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The ability to recognize and assign meaning to shapes and symbols – known as orthographic processing – is unique to humans, a skill acquired relatively recently in human history. Scientists believe that orthographic processing was not a newly developed skill; rather, it built on neuronal mechanisms already in use. Findings from a new study demonstrate that a part of the brain called the inferotemporal cortex facilitates orthographic processing.
The inferotemporal cortex is a region of the brain located on the underside of the temporal lobe, the part of the brain closest to the ear. It plays critical roles in the visual processing and visual recognition of objects.
The authors of the study recorded the activity of hundreds of neurons in V4 (a region of the visual cortex) and the inferior temporal cortex of monkeys while the animals viewed images of letters, words, and non-word letter combinations. The authors used a special computerized model to predict whether the monkeys' brain activity was associated with a word or a non-word. Monkeys are good models for understanding aspects of human visual processing because they share similar behaviors and underlying brain mechanisms with humans.
They found that the inferotemporal cortex of the monkeys could accurately extract explicit representations of written letters and words, suggesting that this region of the monkeys' brains acts as a sort of precursor to orthographic processing. These findings suggest that humans' ability to read arose from other mechanisms that were “repurposed” for this unique skillset.