Just yesterday in my post I said that reading is a complex skill distributed all over the brain and sort of reinvented by each person as they learn to read, which is much easier and more supported if the reader is in a culture where people read and think about the meanings in terms of their own lives. Now today I want to examine something that goes the other way: a tiny little part of the brain that is ALWAYS present when the brain is reading. It’s “a small region at the base of the left hemisphere, always at the same place, give or take a few millimeters.” This is the “visual word form area,” pop-named “the brain’s letter box.” It’s the little gizmo that can recognize the letters of the alphabet. Since the alphabet was only invented 4,000 years ago and the brain was invented a zillion millennia ago, even earlier than mammals, the letterbox was clearly converted from some pre-existing use. After all, until recently most people didn’t read and in many places it is still an elite activity. One clue is that if this “letterbox” is destroyed, one is afflicted by “pure alexia” which means being unable to recognize faces, objects, digits, and Arabic numerals. You might think your wife was your hat. But there would be no problem with speaking and understanding spoken language and some can still write, so long as they don’t have to read it back.
The specific function is processing letter streams: recognizing the actual visual shapes of the letters lined out or as Stanislas Dehaene, the scientist who does this research, puts it, “simple shapes, such as those formed by the intersections of contours of objects.” Some neurons are sensitive to “letter-like combinations of lines such as T, L, X and *. “ These “shape primitives” evolved way back in the history of primates. For reading to be learned, these little shapes must link up with the larger “speaking” territories of the brain, a mixture of places that tend to be on one side or the other. A person might have left-handed or right-handed speech centers, so if the shape recognition gets hooked up with the wrong side of the brain, there’s trouble.
The next problem is that brains allot space according to its use -- if you do something a lot, the brain responds like a muscle: new skills mean new neurons or the conversion of old ones to new uses. Learning to read crowds the brain, so that some neurons on the reading side won’t recognize faces as well and get shifted to the other side to make room. Some dyslexics haven’t done this. Trying to force kids to learn letters with the unnatural side makes trouble.
A third problem in development is distinguishing mirror images from each other: “p” is backward “q”, “b” mirrors “d”. This difference comes from the evolved ability to see shapes like a deer’s head, whether it’s pointing left or right. To successfully read, one must see the shape as a different “animal” if it points in the other direction.
The advantages are that once the reading ability is connected to the all-brain speaking and processing, the latter becomes much more powerful and discriminating, allowing ease in the comprehension of complex sentence meanings. It appears that a small area that manages sound, the left planum temporale, is the gizmo that comes next after recognizing the letter -- it is the part that connects the printed shape to the spoken sound. A person who learns to read nearly doubles the power of this spot and then connects it to other parts of the brain, especially the parts that analyze, evaluate, create, and understand.
There is one more factor in this re-organization of size and connection that so increases the power of the brain and that is the actual construction of the neuronal pathways, a thing called anisotropy, which has to do with the main “trunk” neuron pathways, whether they are well aligned and insulated with the coats of white matter (myelin) that prevent short circuits. These vary according to successful gestation, good nutrition, freedom from trauma, and good blood circulation.
Most of the major changes in the brain when learning to read happen spontaneously and easily so that primary school siblings sometimes teach their younger sibs how to do it, just by showing them that it’s possible and reading to them. Yet schools find it difficult and label some kids as not being able to learn.
The little area, “the brain’s letter box” that has converted from looking for pattern in the world to looking for letter pattern on the page, has been connected to the eye for many millennia, way back through the time of the neanderthals, who had unusually big eyes but almost no prefrontal cortex. Analysis of their bone structure suggested that they were bipedal, but inclined to sit in the mouths of the caves where they lived -- watching while possibly fiddling with carving, weaving, flint-knapping: all incised with marks that often echo the alphabet: X, F, L, O, M.
Research suggests that neanderthals evolved such big eyes because they were in a northern place with low light levels in winter, as contrasted with homo sapiens who originated in bright Africa. But scientists are not always hunters. I would suggest that upright, running hunters in pursuit of herd ungulates like the other predators of the veldt were active, highly oxygenated, and working as a pack -- which demanded the evolution of the qualities we now see as located behind the forehead in the prefrontal cortex: cooperation, empathy, morality (sharing the meat).
I suspect that the more sedentary big-eyed neanderthals were “still-hunters” who found a likely hidden place and waited for the prey. This would explain why they tended to be along rivers and to live in small groups, more family-sized. I suggest they were probably also crepuscular, hunting at dawn and dusk when big binocular (front of the head) eyes could pick up shapes and their own furry bodies were camouflaged. (Besides being also adapted to the northern climate.) Mammals, which first evolved as little creatures who generated their own warmth but were as often prey as predators, still tend to be active at dawn and dusk, the liminal edges of the day/night cycle, the same as they abound at the edges of meadows, neither in the grass nor in the forest, but where the two meld into each other, or along the shores of lakes, or maybe along the mountains in an ecozone like the one where I live between the Rockies and the prairie. We human mammals.
Neanderthals could not learn to read in the modern sense because the parts of the brain that connect with shape perception could not be connected to the prefrontal cortex that evolved in African pack hunters but not neanderthals. Possibly neanderthals were the original solitary artists obsessed with shape -- color not so much, since in low light color is not so primary. Their work may have been more invested with the gut-level feeling we call “the holy” or “the sacred.” The first ceremonial burials involving offerings and flowers were probably Neanderthal. They could not have invented the kind of religion based on books or even the sort of theological systems associated with writing that have typified literate homo sapiens. But neanderthals may have had a direct and contemplative connection to the earth itself that we have lost, possibly because learning to read and write has crowded it out. Nevertheless, our growing electronic means of communication, even over long distances and reaching out into space, may restore to us the big eyes of the still hunter, the melding into nature typical of dawn and dusk.
Two articles discussed here are:
“Neanderthal Brains Focused on Vision and Movement Leaving Less Room for Social Networking’ from a March 19, 2013, article
and “Inside the Letterbox: How Literacy Transforms the Human Brain” by Stanislas Dehaene from The Dana Foundation”
No comments:
Post a Comment