Reading skill linked to differences in brain structure

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Brain scans have given scientists fresh insights into how we read.

A China-US team subjected hundreds of volunteers to a battery of tests before also imaging the brains of some of their participants.

The scans revealed separate parts of the brain were likely to be involved in different aspects of reading, such as being able to sound words out loud.

The work, published in the Journal of Neuroscience, could lead to new ways to help those with reading difficulties.

Gui Xue, from Beijing Normal University, who led the study, said: "By looking at structure function correlations, we can have a better understanding of the neural basis of reading ability. This could help us understand the nature of reading disabilities."

Not only this, but he suggests the research could possibly be used to predict who might go on to develop reading problems, perhaps before a child even starts to read.

However, Xue concedes more research would be needed first, as the association between brain structure and reading ability was only investigated in adults in this study. The relationship may be different in children.

See and sound

Three aspects of reading were identified by the study. These were the ability to sound out written words, how well participants connected newly seen words with sounds, and their ability to read out loud at speed. Skill in one of these aspects seems to be unrelated to ability in another. And, for the most part, they appear to be relatively independent from more general intelligence and mental ability.

The researchers used scanning to investigate the structure of the brain. They looked at grey matter volume, which relates to the density of neurons in a given brain area.

They found that ability to sound out words was associated with differences in an area of the brain called the left superior parietal lobe. This region, they point out, is known to be involved with integrating information from different senses, so its involvement with looking at a word and turning it in to speech is plausible.

Differences in how well participants connected a new word with a sound were found to be related to structural differences in brain areas called the hippocampus and cerebellum. The hippocampus in particular has been shown many times to be related to memory.

Interestingly, this study shows a relatively low association between remembering items and hippocampus grey matter volume. This, the researchers say in their paper, suggests the area is particularly important for remembering connections between things (as in between a word and a sound), rather than simply remembering items.

The final aspect of reading identified, the ability to read out loud at speed, was found to be less localised, with a network of areas across the brain showing different grey matter volume. They also found this ability to be the only one of the three that was also related to general intelligence.

Hard task

The researchers say they are not surprised that different brain areas are involved in different aspects of reading, due to its complexity as a task.

One important issue to note is that a lot of the tasks performed by the volunteers in the study were executed in Chinese.

Written Chinese is very different to many other written languages, as its symbols represent whole words, rather than the sounds that build up words. Because of this, it is slightly harder to know whether the same brain regions would be involved in the reading of other languages.

Xue said, "[Word]-sound associations in the hippocampus and cerebellum might be more general to the world population. But [how to sound out written words] - we think that might be to do with some cultural differences: the difference between Chinese as a language [and other types of language], and the difference in early language experience."

Because the participants also spoke English from their early teens, some findings may not be the same in people who only speak one language, for example, or those who are fluent in at least two.

The researchers plan to look at a different type of imaging in a future study, where participants' brains are scanned while they do a task, to assess whether these parts of the brain are active. If this study shows selective activation in similar areas across these different tasks, it will provide even more compelling evidence of their involvement.

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