© S. Dehaene et al./Science
Reading lesson. A new study identifies several brain regions (colored areas) that respond more strongly to text in people who can read.
Written language poses a puzzle for neuroscientists. Unlocking the meaning in a string of symbols requires complex neural circuitry. Yet humans have been reading and writing for only about 5000 years - too short for major evolutionary changes. Instead, reading likely depends on circuits that originally evolved for other purposes. But which ones?
To investigate, cognitive neuroscientist Stanislas Dehaene of the Institut National de la Santé et de la Recherche Médicale in Gif-sur-Yvette, France, teamed up with colleagues in France, Belgium, Portugal, and Brazil to scan the brains of 63 volunteers, including 31 who learned to read in childhood, 22 who learned as adults, and 10 who were illiterate. Those who could read, regardless of when they learned, exhibited more vigorous responses to written words in several areas of the brain that process what we see, the group
reports online today in
Science.
Based on previous work, Dehaene has argued that one of these areas, at the junction of the left occipital and temporal lobes of the brain, is especially important for reading. In literate, but not illiterate, people, written words also triggered brain activity in parts of the left temporal lobe that respond to spoken language. That suggests that reading utilizes brain circuits that evolved to support spoken language, a much older innovation in human communication, Dehaene says.
