Ep. 209: From Gesture to Language: The Evolution of the Motor System-Language Interface

00:00:00: Welcome to EA Uncast, your weekly source for education research and updates from the European Academy of Neurology.

00:00:15: Hello!

00:00:16: And welcome to UNcast Weekly Neurology.

00:00:19: I'm Elka Stefanova professor of neurology at the Faculty of Medicine University of Belgrade and many years working in a neurologic clinic as neurologic consultant.

00:00:32: My main clinical research is focused on neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease and related conditions.

00:00:42: This month we are exploring the fascinating relationship between language in the motor system.

00:00:50: In todays episode from gesture to language We will discuss the evolution of the motor-system language interface And it is a great pleasure to welcome our guest.

00:01:03: Professor Stefano Francesco Cappa, the distinguished neurologist and cognitive neuroscientist.

00:01:11: He has served as full professor of neuropsychology at Vita Salute San Rafael University in Milan... ...and as professor of Neurology at University in Paria.

00:01:24: His research has made important contribution to the field of cognitive neuroscience, particularly in understanding acquired language disorders.

00:01:36: Professor Kappa thank you for being with us today.

00:01:39: it is an honor to have you as our guest and I look forward to our discussions.

00:01:48: First we can start on set thinking that language movement might be connected rather than completely separated.

00:01:58: Is it the discovery of mirror neurons in macaca monkeys, change our understanding how language is processed by brain?

00:02:09: And why the Brocas area often compares to the monkey's brain area F-V and what does this tell us about?

00:02:23: Can you tell us something about this very, very beginning of the hypothesis?

00:02:31: Thank You.

00:02:32: It's a long story and we try to make it short.

00:02:35: that is people have been humans have been interrogating themselves About the origin language for centuries Of course talking about how did We get language And why?

00:02:51: as far No, only us and not any other living entity.

00:02:58: Of course this is a big question which cuts across many scientific domains such as linguistic anthropology evolutionary theory And of course also neuroscience.

00:03:12: So I needed these introductions because the idea that language could represent an evolution coming out from some further specialization of the motor system, and in particular of the gestural system is quite old.

00:03:31: The most famous proponent was Condillac –the French philosopher-in the eighteenth century–and you can trace this idea going forward following years basically as a contrast between people proposing that language is an evolution coming from further development of the vocal system, and people claiming that gesture actually can be considered as a precursor or language function.

00:04:06: This debate took part mostly in linguistics only minorly in biology A big push towards discussion about the possible contribution of neuroscience, and we can consider in particular some sector of neuroscience such as comparative anatomy on one side.

00:04:30: And also clinical neurologists —as will see at end— is more recent.

00:04:35: As you mentioned... The discovery of the mirror mechanism by Giacomo Rizzoletti's group in Parma played a major role in reviving this debate.

00:04:49: I prefer to talk about the mirror mechanism, rather than the mirror neurons.

00:04:57: The really fundamental discovery by a Ritz-Solati group is actually that in the brain there's this true mechanism of function which was previously unknown... This mechanism involves matching on the same neuron substrate of a sensory perceptual process that is seeing something, in particular an action.

00:05:26: But as you know not only that and the structure which also involves performing have his precursor in the gestural communication system.

00:05:55: Why this was the case?

00:05:58: Well, The most important single determinant I think Was the fact that the area of the brain In which let's call them the original mirror neurons were discovered is an area in the promoter part of the frontal cortex, F-V according to von Ekonomo classification corresponding from a structural point and from that point view of the evolutionary step between humans two other primates.

00:06:41: Two are f-forty four forty five which all the neurologists know.

00:06:47: these are the Bradmans number corresponding to Broca's area.

00:06:53: So, of course this was one of the major inputs for revamping these discussions.

00:07:00: It's a funny story actually that if... This is something which always repeats but it's true.

00:07:04: I checked in eighteen sixty-six.

00:07:08: The French Society of Linguistics issued a veto.

00:07:13: That means it was forbidden to present any paper and discussion society about the origin language And his vetoes were quite effective.

00:07:23: The topic basically disappeared except outside the discussion of philosophers.

00:07:30: Why was that?

00:07:30: Well, it was for a very good reason I think – as people keep saying to my students when they ask me about them.

00:07:37: we were not there and language evolved so off course….

00:07:42: There is a lot of speculation!

00:07:44: And you can build crazy theories on the basis.

00:07:52: the linguistic society of Paris wanted to build a scientific linguistics, so this was considered to be outside the domain of empirical research.

00:08:03: As we can further discuss if you want.

00:08:08: actually you can draw some hypotheses on the basis of empirical evidence and one piece of evidence is homology between an area in the monkey brain which the mirror function and its prominent role in human language, of course play a major impulse from this point-of view.

00:08:37: Not only that!

00:08:38: Of course there are many other interesting lines... And I might add these rebirths between the motor system.

00:08:54: It's highly controversial for several good reasons.

00:09:03: Language is a very complex object, it includes many different aspects.

00:09:11: if you stick to the distinction of classical structural linguistics Of course You have the phonology level... ...you've got the lexical-semantic level and the syntactic level And you also have the pragmatic level.

00:09:29: interface, we produce language through what?

00:09:36: The motor system.

00:09:38: No doubt about that!

00:09:39: So... That link is out of question.

00:09:43: On the other hand What is language?

00:09:46: It's a way to transform thought into sentences.

00:09:54: so on the other side Of this wonderful interface only we humans have in this complete form, that is ability to translate thought on one side into incredibly complex motor sequences which target another very clear brain specialization.

00:10:24: That's the auditory system As an evolution of the language system, it depends what you mean by evolution.

00:10:41: Of course there are a lot things in which the motor systems and the language systems are different.

00:10:48: And so this is another topic of empirical research.

00:10:53: That's long story You make short and now its clear.

00:10:58: Can I ask something?

00:10:59: In the context of cognitive neuroscience What does it mean for a concept or the concept to be embodied?

00:11:08: That's a wonderful question, because this is very closely linked aspects.

00:11:13: It's another of those... As I started saying, The Linguistic Society was right-I think too bad discussion about the origin language at that time and considering only speculation.

00:11:27: Now we have lots active empirical fields and cognitive neuroscience is of course one of the leading fields in this area.

00:11:37: And, as I said language and motor system it's a very long story!

00:11:45: Let us focus on some specific aspects which are most interesting to me.

00:11:51: This is an area where we have been working systematically with Birker research as neurologist and cognitive neuroscientists, that is patient studies which I continue to consider fundamental.

00:12:10: And neuroimaging, neurophysiology all the fantastic array of tools that cognitive neuroscience now has at its disposal.

00:12:21: So let's focus on semantics!

00:12:24: On this very popular concept you mentioned... You'll find it everywhere embodiment.

00:12:32: Embodiment means a very important thing, which of course also in this case is not something completely new but it's different perspective on one of the central aspects of our cognition that is being able to attribute an abstract meaning.

00:13:00: Usually you start from the concrete entities.

00:13:04: This is a glass, this is a class.

00:13:10: I've seen in my life thousands of glasses.

00:13:14: their shapes are very different they have very different functions They can make up different materials but if as we do on classical bedside emergency care evaluation, we ask the patient what is this?

00:13:34: Maybe not a glass usually.

00:13:35: A pen or your glasses and whatever.

00:13:39: you immediately are able to come out with a response unless something goes wrong in these projects which is the lexical label of this as a glass corresponding to the fact that in your mind there's a conceptual representation.

00:14:03: You were born knowing about glasses?

00:14:07: Unlikely, because if you are born in a place where glasses for cultural reasons are more similar to cups.

00:14:13: This is sort of consequence your interaction with the environment Do the motor and sensory system play a role on the fact that you're able to recognize or name a glass?

00:14:31: Quite likely they do.

00:14:34: How did you get this information?

00:14:36: Well, we are visual animals.

00:14:38: We in the sense of all primates not just us who have these supplementary device which is the language.

00:14:46: The first information we get Is related to a shape that typical shape.

00:14:51: but as I said there's a lot of variation.

00:14:55: There are other Information Which Are necessary To form our concept Of glass off A glass.

00:15:01: yeah That is the tactile sensation, perception for example.

00:15:06: You don't expect a glass to be soft unless it's special kind of glass sound not really too much.

00:15:16: well if you have breakable glass falls to the ground might produce specific sounds.

00:15:24: I've been doing several times this movement because i'm putting the glass in screen but It's also the typical moment we do when you have a glass.

00:15:37: So, We have a lot of sensory motor information which is responsible for the acquisition of this concept of glass Which however then becomes sort of independent from different instances I met in my life.

00:15:59: This, by the way is classical neurology.

00:16:05: If you read Wernicke's description of what meaning is, he said it cannot be localized in one place because there are also several kinds of information coming from different sources and this is embodiment.

00:16:28: basically We have an abstract representation of glass.

00:16:32: Yes, we can say that.

00:16:34: Psychologically we had a abstract presentation but this abstract representation is grounded on our sensory motor experience.

00:16:42: We've been working a lot to extend these ideas also besides concrete objects for example some abstract words related to mental states.

00:16:55: What's involved in it?

00:16:57: Which kind of experiences are there?

00:16:59: it's a special kind of embodiment, but in many cases emotion plays the role in producing this embodiment as well.

00:17:08: Of course that language which is something we humans have and increases enormously our possibility to expand our semantic knowledge or semantic memory so... This point indicates strong role for motor knowledge And this is the link with many neuroimaging and clinical observations.

00:17:36: If you want, I can summarize a few.

00:17:40: in the case of neuro imaging.

00:17:44: there are many experiments but an experiment that i like it's an experiment we did in Milan several years ago Marco Tettamante.

00:17:52: he was first author In which this was done also with Giacomo Rizzolatti who was part.

00:17:59: So we put such a bit in the scanner and they were completely blocked.

00:18:08: They are wearing this can, but I couldn't move so... ...they just had earphones everywhere listening to sentences And these sentences could refer to action.

00:18:20: Classical.

00:18:21: I kick the ball

00:18:24: or

00:18:25: I take the handle.

00:18:28: What's the difference between those two sentences?

00:18:32: The effector food typically for the ball, kick.

00:18:37: Take a handle or I can say kiss her face.

00:18:44: so we played around with.

00:18:46: this idea of that had been done previously by another group and has been replicated many times which is subtle differences.

00:18:55: We look at activation while people were listening to sentences compare it when they are listening sentences which were totally similar, from the point of view of their length and syntax

00:19:13: etc.,

00:19:13: very careful matching.

00:19:16: But they're content was abstract at that time.

00:19:20: we are still not interested in abstract concept.

00:19:22: this came later.

00:19:24: basically what happened here?

00:19:26: We have a very famous neuroscientific dimension involved that is somatotopy.

00:19:36: nothing, but they were listening to the sentences.

00:19:43: The activation where corresponding in the motor premotor areas two different sites which are related to classical somatography on the motor street is one example from neuroimaging there.

00:19:58: many others patience.

00:20:02: Patience is most interesting and also the most difficult.

00:20:08: .The idea of simple.

00:20:09: if this motor knowledge is involved in semantic representation,

00:20:16: you

00:20:16: should expect some impairment or reduction of performance.

00:20:25: For motor words typically not only but typical action verbs impatient with neurological disorders affecting the motor system that is, strokes associated with motor impairment or neurodegenerative disorders.

00:20:46: So we work mostly on neurodegenerative disorders because it's easier for many points of view.

00:20:52: you can see them at different stages of progression

00:20:56: and

00:20:58: several others have found the interpretation is different.

00:21:04: We don't go into this.

00:21:05: still what we find there?

00:21:09: Not a major impairment.

00:21:12: It's not that people who cannot move their hands, can't talk about movement but we found some differences in the performance and linguistic performers related to action content.

00:21:29: for example People with front-to-temporal dimension tend to be more impaired in naming verbs at naming options.

00:21:38: these are some of the lines of empirical research, you can follow in the case of semantics.

00:21:46: If there is still time... There's another small point I would like to mention because i find it very interesting.

00:21:54: Yeah let go on!

00:21:57: It's quite interesting

00:21:59: which is outside a clinic and outside neuroimaging with its comparative anatomy.

00:22:06: this Of course, now in comparison to our ancestors such as Paul Broccà

00:22:15: etc.,

00:22:17: we don't have fantastic tools.

00:22:19: they didn't have access too.

00:22:21: We can do anatomy and vivo for example.

00:22:25: This is a major breakthrough because if you put monkeys into the scanner of course it's much better than terrible things that happened in the past From the point of view of animal animal preservation, but also from a point-of-view of having very limited evidence.

00:22:48: So now you can study digital anatomy through taking for example tractography diffusion tensor imaging and analyzing their wide matter tracks in humans and in Monkeys apes sort of difficult.

00:23:10: so most of this that they are on Rizu's monkeys and other primates which are easier to study from many parts of you.

00:23:19: You can compare, with all the tools that we have now to normalize for volume

00:23:29: etc.,

00:23:30: so it cannot do direct comparison... For example this size and distribution of fiber tracks that we know from humans, from clinical neuroscience to be involved in language, such as the famous Arquid fasciculus.

00:23:46: This goes back to Wernicke again.

00:23:49: but not only that also other tracks have been not really discovered because flexing with his anatomy had already described a very good detail on all of these large white metal tracts which were redefined and studied.

00:24:09: using the power of digital anatomy Of course you can study hundreds thousands of humans now.

00:24:16: Anyway, this is his work which has been done in several labs I would cite in particular Angela Friedrich's lab in Leipzig and some results are quite striking.

00:24:28: Some regions... again the awkward fascicula for example.

00:24:33: there is a big difference between humans and monkeys.

00:24:36: we both have proper awkward fascicular but the distribution Aquifasciculus, in particular the left hemisphere is much more extensive than the temporal lobe.

00:24:48: Of course it's a connection tract as Wernicke said but its different and another very recent paper few weeks ago found differences also on an other frontal tract, the Aslan tract between humans and monkeys.

00:25:05: so these are traces of changes to the human brain which are properly related to language.

00:25:14: And it seems that these debates about the motor system and language, they're still ongoing... ...and there's many scepticals but there is a lot of pro-scientists who think this is very closely connected.

00:25:29: Maybe we can conclude that neurodegenerative disorders such as Parkinson's, motor neurone disease and progressive supranuclear palsy teach us about the relationship between movement and language.

00:25:45: We all knew that these subjects with this neurodegenerative disorders have also, at the same time in parallel motor-and-language problems.

00:25:56: we are facing that all of a sudden?

00:26:00: Absolutely!

00:26:02: There is very clear clinical evidence which should never be neglected.

00:26:07: Now because it's going I can share the conclusions that we heard from Professor Kappa, that these contexts and hypotheses of motor-and language system they are very close.

00:26:24: And there is some kind of a real proof in neuroanatomy and comparative neurology, comparative neuronatomy about connection between movement or gestures.

00:26:37: And it is rather a long story, but still in way the point of debate in science.

00:26:50: But nowadays the MRI with functional MRI and PET scanners they are showing us that these structures are very connected.

00:27:02: Also we have proofs at the clinic where you can see many neurodegenerative disorders that they are not pure motor, but they have cognitive either or especially in this context language

00:27:15: problem.

00:27:17: And that brings us to the end of today's episode.

00:27:21: Thank you for joining and thank our guest for sharing his insights.

00:27:28: Until next time.

00:27:31: take care and stay curious!

00:27:34: This

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