It’s Time to Rewrite the Neurobiology of Language
The authors call for a “clean break” from the Classic Model and a new approach that rejects the “language centric” perspective of the past (that saw the language system as highly specialised and clearly defined), and that embraces a more distributed perspective that recognises how much of language function is overlaid on cognitive systems that originally evolved for other purposes.
Flick through any neuropsychology textbook and you’ll hear about the nineteenth century pioneers Paul Broca and Carl Wernicke, who showed that language production and comprehension are subserved by two distinct brain regions, which came to be known as Broca’s and Wernicke’s area, respectively.
Because the simple architecture of the Classic Model suggests a language- centric perspective, the resilience of the model has perpetuated different flavors of the longstanding idea that the neural machinery for language is ‘‘special”, that is, the notion that there exists neural tissue dedicated to the specific task of processing and producing language.
They cite Pinker and Jackendorf, ‘‘The most fundamental question in the study of the human language faculty is its place in the natural world: what kind of biological system it is, and how it relates to other systems in our own species and others” . They point to an overlaid functional system that ‘‘gets what service it can out of nervous tissues that have come into being and are maintained for very different ends than its own”
For followers of our page, you will recall that one of our central points of disagreement with current Implicit neuroscience models is that we believe that language use and the grammar and logic that characterize the way we speak…and thus the way we speak about “both ourselves and the world” are actually determined by more central operation of connectivity systems.
In particular we believe that the manner in which such systems operate is intimately related to the ‘mathematical sense” and that, as a result, what we “speak about when we speak ‘logically’ or “grammatically” is actualy a manifestation of networked coordinations between cortical and sub cortical systems, in particular, involving the hippocampal and parahippocampal area as well as relying upon the parietal areas “mathematical coordinations”
The Classic Model is obsolete and no longer fit for purpose, they say. “What’s more, its legacy and the continued use of its terminology is hampering progress in the field, in terms of research and medical practice.
Broca and Wernicke are dead, or moving past the classic model of language neurobiology: http://www.sciencedirect.com/science/article/pii/S0093934X16300475
While the importance of inferior frontal and posterior temporal regions for expressive and receptive language functions is not dis- puted here, evidence that the network supporting language func- tions is vastly distributed across the brain is now overwhelming. Indeed, speech and language functions engage a very large number of brain regions that extend far beyond ‘‘Broca’s and ‘‘Wernicke’s areas”, in the frontal, parietal, and temporal lobes, in the medial hemispheres of the brain, as well as in the basal ganglia, thalamus and cerebellum
The definitional problem is most acute for Wernicke’s area. There has never been a consistent anatomical definition for Wer- nicke’s area
Respondents seemed to prefer two anatomical definitions of ‘‘Wernicke’s area”, but neither garnered more than 30% of the votes.
We inherit this vocabulary from the giants of previous generations and ‘‘with the vocabulary a certain set of categories, within which we are historically conditioned to think about [the] problems. The vocabulary is not innocent, because implicit in the vocabulary are a surprising number of theoretical claims” (Searle, 1992, p. 14).
Paradigmatic changes, which are occurring in the field of language neurobiology, cause scientists to see the world of their research engagement differently, and these changes cause ‘‘old terms, concepts and experiments fall into new relationships one with the other” (Kuhn, 1970, p. 149)
As we see it, there has been far too much fascination by both philosophers and neuroscientists with a “language centric” view of cognitive and brain functioning..and not nearly enough appreciation of the likely fact that speaking is very much like navigating in space, and the coordination of motor based actions is common to both speaking and navigating via “grammar” and navigating in mazes
It is also quite revealing to see how the orignal Chomskyan notions of the ‘innatist” nature of languages grammar and the importance of narrow focus on the language itself have been abandoned in recent years, and even by Chomnsky himself.
Nowadays, he points to some more global evolutionarily developed function called “Merge” which smacks very much of a mathematically based capability to deal with the handling of ‘sets” as has been worked out in recent work in the foundations of mathematics.
This trend is quite the opposite of that which caused philsophers and those seeking the foundations of mathematics to look for it in the structuring of language based logic. Instead now this research reiterates the what we see in language is likely derived from a deeper set of interacting capabitilies…that are often dismissed as “intuition” but which can be understood as making language and speaking itself possible.
The Classic model, according to this research, which we find very much on target, ‘ suffers from at least four major issues:
(1) the spatial precision of the model is too limited to test specific hypothesis about brain/behavior relationships;
(2) it is centered on two ‘‘language regions”,
(3) it focuses on cortical structures, and for the most part leaves out subcortical structure and relevant connec- tions1, and
(4) because of its limited spatial extent and cortical focus, it is difficult to reconcile the model with modern knowledge about the white matter connectivity supporting speech and language function.
Instead, the authors illustrate the distributed nature of the language connectome, which extends far beyond the single-pathway notion of arcuate fasciculus connectivity established in Geschwind’s version of the Classic Model as well as the difficulty integrating the emerging literature on perisylvian white matter connectivity into this model
Modern perspectives on language connectivity should consider several sets of association pathways: fronto-temporal, parieto-temporal, occipito-temporal, and fronto-frontal connections as well as thalamic radi- ations, and cortico-subcortical loops connecting the cortex to the basal ganglia, cerebellum, midbrain and pontine nuclei. A brief review of the different pathways that may support language func- tions is presented within the article
The importance of this approach as specified in the present research does not seem to be appreciated enough.
The major thrust of this is that “in fact” the notion of “language center” is itself obsolete and the language use and speakingmust be understood beyond this myopic focus. in terms of network connectivity, as well as in terms of the importance of subcortial and hippocampal areas, and the indeed, when viewed as such, the use of language can be seen to be rooted in other more fundamental aspects of cognitive functioning…and not as being as fundamental and primary as it has been.
Most important here is to realize that language use is very much the same kind of phenomenon as is navigation via use of other motor movements and thus is primary dependent on the hippocampus…and only then do the cortical expressions become manifest.
It is also very telling and oddly inappropriate to hear many speak of “mathematics” as just being “another language” rather than fully appreciating the import of the mathematical sense as being foundational for cognitive functioning on a level much more basic than language use.
This also suggests that from the evolutionary perspective we can better understand speaking and the resulting syntactical roadmaps for navigation via use of language to emerge from the same organismic nature that leads from motor movements to notions of “space” and’ time” in accord with which we have come to navigate.
The same considerations work in the reverse direction, and thus, actually, demonstrate the same point: Networking connectivities rather than geographical “areas” or regions must be the fundamental targets of research. Just as the events seen in Broca’s area” in respect to language use can be seen as arising from multiple networks distributed throughout the brain, so we can see that particular neurons or ensembles in that area might also be utilized for more than just language use, and so we see that music and speech both show co-activation.
We know for example that “Neural overlap in processing music and speech, as measured by the co-activation of brain regions in neuroimaging studies, may suggest that parts of the neural circuitries established for language may have been recycled during evolution for musicality, or vice versa that musicality served as a springboard for language emergence.”
Neural overlap in processing music and speech
These author inquiring in to neural overlap between speech and other faculties, here in particular, music, proclaim very much the same new awareness in understanding language:
‘Research in cognitive neuroscience has been guided by the assumption that brain regions are specialized for a function, they write. “Each specialized function would be implemented in a relatively small neural space.”
“Logically, music and speech processing could share parts of their respective neural networks, such as the mechanisms for the acoustical analysis of pitch, and still be distinct, because musicality and language differ from one another in other respects, notably semantics. The idea that parts of the networks are shared is currently very popular.”
The consideration of “Neural sharing” is now seen as a prime aspect of understanding both languaue and other classical “faculties” such as music which might “share” the same neural areas and assemblies
“Brain structures, such as Broca’s area (occupying the left IFG), which is often the focus of interest in music and language comparisons, are relatively large and complex, and thus can easily accommodate more than one distinct processing network.”
In recent research into language syntax, for example, we are told:
“Music and language are both syntactic systems, employing complex, hierar- chically-structured sequences built using implicit structural norms. This organization allows listeners to understand the role of individual words or tones in the context of an unfolding sentence or melody. Previous studies suggest that the brain mechanisms of syntactic pro- cessing may be partly shared between music and language
Music and Language Syntax Interact in Broca’s Area: An fMRI doi:10.1371/journal.pone.0141069
“The results thus suggest that two different cognitive domains—music and language—might draw on the same high level syn- tactic integration resources in Broca’s area.processing demands of musical syntax (harmony) and language syntax interact in Broca’s area in the left inferior frontal gyrus. This supports a shared syntactic neural architecture between music and language.”
Unfortunately too much of the discussion of the hippocampus in today’s neuroscience either focuses upon the “episodic memory/recall” aspects or the navigational spatial guidance aspects. Then, the researchers seek to explain one in terms of the other, without any great success.
On the contrary what this research illustrates is that bot of these hippocampal contributions to our cogntion can be seen to emerge from a common set of considerations..over evoltionary adaptive events from subcortical hippocampal functioning and the organisms’ “self -organization.”
Pick up almost any neurobiology textbook and it will show two language nodes connected via a single tract, and yet “the overwhelming evidence is that multiple fiber pathways support language function in the human brain.”
However there are clearly more than two functional nodes involved – in fact we now know that language function is incredibly widely distributed through the brain, “extending far beyond ‘Broca’s’ and ‘Wernicke’s areas’,” involving areas “in the frontal, parietal, and temporal lobes, in the medial hemispheres of the brain, as well as in the basal ganglia, thalamus and cerebellum.”
Why should the labels be retired? The reason is that the vocab- ulary in use in any scientific endeavor matters, and continued con- ceptual work and elaboration and revision of the standard vocabulary of the field is a necessary feature of science.
We can and do become ‘‘captives of a . . . set of verbal categories” (Searle, 1992; p. 31).
But the question these reesarchers are trying to address as a field is not ‘‘Where is Wernicke’s area?”
The state: “A more interesting question, we believe, might be: How does the brain accomplish and integrate the various sub-functions that comprise human language, can we parse the network implementing these sub-functions into its con- stituent components, and can we identify the role specific patches of cortex (or subcortical nuclei or regions) play in the context of the broader system implementing language?”
What we see here is essentially an extension of the centuries-long attempt to escape from the classic Cartesian dualism, whereby the operation of the ‘mind” had to be considered in terms that were essentially “mental” and not embodied. Indeed the mind was the only means of attaining clarity and distinctness in the ‘mind’s eye” while the sensorimotor experience had to be subject to “doubt”
As the Cartesian cage of outdated verbal categories has loosened its grip, other approaches have struggled to find their footing. Embodied cognition (in various guises) has begun to take hold.
Embodied Cognition is Not What you Think it is
As they say, “once we iidentify that embodied, situated perception-action couplings can produce complex adaptive behavior in other animals, it becomes more difficult to deny the existence of such solutions in our own repertoire”…. Thus, “If cognition can span the brain, body, and the environment, then the “states of mind” of disembodied cognitive science won’t exist to be modified. Cognition will instead be an extended system assembled from a broad array of resources”
“Embodiment.” they write, ” is the surprisingly radical hypothesis that the brain is not the sole cognitive resource we have available to us to solve problems. Our bodies and their perceptually guided motions through the world do much of the work required to achieve our goals, replacing the need for complex internal mental representations. This simple fact utterly changes our idea of what “cognition” involves, and thus embodiment is not simply another factor acting on an otherwise disembodied cognitive processes.
This then surely implies that if “cognition” is indeed embodied and does not sprout from a “mind” with a variety ” faculties” which are all defined by the sorting out of various mental aspects among themselves, but rooted in something that our bodies DO, that resources of the body itself as they are present in our brains and the networks developed for those fundamental aspects of the body’s presence in the world, including motor movements as well as sensory inputs, must be the basis of any of the experiences heretofore assigned to various mentalistic “categories”.
Thus we have these various networks that we then realize that we can see in our own brains, built upon neural scaffolding of motor movements and embeddedness of other mammals in their environments, much as anthropologists see in other species how more sophisticated and diverse multiple functions grew out of very basic organismic bodily concerns.
Our evolution shows itself to us not only in our novel and extended use of the peripheral aspects of our body differently, as with holding or pointing or grabbing or even counting and measuring, but also in the more complex networking of our brains built upon a scaffolding of more primitive connectivities.