Locating Language

Among many myths of the human brain that have securely latched themselves as parasitic brain-worms is that artistic and creative types are right-brain dominant and that scientist-analyst types are left-brain dominant. Phrenology just won’t die. When it comes to language learning, there are similar pronouncements – usually backed up by some experimental evidence. Broca’s area and Wernicke’s area (which I first learned about from a board game over a decade ago) have been implicated as distinct locations for language because of their associated aphasias (language disorders). But then things get complicated. These two areas aren’t located in the same brain areas in different patients. Neither can one distinguish them at the microanatomical level from other brain areas. That’s not to say they are unimportant; there’s just much more to the messy story.

 

I’ve made it through Part 2 of Terrence Deacon’s The Symbolic Species. (Here’s my take on Part 1.) It’s all about brain structure and evolution. I can get geeky about the brain but some of the detail Deacon provides made my brain mushy and my eyes heavy. But there are nuggets, and admittedly I skimmed my way through some parts to feast on those tasty morsels. Here’s one: “Classic high-level models of language functions were conceived in order to explain the large-scale features of language breakdown, what might be called macrocognition. We must now face up to the daunting task of analyzing the microcognition of language: analyzing phenomena at a level of scale where the functional categories often no longer correspond to any of the familiar behavioral and experiential phenomena we ultimately hope to explain.”

 

So where are the language modules located? And are there even modules to begin with? How did the brain evolve to allow for or accommodate the use of language? My take on Deacon’s story (and admittedly I might not grasp what he’s really getting at) is that the facility of language is distributed over many parts of the brain although one does see localized concentration in some parts that might hint at modular subfunctions. The takeaway I found most interesting was his argument on the evolution of neuronal connections in the developing brain. In particular differential signal input can lead to “cell and axonal displacement effects” and subdivision into discrete areas with different functions.

 

As to why humans are unique among primates and other mammals, Deacon uses the morbid analogy of an alien brain transplant experiment. Imagine transplanting the embryonic brain of a giant extinct eight-foot ape (Gigantopithecus) into the embryonic body of a modern-day chimpanzee. Then let the Franken-ape grow. What happens as the organism develops? Essentially, because the body isn’t going to be so large, fewer parts of the developing brain need to be recruited to take care of motor and other physical functions. But evolution does what it does, and neural nets shift their connections (with differential signal input) and get recruited for other things. Like Daredevil’s amazing sense of hearing because he is blind. I’m not doing Deacon’s more nuanced argument justice so I recommend reading his book (dry as it is in parts) and going through his detailed examples if you find any of this even mildly interesting or wildly unbelievable. And if not, you can at least read his take on Hoover, the talking seal, a very interesting story. Hoover’s brain (at autopsy) showed some damage possibly related to early encephalitis. Could that be why he talked? Short-circuit? We don’t know.

 

I close this post by quoting a paragraph of Deacon’s that speaks to the limits of a reductionist approach: “The central problem faced by researchers studying the brain and language is that even the minutest divisions of cognitive function we hope to explain at the psychological level are ultimately products of the functioning of a whole brain – even if a damaged one – whereas the functions we must explain at a neurological level are the operations (or computations) of structures. If there was ever a structure for which it makes sense to argue that the function of the whole is not the sum of the functions of its parts, the brain is that structure. The difficulty of penetrating very deeply into the logic of brain organization almost certainly reflects the fact that the brain has been designed according to a very different logic than is evident in its most elaborated behavioral and cognitive performances. This is precisely where the comparative and evolutionary approaches can provide their most crucial contribution.”

 

When Deacon tries to tackle the problem of consciousness in a later book, he discusses parallels to the problem of the origin-of-life, possibly an easier problem with a similar architecture. Since the chemical origins of life are my research area, my takeaway is that I need to combine both the logic of chemical evolution and how to functionally think about biochemistry in vivo. Well, I just checked out another library book for that but I should first finish reading Deacon’s book. One more part with 150 pages to go!