The evolutionary wonder of reading – hints from intracranial electrophysiology

I don’t know why creationists get hung up with the Platypus or the retina. I think it’s much more interesting that humans can read, despite it only being around for a few hundred years. For example …

Rare Procedure Pinpoints the Location, Speed and Sequence of the Brain's Language Processes: Scientific American

As part of preparation for their [epilepsy] surgery, three adults had electrodes implanted in Broca's area and anterior temporal cortex to allow doctors to pinpoint which areas of the brain would be best to remove. During the procedure, known as intracranial electrophysiology, researchers asked the patients to silently sound-out words they saw on a screen and to fill in the missing verb in the proper tense or the proper form of a missing noun. Meanwhile, the researchers were recording the local electric field potentials from the wired areas of subjects' brains to the nearest millisecond—and millimeter.

After studying the readouts, the researchers found that in these normally reading adults, word identification, grammar and pronunciation all activated parts of Broca's area—and in a very neatly defined sequence. Like clockwork, it took about 200 milliseconds to identify a word, 320 milliseconds for grammatical composition and 450 milliseconds for phonological encoding…

… Previous studies had shown that the brain takes about 600 milliseconds to form vocal speech. So the speed with which each of these processes occurred was not as big of a surprise to Sahin and his colleagues as the fact that these three distinct tasks were done separately, in a tightly timed sequence, and within millimeters of each other in the brain…

… The electrical readouts … help to dispel the theory that another part of the brain, Wernicke's area, is primarily responsible for reading and hearing language. Their data show that, in fact, Broca's area also activated during the reading and identification phases. These findings, "indicate that the role of Broca's area…should be characterized in more general terms," Hagoort and Levelt wrote…

Everyone wants to see this study repeated in persons with reading disorders, but this kind of opportunity is rare. We all owe thanks to these patients who helped out with this study while awaiting some pretty scary surgery.

See also:

• Hyperlexia: an explanation of why we can read? – 2004
• Reading and hand signals (2009)
• Be the Best You can Be- Understanding why reading is hard (Oct 2009)