Reading for your brain

Can literacy change the way your brain works?

While reading and writing are now part of our daily lives, there was a time when mankind relied almost exclusively on spoken language to communicate, and memory to archive and pass on its knowledge to new generations. Strictly speaking, writing is not merely the graphical representation­­­­­­ of things and ideas, rather it is the use of unitary symbols to form scripts that represent these ideas and things. Hieroglyphs and other pictorial forms of semantic expression were used by several ancient societies in various parts of the world, probably as early as 6000 B.C.; however it is thought that writing appeared later, sometimes around 2000 B.C. in the form of cuneiform symbols such as those seen on the image to your left.

Along with writing came reading, the art of deciphering the above-mentioned scripts. Such formalization of language came at a high cost: intensive learning. Originally, scribes were the only members of ancient societies who trained to become experts in the art of reading and writing, dedicating their lives to their craft. Today, as we all know, the reading and writing skills that were once the privilege of a minority have now become widespread. All children are taught to read and write at a young age with some exceptions in developing countries. Learning to read is a long process that requires intensive training but reading (and writing) eventually emerges as one of our effortless cognitive abilities. Like all forms of learning, literacy entails changes in our brain. Neuroscientists think that learning occurs because experience changes the strength of synaptic connections and the wiring of neural circuits leading to the reorganization of patterns of brain activity and changes in our behavior.

While 3000 years – the age of writing and reading – sounds like a lot of time, it is nothing compared to the several hundred thousands of years required for evolutionary changes to occur. Thus, as a relatively recent cultural invention, it is unlikely that reading could have an exclusive processing place in our brain. Instead the act of reading must recruit brain regions that had originally evolved for entirely different purposes. One such region is called the Visual Word Form Area or VWFA and is known to be activated by visual items such as places and human faces and of course written words. When learning to read, regions such as the VWFA could get hijacked and eventually reorganized, potentially biasing their function and focus away from their original role. An interesting question arises from this reasoning: could learning to read have deleterious effects on brain function? Conversely, could the transformative changes that take place with the development of literacy lead to beneficial changes by enhancing certain cerebral abilities?

These interesting questions have begun to be addressed by a group of researchers led by cognitive neuroscientist Stanislas Dehaene in Paris. Although previous studies had looked at these questions by comparing the brain activity of literate and illiterate individuals, they had ignored an important confounding factor, that is, the effect of schooling on brain function. Dehaene and his colleagues designed their experiment so that they could rule out this effect of schooling by including so-called ex-illiterates, who had learned to read as adults (and who had not been schooled). Subjects from literate, illiterate and ex-illiterate groups were asked to sit in a brain scanner to undergo functional Magnetic Resonance Imaging or fMRI (see technical note below). Using this technique, Dehaene’s group was able to look at the impact of literacy on the patterns of brain activity in response to various visual or verbal items, including semantic ones.

As explained earlier, one of the brain regions recruited by written language is the Visual Word Form Area or in Dehaene’s own words, “the brain’s letterbox”. As expected, the VWFA was highly active during the presentation of written words but not so during the presentation of spoken language. In addition, it did not appear as active on the brain scans of illiterate individuals confirming its role in orthographic recognition. Interestingly, the VWFA was also strongly recruited during the visual presentation of faces and places. Did literacy interfere with the representations of places and faces in the VWFA? Yes. The researchers found that the level of literacy was correlated with a decrease in the activation of the VWFA in response to faces. Thus literacy, by co-opting the VWFA, does indeed work at the detriment of other brain functions, in this case certain aspects of visual perception.

What about the other possibility? Can the specialization of the brain in recognizing and interpreting written scripts change brain activity in an additive rather than subtractive way? During presentation of spoken language, the scans from literate individuals showed a larger recruitment of visual areas than those of illiterates. In other words the literates could “see” spoken words through their inner eye. The converse was also true in that literates could “hear” written words via their inner voice. These results demonstrate that the acquisition of reading skills influences the interactions between the brain channels that process semantic auditory and visual stimuli and that these parts of the brain probably get rewired during learning.

In summary, literacy brings two types of activity changes in our brain. First, it allows the reorganization of the visual cortical areas that are important for language processing, including the VWFA. In particular, learning to read seems to introduce a competition between written words and faces. The result is a weaker brain signal in response to faces in literate people. Could this mean that literacy undermines one’s ability to recognize or understand facial features? Maybe… but it is important to mention that the decreases in face signals were small and that it remains unclear whether this effect could have detrimental behavioral repercussions. The potential impact of literacy’s recycling of the VWFA on face perception will be tested in the future, says Dehaene in an interview for the journal Science. The second type of changes that literacy promotes is the recruitment of areas that are important for processing spoken language during the perception of written texts and vice versa. Thus, despite being a late cultural invention, reading can dramatically reorganize the parts of our brain involved in one of our defining cognitive abilities, speech.

Another important message from this study is that literacy acquired in adulthood seems to lead to changes in the brain that are similar to those occurring in childhood. This is surprising as neuroscientists think that as the brain matures after birth, it progressively loses some of its capacity to learn and adapt. Dehaene’s study however shows that the reorganization of the brain’s networks that take place while acquiring literacy are not restricted to young and malleable minds but instead accompany learning at any stage of development. This is true overall but with at least one notable exception: the face competition effect is absent in ex-illiterates. In addition to books, children should perhaps be taught to “read” faces too.

Original article:
ResearchBlogging.orgDehaene S, Pegado F, Braga LW, Ventura P, Nunes Filho G, Jobert A, Dehaene-Lambertz G, Kolinsky R, Morais J, & Cohen L (2010). How learning to read changes the cortical networks for vision and language. Science (New York, N.Y.), 330 (6009), 1359-64 PMID: 21071632

Also, more on the subject of reading in Dehaene’s new book (you can also check a recent commentary on his book here)

S.T.

(technical note: fMRI signals tell us which parts of the brain are active during behavior but also how active these parts are. However, these signals are an indirect measure of brain activity in that they are generated in response to an increase in cerebral blood volume. Such increase in blood volume occurs when blood vessels dilate to accommodate an increase in energy demand.  The more active our neurons are, the more energy they need and thus an increase in fMRI signal is indicative of an increase in brain activity. For example, voluntarily contracting a muscle will always be accompanied by activity in the specific motor cortical areas that control that muscle and these areas will “light up” on brain scans taken during the flexion.)


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4 thoughts on “Reading for your brain

  1. Interesting. I wonder whether a blind person has an active VWFA when she/he touches someone’s face?
    Also, it would interesting to know whether blind people have their language network reorganized (with a bias toward the sense of touch) and whether any type of competition with non-semantic perception exists after they learn to read braille…
    Isn’t the brain a fascinating place!

  2. Hm… so that could mean: more literate = less able to recognize faces?

    I have a friend who reads a lot (he spends a lot more time with books than with people), and he has a really bad memory for people’s faces. Funny if there is a neurological reason for that.

  3. Pingback: Leer cambia nuestro cerebro | Metablogos

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