Understanding Brain Differences in Dyslexia

Dr. Guinevere Eden explains what’s different in the brain of a person with dyslexia. 

There are differences in the brains of people with dyslexia that we can measure with brain imaging, and it's believed that many of those differences already are present at birth. Other differences may be there because of them not having the same kind of reading experience as a person who doesn't have dyslexia. We measure these differences primarily with magnetic resonance imaging, and the differences that we see are reflected in the different kinds of analysis we can do with MRI.

We have people inside the scanner to say a reading task or a sound deletion task, and we look at how the activity in the brain differs. That activity is measured locally in the brain—which areas differ—but also, people use the data to look at the amount of correlation across those different areas, so it's sort of functional connectivity. You can take any of these measures and try to incorporate them all together to get a really good understanding of how the brain in people with dyslexia differs in terms of the anatomy, the function, and as a network, how all these areas fit together. The errors that we're talking about are mainly areas involved in reading or in skills that we know support reading.

The finding that most people agree on is that when you look at the left hemisphere in studies of groups of people with dyslexia and people who do not have dyslexia—and I emphasize it's really group studies—there are differences in the anatomy, primarily in the left hemisphere, in regions that are known to support written language. That's also where we see differences in activity. When those participants are doing a task that involves reading or something like manipulating phonemes, they may under-activate those parts of the brain. They're not using them quite to the same level, even though they were actually doing the tasks; they just aren't engaging those areas quite so much, particularly in the back of the brain, in the areas around the temporal and parietal cortex that are involved in helping us understand how sounds are made up of words and how we map sounds to print.

There's also an area at the bottom of the temporal lobe that's involved in visual word form recognition. This is an area that we use when we read and recognize words by sight. It's an area that a skilled reader trains up; that's how we become automatic readers. And that's also an area that's not activated the same way in people who have dyslexia compared to those who do not.

SUGGESTED CITATION

National Center on Improving Literacy. (2025). Understanding Brain Differences in Dyslexia. Washington, DC: U.S. Department of Education, Office of Elementary and Secondary Education, Office of Special Education Programs. Retrieved from improvingliteracy.org.