"If the human mind were simple enough for us to understand,
we would be too simple-minded to understand it."
The ability of humans to speak and to understand speech requires an enormous amount of brain resources. These resources have to manage information about many thousands of words and many syntactic constructions and their interconnections, not just to one another but to meanings and to the structures that allow us to recognize the sounds of speech and to move the muscles of our mouths to produce speech. This complex combination of brain structures can be called the brain's linguistic system. It allows a person not only to talk and to understand speech but also to read and write. It also gives us the power to think as well as the power to acquire new knowledge and abilities and to learn how to speak in the first place. The Langbrain website is about this system.
Evidence for this exploration comes from several areas, including neuroanatomy, linguistics, aphasiology, and brain imaging.
From neuroanatomy, we know that, like all systems of the brain, the linguistic system has to be a network. Most of it is in the two cerebral hemispheres, comprising mainly the cortex ("gray matter") and the white matter. The white matter contains of billions of fibers providing interconnections among different areas of the cortex.
How do we know it is a network? The neuroanatomical evidence is quite clear: The brain, and the cortex in particular, is a network of interconnected neurons.
But it is also apparent that the system is a network from careful study of the linguistic evidence This assertion is surprising to many and is in fact a minority view among practitioners of linguistics; most of them consider the linguistic system to be made up of rules and lists and the like. Nevertheless, careful examination of relationships among linguistic units has shown quite clearly that linguistic structure is a network of relationships. Only this view can account for all the linguistic evidence — much of which has simply been ignored by theorists who maintain the 'rules and lists' view. Careful study of linguistic relationships also leads to various hypotheses about the structure and operation of the network. We thus arrive at the surprising conclusion that we can learn something about the structure and operation of the brain just from linguistic evidence.
We therefore have two main avenues of investigation:
- Starting from language: building a bridge from language to the brain, a.k.a. top-down modeling
- Starting from neural structures: building a bridge from the brain to language (bottom-up modeling).
Starting from language. This avenue is a form of top-down modeling. This approach has been laid out in the book PATHWAYS OF THE BRAIN . Most of this website is oriented to this approach. This is the avenue of investigation that was followed historically, in the period leading up to the publication of PATHWAYS . The early publications on relational networks in the sixties and seventies didn’t consider neural structures at all. But since a people’s linguistic information is in their brains, the linguistic network must have some relationship to the neural network of the brain. In that case the study of linguistic relationships might provide clues to the neurocognitive basis of language. If so we have new significance for the old notion that language is the window of the mind. The cogency of this notion also comes from the fact that the linguistic system has to be richly connected to other cognitive systems, represented throughout the cerebral cortex. After all, we use language to talk about an enormous range of different kinds and aspects of human experience, all of which also have representations in the brain. The linguistic system must therefore occupy a central position in mental structure, connected to the cognitive systems that register all those other experiences.
Starting from neural structures. Neuroscientists have acquired extensive knowledge of the physical structures in the brain. Nevertheless, this knowledge by itself has so far not revealed how the brain functions to perform the mental processes we use in speaking and in understanding speech. Even the basic question of how the brain stores symbolic information remains a mystery to neuroscientists. Nowadays a lot of research is being done in brain imaging, using techniques of PET, fMRI, and MEG. But brain imaging only provides information about where things are going on, not about what is going on there.
It is easy to understand why neuroscience has not provided the answers we are looking for. Asking a neuroscientist to accomplish such a feat would be like asking an electronics engineer to figure out, from examining the electronic structures in a computer, how a computer calculates the orbits of earth satellites, or how it checks your grammar when you use Microsoft Word. To understand the grammar-checking program, rather, you need most of all to understand linguistics.
By the same token, you can't understand how the brain processes language without understanding linguistics.
It follows that this approach of starting from neural structures evidently can't work without extensive input from linguistics. But based on the evidence obtained from neuroscience combined with evidence from linguistics it ought to be possible to build a bridge between neural networks and linguistic networks.
A good start to such bridge-building has been provided by the detailed work on perception carried out by Vernon Mountcastle and others (see references) over the past few decades, resulting in an emerging picture of numerous properties of the structure and function of the cortical network. In particular, Mountcastle has shown that the neurons of the cortex are organized in columns, and it makes a lot of sense to view these columns as nodes in the cortical network.
So linguistics is an essential component of the investigation. But we have to bring in certain kinds of evidence that ordinary linguistics tends to overlook. Our primary evidence is the same as that of ordinary linguistics. It is the things people say and write, which of course people can also comprehend. We can call them texts (written or spoken). Starting from these kinds of evidence, one can build a plausible model of what information the mental system must have to enable it to produce and understand the texts we observe. The word plausible here is crucial: The model must include a plausible account of how linguistic information is organized, how it is used, and how it is learned. A model that meets these requirements must also be tested for neurological plausibility. In the top-down modeling procedure described in PATHWAYS OF THE BRAIN (see references), neurological data was not brought in until such a model had been constructed.
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