Brains and Vocalization

A week ago a commenter challenged my remark that, “We have direct links between the brain and our vocal apparatus.” The commenter asked:

Animals also have vocal apparati. Aren't the links between their brains and their vocal apparati direct? If not, what is the difference between in the linkages? How does one determine neurologically whether there is voluntary control or not?

My remark had been a quick response another comment and this direct challenge sent me back to the books so that I might better know what the heck I was talking about. I was pretty sure I had gotten the information originally from Terrence Deacon’s The Symbolic Species and sure enough chapter 8 has the story in painful detail along with some useful diagrams.

Faces, as Deacon notes, are very old. Reptiles already had jaws, tongues, breathing passages, and structures for sorting food and air so that the air passed to the lungs and the food ended up in the stomach. The face is used for seeing, hearing, eating, and breathing. Seeing and hearing are irrelevant to our story and can be ignored in this discussion. Eating and breathing do matter. In reptiles these actions are controlled by the reticular premotor region of the brain, a portion of the brain stem, and all of it is automatic. Nobody is likely to call any of its contributions voluntary.

The same basic facial structure and brain control is found in mammals, with one change. There is now a connection running directly from the cortex to the reticular premotor region, perhaps giving the mammal some contextual sensitivity. They can look around a bit before they start chewing. 

Primates have taken even more control, adding direct cortical links to the tongue and facial muscles.  At a blow, this piece of information explains why primate facial expressions are so much richer than that of most mammals. They can use it to signal. And again, because of the cortical links, they can take context into account. A few weeks ago I posted a report on changes in ape vocalizations according to context. (See: Apes Are Shrewd Listeners) Very likely it is this alertness to context that gives them some control over their output. 

When we look at the human brain we have even more direct cortical control over the output. In fact, there is now a direct cortical link bypassing the reticular premotor area for every one of the controls. We have added direct links to the systems regulating breathing and the operation of the larynx. These links do not mean that we have gotten rid of the automatic operation of the reticular premotor neurons, but they can be overridden. Although direct control of the larynx and breathing has obvious benefits in shaping vocalizations, it also has a serious cost. We no longer keep food out of our windpipe as automatically as the other species do. And food that is small enough to pass through the windpipe can end up in the lungs. This cost in choking and seeds germinating in the lungs is serious enough that the benefit had to be quite strong before evolution would tolerate it.

Looking back at the clumsy sentence that started this discussion, I want to revise it: We have direct links between the brain cortex and our vocal larynx and breathing apparatus.

And how about “voluntary control”? That’s a subject for books, but as more and more control becomes dependent on context the individual becomes increasingly unpredictable. I’ll save the discussion about free will for another time.

Comments

[J. Goard]

Seeds can germinate in the lungs?!? Damn.... Why haven't I seen a single PSA about this?

Great post, as usual. As you know, my position is that our best guess about the environmental features behind selection of the hominid developments is that it was an established, fairly rich, linguistic environment. Not only does Deacon argue this, but I think it's the main implication of his subtitle.
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BLOGGER: Seeds germinating in the lungs are pretty unusual but I have heard news reports about it.

[Raymond Weitzman]

There is an interesting article relevant to this discussion at http://cercor.oxfordjournals.org/cgi/content/full/15/12/1835. Here is the first paragraph of their conclusion:

"Taken together, our results suggest that human vocalization is
not exclusively regulated by neocortical or visceromotor
mechanisms, but by a combination of both. That the PAG and paramedian cortices — elements of the species-specific call system that regulates vocal production in lower species — are selectively activated during vocalization in humans, may represent the process of ‘exaptation’ (Gould, 1999), whereby features previously designed for one function (species specific vocalizations that may convey information about emotional state) are co-opted for a different purpose (linguistic and paralinguistic use of voice during propositional speech) in the course of evolution."

I may be mistaken, but my impression is that neuroscientists seem to define "voluntary" as having to do with any movement that is mediated by the neocortex, while "involuntary" as having to do with any movement that is mediated by the visceromotor system. If that is the case, then "voluntary control" simply means behavior mediated by the neocortex. So where does "free will" come in? Are we going back to Cartesian dualism?

[Raymond Weitzman]

The blogger's comment "..as more and more control becomes dependent on context the individual becomes increasingly unpredictable." seems rather contradictory to me. If behavior becomes dependent on context, isn't it the case that behavior is actually more predictable? All one has to do is know what the context is in order to predict the behavior.
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BLOGGER: When somebody looks at a painting, what do you think the person will say? --Looks Dutch. --Remember last summer? --On the whole I'd rather be in Philadelphia. --This is a wonderful painting. --Isn't the frame slightly tilted?

[Raymond Weitzman]

Since I don't know (1) what particular painting the person is looking at, (2) who is with that person, (3) what encounters with paintings the person has had in the past and how he has responded to them, (4) the past interactions that person has had with the other person who might be with that person, (5) the painting's spatial location, etc. I have no idea what the person might say or do, if anything. In other words, I don't know the context, past and present, in which this person has interacted with paintings and other people, so how can I predict with any degree of accuracy what that person will say. Making up situations in which contextual information is almost totally lacking doesn't prove or demonstrate anything. One thing I can predict, however, is that if the person is a monolingual speaker of English, he/she is not going to say, "totemo kirei desu."
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BLOGGER: Hmm. Given the context, I had predicted you would catch the allusion to Chomsky's rebuttal to Skinner when he discussed the predictability of a response to a painting.

[Raymond Weitzman]

I did get the allusion and I would say the same thing in rebuttal to Chomsky. But you were the one who brought it up.

[Raymond Weitzman]

When are you going to reply more substantively to my comments?

[J. Goard]

Play nicely, gentlemen.

Blogger, remember this key line from MacCorquodale (1970):

"Multiple causality is never mentioned in the review; it is mentioned throughout Verbal Behavior."

[BUTSeriously]

The percieved similarities and/or differences of humans with other life forms cannot yield anything of value.

Fir a start, the audio dexterity of many birds and animals are much greater than of humans. Yet speech never evolved, which stands as the greatest blow of all to ToE, despite the advantage of time, which evolution depends on. The sub-set of adaptation is also foiled here: no other life form adapted to the most powerful tool in the universe - 'speech'.

Amazingly, all the multitudes of rationalisations of fossils cannot prove a single speech endowed creature before 6000 years; speech appeared suddenly and aligns with history per se, human populations and mental prowess grads. Does no one find it amazing that we do not have a NAME, the pivotal mark of speech, pre-6000? To boot, we also have no kings, wars, nations, monuments.

I say, don't believe everything told by the white gowns - ask for surrounding on the ground proof to match their theories. Speech is too important an issue to swallow neo age jargon. Demand a NAME - and know that the escapist 'NO WRITINGS' is also a slight of hand casino science - because this inclines only with speech being a tad less than 6000!