Neurobiology and Behavior, Week 8

Paul Grobstein's picture

Welcome to the on-line forum associated with the Biology 202 at Bryn Mawr College. Its a way to keep conversations going between course meetings, and to do so in a way that makes our conversations available to other who may in turn have interesting thoughts to contribute to them. Leave whatever thoughts in progress you think might be useful to others, see what other people are thinking, and add thoughts that that in turn generates in you.

You're free to write about whatever came into your mind this week, but if you need something to get you started: We've begun to move into the space between neurons and behavior, the creation of new properties by interconnected neuronal circuits.   In what ways do ideas like central pattern generation and corollary discharge help to bridge the gap?  Are they enough or do we need more?

 

JJLopez's picture

Central Pattern Generator

I have been thinking about this C.P.G concept and how it relates to the example in class on the crayfish and its swimmerets.  If in the end we conclude that the swimmeretts don't have much purpose in the daily activity of the crayfish, then why is this example useful to us.  I guess I keep thinking that in order for this C.P.G concept to be a valid theory to explain why things in the nervous system happen without inputs, I am trying to conceptualize in my head that any output that occurs has some meaningful purpose.  But then this also makes me think of tourette syndrom and its almost random jerking movements of the body.  Is C.P.G involved in making these jerking movements occur without the need of any apparent input that causes them.  Because it is an inherited gene, I thought of the example of the cricket song and how C.P.G affects why the crickets know this song and perhaps, with tourettes some part of the nervous system has an inherited jerking movement. Or am I just mixing up the two concepts?

kdilliplan's picture

Detriments of Incomplete and Interrupted Patterns

 

The concept of patterned outputs of the nervous system sheds new light on our capabilities and also our limitations. Central pattern generators may help us and other organisms function more quickly and efficiently and in a more coordinated manner, but I would think patterns can also be very limiting. For instance, when I used to play a musical instrument I would often need to memorize the pieces of music I was learning. I occasionally had difficulties keeping the different pieces separated, especially if they had phrases or rhythms in common. I’d begin playing one piece and end up playing a different one because I was relying on the patterns I’d formed for each piece and paying less attention to my performance.

I would imagine that patterns of inputs could be even more limiting than patterns of outputs. Many optical illusions rely on the brain filling in information that it thinks should be there when it is not. Olfactory memory works a similar way: we smell something and the brain responds by setting off a cascade of stored experiences associated with that scent. These examples seem trivial now that I’m thinking about them. However, other patterns of associations and behavior can be detrimental. Stereotypes are made up of patterns, as are superstitions. A great deal of harm can come from someone receiving a specific set of inputs and automatically assuming that other situations they associate with those inputs also exist when they very well may not.

On the other hand, more dramatic disadvantages can occur when patterns are interrupted. For instance, if a person suffers neuronal damage that disrupts the CPG of their walking behavior, that person has to re-learn how to walk. If a person uses addictive drugs, those drugs create patterns of neuronal activity that wreak havoc on that person if they stop using those drugs.  Despite their drawbacks, pattern generators seem pretty essential for regulating behavior.

 

meroberts's picture

Central Pattern Generation and Evolution

It makes sense to me that there is a set pattern, or a central pattern generator, hidden somewhere in the cavernous recesses of the brain to ensure that an individual/animal will be able to survive on their own. Has everyone seen the movie, Bambi? The plot of the movie is that a young deer has to survive in the wild alone (or with the help of his other animal friends) after his mother is shot by hunters.

So Bambi was only able to survive because of these central pattern generators. He has no adult deer model to teach him how to survive in the wild, he only has these innate patterns that allow him to survive. There's a scene in the movie where Bambi learns to walk. His knobby knees buckle under his own weight as his muscles become strong enough to support himself. But he does stand on his own and take some staggering steps. Eventually, he becomes quite adept at walking and running because he HAS to be in order to stay alive.

So central pattern generation is integral to evolution. If a baby was born who couldn't breathe on its own due to the absence of the "pattern" for the respiratory muscles to follow, the baby would die without heroic efforts/life support on the part of the medical team. In order to live and pass on your own genes, these musculo-skeletal patterns must be present. If central pattern generation were not integral to evolution, these patterns would not be present and observable across organisms today.

yml's picture

walking, breathing, CPGs...

As several of others mentioned in the forum, I found the discussion about infants don’t learn to walk but born with central pattern generator for walking.  Since it takes awhile for infants to learn to walk and there are steps they have to develop in order to walk, I never thought there would be a system “pre-installed” in our brain that makes you walk, even before you know how to walk. For the case of breathing, as it is another example for CPG, infants don’t require practice or experiences to have CPG for breathing to take a place. Then is that mean some CPGs require experiences, like walking, and some don’t, like breathing? Also, is this because there are less muscle movements to be learn to breathe than to walk, therefore can be done faster?

Another sets of questions I have for CPG are, so if you were not born with central pattern generator for certain activities, you won’t be able to create CPG for an activity of your choice? Meaning, does CPG always have to be there from the birth or can it be created from experiences, repeated actions, etc? So for example, as we discussed, is playing a piano without thinking an example of CPG that is created after birth? If it is, then shouldn’t we say that CPG can be “learned”?

 

ewippermann's picture

"Learning" CPGs

It's true that it takes a while for children to learn how to walk, but all children instinctively know to try to learn how to walk, which is even cooler. I think you're right speculating that breathing is learned faster (thankfully) because there are less muscle movements required to breathe than to walk, and I guess organisms evolved so that the CPG for breathing is immediately employed.

I don't know if you can create a CPG for piano, but I think all humans do have a CPG specifically for music--which explains why there is music in every known recorded human culture. Same with language and math capabilities. We need exposure to language to learn it, but we don't have to be taught: there are pathways already established that allow us to acquire language very easily within the developmental window for language acquisition.

So maybe CPGs can't be "learned" in the way we typically define learning, but for many CPG functions like learning music and language, we require experience and exposure to supply the information that will then be processed using the neuronal pathways established by the CPG.

smkaplan's picture

Central Pattern Generators and 'Learning'

 

Sort of along the lines of what a few other people have been addressing here, to me the most interesting thing that came out of Thursday's discussion was the concept of Central Pattern Generators, which for me seems to really destabilize a lot of our most common notions about what it means to "learn" something.

I feel like there's a linguistic or conceptual issue at the root of this idea of Central Pattern Generators—that is, what is "learning?" If, for example, a CPG exists for walking, does that mean children do not "learn" to walk? Can we "learn" a new action if the blueprint for that action is already present in our nervous system, just waiting for us to use it? What exactly is going on as children try and try to walk—or as birds try, over and over, to fly out of their nests those first few times?

I would say that our impulse, after Thursday's class, to reject the idea that such efforts constitute "learning" is premature. Maybe what we require is a more specific vocabulary to describe how exactly we acquire and store information, because "learning" as a catch-all term is clearly causing us problems here.

On a related note, I'm interested in how CPGs become part of the nervous system. It seems like there are some that we have from birth—walking, for example, or other subconscious neural and bodily activities—but that there are others we are able to acquire through experience. What's the distinction between these two types of CPGs—say, learning to walk vs. learning to play an instrument? How is it that some CPGs are passed on to future generations and seem to be part of our genetic structure while others are only acquired?

I guess overall it seems like there must be some kind of spectrum, a continuum of learned behavior ranging from the most instinctual to the most acquired, and that various types of CPGs would lie at different points on that spectrum. I'm interested in investigating this further.

Finally, I'm curious about the CPG as a metaphor—because that's essentially what it is, right? In class, we used CPGs to talk about activities ranging from breathing or our hearts beating to playing a sport or instrument. The brain must have different ways of handling such diverse phenomena, and so I'm interested in what differences are paved over by the concept of the CPG—that is, a metaphor for some kind of activity becoming more-or-less permanently "engraved" (or something) in the pathways of the nervous system.

 

Hannah Silverblank's picture

This comment only partially

This comment only partially responds to Sam's, but after reading his thoughts, I became curious  about the process of memory "engraving" vs. memories that don't seem to really "make a mark."

 

I found myself led to a NY Times article entitled "Forgetting, With a Purpose" by Sindya N. Bhanoo (http://www.nytimes.com/2010/02/23/science/23obflies.html). The article explores how short-term memory might not just fade, but rather is actively erased in order to clear up space for the brain's storage system. Fruit flies, according to Bhanoo, exhibit behaviors that suggest that the "memory-eroding protein", Rac (which also is present in the human brain) allow for this constant emptying-the-trash of our minds. When Rac was obstructed for the fruit flies, the experiment showed that the flies tried to construct two different (and contrary memories) that layered upon one another and caused "chaos."

 

The protein, according to Bhanoo, acts such that "short-term memory is erased by the brain on purpose, so that new, more relevant memories can be recorded." I find this idea quite intriguing, that the brain takes an active role in determining the information that "matters" most. While this "relevant information" might just function in relevance to survival or health, the fact that the brain prioritizes and makes its own decisions about what is useful, useless, and worthy of its space seems to make our brains and what we consider to be ourselves peers.

 

molivares's picture

Central Pattern Generators in the Common Cuckoo

Hearing about the experiment with the birds in straightjackets and its affect on its ability to fly made me think of another behavior in a particular kind of bird that I now recognize as a central pattern generator. The Cuckoo is an interesting species in that it is a brood parasite species, meaning that the offspring of the Common Cuckoo require parental care from unrelated host parents (usually a Reed Warbler) while the host parents gain no reproductive rewards from the cuckoo nest-invader. A female Cuckoo simply drops its egg into the nest of a Reed Warbler and leaves it there to be raised by host parents. The parasitized nest is detrimental to the host species because the Common Cuckoo not only requires food and care from its host parents, but it also ejects the eggs of the host parents out of the nest within hours of first hatching.

Upon hatching in the Reed Warbler’s nest, the baby Cuckoo, blind and featherless, begins what is believed to be a natural instinct for baby Cuckoos. Unsteady and wobbling, the baby Cuckoo positions the unhatched host’s eggs onto the dip in its back and pushes them toward the edge of the nest and with a determined thrust, expels the egg out of the nest.  The Cuckoo repeats this action until all the remaining eggs are rid of the nest. (If you want to see this behavior for yourself, watch this http://www.youtube.com/watch?v=DbvDQjhO9nY&feature=player_embedded)

I found this behavior quite fascinating. At first was hard for me to understand how a newly hatched Cuckoo could carry out such a complex, nonlearned behavior.  I now see that it is a central pattern generator, or a circuit of neurons, that allows this behavior to play out so early in life. The egg-ejecting behavior is clearly a highly developed survival mechanism and I am interested to learn more about how evolution shapes the formation of central pattern generators.  

 

Saba Ashraf's picture

Central Pattern Generators/Functions and Nervous System

            The correlation we talked about during class between functions and removing a part of the nervous system was very interesting because it is an idea that is misunderstood by many. Usually, we assume that we can locate a function by showing the function is nonexistent when part of the nervous system is removed. This seems to make sense at first, but we don’t actually know all the parts of the nervous system that account for this function using this method. Basically, we can’t conclude right away that the part nervous system that is removed is the only thing needed for the function. However, the opposite appears to be true because if the function exists when part of the nervous system is removed, then we know for a fact is it not needed for that function to persist. 

The concept of the central pattern generation and the bird example used in class was also very amusing. Initially, I was certain that the removal of the straightjackets on the birds would prompt the birds with these jackets on to fall directly on the ground.   The fact that they were still able to fly was surprising because birds and even humans spend so much time trying to learn how to fly or walk, so you would expect those with the experience to have an upper hand in flying/walking.  Another surprising idea was that both types of birds, those with and without straightjackets, were able to fly at relatively the same time despite the lack of experience in some of birds because of the presence of a central pattern generator. I wonder if this would be true for humans or if humans without the experience of trying to walk would walk much later than those with the experience. The idea of acquiring a new central pattern generator that is not in the I-function such as playing an instrument was somewhat relatable because I used to play the violin at a younger age. Because I haven’t played in many years, I don’t remember whether I would think about the movement of my fingers while playing. However, it seems very reasonable that many can’t play as well when they are actually thinking about the action since the central pattern generator is not included in the I-function.    

natmackow's picture

CPG's, innate and learned

To me, the idea of innate central pattern generators (CPG) and their coordinated control of specific actions, like walking, is startling but makes sense. I always thought that children learning to walk, or reaching out to grab anything within reach was a visually learned process and that their development of these behaviors would be different if they grew up in a different situation (without human contact, etc.). Despite this, there are clearly behaviors that we (our neurons, muscles, bodies) can just do. Breathing, the beating of a heart, and flinching away from something hot or sharp are not learned actions, nor are they controllable by an “i-function”. The motor symphonies for these actions have already been composed by our genes.

I find the ability of organisms to create new CPGs for other behaviors fascinating as well. I began playing soccer when I was six and it was definitely not an innate set of actions. Kicking a ball, aiming my passes, and using my non-dominant foot were awkward, frustrating actions. I knew what a specific move looked like but, no matter how hard I tried, I could not will my body to to recreate it smoothly and skillfully. It took me a while to realize that if I practiced passing, shooting, or even certain moves over and over again, they would become almost instinctual when I played with my teammates. And so I began creating CPGs that worked together to create a motor symphony of soccer skills. Now, when I come back from a few months off from soccer, it takes only a couple of days to get my feet moving fluidly again. I wonder if, having now created these CPGs, they can ever be destroyed? Does disuse of a certain CPG over a long period of time affect its existence? Or, can the CPGs we create during our lifetime become as innate as those responsible for breathing? In other words, when someone sits back at the piano bench after fifteen years without practice, is it just the motor neurons that aren’t used to being utilized in that manner or is it the CPG that has become weaker?

 

cschoonover's picture

CPGs

 Towards the end of class we concluded that the nervous system consists of a bunch of interacting parts with no one in charge, meaning it is a fundamentally distributive system. At first it seemed odd to me that a complicated system could produce such sophisticated behavior without a conductor, without someone to report to. However, after going back to the examples used in class, it’s starting to make more sense and it even seems like an advantage to work this way. Without a central commander, different parts of the nervous system can be doing different things. A simplification of this is evident in the ability to rub your head and pat your stomach at the same time. I think a more complicated example and manifestation of this is our ability to multitask. Thus it makes sense that there is not just one but many central pattern generators and that the coordination of individual central pattern generators results in a particular pattern (i.e. movement). I found it extremely interesting and exciting that the communication between the ganglia is responsible for the coordination of central pattern generators. And that changes within this communication are responsible for changes in the generated patterns.

Following this train of thought, I wonder if severe enough changes to the nervous system can alter the central pattern generators. For instance, someone who is deaf and has never heard another person speak is unable to articulate sounds that are produced by the linguistic majority. However, they can still produce sounds that have the potential to be understood. This is the result of a lack of sensory input, but does it extend beyond this? If the central pattern generator is still functional, is it deactivated? Or if it is still activated, is there a component related to the reafferent loop?

I think these ideas are very helpful, but I still think we need more to fully understand what is going on and how behavior is manifested from the patterns generated by neurons.

Colette's picture

        It seems like we

        It seems like we moved into a pretty big seemingly empty space. The starting point are billions of neurons of different sizes and shapes that each function in the same way collected into discrete groups and connected to each other. Their outputs are specific activities. How their output are specific activities. How we get from the starting point to behavior will fill in the empty space. Central pattern generation and corollary discharge functional ways of organizing some neurons. In central pattern generation there seems to be a fairly fixed protocol for a set of neurons which produces a specific repetitive output such as the song of a cricket or contraction of an organ resulting in speech or locomotion. Depending on the input the input the output can be modified or shared. In corollary discharge neuron sets are organized to preserve a copy of actions for comparison purposes. Organization of neurons to produce specific activities helps fill in the space, but there are still a lot of activities to be explained such as consciousness, culture, reality, and purpose and meaning.

Congwen Wang's picture

Questions

I have to say that after our classes this week, I'm feeling stupid now, which is a good thing in learning science. There are just too many questions for what we have discussed. For example, although there is a pattern stored in the central pattern generator, how do we adjust it to suit different conditions? It seems to have something to do with the reafferent loops, but how do the two processes interact? Also, what kind of role does cerebrum play in the adjustments? Why do some patterns, such as riding a bike or drawing pictures, can be created even when we are fairly old, but patterns such as playing an instrument can't?  Is that because playing instrument is more complex, or because there are also limitations in other parts of our bodies (for example, our fingers)?

Raven's picture

CPGs

After reading the notes and some of the comments posted, I have many questions on CPGs. CPGs make sense to me as patterns of neuronal activity that are stored and then create a physical action (i.e. typing, picking up objects). However some of the comments suggest CPGs may be involved in non-physical brain activities like thinking and learning. While this is an interesting notion, I find it difficult to understand. Thinking can't be caused by a CPG, maybe the act of thinking, like knowing when to think, but maybe not the actual thoughts. Thinking never occurs in the same manner though. I am confused on this.

Furthermore, I have questions:

What is the prerequisite for creating a CPG?

Are there disorders where motor symphony doesn't occur?

How common are CPGs in the nervous system?

I like the fact that we have AN explanation for the large percentage of interneurons in the nervous system(CPG) and circuitry.

Serendip Visitor's picture

Central Pattern Generation

After digesting some of the comments on central pattern generation, and on the ability to walk (without being "taught" it) I also started to wonder less on how central pattern generation occurs, but more on how it is weakened or lost. From life experience, it seems that with walking specifically, there is only a very basic central pattern generator. For example, a friend of mine who experienced TBI (traumatic brain injury) did have to 'learn' how to walk again, even after only a few months in a coma. She continued to receive physical therapy long after waking up in order to walk efficiently (and not like a toddler). Without therapy, I do believe she could have walked again, but doubt that she or other patients would walk very well.

The fact that you have to 'relearn' how to do something after not doing so for extended periods of time proves that something is lost. Maybe then, if this central pattern generator isn't put to use by the nervous system, then it is the fluidity of exchange between neurons that is weakened, and not the c.p.g. itself. This would explain why you could still play basic melodies on the piano after years of not playing, yet it would take some time to 'relearn' the complex ones; you are not rebuilding a c.p.g. but strengthening the relationship between surrounding neurons. Of course, this idea could be wrong, but it is 'less wrong' in my mind, and helps me understand that central pattern generators are somehow innate, such as the central pattern generator for walking.

Schmeltz's picture

The concept of "muscle

The concept of "muscle memory" raised some interesting questions for me. Because we have memory stored in the form of central pattern generators in parts of the nervous system other than the I-function, I finally was able to convince myself that a paraplegic dog does in fact have the ability to wag its tail.  Perhaps the dog has sensory neurons located caudally that respond with tail movement when the dog is pet; therefore, the dog is not necessarily wagging its tail because the dog is happy, but because an external stimuli is generating the firing of central pattern generators that produce tail wagging. Thus, I guess it could be said that the dog's spinal cord was happy and not the dog itself. Another explanation could be that the dog, in the presence of food, gets excited and induces a firing of neurons that create a hormonal output that generates tai wagging.  This leads me back to Christopher Reeves.  If Reeves became sexually stimulated would his brain activity generate hormones that then induce an erection?  Based on the dog model, I would say yes.  Can quadriplegics and paraplegics have sex?  

Additionally, in response to "muscle memory", I began thinking about the influences of drugs.  I was thinking about different eras of music, i.e. Bebop jazz, when heavy drug usage was common for the musicians.  I was wondering if a lot of the creativity that came from this era of music partially resulted from this heavy drug usage that I believe could have led to a detachment from the I-function and greater reliance on central pattern generators.  Drugs, may perhaps, have the power to inhibit the I-function and enhance musical or artistic creativity by giving the individual the ability to escape themselves and their inhibitions and trust the musical/artistic patterns and abilities located elsewhere.  We kind of touched on this during class when we talked about how in order to play a memorized musical piece accurately and convincingly one had to detach themselves from the situation and just let it happen.  I wonder if drugs provide one with the increased ability to do so. 

kdilliplan's picture

 Mary Roach addresses the

 Mary Roach addresses the question of sexual response in people with spinal cord injuries in her book Bonk: The Curious Coupling of Science and Sex.  She recounts several studies which have shown that the right stimulation can produce erections and orgasms, even if the people are unable to feel it.  The book as a whole is really interesting and well-written.  You should read it if you have the chance.

AndyMittelman's picture

          I found the

          I found the experiment with the baby birds in straightjackets to be very interesting. Unfortunately, I could not find video of it, but I can imagine this would have been pretty funny to watch. It is fascinating that the baby birds, like babies, have a certain innate ability to walk. In this sense, “learning” to do something like this seems to be more of a time-activated genetic feature. What are the limits of this innately-acquired skill set? If babies intrinsically know how to walk, and birds intrinsically know how to fly, then surely there are other skill sets we unknowingly possess in our genetic code. What if we innately “knew” how to ski or how to shoot a bow and arrow? I’m curious as to how this applies to swimming. For evolutionary purposes, certainly we must have some basic ability written into our genetic code.

          Jeannette raised an interesting point about “unlearning” these skills stored in the central pattern generators. Perhaps these motor pattern scores are archived in our CPGs, but can become “dusty” if not used for extensive periods of time. [Maybe this explains what people say about learning a second language- if you don’t use it, you’ll lose it.] So why is it that these motor scores can atrophy with time? Imagine a young boy who likes to run a lot. His motor score for running is routinely being accessed, and his nervous system is extremely adept at performing the set of actions called for by the CPG. Now imagine he doesn’t run at all for a few years. If he were to try to run again, it would be the same impulses as always, and the CPG would be sending the same set of commands. However, he has grown a lot, things have changed, (size of limbs, chemistry of his body, etc) and now the old score is not as appropriate for his new bodily conditions. In other words, maybe the CPGs dictate very precise signals that are attuned to bodily conditions. If bodily conditions change and CPGs do not change with them, we may not be able to execute the motor symphony as adeptly. It would be like playing the same old song but with a different instrument; it may not work as well at first.

          I am excited to learn how this all integrates with mental scores. Just as we have physical motor scores, we probably also have mental scores. Maybe this explains why certain things are engrained in our brain and it doesn’t take cognitive effort to recall them. If you ask a small child their address, they would probably give it to you in one unbroken continuous memorized sentence. This bit of information may be stored in a mental score, just as the swimmeret movement is stored in localized CPG. The mental scores seem a little more ambiguous at first, but I’m sure we’ll get to them soon.
 

MEL's picture

Central Pattern Generation

 

I think central pattern generation and corollary discharge help to bridge the gap between neurons and behavior. Now it’s easier to understand how we perform common daily activities so easily and effortlessly. I am confused about how exactly these central pattern generators are formed and how they adapt to new situations. Although I repeatedly perform daily activities, I never do them in exactly the same way. Do central pattern generators create the action in its most basic form and then other neuronal pathways tweak the output?

I found our discussion about innate central pattern generation very interesting. I can understand why humans are born with a central pattern generator for walking. If a baby is born without a central pattern generator for walking then will he/she ever learn to walk? Can the baby form a central pattern generator after birth? In this case, will the baby ever be able to walk as well as other babies? I am also wondering, if a person is born with an innate central pattern generator what happens if that person never uses that central pattern generator? Can a person lose a central pattern generator due to disuse?      

 

aeraeber's picture

CPG and Memory

Central pattern generation and corollary discharge go a long way towards bridging the gap between neurons and behavior. They give a good explanation of how a pattern of activity in motor neurons can cause a coordinated physical action, even in the absence of some overall guiding force (a conductor). What they don’t really explain all that well is how thinking is a pattern of neuronal activity. Physical activities require similar patterns each time they are enacted, throwing a ball, even if you change the angle or the force, is the same base action each time, so it makes sense that it involves a definable pattern of activity in motor neurons. Thinking, however; doesn’t seem like it should work that way. Even if we think about the same idea more than once, we think about it in different ways each time and while changes in physical actions tend to be based on changes in sensory inputs that is not usually the case with thinking.

On a somewhat related note, Thursday’s discussion made me wonder why we tend to forget memorized information so much more easily than memorized physical actions. It’s not very difficult to ride a bicycle again after several years of not having done so, but much more difficult to repeat a poem you memorized in the 5th grade. Why do these types of memory work differently? And how does forgetting actually work? If a memory is a network of connected neurons, and remembering is an activation of that network, then is forgetting just a loss of one or more of the connections in the network, or is it more complicated than that? Does a stronger memory equate to stronger connections in the network?

 

mcurrie's picture

More Questions

 I like the whole notion of that there are groups of neurons that are central patterns and can lead to certain behaviors although it still seems difficult to figure where the central pattern is located since you can get the same function through different pathways. My thoughts go the horse cantering, trotting, etc, and how it's the same pattern just different communication. Since it's the same pattern if one neuron is taken out does the whole pattern fall apart or can the other neurons make up for the loss, keeping the pattern and making it so there is still a communication that can lead to the function or behavior that was connected to the neurons communication? Is there any support system for neurons in case something goes wrong or is there nothing that can be done? What about like when someone stops playing an instrument for a long time say 30 years or stops using some central pattern, can the neurons be re-wired or re-used for something else or do the neurons keep their function until at 30 years your still able to play the piano. Or how about when changing a behavior, like the term turning over a new leaf. Can you really erase that behavior or will it stay with you, just less pronounced? More questions to contemplate and figure out if there is an answer to them.

emily's picture

CPG...memory(again)...concussions...what is corollary discharge?

 CPGs make sense to me for motor function. Our actions are based on sensory input for direction/purpose; however, they cannot be purely based on sensory input, because certain actions can happen without "thinking", like we talked about in class and like what others have been mentioning on the blog thus far. Our actions must have some intuitive quality. While I think we have a pretty good understanding of motor functioning now,  I do not think CPGs fully explain interconnected neuronal circuits in general. Our actions are very fluid; we can most often move without thinking about it. But what about THINKING? Of course thoughts are influenced by other inputs, certainly sensory, but are there CPGs for thoughts as well? Are CPGs specific to motor functioning or can they be applied to different functions within the brain, even more "intangible" things? I was talking about memory in last week's post and the idea of learned CPGs causing memory make sense to me: a memory is just a learned pattern of activity, so when we are reminded of a certain thing, it is just that pattern being activated, so potentially a running CPG. 

On another note, I am not sure I completely understand the full definition of corollary discharge. Something to do with the "coordinated performance of independent players", a motor symphony without a conductor (sort of like Stomp?). What specifically does corollary discharge refer to?

Lastly, I just wanted to share my experience applying this class to daily life! This past Monday I got a concussion in lacrosse practice, and in the context of this class, I have been thinking about what is going on inside my head. My symptoms are very mild: "pressure" in the head, photosensitivity, and headaches from the photosensitivity. But what is going on in there??? "Pressure" in the head -- what is that, in terms of neurons? Why am I sensitive to sunlight, when I was hit in the front of my head and not the back of my head where info. from eyes are first processed? In more extreme cases of concussions: people lose memory, but are able to get that memory back...if memory is based on CPGs, or something of that sort, how could a pattern be "lost" and then returned? I think it may have been Jeanette who mentioned in her post that she used to play the piano and now she hardly remembers anything besides a few melodies...I am sure if she wanted to learn piano again it would be very easy for her to improve. How can something that was so ingrained and then lost come back to us? Does "practice" strengthen neuronal connections that were once strong and had been weakened/turn off inhibitors?

Lauren McD's picture

'Learning' to Walk

I think the most surprising piece of information that we learned in class this week is the fact that babies don't learn to walk but instead have the innate ability to walk once a physical maturity level is reached. I can definitely understand where this comes from. Experiments restricting the usage of wings in baby birds still allowed the birds to fly at a typical age. It makes sense that after a certain period of time, walking or flying becomes possible. Instead of being interpeted as learning, this can be interpreted as a sort of 'muscle learning.' A baby has never used its legs before and must build up and practice using the proper muscles before being able to walk.

However, I would be more interested in an experiment in which the baby birds were completely isolated from other birds. Learning is mainly interpreting observational behavior or thinking. If a baby bird with its wings clamped wasn't able to observe other birds flying, would it still be able to fly? The topic discussed in class that babies do not 'learn' to walk suggests no, but this is difficult for me to understand. Isn't a baby more likely to walk at an earlier age because of observation of other humans? Surely this must play some role in the beginning stages of walking, supporting that a learning process is actually occuring. There have certainly been cases of previously isolated children that are not able to communicate verbally at all since language development has a critical stage at an early age. A baby cannot learn to talk without other humans talking around it, but is walking something completely different?

I think it's also difficult to NOT describe walking as a learning process because it develops over an extended period of time. An ability to walk once a level of physical maturity is reached seems like it would almost be instantaneous. I know these relations may not spring to other people's minds, but I immediately associate walking with learning because of the time span.

The idea of NOT 'learning' to walk is certainly a difficult one to get used to.

egleichman's picture

instinct for thought

 I had some of these same thoughts. It seems to me that there might exist two distinct categories (among others) that might have some influence on "learned" versus "not-learned" when it comes to the central pattern generator; those categories are instinctual and not. For instance, it seems that walking (humans) and flying (birds) are instinctual behaviors and so require no learning in order to occur. But what makes something instinctual? What about, as you suggest, talking? In an environment with no talking, would a human instinctually try to speak (can we ever know?)? Since biking is not an instinct (in response to the bike-riding comment), isn't that why it must be learned from observation and practice? What makes something instinctual and another thing not?

Hannah Silverblank's picture

Language & Instinct

Eve, you ask, "What about, as you suggest, talking? In an environment with no talking, would a human instinctually try to speak (can we ever know?)?"

Several experiments or instances of torture have occurred in various cultures and eras that have attempted to accomplish just what you ask: isolation from human language in attempt to discover if speech is innate, or in attempt to discover a pure, unadulterated, divine language.

A few examples (though literary) might interest you:
-In Herodotus' Histories, the pharaoh Psamtik attempts to discover which ethnic group "came first" by isolating two infants from speech and seeing what language they spoke. Psamtik's logic was such that whatever word was spoken must belong to the language of the "first culture." Since the first word uttered was the Phrygian translation of "bread," the Phrygians were ruled the first culture.
-Frederick II tried a similar experiment "but the children died before they ever spoke any words" (Paul Auster, City of Glass).
-Paul Auster's novella "City of Glass" portrays a character whose father isolated him from language and human contact in order to find God's language and to return to the pre-lapsarian connection between language and meaning/function. (READ THIS NOVELLA!)

Jeanette Bates's picture

Loosing CPGs?

            I think that the connection between central pattern generation and learning is very interesting. As we discussed in class, there are some things that require learning and will later establish their own central pattern generations. For example, someone would have to learn piano, and after sometime, they would develop a muscle memory for the songs that they play. They wouldn’t even have to think about them. This means that they now have a central pattern generation for playing those songs. The thing I’m curious about is the “unlearning” of this muscle memory; is it possible to get rid of central pattern generations? Based on my own experience, I would think that it is. I took piano for several years; I would say that I was even pretty good at it. I quit it in 10th grade, but a few years later, I tried to sit down and play it again (without touching it since that period). I could only play simple melodies. This makes me think that I could have lost the central pattern generation for it, or at least for anything complex. However, there is a part of me that thinks, perhaps, it is not that I lost it, but that it is weakened. I don’t know if it’s possible to weaken a central pattern generator or not, but I do know that I could still play the piano after several years of not playing it, even if not well, and if I tried to learn the songs that I knew before, they came much more easily than they did the first time. I think that it’s possible that the connections could still be there even when they aren’t being utilized-they just might be weakened. Practicing again could help strengthen them again. But I still have to wonder, is it possible to loose central pattern generators in ways that don't involve massive brain damage? Is it possible to weaken them?  And if so, how and why would this happen? Would there actually be an advantage to getting rid of some of these “motor symphonies?” 

gloudon's picture

Difference between humans and horses...

 This is kind of in response to Morgan's comment.  So, in class we talked about how most animals and humans are pre-wired to walk.  Further, we don't learn how to walk, we practice to gain strength to be able to walk, (but we knew how to walk the whole time).  In the case of newly born horses, do they walk hours after birth because they have more developed muscles at birth?  The gestation of a horse is about 340 days compared to a human which is 280 days.  Does this extra time allow them to develop strength before they are born?  This would make a lot of sense being that many animals need to walk the day they are born to protect themselves from predators (ie. horses, giraffes, zebras).  

lfrontino's picture

Learned vs. Acquired

In class, we discussed how behaviors are either learned or acquired through genetics. It's interesting to think that something perceived as such a critical learning process in our lives is really not learned at all, but would be reached eventually anyway. What other processes are actually inborn in us? 

It is also interesting to me from a developmental perspective. Humans are not able to walk until a certain point in their lives, usually around the one year mark. When horses are born, they can walk right away. What developmental differences exist between these two species that allows one to walk right away but the other to grow and change before walking? Are there brain connections that need to be made in humans after birth before they are able to implement the process of walking?  

mcchen's picture

Riding a bike

During class, we discussed "muscle memory' in which a central pattern is generated somewhere other than the I-function.  After Grace's comment about piano playing and piece memorization, I realized that during several piano recitals I did have to try and not think about what I was doing.  When I started thinking about the piece I was playing or the what the next part I had to play sounded like, I would mess up.  I realized that I had to actively not think about anything, I had to clear my mind completely in order to play a piece from memory.  As our discussion of central pattern generation continues, I was just wondering how riding a bike fits into the picture.  It has been said that "you never forget how to ride a bike", so does this mean there is a part of the brain that registers certain movements and once you learn how to ride a bike, it never really goes away?  In this article http://www.physorg.com/news167053363.html, it claims that scientists have found why we don't forget how to ride a bicycle.  It talks about "gate-keeper" neurons that control electrical signals that leave the cerebellum and they can transform that signal into memory.  What I am wondering is that if there are such neurons that are able to take coordinated movements and turn them into memory, then why is it so selective? Why do we only "put away" the movements for riding a bike (and skiing and eating with chopsticks too based on the article)? What is it about these movements that make them essential so that we need to keep them for the rest of our lives?