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The number of people who read for fun seems to be steadily declining. According to research from the Reading Agency, 50% of British adults say they don’t read regularly (up from 42% in 2015) and almost one in four 16-24 year olds say they have never been a reader.
But what are the implications? Will people’s preference for videos over texts affect our brains or our evolution as a species? What kind of brain structure do good readers actually have? My new study, published in NeuroImage, found this out.
I analyzed open-source data from more than 1,000 participants to find that readers with different abilities had distinct traits in brain anatomy.
The structure of the two regions of the left hemisphere, crucial for language, was different in people who were good at reading.
One was the anterior part of the temporal lobe. The left temporal pole helps associate and classify different types of meaningful information. To assemble the meaning of a word like legThis region of the brain combines visual, sensory, and motor information that conveys the look, feel, and movement of the legs.
The other was Heschl’s gyrus, a fold on the upper temporal lobe that houses the auditory cortex (the cortex is the outermost layer of the brain). Better reading ability was linked to a larger anterior part of the temporal lobe in the left hemisphere compared to the right. It stands to reason that having a larger brain area dedicated to meaning makes it easier to understand words and, therefore, read.
What might seem less intuitive is that the auditory cortex is linked to reading. Isn’t reading primarily a visual skill? Not only that. To associate letters with speech sounds, we must first be aware of the sounds of the language. This phonological awareness it is an established precursor to children’s reading development.
A thinner left Heschl’s gyrus has previously been linked to dyslexia, which leads to severe reading difficulties. My research shows that this variation in cortical thickness does not draw a simple dividing line between people with or without dyslexia. Instead, it extends to the broader population, where a thicker auditory cortex correlates with more proficient reading.
Because size matters
Is thicker always better? When it comes to cortical structure, no, not necessarily. We know that in most people the auditory cortex has more myelin in the left hemisphere. Myelin is a fatty substance that acts as an insulator for nerve fibers. It increases the speed of neural communication and can also isolate columns of brain cells from each other. Neural columns are thought to function as small processing units.
Their greater isolation and rapid communication in the left hemisphere may be thought to allow for the fast, categorical processing necessary for language. We need to know if a speaker uses the category D OR T when it is said Dear OR tear rather than detecting the exact point at which the vocal cords begin to vibrate.