicator of dyslexia. This rapid automatic naming, and the ability to recognize and work with the sounds of language, are often impaired in people with dyslexia. Both skills can be used in observing preschoolers and kindergartners to predict their later reading skills. Research suggests that treatments targeting phonology, as well as multiple levels of language skills, show the greatest promise. 

Adapted from the 8th edition of Brain Facts by Karen Weintraub.



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