Dehaene et al. have done an interesting study of how our brains deal with written language, which appeared only about 5,000 years ago and thus must use brain circuit evolved for other purposes. Not surprisingly, areas that originally evolved to process vision and spoken language respond more strongly to written words in literate than in illiterate subjects. This repurposing may have involved a tradeoff: for people who learned to read early in life, a smaller region of the left occipital-temporal cortex responded to images of faces than in the illiterate volunteers. (The figure shows brain regions that respond more strongly to text in people who can read.):
Does literacy improve brain function? Does it also entail losses? Using functional magnetic resonance imaging, we measured brain responses to spoken and written language, visual faces, houses, tools, and checkers in adults of variable literacy (10 were illiterate, 22 became literate as adults, and 31 became literate in childhood). As literacy enhanced the left fusiform activation evoked by writing, it induced a small competition with faces at this location but also broadly enhanced visual responses in fusiform and occipital cortex, extending to area V1. Literacy also enhanced phonological activation to speech in the planum temporale and afforded a top-down activation of orthography from spoken inputs. Most changes occurred even when literacy was acquired in adulthood, emphasizing that both childhood and adult education can profoundly refine cortical organization.
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