Dear Students!
This week we will get an overview about
the anatomical facts - why non-human primates cannot produce speech,
even if they try really hard - remember Vicki, the chimp?
Our presenters for this time are:
Yuna - Schultz et al. 05
Abby - Juergens 2009
You will find the papers again on the UMdrive, as usual!
have fun!
Uli
Before taking the seminar, I wonder that non-human primates/animals may have languages but we cannot observe it from their behaviors because we always use our ways to look at them. It’s like exploring life outside the earth. We have been looking for water on Mars because water is a must for the emergence of life, but what if creatures on Mars do not need water at all. After joining the seminar, I gradually gave up the idea that non-human primates/animals have languages. The articles this week support Dr. Owren's articles and talk. For example, voiced speech and unvoiced speech sounds are different emotionally and anatomically. Two vocal pathways is also an important point mentioned in Dr. Owren's talk. Besides, I like these articles because the authors suggest further implications on voice disordered population.Sometimes I wonder how the topics are related to language evolution, but I found that all the topics will eventually come together as the semester goes.
ReplyDeleteAmong other things, Jürgens’s review shows the dissociation between non-verbal emotional utterances of humans and monkey calls, and learned vocal utterances. The former are based on the activity of the reticular formation in the brainstem, the latter involve also the motor cortex, cerebellum, basal ganglia, and thalamus. What is the role of the thalamus? Is it true that thalamo-cortical connections are involved in consciousness?
ReplyDeleteI must admit that Jürgens’s experiments on squirrel monkeys sound a bit invasive. What are the consequences of these experiments on monkeys?
Perhaps the most interesting result provided by Shultz et al. is the fact that the mesencephalic periacqueductal grey matter (PAG) and the paramedian cortices are activated by language in human, just as they are active during vocalization in monkeys, or, more precisely, during species-specific calls in monkeys. Shultz et al. suggests that the system may have evolved in humans through the process of “exaptation”, whereby structures that carry out a certain function assume another function in the course of evolution. I wonder if this change at the level of functionality always requires a genetic variation (that is reflected somewhere in the nervous system) or if it is possible to think that sometimes in evolution there is a change in functionality without a change in the DNA. It seems improbable, still the role of behavior seems to be important in exaptation and to precede genetic mutation in a certain way.
Humans have more voluntary control over phonation than other species. Shultz et al. claims that this can be explained by neocortical regulation of visceromotor structures. How did the neocortical structures evolve? Shultz et al. also suggests that there are structures such as the premotor cortex or elements of the basal ganglia-thalamo-cortical circuitry that can provide voluntary control over phonation. How would these areas provide this type of control?
I’m not sure that it is clear to me what we mean by voluntary control. From the readings I can deduce that it means something like “spontaneous”. A vocalization would be voluntary when the subject produces the vocalization autonomously, not in order to respond to a stimulus. Thus, the call of a vervet monkey would not be voluntary because it’s produced every time the monkey sees a predator. Is it wrong to say that the monkey wants to produce the call? Are there degrees of the instinctual and the voluntary?
The function for thalamus is probably to gather information from the 3Ps and 1C (see figure 9 ) and coordinate symmetrically the info received before split out to motor cortex. It is a transitional structure sitting between the cerebrum and the brain stem, a major structure of Diencephalon "between brain".
DeleteFrom what I gathered in the Jurgens (2009) paper, the reticular formation of the lower brain stem handles "species-specific
ReplyDeletevocalizations", like growling, hissing, or meowing in a cat. What are some species-specific vocalizations in humans? Is it the non-verbal laughter? Is it crying?
The PAG area seems to act as a "relay station" where vocal information processing takes place -- specifically responsible for
initiating vocal "reactions" and the intensity of these reactions, but not the patternization of these vocalizations. I would imagine
that there is an important difference between the "reaction" quality of these vocalizations and consciously and purposefully produced vocalizations (ie, a dog yelping from pain vs a dog barking at an intruder). Later on the author explains that the PAG
is responsible for vocal initiation at an "elementary" level and provides the example of production of a pain cry, which is why I am
assuming the "reaction" quality mentioned earlier is an important quality of the vocalizations controlled by the PAG area.
The anterior cingulate cortex appears to be responsible for speech motivation. I found this to be very interesting, as people who
have the bilateral lesion in this area are still able to talk, but do not start conversations on their own. Instead, these people only
respond to questions posed by others. Is this ability to respond to questions due to the still intact PAG (which I have been lead
to believe deals with "reaction" vocalizations)? I would have assumed so, but the confusing part to me is that the grammar and
articulation of these responses are correct.
Jurgen’s article (2009) is such an interesting read! The evidence provided to support the relations between each anatomical structure and its function is clearly laid out. Generally, I only have two minor comments: I noticed that people in the area of voice research used nonverbal/verbal to substitute for a more common used term-nonlinguisitc/linguistic (see the thesis statement of the introduction paragraph). The words “verbal” and “linguistic” might be interchangeably used, but I prefer using the latter because the article is about Language in general, not just “Word or Verb.” The second point is the graph presented on page 9. The arrangement of boxes is confusing. Say, thalamus, cerebellum, pontine gray, pallidum, and putamen do not rank higher than motor cortex anatomically.
ReplyDeleteIt is a pity that the author provided good evidence to support his model, but did not elaborate his reasoning about the question of human/nonhuman distinction based on his model.
The Shulz et al. (2005) article is more challenging to read, esp. for the Results section. The role of perception is more emphasized in their study given the task design; however, the finding of this self-monitoring feedback loop is significant. Yet I am more interested in knowing why in Schulz et al.’s article they addressed the question of involvement of both visceromotor and neocortical systems (supposedly the two pathways mentioned in Jurgen’s article) and they ended up talking about the distinction among rest/whispered talk/and normal talk? It seems like Jurgen was claiming the distinction between voluntary vocal control and a more reflexive species-specific calls without pursuing much, and Schulz et al. was experimenting another matter of speech?
In the Schulz et al (2005) paper, the introduction states that animal studies suggest that there are a network of brain regions designed to regulate phonation and control species-specific calls. Somewhat intuitive, non-human primates (e.g. monkeys, birds, etc) communicative system seems to dominated by these species-specific calls. Moreover, at the center of this network, the PAG regulates vocal fold tension and respiration; thus, directly impacting these species-specific calls. But more importantly, as noted in both papers, the PAG plays a role in the "encoding of information about the emotional status and behavioral arousal in a repertoire of vocal calls over which voluntary control (in non-human species) appear to be slight." After reading this last sentence, I am now wondering how can we unobtrusively detect the emotional status of non-human primates. Throughout the seminar I have learned that researchers can detect levels of arousal by observing species specific calls (e.g. alarm calls); but, to what degree do they tell us about the emotional status of the animal? Also, what are some species-specific calls in humans? Are these the involuntary emotional vocalizations such as crying and laughter?
ReplyDeleteFinally in the Jurgens (2009) paper, I found the section about the PAG's role in vocal initiation to be quite interesting. Even more interesting was how studies have revealed that both animals and humans with bilateral lesions were responding somewhat similarly to unconditioned stimuli. It seems to me that the PAG is the most essential component in vocal control.
The technical language of both these papers (but especially Jurgens) made it very difficult to understand what was being reported (for me, anyway). But, I think, Jurgens (2009) investigates how the brain and body work together in order to produce nonverbal voice production.
ReplyDeleteInitially, he looks at how the reticular formation and phonotory motoneuron pools work together to help in the production of nonverbal voice production. To clarify, the reticular formation of the brain, is a part of the brain stem that is made up of over 100 neural networks. It plays roles in various functions, such as balance and posture control, cardio control, pain control, and sleep-consciousness control (just to mention a few). I had a little bit harder time Googling "phonotory motoneuron pools", but from what I did find (and deducted from the context of the paper), I'm guessing it has something to do with motor neuron networks that affect/control the production of phones.
All that being explained, Jurgens goes on to more fully explain how reticular formations and phonotory motoneuron pools aren't enough for vocal prodcution. Due to a study of lesions that were "carried out" in cats, Jurgens reports that the periaquaductal gray (PAG) region of the brain appears to be responsible for muteness when lesioned. The interesting thing to note is that even when muteness occurs, the animal's other motor functions are still intact. The PAG is also known as "central gray," because it is located mid-brain. It is responsible for functions similar to those of the reticular formation and phonotory motoneuron pools with the exceptions of roles in reproductive and defensive behaviors.
Exactly HOW the PAG functions in vocal production is undecided, but it appears that it is more responsible for its intensity and initiation than it is its patterning.
The second paper by Schulz was slightly less confusing to me, only because I had researched a little about fMRI and PET scans last semester. Incredibly fascinating stuff, and thank goodness for this type of research so that people like Jurgens can quit cutting up cat brains to figure out whether or not that's the part that "does it" or not. Good grief.
Try google "motor neurons" instead of "motoneuron," because I found the later is less freq. used.
DeleteYes, that's what I ended up doing! Thanks so much for the suggestion, Yuna. =)
DeleteMy only question is concerned with the Jurgens article. One of the main questions I have is regarding that if the PAG is damaged, that then speaking and singing are stopped but they can still laugh and cry. (pg. 6) However, I vaguely remember that in some cases of damage in human brains that creates aphasia is strange because they often are able to sing but not speak. A few articles that cite this include “Revisiting the dissociation between singing and speaking in expressive aphasia” (Herbert, Racette); “From singing to speaking: facilitating recovery from nonfluent aphasia,” (Schlaug, Norton); and “Preserved Singing in Aphasia,” (Wilson, Parsons, Reutens). Could this be specific to squirrel monkeys/cats or is this specific to the PAG induced aphasia versus aphasia caused both other types of brain injury?
ReplyDeleteFor me, this is very important because I am wondering if music may be more derived from the type of communication associated with laughter that Owren has studied. So, a lot part of this may be my misunderstanding Jurgens—he may only mean certain types of singing or have a different definition. However, it seems that there is quite a bit of evidence that musical processes, even if they are singing words, uses a similar but distinct neurological process from language. It seems that Schultz's study of voiced versus whispered speech may in fact support some of Owren's studies. In the field of music therapy studies involving children with autism and aging adults that have Alzheimer's disease, music seems to involve a strange place between memory, communication, and language. I suppose this may all be reactionary when Pinker referred to music as auditory cheesecake; however, I think that this is somewhat dismissive from an evolutionary as well as from a practical therapy perspective. His statement, while incomplete, seems to reduce music to function no greater than an early video game that stimulates without any real purpose.