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To read, humans 'recycled' a brain region meant for recognizing objects

To read, humans 'recycled' a brain region meant for recognizing objects
Researchers used the neural activity of macaque monkeys to prove humans recycled a region of the cortex for the purpose of reading. Photo by Rocktendo and Adam Gman/Wikimedia Commons

Aug. 4 (UPI) -- Humans began reading just a few thousand years ago, a relatively recent phenomena -- too recent to be supported by brain regions specifically evolved for the activity.

Previously, neuroscientists have hypothesized that humans repurposed, or "recycled," parts of the brain for reading. Now, they have proof.

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New research by scientists at MIT showed even the brains of nonhuman primates are predisposed for distinguishing words from non-words.

The findings, published Tuesday in the journal Nature Communications, suggest the inferior temporal cortex, or IT cortex, was recycled by humans for the purpose of orthographic processing, or reading.

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"This work has opened up a potential linkage between our rapidly developing understanding of the neural mechanisms of visual processing and an important primate behavior -- human reading," senior study author James DiCarlo, head of the department of brain and cognitive sciences at MIT, told MIT News.

Previously, researchers have shown that baboons can be trained to distinguish between real words and nonsensical strings of letters. But the neural architecture underpinning this ability has remained a mystery.

For the new study, researchers recorded neural activity in the inferior temporal cortex and visual cortex while untrained macaque monkeys viewed images of letters, some words and some random strings of letters.

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The team of scientists then fed the inferior temporal cortex data through a computer model called linear classifier. The model was able to recognize data signatures that correctly predicted whether the letters that sparked the activity patterns were words or not.

"The efficiency of this methodology is that you don't need to train animals to do anything," Rishi Rajalingham, an MIT postdoc and lead author of the new study, told MIT News. "What you do is just record these patterns of neural activity as you flash an image in front of the animal."

Researchers used the model to distinguish words from non-words, as well as recognize letters in words. The model achieved 70 percent accuracy using the inferior cortex data, but when scientists used data from the visual cortex, the model was significantly less accurate.

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The experimental results suggest parts of the primate brain that evolved for object identification and uniquely predisposed for the task of reading, researchers said.

"These results show that the IT cortex of untrained primates can serve as a precursor of orthographic processing, suggesting that the acquisition of reading in humans relies on the recycling of a brain network evolved for other visual functions," researchers wrote in the study.

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