Rather than having to sound out each word as we did in first grade, the brains of skilled readers can quickly recognize familiar words as pictures.
This works because each word you learn to read is stored in your brain’s ‘visual dictionary.’ This area functions separately from the part of the brain that processes the sounds of written words, according to a new study by neuroscientists at Georgetown University Medical Center (GUMC).
This visual dictionary theory challenges the common notion that the brain needs to “sound out” words each time we see them.
“One camp of neuroscientists believe that we access both the phonology and the visual perception of a word as we read them, and that the area or areas of the brain that do one, also do the other, but our study suggests this isn’t the case,” said the study’s lead investigator, Laurie Glezer, Ph.D., a postdoctoral research fellow.
“We show that the brain has regions that specialize in doing each of the components of reading. The area that is processing the visual piece is different from the area that is doing the sounding out piece.”
The findings help unravel how the brain solves the complex task of reading and may help pinpoint the underlying issues in reading disorders, such as dyslexia, say the scientists.
“Beginning readers have to sound out words as they read, which makes reading a very long and laborious process,” said Glezer. “Even skilled readers occasionally have to sound out words they do not know. But once you become a fluent, skilled reader you no longer have to sound out words you are familiar with, you can read them instantly.”
Using fMRI, the researchers tested word recognition in 27 participants in two separate experiments. They found that pairs of words that sound the same — such as hare and hair — activate totally different neurons, similar to accessing different entries in a dictionary’s catalog.
“If the sounds of the word had influence in this part of the brain we would expect to see that they activate the same or similar neurons, but this was not the case — ‘hair’ and ‘hare’ looked just as different as ‘hair’ and ‘soup.'”
This finding suggests that this particular region of the brain only uses the visual information of a word and not the sounds, said Gezer. In addition, the researchers found another distinct brain region that was sensitive to the sounds, where ‘hair’ and ‘hare’ did look the same.
“This suggests that one region is doing the visual piece and the other is doing the sound piece,” explains study leader Maximilian Riesenhuber, Ph.D.
Riesenhuber says that these findings might help explain why people with dyslexia have slower, more labored reading. “Because of phonological processing problems in dyslexia, establishing a finely tuned system that can quickly and efficiently learn and recognize words might be difficult or impossible,” he says.
The study is published online in the journal NeuroImage.