Motor symphony and central pattern generation create a whole new view on behavior. They say that for many types of behavior it is not necessary to have any visual or other input, and furthermore, the organism (nervous system) can create the behavior on its own. The phenomena that are directly related to these concepts are the phantom limbs, cat and cockroach walking without higher nervous system, headless rooster running, tongue rolling, etc.
The phenomenon of the phantom limbs, described in the article written by Ronald Melzach, shows that "we do not to have a body to feel a body". People that can feel phantom limbs, their movement and pain, probably, experience the action of the proprieceptors that bring the information from the "remaining neurons in the slump" to the nervous system. This is what I think the author has meant by the "neuromatrix"--the network of proprieceptors that carry the information from the body to the central nervous system.
Also, the experiments on cats and cockroaches that were described in "The Control of Walking" show that having proprieceptors carry the information to the brain is not that important, because some of the information about walking lies in the nervous system itself, and it can be "replayed" without any input to the brain from the outside. The same fact is illustrated by the fact that if the rooster's head were cut off, for the first number of minutes the rooster will still be running around.
I think that this notion of the stored motor sympony and CPG that allows one to be able to perform some actions without any input from the body and environment shows that it this "stored motor symphony and CPG" have to be genetic. I remember the experiments we did in General Biology to show that tongue rolling is genetic. I think this phenomena of tongue rolling depends on whether the "motor symphony" for the tongue rolling is present among the person's genes.
Since the "motor symphony and the CPG" are genetic phenomena, the experiments that were made to show that motor symphony can be learned only show that motor symphony is active. For example, in one's learning how to dance, type, etc. one just adjusts his/her general stored motor symphony to the new task, as opposed to creating a new motor symphony.
Tongue rolling interesting, may indeed be a difference in genetic information and their role in CPG creation. Worth looking into more. Be careful, though. The running rooster still has lots of input, so that doesn't quite show the existence of a CPG (though it does say some important things about how they are controlled). And CPG's needn't be genetic, can be learned through experience. AND adjusted while being played using sensory input. PG
The concept of the motor symphony has the most effect on me in terms of my thoughts about behavior. I came into this class thinking of the general black box model where you put in a stimuli, something occurs which we can't see: some processing of the stimuli, and then a response comes out the other side. However, the idea of the motor symphony which is able to occur without inputs from the outside break up the whole input portion of the black box theory. In class an example was given where you picked up a cup, and it was suggested that it was a visual process: observation of and compensation for previous movements. But than it was demonstrated that you could pick up the cup without looking at it. How does this action occur? The immensely intricate motor symphony must have some kind of guide by which it finds the cup, and that guide is memory. When you put that cup down on the table in front of you, a part of your brain noted the placement and several other notable aspects of the cup's situation. These noted aspects were stored in a reachable place where they could be accessed at the point when your body began to feel thirsty. When this occured, it was easy to draw up that memory and use it to guide the motor symphony. One bit that I was unsure about, is the actual definition of the motor symphony. Obviously I have come up with my own meaning for it, and the idea seems to fit well, but perhaps there is more to it than what I am suggesting. I guess I think of the motor symphony as a large grouping of many minutely small mechanisms that make up our general motor outputs. i.e. the many muscles that must contract just to bend my arm at the elbow. Please clarify my definition if I am not exactly getting it.
Very close, I think. Is (since you wrote this) now clear from class that the motor symphony is indeed all the small movements (actually the motoneuron discharges)? And yes, it does help to get rid of the black box, stimulus/response model. PG
please refer to erin hunter's email with the subject "a dialouge...." for my response this week.
And well worth doing so. PG
The idea of a motor symphony and a central pattern generator causes me to think about behavior differently by giving a form to the physical complexity of it. It is one thing to say that behavior is a complicated thing and that every motion involves most muscles in the body. It is another to say that there is a stored catalog of movements that each muscle must make in order to do these movements. It also makes learning new motions and coordinations seem much more complex. For instance, it causes me to wonder at such things as learning a new dance step, or a new play for sports.
This also explains problems with behavior following strokes or brain damage. If the areas of the brain controlling the motor symphony or containing the central pattern are damaged, it follows that the motion must be 're-learned.' This re-learning seems as if it would be even more complicated considering the permanent damage to that area that might cause difficulty in re-forming any patterns. Not only is the score erased, the paper which it must be written upon is damaged. This helps me to understand the reasons for problems in coordination following brain damage.
Nice thoughts, both of them. Yes, CPG's give one a way to specify the complexity in terms of its subunits. And indeed explain why one might lose some behaviors while retaining others in cases of brain damage. PG
The motor symphony and the central pattern generation are vital for understanding behavior. Central pattern generation can be seen as a way of explaining instinct. This is opposed to a motor symphony which is a coordinated movement in a specified pattern. The most important aspect of a motor symphony is that it is being updated in parallel with its action. The distinction between the two modes, is the importance of sensory input and how it affects output. Is it that there is some sensory input which then generates the output, and thus there is a reafferent loop, or that we create new outputs in response to some input ? Do we affect our reality or does it affect us ? Our behaviour is tailored to allow us to survive in our world, and to be able to deal with all the changes that come about. Some behaviours are instinctual, and others must be tailored to suit the situation.
Some central patterns seem to be inherited between generations, such as the sucking reaction. These are behaviours vital for our survival and they are programmed into us before we are even born. In this way central patterns do seem to have a function in our daily lives. There are some variations on the basic central pattern because adaptation is the only way we can survive, we must have some change. The variation of "scores" present is like the recombination of genes in the processes of creating a new human being. There must be a way of passing on instinctual behaviours which are necessary for preserving our species.
A motor symphony on the other hand must be adaptable, we must somehow adapt to ourselves to the outer reality, and create something within. A motor symphony must be adaptable because conditions are constantly changing, and it order to survive we must accommodate these changes. This adaptability is a way of surviving in our ever changing reality. A motor symphony can be seen as coming from the cerebral cortex, where the higher functions are thought of, whereas a central pattern generation seems to emerge from the spinal cord. A specified pattern is a product of sensory neurons talking to motor neurons in the spinal cord, and in most of us the conversation being relayed to the cerebral cortex, where a plan of action in approved. This is what is so important about a motor symphony, it is the product of higher thinking.
The two forms are vital for our survival because we must both be able to> adjust our movements through sensory perception, or we must be able to make instinctual movements to survive.
General points important, but don't link them too tightly too a "motor symphony"/CPG dichotomy. As I use the phrase, motor symphony is simply a descriptor of the complex motor neuron discharge underlying movement, any movement. And a CPG is one possible way of accounting for that motor neuron discharge. Your broader concerns are, on the other hand, intriguing and important. One must, in general, have both stabilty and variability in biological systems. And the latter is present at several different levels based on several different mechanisms. PG
The idea of plasticity and that the brain contains stored symphonies is intriguing. Perhaps these phenomena at work can be seen in stroke victims. Does damage to a certain part of the brain effect motor symphonies and CPG? However, we do know that the brain has more than one way of doing one thing. In stroke victims or people who have damage to their brain because of disease or disorders, it would probably be interesting to see how the brain re-networks itself and accomodates to an injury that will effect motor output.
In a cat, where all input pathways are cut(optic, olfactory, dorsal roots, and connection between spinal cord and the brain), communication to the outside world was disturbed. Even so, the experiment showed that motor patterns existed and walking was possible to the cat. How is it that a human who has his spinal cord severed cannot walk? If one must tell the CPG if one wants to walk, doesn't that indicate an internal input system must exist and that cutting the spinal cord will result the person's inability to tell his spinal cord to walk?
Yep, humans lack ability of the rostral part of the nervous system to activate walking CPG's, located in the spinal cord. And yes, stroke both may damage CPG's and are interesting in terms of the "multiple ways to do same thing (more or less) idea", which provides some optimism for recovery. PG
The answer to this question is clearly yes. One can understand that for behavior to occur there needs to be three things: a permeability change in the membrane, a concentration gradient and a passive current flow. The onset of this can occur by molecules triggering nerve endings or it is also autonomous. The path in which the potential follows and where it goes depends on what the molecule was and what changes that molecule caused. This explains a lot because molecules float all around us, they are detected through the scent, the touch, hearing and sight. The brain registers each of these behaviors in a different location with different paths of potentials and different firing even though the underlining process is the same. So, yes behavior is better understood, but one question remains. While, running the other day, I became tired, but I had about 600 meters left, I don't recall consciously (for lack of a better word) choosing to run faster, I felt exhausted but my pace grew increasingly faster. Now I understand what causes my legs to move in order to run, but the inputs to my system were constant, so what causes the slight change in my "behavior" for me to run faster. Why was a neurotransmitter (like adrenline) released, if this is what caused it? I understand the action potential was firing more rapidly but what cause it to do so?
Nice question. IF inputs constant, then change must have originated within the nervous system. Perhaps an endogenous thought? Changes in action potentials must be because of changes in action potentials, which might be due to sensory input or to things going on within neurons themselves, yes? Is the origin of the latter which bothers you? Won't have more time for that in this course, but there are lots of possible explanations if you'd like to read more (or take some more neuroscience courses). PG
Now that we are seemingly convinced that a central pattern generator exists, we may move on to questions involving how this affects the brain and behavior. We see outputs generated by the nervous system that required no input. Indeed, it may be the brain's perception of the world around it that may lead that may differentiate the outputs of the nervous system. Are the CPG outputs of those people who are raised in different backrounds and styles of life than other people, comparatively different?
I was equally perplexed when I encoutered the following text in "Valis" by Philip K. Dick:
"Thoughts of the Brain are experienced by us as arrangements and rearrangements--change--in a physical universe; but in fact it is really information and information processing which we substantialize. We do not merely see its thoughts as objects, but rather as the movement, or, more precisely the placement of objects: how they become linked to one another. But we cannot read the patterns of arangement; we cannot extract the information in it--i.e. it as information, which is what it is. The linking and relinking of objects by the Brain is actually a language, but not a language like ours (since it is addressing itself and not someone or something outside itself).
I want to know how the brain interprets change. I would like to see how time effects the brain. How the brain constructs, or doesn't construct time. I would like to learn how the brain affects our outside world. Not only our everyday life, but the rules we make for the universe itself.
Fascinating set of reactions/issues. Time very much a frontier problem in terms of thinking about the nervous system (there are some very interesting time "paradoxes" related to the nervous system which people have begun to think about; you might want to look at Daniel Dennet's Consciousness Explained. Indeed, time a frontier problem for physics and other things as well (have read Borderliners by Peter Hoeg?). Will talk more about how the brain affects "rules we make for the universe itself" as we get into sensory systems. PG
The knowledge of there being genetically based series of behaviors raises many questions. So, far, the direct scope of research has been limited due to the complex nature of the nervous system, but there are many things that can be inferred. We know that coordinated movements are either learned or genetic patterns of neuron firing. The independence of these patterns from input has been shown by cutting cats spinal cord from the brain and cutting their dorsal root. That cats still have the ability to walk on a normal pattern, proving that the pattern is contained in the spinal cord and is not dependent on input. In humans, we often practice things to become better at them. This accounts for the coordination of typing fast, or a pianist playing a specific piece. This would also account for the ability to ride a bike, and how once learned is never lost. The specific coordination of the balance muscles necessary for staying on a bike must be learned. But once it is, a person can ride a bike for the rest of their lives because this balance become a specific pattern in the spine.
But there are other more interesting behaviors that can be examined from this approach. In crickets, it was shown that their output of mating songs in males and the preference of songs in female is genetic. Some interesting studies on humans have been done on identical twins. While these studies are obviously not as conclusive as crickets because many more variables are involved, they do show some interesting things. Two of the most dramatic behavior related similarities in twins were in alcoholism and homosexuality. In a study of separated fraternal and identical twins traits were ranked by what percentage they appeared in both twins. In identical twins, if one twin was homosexual or alcoholic, there was a 100% correlation with the other twin having this behavior. Only 70% of fraternal twins were alcoholic and 50% of fraternal twins were both homosexual. Additionally, it is popular knowledge that alcoholics often have alcoholic children. But this could be because the children grew up in a house with an alcoholic parent, and so we must be careful to designate this trait as fully genetic, as it may be partially environmental. Since there are many environmental factors in the life of a human, these numbers and studies are not conclusive, but they are very interesting. They indicate that there may be a much more genetic aspect to our behavior than we realize.
Yes, but careful with numbers (I think yours are higher than studies I've seen) and with the notion of a genome/experience dichotomy. Almost all behavior, certainly all "complex" behavior, is influenced by both genes and experiences. PG
Behavior in terms of a motor symphony and central pattern generators, seems now to be dictated by both the individual and nature-genes. In the case of central pattern generation the hybrid crickets' hybrid song shows how there is a genetic basis for some central pattern generation. But also, there seems to be some choice in how one uses or puts together their own motor symphony. As is the case when you start an action but do not complete it, because you do not want to. Thus, some behavior is monitored by the conscious individual, and some is almost completely influenced by genetics.
Careful not to equate CPG with genetics: such capabilities may result from genes or experience (and, most generally, both). Your more general point though is correct and important. CPG activity can be modified by a number of things, of which the "I-function" (in organisms that have it) is certainly one. PG
At first I was rather uncomfortable with the idea of a central pattern generator in the nervous system, functioning to automatically determine our behavior. Seeing the central generator as somewhat of an intermediary between a higher command center that generates an excitatory impulse (input) and the patterned motor output makes the central generator fit better into the nervous system. Given the importance of interneurons in the nervous system, of intermediary connections and communication between various regions of the NS, the idea of a central pattern generator acting as such an intermediary follows this common theme that is so important to the nervous system as a whole. The central pattern generator is tied with our genetic selves, our unlearned and "preprogrammed" operations that are most likely to be a early adaptation in our evolutionary history. The fact that the behavior of many "lower" animals is attributed to these innate behavior patterns is convincing that the central pattern generator is more related to survival behavior and basic functioning than to "higher" behavior--behavior that reflects a higher cognitive development.
What I am most uncomfortable with is the way in which we go about determining the methodology and organization of the nervous system. I cannot completely accept the procedures used by scientists that result in the death or disfigurement of the subject animals. I was particularly uncomfortable when you were describing the experiment involving the separation of the nervous system from the body of the crawfish. It does not seem right that we use life in this way. Unfortunately, I do not know of any other way to learn about the nervous system besides hands-on experimentation and observation.
Glad CPG fits, helps to link neurons and behavior. Careful, though, about equating CPG's with genetics; they can be expressions of both genetic and learned information (usually both). And have a pretty great degree of flexibility.
I share your concern about animal usage, even if (perhaps) it didn't sound like it in class. I don't like to see animals in perturbed states. But no, I don't know of any other way to become more knowledgeable and wiser, hopefully for the benefit not only of humans but of living organisms generally. Happy to talk more about this, if you like. PG
The idea of phantom limbs although a little abstract at first does not seem to be odd or inconceivable upon further thought. A person who has had an arm for example which has been amputated has experienced years of neuronal inputs from this limb. These pathways, whether "hard wired" or developed, still exist after the limb has been removed. They obviously do not receive much of the sensory information that they once did, but given the elaborate nature and multiple-channel capacity of the nervous system, the maintained use of these pathways is not all that surprising. I would suspect that phantom limbs and other such perceptive senses are not as detailed as their fully functioning predcessors; however they obviously do exitst and function on some level.
I was particularly interested from the article in the feelings of extreme pain which many people claim to suffer from. The perception of pain in a lost limb is not hard for me to understand, however, the extreme and sometimes constant pain are what really intrigued me. Could this possibly be because (at least for those who have lost the limb for one reason or another) that the last time the neuronal pathway was used, it was under extreme stress (ie amputation or injury)? This theory has a flaw though because the article specifically states that even people who were born without a limb still report both perception of the limb as well as extreme pain there. This suggests that the pathway is at least basically internally generated, but somehow this seems to suggest a system too complicated in its intrinsic design. The number of internally programed pathways seems to be almost beyond comprehension. However, as we have discussed before, perhaps only certain--most likely those most essential to basic existance--pathways are totally hard-wired thus reducing the demand for a huge predetermined system.
Fascinating/appropriate thoughts/issues. I'm not sure, though, that the "hard-wired, essential" vs "soft-wired, more flexible" distinction is a good or reliable one. The brain differs from computers (the source of the metaphor) in that its circuitry is both doing the information processing and storing resulting information, so there is probably no sharp border between "hard" and "soft" (and maybe no sharp border demarcating "essential" from everything else). In any case, it is true, as you note, that phantom perceptions needn't depend on prior experience. What do you think of the class suggestion that the discomfort may reflect a mismatch between corollary discharge and (absent) afferent signals? PG
The idea of a motor symphony would account for behaviors, simple to complex. Since an earthworm can move whether its nervous system is intact and its muscles aren't and vice versa suggests that the nervous system can cause movement either through a direct line or through feedback or both. The earthworm experiments don't indicate wheth the nervouse system does both all of the time or if it uses one only if it can't use the other.
When a muscle contracts, proprioreceptors experience an action potential that has the potential to travel to neurons that affect the movement of another muscle. Since contraction of one segement is simultaneous to the extension of the next, it is probable that in an earthworm a perfect motor symphony requires both to occur. I'm unsure if in the experiments the movement of the worm was at all slower when either the muscles were disjoined or whether the nervous system was disjoined. It may be that what appears to be motor symphony attained by a stored score is really just a condition of feedback that is too quick to detect by means other than with electrodes. If this is true, then to what extent is human behavior dependent upon simultaneity of movements or neural signals. The concept of motor symphony and central pattern generation could explain the differences in coordination between people or within one person. Perhaps, someone can engage in a behavior because of some central pattern generation but the behavior isn't smooth and coordinated because the feedback system is imperfect and the motor symphony is inadequate.
I still don't understand if the genes give the organism the potential to develop central pattern generation through some feedback system or if the genes themselves, enable certain behaviors immediately. It seems that comparing a human babies development to that of an adult, the stored score is very rudimentary. This implies that to understand central pattern generation and motor symphony, we need to incorporate learning into the picture. Although, in some organisms, infants can do almost exactly what their parents can and with almost as much coordination. Is central pattern generation just the idea that scores for the motor symphony are written and stored in the nervous system?
Yep, to the last. And the issues related to poor coordination are interesting/directly relevant. Are you clear about the distinction between symphonies that play out completely in the absence of sensory input during their performance and those that need sensory input during performance? That is an issue separate from what was needed to write the symphonies, which may be experience or genetic information (or, most typically, some combination of both). PG
The structural and functional construct of a motor symphony as a description for the organisation of the nervous system seems reasonable. In tune with our earlier models of the nervous system as a multitude of boxes within boxes, the motor symphony can be used to describe both structure and function in a way that implicates both aspects of the existence of the nervous system simultaneously- structure cannot be separated from function if we choose to question why an organism has a particular structure. Thus each section of the orchestra is analogous to the various centers of "higher" function, and each instrument is analogous either to the neuron itself, or to extremely simple and repeated combinations of neurons.
A motor symphony hence implies that a score is stored somewhere, which leads to the idea of central pattern generation. Behaviourally, a stored score is analogous to a certain type of behaviour being genetically determined.
We are taught that phenotypes, the physical manifestations of the genetic makeup of the organism, are influenced partly by genes and partly by the environment, and partly by developmental noise. It is the degree to which each component acts on the organism that results in the final masterpiece that is the behaviour in question. Thus a stored score may not have a component that is environmentally determined. It is usually the environment that ACTIVATES the score, and causes the harmonious (or not so harmonious) interaction of the various instruments, but the score is predetermined.
Perhaps all behaviours, when reduced to their fundamental characteristics, are predetermined. Perhaps the different complex behaviours that we observe in our daily lives are merely different patterns of interactions, different sections of the symphony playing different pieces at different times relative to one another and to each other within the section as well.
Perhaps learned behaviour is only the activation of existing circuits that have never been used before. Much of the neural matter that we are born with degenerates as we age. Theories suggest that this occurs because these pathways fall into disuse, or are never used, and so are destroyed to increase the efficiency of the functioning of the nervous system. This supports the view that much or all of what we do is based on predetermined circuitry, the infinite combinations of which give rise to variation in observed behaviours.
But all this implies a central pattern existence, not a central pattern generation. The latter implies that the pattern does eventually become a stored score to be used perhaps periodically by the motor symphony, but that its initiation occurred not as a function of it genetic makeup, but due to other factors which could be internal or external.
Thus the concept of a motor symphony, in conjunction with that of central pattern generation, seems to be reasonably adept at explaining behaviours that require the pre- existence of deterministic factors. The various sections of the orchestra look to the conductor for instruction, as well as to the score. While each individual is aware of his/ her individual role, it lies with the conductor to coordinate the various movements, while adding a bit of his own style in so that the whole is more than just the sum of its parts. This could be used to describe the functioning of the brain as the central processing house, but it doesn't explain very well the observation that some behaviours seem to bypass the brain- the autonomy of the spinal cord distributes labour that is not described by the motor symphony construct. Perhaps we need another addendum to the integral idea, to encompass a wider range of observed behaviours.
Very interesting wrestling with the concepts and their broader implications. Certainly the ideas of motor symphony and central pattern generation can generalize to wider spheres of behavior, as you do. Careful, though, about the simplification (and fatalization) that everything is there at the outset, with nothing really "new" ever happening. Yes, there is a lot of initial structure, but there is also a persistent capacity to create new structure (hence, not all behavior has to be a subset or reorganization of what originally there). Careful too about looking for a "conductor". What we'll find (I think) is that the "brain" is just a collection of interacting boxes, in the same sense that the "brain" and "spinal cord" are interacting boxes (and in the same sense that swimmeret beat emerges from the interactions among the boxes, rather than having a master box or conductor). "Coordination", in general, has to come out of the interactions (somehow). But yes, we'll need another addendum "to encompass a wider range of observed behaviors". Not a conductor, but at least one other box, the I-function. PG
The concepts of motor symphony and central pattern generation not only add to the understanding of the generation of behavior, but also add aspects of continuity and definition to behavior. The combination of the motor symphonies and central pattern generation define the generation of behavior in that one no longer has to speculate how a bundle of neurons can create the complexities of action that we call behavior. The transition from molecules to neurons to behavior becomes more evident when the concepts of motor symphony and central pattern generation are added. These two concepts supply a further sense of continuity between what appears to be purely biological and the ulitmate human actions that result from the nervous system.
As much as motor symphonies and central pattern generation help one better understand behavior and its generation, they also raise a potentially disturbing question: To what extent is behavior pre-determined? If the nervous system depends on a series of motor symphonies and the central pattern generation, does that imply that human action and ultimately the scheme of behavior is already determined because of the fact that the expression of behavior is stored? Before one can assert that behavior is pre-determined, there must be distinctions made between certain types of behavior and what has the potential to be pre-determined and what does not apply to the possibility of being pre-determined. It seems as though one may be able to assert that certain simple actions such as bodily movements may already be patterned by the nervous system, but more complex actions may not be justified by the combination of motor symphonies and central pattern generation.
Once again, the question of differentiation among behavior of different individuals also presents itself. If there is a specific set of rules followed by the nervous system for certain actions and behaviors, where does the differentiation come between individuals? It is certainly possible that such differentiation lies in the concepts of motor symphonies and central pattern generation because different individuals may have different patterns stored that create the ultimate expression of their behavior. However, there still remains the possibility that behavior differences lie at another level entirely, and therefore the supposed set of rules that directs behavior at the level of motor symphonies may be the same in all of humanity.
Interesting issues. Certainly the possibility of predetermination and lack of differentiation is there. But so too, as you say, is the possibility of differentiation. So too the possibility of non-determination, perhaps in the creation of CPG's, perhaps in their selection, perhaps in additional things we have yet to come to. Will, of course, talk more about all this. PG
The views of the nervous system that we've been studying so far seem to support the definition of behavior that this class has come to agree on. On oth\ er words, behavior can be explainedin terms of the workings of the nervous system, which include the concept of CPG. CPG can be used to explain inherent behavior in humans--such as the ability to react in a ceratin manner to a stimulus that the person has never before experienced.CPG, therefore, helps to account for behaviors that cannot or have not yet been scientifically proven and explained.
Can indeed be used to (potentially) explain "inherent behavior". But remember that CPG's aren't necessarily based on genetic information; they can also be learned.PG
picture it.
computer center.
1997. A typical sunday after the x-files
amber baum and erin hunter are deep in thought about neurobiology.
amber: Hey erin, what do you think about this motor symphony idea?
erin: i don't know. it makes sense to me in most cases. i mean, almost
all of our actions are fluid, and that fits in with the whole symphony
idea. but i have a hard time understanding the typing example from class
where you type without fully processing each letter individually, maybe
becuase i just can't type that well.
amber: but you play tennis, right?
erin: yeah. your point being?...
amber: Well, I play softball (or I did) and like with any sport, I had to > practice...so did you for tennis. So in pg's words we can call that the
learning of a motor symphony. I can now pitch beautifully---you can
serve like a rocket---but we had to learn these things, our symphonies
weren't perfect on first playing. This actually relates to my CompSci
class, where we're studying neural nets, which are computer
programs that are capable of learning. They model the brain (pretty
crudely, but it's clever) with "neurodes" (for neurons) that have some
basic (to a biologist) abilities. It's their connections that matter,
not the neurodes themselves. I actually think that pg got the typing
example from one of our readings.
erin: ok, i see your point about learning motor symphonies. i know
nothing of these computer neural nets, though i do see how they would
correspond to neurons and the nervous system. personally, i think it
would be kind of weird to have a computer that was able to act
independently and uniquely like our nervous system. what would really
draw the line then between human capabilities and computer capabilities.
i guess the I-function is unique to humans, but i don't even really know
that i can say that because i don't understand it well enough to say that
it couldn't somehow be inputed into a computer. at any rate, i find it
scary that a computer might be able to function as similarly to humans as
to replicate its nervous system.
the other thing that the whole idea of learning, using the sports
example, is how one person is somehow innately able to develop a motor
symphony that is better than another person's (ie. how someone is
talented at a sport). what is there is one person that allows them to
pitch better than another or to hit a better forehand than another
person. yeah, practicing will help, but some people can pick up sports
like nothing and play them better than people who have been practicing
for years.
amber: hmm...I guess I would attribute "natural skills" like sports
ability etc. to luck of the draw, or genetics, whatever you want to call
it :) Some networks (my other class again) are faster at learning a
specific thing than others. It's all in the way that they are intitially
set up, and that is made random by the computer. I guess biologically,
you would say that peoples' varying genetics and environments create
abilities and deficiencies in certain areas.
As for the I-function...I don't know about that. It seems like a
cop-out, kind of--like a way to deal with those who bring up the soul.
These are pretty scary ideas, things like "the brain is behavior", and
they threaten a lot of people...the i-function is kind of a shield from
the ramifications of the ideas. Because if you really, really do
believe that the brain is behavior, then you think that computers will be
able to have an I-function someday. But don't worry darling, let me tell
you this: from what I see in my class, that day is _very_ far off! :)
So, hm, motor symphonies...they can be written on the fly or
learned, and learning them makes them more refined...
erin: excuse me amber darling, but i don't think that you want to say
that learning makes them more refined, but i think what you mean to say
is that practicing learned motor symphonies makes them more refined.
amber: d'oh! you're right. I misspoke. Distracted by thoughts of scully
and mulder. :) anyway, what was I saying when I slipped up....I was going
to say that some motor symphonies are even innate, as we discussed
in class this week.
erin: how do they start?
amber: maybe they don't start--maybe they're part of a continuous process > of input-output loops involving various parts of the nervous system and
the rest of the world.
erin and amber: oooooo. aaaaaahhh.
amber: wow, I *can* absorb something at 8.30 am.
erin: me too. well, most of the time anyway. you know what i was just
wondering...well, when i don't play tennis for a few months, and then get
the urge again and go out and hit some, i am able to play better than
normal. but if i play again within the same week, the fact that i haven't
played in a while really shows. whuz that 'bout?
amber: weird...I notice the same with pitching. if I'm needed in a game
or something I can do well without practice, but I can't just pick up my
glove and throw strikes against a wall with no warning.
erin: you know what it might be? maybe that initial time, you forget to
think about what you're actually doing and just do what comes naturally
(which is what you learned by practicing in the past). the second time,
you have kind of fallen back into analyzing the whole game and what
you're doing wrong instead of simply playing the game. thinking about
what you need to do interferes with the motor symphony. what do you think?
amber: I can totally see that. The boxes are getting in each other's
way and not letting each other do their jobs. It also goes with the "in the
groove" feeling you get too...when you're thinking and playing poorly and
then all of a sudden it all just clicks and you're coasting...you know?
It's when you stop thinking about what you're doing and let the motor
symphony do its thang.
erin: you think that that would work for neurobio? that would be pretty
cool. just sit down for the test, put a pen in my hand, and then blank
out. the next thing i would know, the entire test would be done, making
perfect arguments, of course, and i wouldn't remember how i did it.
yeah. cool.
amber: at first I was thinking you were joking, but you know, I think you > have something there....I bet most teachers would say that the spazz
studets in their classes are the ones who make small math mistakes, leave
out points they know, etc...the relaxed students generally do better.
That's why mom always told ya to get a good night's rest before the exam :)
erin: that's it. i'm never thinking again.
Nope. I knew about typing before we did the readings in the other class. Nyah, nyah. Wonderful dialogue, though. What's to say? Yes, indeed, thinking can sometimes get in the way (which provides VERY strong evidence, by the way, that the "I-function is NOT a cop out; the observational/experimental evidence REQUIRES such a concept). And yes, there's a lot to learn about brain function from thinking about athletics. PG
The concepts of a motor symphony and central pattern generation express the fact that the nervous system is a highly organized system of neurons which interact together in many ways to express behavior. The motor symphony itself is very organized depending on numerous neurons being active in relation to other motor neurons. Central pattern generation is interesting that the nervous system has the ability to play out motor symphonies without sensory input.
In the experiment done with the earthworm, where it's nervous system connection was severed, it was still capable of movement when it's skin was sutered. Here the motor score does not exist but the motor symphony is created when played based on sensory input which allows for movement.
Another experiment which involved central pattern generation was in the absence of input that the worm was able to move. Although this experiment was not entirely proof positive, it was interesting to know that it generally was successful. The worm's midsection's muscle and skin were removed and all was left was the nervous system. The referent path was destroyed but movement was possible.
A number of motor neurons can be activated because of some muscle movement therefore resulting in a lot of action potentials which will result in the activation of numerous motor neurons. This is characteristic of a motor symphony. This activation can be described as what results in behavior. The previous experiments mentioned above on worms give us a lot of information on how the nervous system may work on invertebraes but not exactly for vertebrae species. If we were able to come up with more specific ways to learn more about the nervous system, we may find a way to cure those who have been paralyzed. Looking at these earthworm experiments seems to add to this future possibility.
Yep, and it really is true that the same concepts hold for vertebrates and invertebrates, with the latter being (in general) much easier to study (at least for many sorts of problems). PG
Now that we know that CPG's exist and that they may be genetically based, many details of the intricacies of behavior are falling into place. I think we are at a crucial point in class that really is the whole reason why I decided to take it in the first place. I knew of neurons and action potentials and things but I really did not know how any of this could lead to teh complex behaviors that we all experience every minute of the day. My questions about why we can learnto ride a bike so fluidly after having mastered it once can now be explained by CPG. It is not necessarily the we were wired to ride a bike but a motor symphony was being written while we were learning to ride a bike and now we can ride it without thinking twice about it. Our mucles know the movement so well that we can balance on two wheels and navigate etc without realy concentrating on the task at hand. Knowing about teh involvement of Genetics is very helpful in understanding complex behaviors such as walking and flying in birds. It just provides more evidence for the nature-nurture theory. I am not saying that we are more one or the other but that this is yet another piece of evidence that we are indeed programmed to do certain things at certain stages in our lives. And there are also other things that may be learned that become so fluid over time that it itself becomes a motor symphony inexplicable through simple sensory input--output mechanisms (like piano playing). I am really looking forward to learning how the CPG is stored and how it works in terms of neurons.
Nice extensions to other behaviors, glad to works for you. CPG indeed probably some part of riding a bicycle, but so too is something quite different and equally interested: an improved ability (probably) to make use of sensory input for the task at hand. And yes, not nature OR nurture but contributions from both in most cases. PG
I sat down to write this essay with, what I thought was a pretty thorough understanding of class on Thursday, but it turns out, I have myself confused. Originally, I looked at CPG's and the motor symphony as opposing views. I knew that behavior wasn't an "either/ or" situation (meaning that behavior is not result of one or the other), but rather a combination of the two. I had thought,though, that the main ideas of each were considerably different. I was confident that when I began my essay, I could write about how the two work together to produce the behaviors we see everyday. BUT when I flipped through my notes from class, I reorganized my ideas. Now, I think that motor symphonies are simply an extension of the CPG idea. Now I may be wrong about this (hence, my confusion), but if CPG's are generations of output even in the absence of input and a motor symphony says that any output is an enormously intricate coordination of motor nerves, then OF COURSE the two work together. This just means that a motor symphony can occur without an input. We know that CPG's exist from the earthworm experiment that demonstrated movement without nervous system connections, as long as the skin is re-stitched. This supports the idea that there are pre-written scores that are housed in the nervous system which can occur regardless of the input and can also occur without connections throughout the entire nerovus system.
The notion of pre-written scores is what strikes me as more interesting than the motor symphony and the CPG's. If we do indeed have such pre-determined (possibly learned, possibly genetically determined) templates for movement and behavior, how many do we have? If these movements and behaviors are independent of brain influences and sensory input, what provokes them and what, if anything, has control over them? I am sure that these pre-written scores are limited to very basic movements, but it is eery to think that our bodies can carry out functions such as walking or moving our hand without our brain's control--these can just "happen". This makes me think back to the article I read on Phantom Limbs.....maybe the patients who feel phantom limb movement are simply experiencing the nerves attempting to carry out these scores of movement that had been determined before the limb had been lost. The detailed network of nerves that are involved in a motor symphony are obviously used for CPG's and for responses to input. The symphonies are involved in every type of movement because no output requires just one nerve-there has to be a series of communications from nerve to nerve to nerve....from sensory to interneuron to synapses to more synapses to more interneurons to the brain to other motoneurons, etc. This idea supports how I have looked at behavior all along. The CPGs and pre written scores, however, have made me reconsider behavior as more than reactions to input. I always accepted the autonomous functions of the nervous system, but I always thought that the brain still had some sort of control over this autonomy. Now, with this pre-determination factor, maybe the brain isn't as in control of EVERYTHING as I had once believed.
Interesting thoughts. Yes, YOU probably have less control than you once believed, and that is important to understand. Don't, though, automatically equate "you" with the "brain". There are CPG's in the brain, as well as in the spinal cord. The distinction is really between "I-function related" (a PART of the brain), and non "I-function" related. Are you less confused now about "motor symphonies" and CPG's? The former is simply a fancy way of saying movement corresponds to complex spatio-temporal discharge patterns in motoneurons. The latter is (one) explanation of how those patterns are brought about, another possibility being through the use of sensory input. PG
The phantom limb phenomenon is extremely surprising at first, however taking into account what we've learned about central pattern generators and corollary discharge it makes sense. Though the limb has been lost its connections to the rest of the nervous system still remain. Those connections are kind of like loose wires in a machine that keeps sending electricity towards another part of the machine without realizing that the other part is not receiving the electricity. Instead the electricity is being given off as sparks. The machine may keep sending electricity out until it breaks down or somebody turns it off.
The person can feel their missing limb because their nervous system tells them where the limb would be doing and what it would be doing, through the corollary discharge that the remaining central pattern generators (the remaining connections)send to surrounding neurons. This means that our perception of where our limbs are and what they are doing is a combination of sensory input we receive from the limb and other sources of sensory input as well as the information our nervous system receives from corollary discharge. Corollary discharge also represents what our nervous system wants our limbs to do, it is the message it is sending to the motor neurons. What happens however when the motor neurons can't do exactly what the nervous system tells them to do? What if they don't receive the message or if the muscles are not working properly? Who does the nervous system "believe", the corollary discharge that says that the limb has moved or the propioceptors that say the limb has not moved?
If the nervous system believes the propioceptors and the sensory input from the eyes, then the person should be able to convince themselves that the limb hasn't moved for some reason. If this is true then a person who faces the phantom limb syndrome should be able to convince themselves that their limb does not exist therefore they shouldn't be experiencing any sensation from it.
If the nervous system believes the corollary discharge signals then the person would have a very warped sense of reality and what is actually happening with their bodies in the world around them. This must be the dillema the person with phantom limbs must experience. They must be somewhere in between these two extremes.
Nice phrasing of the problem. Be a little careful, though, about details. The motoneurons are still around (though not connected to the muscles, which are missing). The CD signals almost certainly don't come from the motoneurons, but rather from CPG's which still also activate the motoneurons (actually, the motoneurons may, in time, disappear, and other secondary reorganizations may also take place in the nervous system). PG
These new concepts of a central pattern generation and a motor symphony bring a new perspective to behavior, such that we can account for actions in a larger picture- that of groups of potentials that can be organized into intermediate sized boxes instead of a minute picture given by looking at the level of the neuron. Thus we can expand our concept of potentials to actually link and refer these mechanisms to behavior that we are familiar with, such as walking. The experiments with the baby crickets provide compelling evidence for a genetic basis to the central pattern generation. One's predisposition to certain talents can now be understood to involve hereditary units that play a role in directing movements that are connected to the nervous system. Thus we can truly see the nervous system as having neurons which each act as computer central processing units. The existence of a memory capability, of which some information is genetically determined is pretty amazing-- that such information is stored before it is used, and that it has been there since the development of the embryo nervous system. The storage of memory also seems like it might be an evolutionary-related mechanism, which helps us to prevent having to write a new symphony every time.
Interesting thoughts/extensions. Be careful, though, not to equate CPG with genetic information. They can also result from experience (and, in general, involve both). PG
I am going to digress a little this week. I enjoyed class a tremendous amount on Thursday. The one thing that has stuck in my mind the most is the typing example. I never (or rarely) look at the keypad when I type. But, I had never thought about it much before. I have always assumed that the little bumps on the 'k' and 'd' were guiding me, but I never knew why or how. I also find it interesting that when I misspell a word, I fell it rather than see it on the screen. It seems as if my mind says a word and my fingers respond, and if something goes wrong, I notice it after it has already been sent to my fingers, and I can't do anything about it except use the delete key. I have been thinking of other situations that might fit into the same category of "unconscious"--quotes because I'm not real sure if that is the right word--actions that seemingly use the eyes as input, but really rely mostly from repetitive actions. 1) snooze bar. How come I can hit the snooze bar 3 or 4 times and not notice it? All of a sudden it is 14 minutes after the alarm was set for when I hear it for the first time. Clearly, I hit the snooze bar, but I certianly don't remember? 2) driving the car. I made an hour communte to Princeton several times a week last year from Phila. sometimes I would "space" and find myself 15 miles down the road and be able to tell you what was on the radio but not on the road. I just seemed like I knew where I was going so well, that I didn't really pay attention that much--not all that safe, I suppose. my third example was hitting the baseball during batting practice, but now that I am typing it, it doesn't seem to fall into the same category. I feel like I can tell where the ball is going the instant it leaves the pitcher's hand and I know when to swing and when not to swing (not that I always hit the ball). It seems that if the ball moves at 75 mph and it is travelling 60 feet, I only have .55 sec to react and hit the ball. Surely the neurons don't react that fast. What is the explanation? I'm not sure if it is the same phenomenon.
I wouldn't call all that digression, its right to the point. And fascinating. Many thanks. Let's be a little careful, though. At this point in the course we haven't really yet said much about the "I-function", other than that it exists and lots can be done without it. Most of your examples are in fact about doing things without the "I-function", rather than doing things without ongoing sensory input. Your last point, though, is entirely CPG related, and has even been studied to some degree. Neither you, nor anyone else, has time to respond to sensory input once the ball has left a good pitcher's hand. So the swing is (pretty much) a CPG. Presumably a good hitter collects a LOT of information which (.333 of the time) adequately predicts the path of the ball so the right CPG can be selected and played out (the "pretty much" has to do with the fact that there may well be some dependence on more or less steady state sensory input during the movement). Yes, your experience of having to use the delete key instead of realizing and correcting in progress a typing mistake is probably because of a CPG. The interesting question (maybe later in the course?) is how did the I-function get involved (whoops, I KNOW I mistyped). And its actually the I-function not involved that characterizes driving more than CPG's. Much of driving involves unconscious adjustments based on sensory input rather than the playing out of motor symphonies unperturbed by sensory input. PG
Imagine that every time you tried to move was like learning from scratch what movement was and how to create it. This is fundamentally where we would all be if we did not have such a concept as a motor symphony. The construct of the motor symphony erases all this re- creation and gives us a basis to start from because movements are 'recorded' and stored for later use.
Another wonderful thing about motor symphonies is that coordination is basically made easy. I cannot think how many times I have stepped or moved multiple limbs in coordination with each other to fulfill only simple actions. These kinds of things are daily or even hourly activities, such as walking, and cannot be done without working together in perfect timing. Of course, some of us are lucky to have more coordination than others--I cannot count how many times I might have mistepped and tripped, or dropped an object due to mis-coordination.
It is important that behaviors can be seen as at least a part of motor symphonies. By understanding that there are automatic mechanisms for movement functions we can begin to understand why many people exhibit similiar behaviors and also why people vary in the particulars of their motions. I think it is also important to have theory such as motor symphonies and CPG so that there is a starting point for understanding the physical outputs of the nervous system. By building up the 'symphonies' we will be able to obtain a larger picture, eventually, of complex behaviors such as facial expressions and gestures. This is only the start!
Yep. And practically a pretty good start (in my experience, anyhow), for exactly the reasons you mentioned. Gives a foundation which helps to define the next questions. PG
I thought a while about the topoic of central pattern generation and the idea of having the motor symphony stored somehow in the brain or body and the implications of this idea. I'm not sure how that would necessarily change behavior, but it raises many questions in my mind about how the patterns are stored and when we develop the tools or hardware to store certain types of behavior. Does the idea of CPG mean that we basically have a blueprint of reactions to set patterns of received stimuli? Also, is the idea of CPG related to the controversy of whether we are pre-wired for certain behaviors or not?
One implication of CPG is that, again, how much of our behavior do we actually have control over? If a stimulus sets off a stored pattern of behavior that was imprinted in our brain by the environment, where does that leave free-will again (hey, maybe that's how we can explain phobia's), but then we talked about the idea of getting outputs without the necessity of an input.
Interesting/appropriate thoughts/questions. Probably due have "blueprints", but not sure its appropriate to call them "reactions". Remember that normally they are modified by sensory input at the time (we got rid of that only to sure their existence). Pre-wired? More or less for some things, less or more for others, since CPG's can relate to learned behaviors. Free-will? Hmmmm. We're not quite there yet (but will get there). Suspect it will turn out that CPG's help with rather than hindering that argument. The more one has to work with, the greater the range of possible behaviors; hence more choice? PG
In light of the evidence that an input is not a necessary precursor to an output, the idea that outputs are constantly generating inputs is not farfetched at all. Without movement, after all, our interaction with our environment would be limited greatly. At the same time, the influence of inputs cannot be discounted--as shown by the difficulty involved in removing all input sources to create stable experimental conditions. The coordination of our motor symphonies and our awareness of our actions would also suggest a constant interplay between input and output.
However, many of us thought differently before this course began. We had several internalized misconceptions about the nervous system--for example, we thought we could phrase behaviors in terms of stimuli and responses. Well, according to the new dimensions of our study, outputs can be stimuli and inputs can be responses! What a confusing jolt of logic!
This is just an example of the many interesting ways we humans are socialized and have never thought about. Even at this level of education our thought processes are "programmed" to analyze issues in terms of concepts we have never really contemplated. In this culture the stimulus-response paradigm is as natural as the application of some kind of excuse to every human error--admitting that a fault comes from within occurs seldomly.
If you say stimulus, my brain instantly says response. What is that? It isn't an instinct, but it isn't really a thought either. I certainly didn't pull the letters of the word out of thin air and then randomly assemble them. The behavior is automatic and internalized. Is it a product of Central Process Generation, like typing or playing the piano? To what extent is CPG a learned mechanism of behavior in humans? Learning probably plays a much greater role for humans than for animals, by virtue of the scope of our behaviors, bulk and organization of our nervous systems, ability to learn and analyze rapidly, and prolonged period of growth and development--which makes us dependent on interaction and socialization for gaining the survival skills we need as adults.
If our thoughts are often socialized responses, our tastes and dreams cannot be exempt. Many of the behaviors we might explain as instincts, such as saying "ouch!" when we are hurt are also the product of the reciprocal loop system that we can now visualize. We learn to say ouch by watching others--and the more we say ouch the more the brain equates it with pain, until finally it is an automatic expression of pain. (Here the input would come from the environment but also be reinforced by our own output). In other cultures and languages, there must be different "instinctive" words and behaviors associated with pain, and this would indicate that there is no gene for a specific verbal output regarding pain, although there may be an instinctive physical output. Another example would be the standard use of the smile by humans to express happiness. In primates and many of our other mammalian relatives, the arrangement of face muscles we associate with delight are a natural result of fear. I think it is quite possible that we start internalizing smiling on the day we first see happy faces gazing down into our crib, and by socialization this and other behaviors become predictable and automatic--to a much larger extent than we can realize. Understanding the more complex CPG of humans seems closely linked at this point to socialization--that is, how the nervous system takes in and incorporates the repetitive patterns it senses into its repertoire of automatic outputs.
Very interesting/thoughtful, appropriate extension of ideas discussed in class. But let me add one additional complexity to your thinking. One might well see commonalities in tastes/dreams/thinking because of commonalities in brain organization which transcend cultural differences. Or, to put it differently, it may well be that the inclination to think in terms of "stimulus/response" has some genetic component to it which can be reinforced (or opposed) both by culture and by individual experience. I certainly have the feeling that significant parts of education involve "unlearning" things which are deeper and stronger than simply cultural norms. PG
I think I need more exapmles and evidence for both the motor symphony and the CPG. I am certainly not convinced that it is one or the other; as I shouldn't be because things are rarely absolutely one or the other when the nervous system is concerned. I'd like to say that both are involved, which I think is true, but I really want to know how. The notion of a motor symphony, as of now, has a stronger base with me because it concerns integrating inputs immediately, and I suppose we have simply talked about more examples of it in class. What concerns me is the notion of where the CPG arose. Do we already have such information stored when we are born and it just takes time to come out? Or do we need to learn it and it develops its own CPG once we have learned it. Not to say that it needs to be one or the other, but I'd like to look further into the subject; possibly the issue of nature vs. nurture could arise, which happens to be one of my favorites. I think that we do hold a lot of information when we are born, but also that most of what we know and do is learned. So, we could already have a(or several) CPG at birth for certain behaviors, but many behaviors are learned. Those behaviors, however, that we have praciticed and can do without needing inputs(though we may not know whether inputs were included), have they created their own CPG? Is that possible? I think both motor symphonies and CPG can exist simultaneously and both work to create behavior, but the CPG nothion fascinates me, and I 'd like to learn more.
Clearer after more class discussion? Motor symphony is just the complex spatial temporal pattern of motoneuron discharge which underlies any movement. CPG is one possible explanation of such symphonies (use of sensory input another), which may or may not be strongly influenced by genetic information (yes, nature/nurture and important and interesting subject). PG
I was interested by the experiment you described with the nervous system of the cat-- After cutting the dorsal roots and severing the connection between the spinal cord and the brain, the cat can still be made to walk, given the proper stimulation. That leads to the conclusion that the "motor symphony" for walking is stored in the spinal cord. What is it, then, that stimulates this "symphony" in an intact nervous system? And doesn't this hold implications (albeit at a long, long stretch) for human paraplegics, in terms of artificially stimulating certain limited types of movements in the spinal cord below the point of damage (and thus regaining some function)?
Presumably descending signals normally activate the CPG's (although this can happen as well from sensory input into the spinal cord). And yes, indeed, it provides a possible route, which people are exploring, for human paraplegics to regain some control over "paralyzed" body regions. There are real problems with this approach, however, since many inputs relevant to walking (sight, balance) would also need to somehow be conveyed to the spinal cord to get generally effective movement. PG
A professional ballerina trains for years to learn to gain ultimate control over her body in terms of muscles, flexibility and learning the basics of the classical dance. Time and time again in the standard "arabesque" which accompanies each warm-up and performance...she raises her left leg in opposition to her right arm and vice versa. However, upon taking a modern dance class of different style where there are different conventions, she finds it difficult to raise right leg with right arm for instance. It's almost as if her body is discouraging her from this movement. But why? One would think that due to such a remarkable life of training that such an elementary movement would not cause her to think twice. The answer to this riddle is exactly what we have discussed in class...Central Pattern Generation and Motor Symphony movements.
Central Pattern Generation is the human body's remarkable ability to play out a motor symphony of movements in absence of any input from the body or the external environment. As discusseed in class, this can be seen clearly in isolating the nervouse system of a crawfish (without skin, muscles...etc.) As a result, we see that patterns of the crawfish nervous system movement can be observed and emerge without any other stimuli. In addition, stimulating the axons in a random order can result in the old pattern of movement.
Many refer to this as "learned behavior". As with the dancer, actions performed over and over again seem to create a "musical score" for the axon's motor symphony whichgets stored away. However, this explanation does not account for behavior displayed such as this foer the first time...such as the cricket's mating chirp. How does it first know when and how to chirp?
Whether this Motor symphony and Central Pattern Generation is a type of musical score stored in our Nervous System memory, sent through genetics or falls somewhere in between, I can not be sure of thus far in my research of CPG and MS characteristics. However, I am assured that SOME type of internal organization exists within the Nervous System. It seems as though we have stumbled upon yet another "box within a box". The questions which arise in my mind however are WHERE this information fore CPG is stored?How is the signal to react turned ON and OFF? And WHAT causes it to be turned on and off? These two characteristics have effected my view of the human Nervous System by taking it to such an arbitrary, microscopic sub-sub-box level, that complete comprehension seems intangible to the human mind. As for the ballerina, she will just have to un-learn and re-learn any new "basics" for the time being. And although she may seem frusturated by it initially, to stop and think about why such "control" over her body has resulted in such a lack of "control" may help the realization of a dimension of memory she has never pondered before.
The ballerina example a delightful and highly appropriate one. Yes, because of CPG's (among other things) movement has to be unlearned to be learned. And that insight does help (me at least) to bridge between the "arbitrary, microscopic, sub ..." to things that are demonstrably behavior. Doesn't do that for you? PG
Seeing how complex movement is has yet again made me gawk at the fact that we are able to move at all, let alone think or do other "higher order" processes. Since so many things must go right in the nervous system just to move a leg, it seems that our notion of lower organisms as simple needs to be placed in a new context. Also, it is now clear to me why the idea of a reflex is not only wrong but grossly misleading. Not only is a reflex not "reflexive" as per the harvard law, but movement such as leg withdrawl is a highly complex ordered procedure.
As a sci-fi aside: I wonder about wet-wires as in William Gibson's classic
"Neuromancer". For neural systems that are highly ordered (and generally
linear??) such as for visual input or the activation of a central movement
pattern, would it be possible to "wire in" false neurons that could be
used to artificially control the motor pattern or translate the visual
input to a processor and video card and display it on a monitor?
Theoretically, it seems that this would be plausible so long as we can read
the membrane potentials of specific neurons and if we know where those
neurons recieve input from. This latter problem of where the input came
from should be simplified in the two above cases. Neurons normally receive
input from thousands of other neurons, but in cases where the nervous sytem
is operating in a linear fashion, such as very low level visual input and
motor output, perhaps the pathways could be determined and mapped in an
individual brain. The trouble would be that neuromechanical interface- the
so-called wet-wire. But what with advances in brain surgery and the 3D
stereotaxic (sp?) imaging equipment available, who knows?
Here are some related links:
Check out the first project:
Bioelectronics
and Neurobioengineering Group, University of Genova, Italy
and Neuronal Pattern
Analysis Group, University of Illinois
Thanks. Try out the links, they should work. As should Serendip's list of neurobiology places. Yes, the complexity indeed contributes to making "reflex" a misleading concept. And to uncertainties about the likelihood of Gibson's cyberspace visions. It is not that one can't do implants which affect nervous system activity (one can, and its done fairly routinely in a number of cases). The difficulty (as with many really interesting biological phenomena) is the inordinate three dimensional precision with which one has to produce multiple effects in order for the result to be coherent. PG
This essay will address the question: How does one think differently about the nervous system and behavior given the concepts of motor symphony and central pattern generators.
These two concepts have clarified a lot for me regarding movement. Central pattern generators explain how one can perform a movement at a fast pace without the benefit of sensory feedback (for example, my typing on the computer or riding a bike); but also how movement can be modified by the constant flow of sensory feedback. It seem that the constant proprioceptive flow that we get to the cerebellum will impact on the motor output but that this is a continuous, subcortical feedback that serves to modify the motor symphony. For example, when riding a bicycle, the motor symphony is the pattern that has been written regarding the movement of the legs to keep the pedals going. There is a constant proprioceptive flow from all the muscle receptors in the legs telling the cerebellum about the length, tension and position of the muscle. If one hits a pothole in the road, for example, the sensory feedback quickly changes and the motor symphony hopefully quickly adjusts so that the pedaler can keep the bike upright. So although sensory feedback is not necessary to generate the movement, it is a necessary component of a smooth and coordinated movement. Although the score for this motor symphony has been written, it can easily and readily be modified by sensory input.
This idea of central pattern generators also helps to clarify pathological motor behavior such as what we might see in an individual who sustains a head injury and has resultant spasticity; and also raises some interesting questions. Is the spasticity explained by the possibility that the individual no longer has the ability to modify the motor scores? Are the central program generators running out of control without inhibition/modification of higher centers? If this is the case, then it would suggest that the higher centers serve to provide modification and inhibition, not facilitation. However, how then do we account for the activity that is generated in the cortex which results in direct alpha motoneuron activity? Also , is the stretch reflex, which is proposed to be hyperactive in individuals with spasticity, really the thing that is running out of control or is it a more complex central pattern generator of activity? These issues are important when considering intervention for individuals with motor disorders. Should the intervention focus on modifying the central program generator activity, and if so, how might this be accomplished? Are central program generators modifiable or is it the score that is modifiable? And how would one have an impact on either of these?
A final thought that has been generated based on our discussions of CPG and motor symphonies, is related to the concepts of genetic versus influenced by experience. I agree that certain motor symphonies are genetically wired, such as walking, coughing, talking, etc; and that others are created by need or desire (such as driving a car, playing the piano or riding a bicycle). Is there a difference between the innate CPG and the created ones? How is it that innate motor patterns can be modified based on culture or experience (for example the gait patterns and stance may differ depending on culture). And finally, what constitutes writing a score for a new CPG such as learning to ski or ride a bike? If new scores can be written, is it easier to write them when the nervous system is young and plastic? What makes a motor score more easily composed? Is it sensory feedback or motor repetition, or something else? These will have important implications for working with individuals with motor dysfunction. For example, the individual who has sustained a stroke and now has a non-functional arm. What kinds of intervention will best help this individual re-learn how to move that arm? Will increased tactile and proprioceptive input that helps them "feel" the arm assist them with regaining movement? Will passive assisted movement of the arm help them? Will attempts to get them to consciously and volitionally move their arm help them to modify the CPG to the just right degree for movement? Since none of these scenarios work well in all (or even many) individuals I wonder if there is something else that we are missing.
Sophisticated/interesting thoughts/questions. Yes, motor scores modifiable by sensory input. But there is an interesting question about how fast. Sensory input averaged over time can modify output, but whether output correctable when hitting a pothole depends on how quickly one wants a correction. Yes, spasticity tends to imply loss of inhibition rather than facilitation, but both operate. Directly, as well as by gating sensory input. Yes, certainly encourages thinking about therapeutics. Not sure there is a general answer though. Suspect one has to explore variety of possibilities raised for each syndrome separately, and, potentially, for each individual separately. PG
The origin of motor symphonies is an interesting problem because it is not possible to exactly determine whether one is learned or contained in the genetic material. Some motor symphonies are more likely to be inborn than others. In this category are those that allow a newborn animal to survive in the first moments of its life. For example a tadpole needs to know how to break out of the egg and then imidiately swim away which involves a series of complex motor symphonies. A bird is in a similar situation when its trying to fight its way out of the egg. These animals do not have time or opportunity when to learn these symphonies, thus these are more likely to be genetic in origin. Some of these behaviors become more sophisticated(swiming) when the organisms is exposed to inputs because they allow it to learn and incorporate the new knowledge into the old symphony.
Functions that are not essential for survival are less likely to be storred in the genetic material. The ability of some people to write does not offer enough selective advantage, over the people who cannot write, so the evolution mechanisms did not have enough incentive, or time, to store this pattern into our genome. However, writing and other human behaviors, such as lifting a coffee cup, are in a way peculiar. Every person has a characteristic way of performing these tasks. We all engage same muscles to do it but the sequence in which we use them and extent to which we use some of them and not the others varies from person to person. This is why experts on handwriting are able to distinguish one persons writing sample from that of another person. This also shows that there is a pattern, or score, for the motor symphony storred somewhere in the nervous system. This is the only way we can explain why a letter "A" always looks the same or very similar when the same person writes it or why we are able to recognize a person's walk by the beat of their footsteps. If everyone of these behaviors had to be reinvented every time according to the outside inputs these characteristics would not be possible. A genetic element in all of the "learned" behaviors must exist in order to explain how we are able to learn and produce any movement, in case of writing it would be ability to hold a pen and move our fingers.
It would be reasonable to say that in general motor symphonies are generated as a combination of the genetic and learned material. This statment is true for all behaviors until we are able to prove otherwise(that the behavior is purely inborn or learned).
Very interesting. Yes, good bet, in lieu of other information, is combination of genetic and learned (is, in fact, what usually turns out to be the case). Certainly some early needed behaviors are heavily dependent on genetic information. But some later appearing ones may be as well (bird flight, despite appearances). What really intrigues me, though, is your thoughts about the variabilities even in stereotyped behaviors and the meaning of that. Yes, they do tend to be variable (and not only in humans). And they show constant general characteristics despite the variation (try signing your name with your opposite hand, or with your foot). That raises some quite interesting questions about exactly what one means (at a more sophisticated level) about CPG. Stop by if you're interested in talking more about it. PG
When I start thinking about behavior the number of questions that i don't know how to approach answering is simply overwhelming. Even though I do beleive that many of these questions will be answered in the future (I believe in science), it is still incredible how much work has been involved> in research of the Nervous System as well as behavior. When I think about the fact that we are discussing the chemical constitution of our thoughts, movements,beleifs I can't help but think that five hundred years ago even the > thought of such explanation were unconceivable. I just think that this is incredible.
All the suggestions made in class in order to explain the connection between Nervous system and behavior are perfectly reasonable and seem to make perfect sense in realtion to the experiments proposed. Yet, it is incredible to think about how much is yet to be explained!
The behavior can definetely is better explained by the recent propositions made in class, since we can use our model of motor symphony to account for more general occurences and not just for tiny (yet, incredibly important) events such as action potentials. For example the fact that we can now somehow rationalize memory and learning (as in the example of remembering how to type). I wonder if this model can also explain forgetting? In other words, do motor symphonies get erased? I know that Freud would not agree with even the formulation of the question, since, as far as I know, he did not beleive in forgetting, just repressing. Yet,it seems interesting that even with the example of typing, if we have not typed for a while we are not as quick as we used to be. Does it mean that the motor symphony has to be rewritten again?
Interesting issue: forgetting versus repressing. But certainly some patterns of change in the nervous system can disappear with time (although others remain remarkably stable, like knowing how to ride a bike even if you haven't for a long time). I don't know of anyone looking at "erasing" of motor symphonies and it might well be interesting to do so. Yep, lots yet to be explained (which, incidentally, is a good sign for the idea that brain=behavior: "good" ideas can usually be recognized by how many new and approachable questions they raise). PG
At the end of Thursday's class, we discussed the possibility that the motor symphonies involved in cricket singing are genetically preprogrammed. When discussing the role of genetic factors in behavior, it is essential for one to distinguish between the implication that such behaviors are preprogrammed as in the concept of fixed action patterns and a conceptualization of the pattern for motor symphonies as an interaction between genetic factors, an input/output loop involving the organism and its environment, and information of such interactions in the past store somehow in the brain. That is, rather than approaching behavior as the turning on of a motor symphony, the click, and the playing out of a behavior, the whirr of a recorded message, a more appropriate model of human behavior would be more of an interactive satellite video conference with an archive of past behaviors built in. What is genetically programmed, rather, is the structure of the muscles which are utilized in these behaviors. The utilization of these muscles is what is being learned from day one. In fact, the oral motor activity displayed by neonates, which emerges prenatally, involves the constant conveyance of information between the environment and its behavior. By putting objects in their mouths and sucking on them, neonates' activity serves as a means by which they explore objects in their immediate environment as they conform their mouths to the shapes of the objects. This conceptualization of motor symphonies raises the question of whether or not these motor symphonies are also, like other behaviors, malleable/susceptible to reorganization from experience. Let us consider the case of Ralph, a worker in a soap factory. Ralph falls into a soap vat one day at work and looses his right leg. Will the motor symphonies for walking, running, etc. which are supposedly turned on by the CPG reorganize to accommodate the absence of this limb? Approaching the issue of amputation from the input side, the article on phantom limbs described amputees' perception of pain from the missing limb and of the movement of the imaginary limb in coordination with other movements as being the same as they were prior to the amputation. Furthermore, the authors' suggestion that the pain perceived at the location of the amputation is due to continual motor output from the motor cortex indicates that the motor symphony does not in fact reorganize after amputation of a limb. To the contrary, a recent article by Latash and Anson, "What Are Normal Movements in Atypical Populations?" suggests that motor symphonies are coordinated "priorities" and form the basis for patterns of motor outputs. They hypothesize that, "disorders of perception of the environment and decision-making, structural or biochemical changes within the central nervous system, and/or structural changes of the effectors, the central nervous system may reconsider its priorities. . . may lead to different patterns of voluntary movement." According to Latash and Anson, what amputation involves is a "major disruption of the biomechanical and neurophysiological relations developed during the lifetime." The subsequent loss of input from proprioreceptors regarding balance of weight, position, etc. would result in the person's not being able to walk even with a prosthetic limb if the central nervous system could not reorganize to take into account the loss of this information. This assertion implies that post-amputation, the person must learn to walk all over again relying on primarily visual information rather than input from proprioreceptors. In strong support of the notion of motor symphony reorganization and accommodation is that of the large number of amputees who continue to run and to participate in other physical activities with the aid of prosthetics. These arguments suggest that the click whirr notion of behavior as motor symphonies which are activated by CPGs does not sufficiently account for the plasticity of the human brain and its ability to organize and reorganize (to learn) through experience. For further discussion of other examples of CNS reorganization of motor patterns, I highly recommend reviewing this article posted at: this article.
Interesting and highly approriate concerns. The CPG notion was essential to (help) move beyond "reflex" based conceptualizations of behavior. But the "click whirr" idea associated with it is clearly proving incorrect in its own turn. We've actually been testing this very proposition in frogs in our lab, and coming up with observations quite similar to those you outline. PG
Logically, it does not seem possible for there to be a motor symphony because of the tremendous adaptivity and learning capability of many organisms. It also goes against my thinking in a way such that a baby can LEARN to walk, I can LEARN to play tennis, you can LEARN how to pick up a coffee cup and so on meaning that part of the LEARNingness is taken out of the picture. Instead of learning certain activities, it is learning how to read the central pattern generation inputs. I never really thought that we can have so much stored within us. It would mean that even more of a person is a result of heredity instead of environment. In other words, that the environment shapes whether or not CPGs are read in a correct way, but that essentially it is all there. Life is about nature AND nurture. Whereas we knew this already, it just adds more strength to the whole argument. Looking on the level of motor symphony and central pattern generation makes our original assumption about behavior more probable. The brain is behavior - it is more evident based on what we continue to learn. I assume that this is what we are ultimately aiming for. We want to be convinced by the time we are through with our studies that the brain is behavior. Interesting how we keep getting closer to that point, and when it seems like we may be there, we still know that there is more to come.
Actually, there will always be (of course), but I'm glad the target at least hasn't receded. Careful about equating CPG with genetic information. No, you don't have every CPG when you're born, with the problem being only to read it. Many CPG's are acquired (a tennis serve certainly being one of them). PG
Behavior in terms of a motor symphony and central pattern generators, seems now to be dictated by both the individual and nature-genes. In the case of central pattern generation the hybrid crickets' hybrid song shows how there is a genetic basis for some central pattern generation. But also, there seems to be some choice in how one uses or puts together their own motor symphony. As is the case when you start an action but do not complete it, because you do not want to. Thus, some behavior is monitored by the conscious individual, and some is almost completely influenced by genetics.
Careful not to equate CPG with genetics: such capabilities may result from genes or experience (and, most generally, both). Your more general point though is correct and important. CPG activity can be modified by a number of things, of which the "I-function" (in organisms that have it) is certainly one. PG