The Frontal Cortex

Over at Mind Matters, the expert blog I curate at Scientific American, we've had some really good posts lately. The most recent post, by Maryanne Wolf (author of that other Proust book on neuroscience, Proust and the Squid), Mirit Barzillai and Elizabeth Norton, looks at the reading brain. They discuss a recent paper by Laurent Cohen, Stanislas Dehaene and colleagues. (Look here for a recent profile of Dehaene in the New Yorker.)

The late, eminent cognitive scientist David Swinney of UCSD described how it is only in the acquisition of routines that later become automatic that we can see processes exposed before they become so smoothly conducted by our unconscious that they are impervious to our investigations. In their most recent study in Neuroimage, however, Cohen, Dehaene, et.al. found ways to explore aspects of these larger questions through several inventive and probative methods with adult, expert readers. In essence, the researchers tricked the mature reading brain into revealing what it does when the text to be read is unfamiliar, and can't be automatically perceived and processed. Previous research by their group demonstrated that the brains of expert readers who are looking at typical, routinized passages involve parallel activation of letters and words by neural detectors in an area of the brain often referred to as the visual word form area (VWFA), a region located in the occipital and temporal cortex in the left hemisphere. Although the entire reading circuitry is not yet fully established, it is believed that this pathway (called the ventral system or route), processes words that are familiar at virtually automatic speeds.

In the latest study, the researchers sought to determine the limits of the ventral system. They asked 12 adult participants to read words of different lengths that were either intact or degraded (transformed) in one of three ways: they were rotated up to 90 degrees in either direction; extended visually in length, with up to three spaces between letters; or shifted into the far right or left visual field. As one might expect, the more degraded the visual representation of these words, the longer it took to comprehend them. Furthermore, reading time was related to the length of the words only when they were very degraded, suggesting that degraded words were being consciously deciphered. So far, so predictable. Results from functional MRI scans, however, provided far more interesting insights. Although intact or slightly degraded words activated the VWFA and the ventral route, text that was highly degraded activated another area often described as part of the dorsal route. This route has been linked to letter-by-letter processing especially in children who are learning to read.

The brain never ceases to impress me. It's easy to forget that reading - this ability to make sense of abstract symbols - is a purely cultural invention. Back in the Pleistocene, when natural selection was engineering the human brain, it never imagined that we'd get so obsessed with written language. And yet, thanks to the wonders of cortical plasticity, the mind has managed to internalize the skill, so that we can read this sentence without even thinking about it. It's as if your computer sprouted new microchips depending on how you used it.

The other thing I like about this study is that it helps explain why my least favorite class in college was a seminar I took on The Canterbury Tales, which required us to read the text in Middle English. I now realize that the archaic words activated my dorsal reading system.