In learning
to read, squiggles and lines transform into letters or characters that carry
meaning and conjure sounds. A trio of cognitive neuroscientists has now mapped where
that journey plays out inside the brain.
As readers
associate symbols with pronunciation and part of a word, a pecking order of brain areas processes
the information, the
researchers report August 19 in the Proceedings
of the National Academy of Sciences. The finding unveils some of the
mystery behind how the brain learns to tie visual cues with language (SN
Online: 4/27/16).
“We didn’t evolve to read,” says Jo Taylor, who is now at University College London but worked on the study while at Aston University in Birmingham, England. “So we don’t [start with] a bit of the brain that does reading.”
Taylor — along with Kathy Rastle at Royal Holloway University of
London in Egham and Matthew Davis at the University of Cambridge — zoomed in on a region at the back and bottom of the brain,
called the ventral occipitotemporal cortex, that is associated with reading.
Over two
weeks, the scientists taught made-up words written in two unfamiliar, archaic
scripts to 24 native English–speaking adults.
The words were assigned the meanings of common nouns, such as lemon or truck. Then
the researchers used functional MRI scans to track which tiny chunks of brain in
that region became active when participants were shown the words learned in
training.
The way
letters look — curves or staunch lines — takes hold in the back of the
ventral occipitotemporal cortex, the team found. But when sounds and meanings come
into play, an area further forward in that brain region that better handles
abstract concepts seemed to kick into gear.
The study
“very clearly depicts the transition of a word … as you go from the eye to
the cortex, and as you move along the cortex,” says David Rothlein, a cognitive
neuroscientist at the VA Boston Healthcare System not involved with the work.
Words in the
two scripts that had similar pronunciations or meanings triggered similar brain
activity, the team found. The brain can make sense of words written in
different fonts or sizes not just from the visual cues, but because the brain
also connects the information with what it knows about spoken language, Taylor
says. And eventually, “when you see a word, you immediately get its sound and
its meaning without any effort.”
The brain
region mapped in the study is known to process visual information. A few recent
studies suggest that learning to read makes parts of the ventral
occipitotemporal cortex more tuned into reading by displacing other functions,
such as recognizing objects, or by encroaching on areas that are less tied to
specific functions, Rastle says. This reorganization could be how reading
becomes automatic. “Without that pathway … we would be like children reading
letter by letter,” she says.
This content was originally published here.