There are certain skills that, once you learn them, you can reasonably expect to remember forever. Counting, reciting the alphabet, signing your own name — all things that stick with you, unless illness or injury takes them away.
Which makes it all the more jarring when one of those basic skills suddenly disappears. In Scientific American yesterday, Yale University psychiatry resident Daniel Barron described the case of “Mike Brennan” (a pseudonym), a 63-year-old man who went to work one morning in 2010, sat down at his desk with the morning newspaper, and discovered he no longer had the ability to read. He hadn’t suffered any trauma, wasn’t battling any neurological disease — it was like his reading ability had been lifted cleanly out of his head, leaving him otherwise healthy and intact.
The problem: Brennan, a cardiology technician, was a former smoker who had struggled with high blood pressure, both of which he knew to be risk factors for stroke. Fearing that might be what was happening, he went to the ER for testing, which revealed no other symptoms — his vision and hearing were normal, he still knew the names of objects and colors, and he had no trouble thinking clearly. The only issue was reading: He could recognize letters, but he couldn’t string them together; he could write, but he couldn’t make sense of what he’d put on the page.
The diagnosis: Brennan was diagnosed with “pure alexia,” defined as “a selective impairment of reading in the absence of other language deficits [that] occurs as a consequence of brain injury in previously literate individuals.” In his case, as he had suspected, the injury turned out to be a stroke – a tiny one, in a part of the brain called the left inferior occipitotemporal cortex, which helps process visual information.
Mystery solved. Except, Barron wrote, two things were particularly unusual about Brennan’s diagnosis: One, it was the first time that such a small stroke had caused the disorder, which usually results from much more significant injuries. And two, it pointed to the existence of a part of the brain that scientists had been hotly debating for years.
The “visual word form area” — a brain structure specifically devoted to processing letters — was first proposed in the 1990s by researchers who noticed that reading caused an uptick in activity in the left inferior occipitotemporal cortex, where Brennan’s stroke occurred. The theory immediately led to controversy, Barron wrote — “the kind that, at a conference, provokes shouts and screams from otherwise calm and collected scientists”:
For one thing, the very search for a “visual word form area” was misguided because it personified the brain’s real work, which is to process and decode visual information. Brain regions act as an assembly line of neural groups that each contribute some cognitive rivet or weld to a larger percept. A visual word form area confused an assembly line for a one-man-band.
Finally there was the problem of evolution. Because reading was a relatively new cultural invention, humans couldn’t have evolved to read text in the same way that mammals evolved to recognize faces—there simply hadn’t been enough time. This made it hard to believe in a brain structure expressly devoted to reading.
Over the next several years, though, a series of studies incrementally pushed scientists closer to accepting the possibility. One experiment — conducted on a group of illiterate Colombian guerilla fighters trying to reintegrate into society — found that as adults learned to read, gray matter builds up in specific parts of the brain. Another, comparing literate and illiterate adults, zeroed in on changes in the left inferior occipitotemporal cortex: “When one learns to read,” Barron explained, the area “is recycled from a general visual recognition center to a specialized word recognition center, at the expense of other tasks.”
And then came Brennan’s case — “the final piece of the puzzle,” as Barron put it, proving the existence of the visual word form area by showing what happened when it was damaged. It’s also a powerful example of the brain’s flexibility: “The way in which the area is repurposed from general visual recognition to word specialist,” he wrote, “is a reminder of how powerfully the brain can retool and adapt—essential processes both in learning and healing.” There’s plenty scientists still don’t know about this part of the brain, but in the meantime, as they work to figure it out, Brennan — with the help of a speech-language therapist and repeated grade-school style vocabulary drills — has relearned how to read.