Forum Archive - Week 9
We now know that interconnected circuits of neurons can constitute pattern generating circuits, that these may be coordinated by internal corollary discharge (efference copy) circuits, and that the latter can affect as well the interpretation of sensory input. What aspects of behavior generally might this help us to better understand? What new questions does it raise?
Subject: equilibrium; free will
Date: 2003-03-25 10:02:32
Message Id: 5170
First of all, I am very glad that we are discussing free will to the extent that we are in the forum, as the question of its existence in the brain=behavior model has been worrying me since the beginning.
Also, I have been thinking about the brain's ability to "filter" information, as brought up by Laurel. During our daily lives, we are put into contact with so many stimuli that it is essential to be able to filter through these stimuli, in order to function efficiently. The Brazilian writer Luis Borges has written a beautiful story related this, called "Funes the Memorius," in which a man is plagued by his inability to forget. Instead of being able to filter images and consolidate them, Funes remembers every image at every individual moment and is not able to collapse these images into a continuum. His memory is so vast and so precise that no detail of any perception he has is ever lost to him. The patterns of clouds in the sky at 8:05, for example, would be absolutely distinct and disconnected in his mind from the way they looked at 8.07. Being unable to filter, he finds it difficult to even think and sleep. One can see how this could cause torment and a fear of infinity.
However, there is something about the mind's ability to subconsciously filter and order information that makes me uncomfortable. To state a recent personal experience, I was sitting on the moon bench yesterday, noticing the large trees along senior row. I noticed there was something tied around the trees, but it took me several minutes to consciously acknowledge that they were yellow ribbons tied there. We are so used to filtering out extremities like construction tape and excess, that the intentional yellow ribbons were hidden, at first, from my view.
Finally, I think about the idea of equilibrium. It seems that these ideas of "filtering" come back to this, and this relates to Laurel's comment of the "closer to neutral" idea. Our bodies are continuously in the search for equilibrium. We find this to be true throughout many physiological processes which go on even without our knowledge. These processes are essential to our life and health.
However, isn't there something fundamentally disturbing about this constant equilibrating? Our bodies equilibrate so that we cannot even feel the seat we are sitting on. There must be some distinct reason why the body is doing this. Yet, in this search for equilibrium, is consciousness being negated? Are we being dulled? It seems, actually, that what allows for consciousness is a certain type of pain, and this implies imbalance. Therefore, I am not comfortable with the notion of equilibrium as the singular goal.
Perhaps this is the lure of free will, as it allows for the choice to offset equilibrium.
Name: Grace Shin
Subject: Central Pattern Generation
Date: 2003-03-25 15:45:08
Message Id: 5172
Today's discussion on the Central Pattern Generation (CPG) was VERY interesting to me! So we learned that crickets and crayfish have a genetics that allow for their CPG, but humans, now that's another story... or is it? Couple things came to my mind during class and I thought I'd put them up on the forum and see what you guys have to say about it.
(1) The CPG via experience as PG stated in class is unconcious. And I stated in class that some people do have the "genes" that allow them to be more athletic or more muscially talented. But if these CPG is unconcious, then maybe these genes are not really coding for people who are musically inept or just unathletic. Rather, people who cannot generate these CPG as well as others, maybe are less able to switch to their unconcious states... meaning, they hold onto their "I" function more. This sounds vague I'm sure, but maybe the key to being a good musicain or athelet doesn't necessary start with physical training but mental training.
(2) Someone mentioned in class today that learned more about these unrealized inputs (and outputs) will be helpful to us to better understand why we behave the way we did. I was saying this to my friends over lunch after the class and couple of them were saying that much of the problems that we see now a days ARISE from people always wanting to know more. "Ignorance is bliss" kinda mentality. They were saying that many of the neurological diseases or even habits may be better left alone... so maybe one of the problems in our society is that we are unwiling to go into the unknown? Why do you think that is?
Subject: the unknown
Date: 2003-03-26 01:18:09
Message Id: 5178
It is very interesting about what Grace have said about the CPG. Although, I understand the concept of the CPG and its role, I still feels that there countless of processes that are involved and interacted with one another to produce a characteristic behavior. Its unfortunate but I am more curious about the whole picture rather than small clips.
Also, it strucks my curiosity when Grace question about people fear for the unknown. I have always been curious about this aspect in humans and in other animals. Fear for the unknown seem to play an important role in our interaction with others and the environment and in how we developed our behavior. These two ideas are very interesting and I sure hope that our class discussion will sometime lead into this topic (our fear of the unknown).
Subject: CPG/genes, unkown
Date: 2003-03-27 00:46:41
Message Id: 5190
Thinking about the CPG and its role in shaping our abilities made me think: is it more genes or the central pattern generator that makes us musically talented or athletically inclined? I can't help but think of Venus and Serena Williams (and their father), and Judy Garland and Liza Minelli: they obviously have genes which shaped their talents, but do their central pattern generators play a larger part in forming their talents than their genes did?
as for fear of the unknown, perhaps society feels that neurological diseases are better left alone because there is always the chance of failure: failure to properly diagnose, failure to find a cure. Somehow, it seems that whenever the potential for medical setbacks exists, the public shies away from the issue. This seems natural, in that it is frequently our natural instinct to desire to be correct 24/7 (which we learned is, of course, not possible)
Subject: corollary discharge
Date: 2003-03-27 20:42:15
Message Id: 5196
Today's lecture struck my curiosity. Before the introduction of proprioreceptors, I was awared of their existence, although I could not explained them in great detailed and understandings. I also realized about the existence of the motor symphonies and the central pattern generator, and again not in much details. However, the understanding of the corollary discharge is a very new concept for me. It's amazing that the nervous system have neurons that tell the NS events that are occuring within the NS! It's so incredible that the nervous system have so many pathways and mechanisms for regulations and functioning.
I find the topic on the phantom limb to be particular interesting. I have always been so curious about such phenomenon, whether its what people actually feel or a psychological problem or even an act. Now I kinda understand why people do experience such feelings from their missing limb. However, I would like to discuss more on what people think about phantom limb and whether corollary discharge is the and maybe the only explanation. As for me, although corollary discharge did bring some comfort and understanding to this particular mystery, I feel that there is more to this (as always right!?). If the answer is corollary discharge, where did those inputs come from?
Subject: Recent news
Date: 2003-03-27 23:48:37
Message Id: 5200
This article addresses the same phenomenon my webpaper did:
Time to Think?
Subject: Missing Limb...
Date: 2003-03-29 16:59:54
Message Id: 5206
I have a story I thought I'd share... we discussed in class about a person missing a limb can "feel" it's presence and know it's position. I have a family friend who lost 2/3 of his right index finger when he was like 13 while he was climbing a ladder and the ladder collapsed on his finger. So his right index finger only has a "stump" of the last third of the finger. Now... in our families, we use chopsticks often to eat meals... and I remember how he had a hard time regripping his chopsticks after the accident. He KNEW that the part of his finger was missing and yet when he tries to grip the chopsticks in the new way (to accommodate for his finger), he'd grip it as if the finger was all there... and get a bit frustrated that it wasn't... i thought he was just being stubborn... but the class discussion helped me realize that maybe its the part of his brain that is being stubborn... unable to realize that the finger is missing!
Subject: recap/new questions
Date: 2003-03-30 14:29:41
Message Id: 5208
In talking about outputs that we are unaware of and of some that we can never become aware of, this sort of puts a cap on free will, doesn't it? Because if we're not aware of certain outputs, how can we control them? Second, I strongly agree with Neela's comment and I think it summarizes exactly what I've been thinking about free will, that maybe it isn't physiology that is limited in its ability to explain free will, but our inability to explain what free will is and to fully comprehend all of the functions of our brain. Furthermore, what is the big deal if our brain does control all of our behavior- it's still our brain, our experiences, etc. As Cordelia stated, "we are our bodies"- right? Third, some people seemed to have trouble explaining how emotions can be explained by neurons. I've been doing some research on love, actually, for our next paper and what I've come across so far is that emotions we feel reflect the level of certain chemicals in our body. These chemicals are released based on the inputs that we receive through out neurons. Moreover, their release is triggered by neurons. Hence, our emotions are controlled by our nervous system and, what types of inputs we choose to expose our selves to. These choices, in my opinion, are based on memory/learning from experiences stored in our brain and genetic information. Here's a question then, how does genetic information get transformed into an individual's personality? And what is the brain's involvement in it?
Subject: Sensory Inputs and Missing Limbs
Date: 2003-03-30 19:54:24
Message Id: 5209
I was interested in two aspects of the nervous system being discussed in the forum this week. First of all, I found it extremely intriguing to discover that we have sensory inputs that we are unaware of and that in turn we may produce outputs we are unaware of. On many levels it seems logical to think that we are not conscious of many of the functions of our body. On the other hand, it seems rather amazing that we don't recognize some of these inputs and outputs and yet when we were discussing missing limbs our brain seems to falsely assume that the limb is physically there when in fact it is not. To me it is extraordinary the amount of power the nervous system has over our existence (although this may seem obvious). In many ways this missing limb example, which sort of makes the argument that the mind is stronger than our physical existence, asserts that maybe mental illness including depression can be the hardest diseases to overcome merely due to the power and all encompassing aspects of the brain.
Subject: forum 8
Date: 2003-03-30 19:54:50
Message Id: 5210
The central pattern generation idea really grabs my attention, b/c it would account for the mysterious ways in which the CNS is still able to continue functioning even when a part of it is damaged. I find it amazing that the NS is structured so that it ALWAYS finds a way to do what it's supposed to do. Another plus is that it is independent of many other functions, like the reafferent loop-for example-when we discussed in class how one is able to still pick up the remote control without having to look at her or his hand.Indeed, the central pattern generator is a prime example of how the NS has many different ways of getting the same job done.
Date: 2003-03-30 22:49:01
Message Id: 5213
The idea of fear is very interesting to me also. Fear and the brain have such an strange link. When I think about animals experiencing fear, there seems to be multiple reactions that manifest themselves in the body (which, obviously, must be triggered by the brain.) So in animals, like a cat, there's the arching of the back, hissing, crouching low to the ground, etc. These reactions seem instantaneous, and seem to be the brain's way of preparing the body for a struggle - or any basic means of defense. I wonder what these brain signals are parallel to in the human brain, and if proprioceptors have anything to do with it.
Date: 2003-03-30 23:48:24
Message Id: 5214
I was intrigued by the discussion of fear in this weeks forum. When Kathleen mentioned the reactions that fear causes in the body of a cat, I was reminded of when I watched a movie with one of my friends over Spring Break. We were watching Scotland, PA, which is a take-off of Macbeth. When Duncan was killed in a very unexpected way (he was accidently pushed head first into a fryer), both my friend and I jumped and made noises as we were very startled. Kathleen's comments reminded me of this and something that I remember hearing about back in high school - the fight or flight response. If I'm remembering correctly, when an animal (or a human) is startled, they recieve a rush of adreneline that readys them to either flee or fight.
Date: 2003-03-31 02:45:06
Message Id: 5215
As the class' comments on free will continue, it seems that there are two camps to the issue. First is the idea that we do have free will, and that our study of physiology furthers our knowledge of it. Second is the idea that our Nervous System is responsible for all of our reactions and free will does not exist. However, the fact that we argue about free will, and choose to study our physiology is a strong point in favor of the existence of free will.
A world without free will is a world without choice. Through the demonstration of our opinions is it not clear that humans have a capacity to generate a cornucopia of different ideas? Just as with any other species, humans all have the same basic physical structure. This means that the basic structure of the NS is the same in every one of us. For example, we all have nerves that lead from our spinal cord to our brain, that then branch out through the rest of our body. If our physiology is so similar, the fact that we are all so very different is proof of free will. If the human species were lacking free will we would all make the same decisions. As you look at your classmates and see the diversity of style, expression, emotion, and opinion – how can the existence of free will be doubted?
Name: Paul Grobstein
Date: 2003-03-31 07:52:16
Message Id: 5216
The forum seems to have taken on its own momentum this week, as it frequently does. But, in case you need a reminder of what we were talking about in class last week:
We now know that interconnected circuits of neurons can constitute pattern generating circuits, that these may be coordinated by internal corollary discharge (efference copy) circuits, and that the latter can affect as well the interpretation of sensory input. What aspects of behavior generally might this help us to better understand? What new questions does it raise?
Subject: Genes and CPGs
Date: 2003-03-31 19:24:12
Message Id: 5220
Rachel?s posting on the question of genes vs. CPGs made me think about prodigies. A prodigy is generally defined as a child who by age 10 displays mastery of a field usually undertaken by an adult. For the most part, scientists agree that intelligence is inheritable. But not all smart kids are prodigies. What are the biological differences in a prodigy? Is it the recruitment of different systems within the brain, or recruitment from different areas of the brain? I have heard that PET scans indicate that prodigies tend to make use of episodic memory and long-term working memory, as opposed to the general populations? use of short-term memory. Is it the ability of the child to concentrate on a topic, not to be distracted by irrelevant circumstances? If so, are the specific pathways of concentration directly related to central pattern generators of thought? Perhaps genes predispose someone to be a prodigy, but there has to be more to it than genes...
Name: Danielle McManus
Date: 2003-03-31 21:06:29
Message Id: 5221
In our little poke-ourselves-in-the-eyeball experiment, we learned how our being aware of the source of sensory input effects how we understand it. That is, if I jab myself in the eye, the world looks like it's "jumping around;" however, if I follow my finger as it moves back and forth against a stationary background, the world seems still and it's the finger that's moving. All this despite the fact that in both cases the image of the world refracted onto my retina is sliding about. All right, fine. So the difference is that in the first case my eye isn't orchestrating its movement and doesn't tell my brain to expect the world to jump around. But why can't I (ie, my "I-function") tell my brain, "Okay, I'm poking myself in the eye now, expect the world to move around," and thus prevent the world from seeming to jump, as in the case of having my eye do its own moving? In both cases I'm controlling the movement of my eye, why can't I just tell my brain that my finger's making my eye move? I know it, why doesn't my brain?
Date: 2003-03-31 21:44:01
Message Id: 5222
A very provoking question Danielle. It seems that our eye-function (ha ha ha...um yeah) does not have input into certain CPG circuits and therefore can't directly effect/control certain sensory interpretations. Despite our cognitive knowledge of our eye being pushed, this knowledge cannot be translated or communicated to the part of the brain that controls the automatic adjustment. While this seems to be a weakness of the system (or a potential site of our evolutionary progression into superhumans), it's reasonable that our I-function should remain distinct from other functions. If we were capable of controlling certain functions of the brain, who knows what sort of trouble we'd get ourselves into. The possibilites for unmedicated highs seem endless. We would probably flood our brains with toxic levels of happy neurotransmitters and eventually just burn out as a species.
Date: 2003-03-31 22:34:50
Message Id: 5223
I have to admit i am intrigued by the current model that explains the various series of actions as a motor symphony. It seems that our current explanation of utilizing inhibition in the pathways or possibly the disruption caused by corrollary signals (involved in coordination) helps explain the multiple symphonies that we can exhibit. Does the illustration that motor symphony adjustments can occur demonstrate or portray the concept of 'choice'?
I think that corrollary discharge helps explain why we all percieve things so differently, but what triggers the discharge still remains unclear to me?
Date: 2003-03-31 22:54:09
Message Id: 5224
Danielle makes an interesting point. Why can't our I-function inform the rest of our NS of what's going on? It seems that our I function cannot make use of the various chemical pathways that other parts of our NS use. It can't fake corollary discharge -- but it also can't affect heart rate, it can't restore homeostatic temperature, it can't detect imbalance of chemicals in our blood stream... It seems we aren't really in control of everything, are we? Our I-function seems to be at the wheel of a car, generally "controlling" things but helpless when it comes to the underlying mechanisms. Maybe this is one reason brain=behavior isn't so hard to accept, but brain=me is.
At the same time, psychosomatic effects are sometimes shocking. I remember in middle school history, learning about some queen who managed to convince herself that she was pregnant. She believed it so completely that her stomach actually began to swell. Like the hypochondriac who believes he is sick and so starts having symptoms, or the placebo effect, the I-function can sometimes do strange things not usually within its realm. So what unusual pathways can the I-function affect, and which can it not?
Name: Christine Kaminski
Date: 2003-03-31 23:28:49
Message Id: 5225
The eye-jabbing experiment does pose an interesting question. Why aren't we (using the "I"-function) able to control the way our eyes will react to such a stimulus? As I sit at this computer, I see trying to explain the difference between your finger simply moving and your eye actually being attacked and thus reacting without any control. Yes, the difference exists in effects seen from either affecting the body physically or stimulating it externally, by not actually doing anything physical to the body. So in mistreating our bodies we see this lack of control in the eye's response. Should this same idea be used in trying to explain the effects in other parts of the body? Suppose I'm out jogging one day and trip over an incredibly short fence even though I see it coming in the last second. And say my foot for some reason goes into spasms. There is no way that I will know exactly what is happening in my foot to determine what should definitely be occuring to control it. I can't see a possible way to associate the way we always want our body to respond with how it actually does. We are only conscious of so much of what really happens in our body. Our body takes care of the rest. I can't tell the nerves and muscles in my foot to not spasm or likewise let my eye know that it shouldn't be distorting its visual capacity-they've both been injured. That's why we do need to have this lapse in connections between everything that's going on and our I-function. Neela's right, otherwise we might burn out by trying to control every single reaction ourselves.
Subject: regarding prodigies and talents
Date: 2003-03-31 23:41:13
Message Id: 5226
After reading both Laurel and Rachels analysis on talents being somehow innately within someones genetics, I was swept back into my previous postings regarding brain and behavior. In weeks passed, it has continued to intrigue me that it is possible that certain persons may be more blessed than others in mental capacity or artistic talent in accordence to their genetic history. I definately believe that traits such as "prodigal" behavior and musical talent can be passed on from generation to generation without having it enforced within ones upbringing. As a personal anecdote to display such a notion...I am somewhat of a singer. Nothing super impressive, but my voice is not difficult to listen to either. I wasn's at all aware of having any sort of vocal talent my entire life until one day I was just playing around with some Christmas carols at a holiday party and somebody noticed. I was not trained to sing, and although I have minimal background in piano and violin, I never tried to use my voice beyond singing along with the radio. When I realized that perhaps I had a voice, a lot of people around me were shocked because I was never trained and neither one of my parents sing. When confronted with this, I realized that in my family history there turns out to be a family member or two involved in opera conservatory. I did believe that there are inherent genetic talents, but they all get mixed into the mesh of DNA that creates every single one of us. I also believe that such inclinations can be altered by ones environment, but not sufficiently enough to completely destroy them. I do think that there is involvement on behalf of the CPG in bringing about someones behavior and talents, but that depending upon genetics, the passing down of whatever it may be might be limited or altered by the CPG itself.
Name: alex lippman
Subject: more about the I-function
Date: 2003-04-01 00:01:22
Message Id: 5228
First of all, I would like to say that I was excited when PG gave us an example of how central-pattern generating circuity might actually work. It suddenly made a lot more sense to me.
Also, however, I was wondering why people who experience the phantom limb phenomenon often feel pain? Why would they feel pain rather than pleasure or some other sensation? This also struck me as odd since I know that for me I often don't feel pain of having, for example, scraped my leg until after I notice blood. This would imply that the realization plays a strong part in the perception of pain and since this consciousness is connected to the I-function, the perception of pain would also be connected to the I-function. The only reason that I can think of that might explain why the correllary discharge signals would send out a signal for pain in the amputated limb would be that the brain might be "worried" about that limb. Since it hasn't received sensory input from the limb in a long time, generating the sensation of pain in the limb(or rather non-existent limb) might be a way to force the body to check up on that limb even though it is not there anymore. Although this does not quite make sense it is the best explanation that I could think of. The feeling of pain in a non-existent limb might also imply that much pain that we perceive is actually not based in physical reasons, but I don't really buy into that. Also I was wondering if people suffering from pain in non-existent limbs can tell the pain to go away? The answer to this might indicate if the I-function or the correllary discharge signals is "more powerful."
Subject: two year old brain
Date: 2003-04-01 00:23:28
Message Id: 5229
in doing some reading for another class i came across the claim that the brain of a two year old child has twice as many synapses as that of an adult. to say the least it is counterintuitive, and i don't get it. it goes against the way that i have learned about brain development and how i have thought, in our discussion, about central pattern generation.
my concept of brain development always had to do with forming new circuits, as well as strengthening certain ones, but never killing off others. the point was being made (in the reading where the fact was) that brain mass or density does not necessarily imply intelligence, as we have found with our own examples (einstein's brain being relatively small).
what does this say about central pattern generation and what we are or are not born with? my first thought would be that we are born with some standard central pattern generators and that those can be either ignored and die out or fine tuned from repetitive use. i would like to learn more about how we learn and how a central pattern generator is formed or maintained in terms of synapses, that might account for this massive overhaul of synapses as we mature.
Name: Nicole M.
Date: 2003-04-01 01:26:01
Message Id: 5230
I don't mean to get off topic but I was thinking more about the experiment we did in class earlier this week where we were told to synchronize our clapping. It didn't take long before the entire class was clapping in unison. This reminded me of a discussion I had with a European friend who said that in some places in Europe, an audience claps in unison after performances. He tried to explain to me that this wasn't necessarily a culturally dictated custom but that everyone just does it because it is natural. However, if simply told to clap without the instruction to clap in together, our class would not have clapped in unison. We had to be told to do clap together which engaged our corollary discharge function—the processing of input in the brain-- and yielded the resulting motor output. Why do we (in the U.S.) ignore the clapping rhythm of others while some other cultures engage their corollary discharge function so as to clap together? My suspicion is that cultural values, like being self-conscious or sensitive to the actions of others, being more socially conservative, or valuing order or equality, may play a role rather than explaining clapping in unison as the natural way to clap.
Also, I recall trying to teach VERY basic dancing skills to a group of guys in high school. I asked them to synchronize a step-clap motion with the rhythm I set. You would think that a basic step-clap rhythm would engage the corollary discharge function, thus yielding a room full of guys moving in unison BUT it was simply not possible! They could not all match the rhythm of others! This makes me wonder, when actions are complicated by adding multiple movements, are some people better at synchronizing the signaling needed to match a rhythm? If so, is it a learned skill or inherited trait? For example, are those more musically inclined better at matching their body movements to rhythms because they are trained to be more sensitive to rhythms? Are both factors responsible?
I'm guessing that I am not making much sense because I'm just using this posting as a place to lay out my thoughts (which are a bit tangled)! So I'm sorry if you read this and your head spins uncontrollably and explodes.
Name: Tiffany Litvine
Subject: I-function and PGCs
Date: 2003-04-01 01:26:37
Message Id: 5231
It makes sense to me that our I-function is unable to control/affect certain pattern generating circuits even though we might be conscious that something is occurring to our body such as the eye poking. The reason it makes sense is that the body performs many vital functions that we are unaware of. It is impossible for our I-function to control all these functions. As Sarah said previously we cannot tell if our hormone levels are changing or whether our blood glucose levels are high. These are things that must be controlled without our control, otherwise we would be constantly ill because we would forget to regulate some sort of function such as our heart rate because we were distracted. So I think that it is normal that certain PGCs occur without our control. Despite this fact, I do think that the I-function still plays an important role in our PGC even though it canâ€™t affect all PGCs. We are able to regulate the pace at which we walk, eat, or write.
Subject: New votes for Emily?
Date: 2003-04-01 01:55:20
Message Id: 5233
As we continue to investigate those neurological mechanisms, which contribute to human activity, we must recognize how very close we are to decisively equating the brain with behavior. We are rapidly discovering that even an external environment is not prerequisite for human behavior: central pattern generators produce self-sustaining patterns of activity, which are independent of sensory input. The body's ability to coordinate and manage a variety or motions depends, instead, upon complex neural organization, which enables the delegation of responsibilities to distinct networks of nerve cells. This extraordinary ability demonstrates, not a dependence of behavior upon the brain, but a true unification of the two. Activities, ranging from breathing to running are controlled by specialized circuits, central pattern generators, which steadfastly execute those actions again and again without conscious effort and without the involvement of the I-function. However, I am still anxiously awaiting a more explicit link between perception and patterned activity. What properties define an action as one coordinated by these neural circuits? Furthermore, at what point does the acquisition of a skill governed by CPG's occur? Although a human being is able to breath immediately after birth, walking is postponed until the skill is well practiced. I would be sincerely interested in discovering more about the development of such (eventually) repetitive behaviors and the mechanisms by which repetitive skills are learned. Finally, I hope to better understand the generation of rhythmic neural signals. Although there are intrinsic cellular properties enabling the production of rhythmic signaling, there are also interactions between cells, synaptic properties that produce action. In what way can the combination of these generation two strategies become efficient?
Date: 2003-04-01 02:13:57
Message Id: 5234
I was reading amelia's posting that made slight reference to the "fight or flight" response in a fearfull situation, and it reminded me of a paper i read several years ago. I cant remember the article's title or author, but I do remember the general idea. It suggested that children who grew up in situation that are fear insipiring, such as an abusive home, but are constantly exposed to the situations such that they become habituated and come to regard a scary situation as a typical environmental stressor are likely to carry the "fight or flight" response into other stressful situations, regardless of whether they involve something that is typically fear inspiring.
I began to wonder how this could be explained in our terms of discussion: Does the "response" have to do with the typically messenger pathways of the NS? Are these pathways innate, or are they made automatice through use?
Name: Andy Greenberg
Subject: Neurons should not gossip about each other
Date: 2003-04-01 02:40:25
Message Id: 5235
The discussion at the end of the last class, regarding phantom limbs, left me with some questions. Prof. Grobstein told us that phantom limbs are created by the residual sensation amputees feel due to corollary discharge from neurons in other parts of the nervous system. However, I'm still confused as to why other parts of the body would be telling us about the specific location of our limbs. Why would the feedback from a limb not originate only in the limb with which it is concerned? I can understand why a limb would want to be able to communicate its status to other parts of the body, but I can't imagine why other parts of the body would want to communicate that limb's status to a third party. Obviously, this sort of "gossip" by neurons about other neurons can cause problems when the limb's neurons are amputated, but it seems that the unnecessary complexity of the system could also cause problems in more standard situations. If amputee patients imagine their arm being raised when it doesn't exist, there must be a system of neurons sending arbitrary signals about that arm. Why don't those signals conflict with the arm's actual location before the arm is amputated?
Date: 2003-04-01 02:57:36
Message Id: 5236
Earlier today, I watched the movie "Psycho" in which a man kills his mother, who had been the greatest influence in his life. Then, after having killed her, he recreates her personality in his own mind, often times "becoming" his mother in order to maintain her influence in his life. His multiple personality becomes like a phantom limb, or a phantom personality, so to speak. A part of his life was missing, so his brain created this shell of another personality within itself. How can a second or third or even fourth personality be seen in a neurobiological sense? Can these other personalities be seen as separate boxes within the big box? What causes these additional boxes to form? If a person were to be diagnosed with multiple personality disorder, how would his/her brain be physically different, if at all, from that of a non-disordered brain? Why would the brain bother to make separate boxes for personality traits, that could just as easily be part of the big box that controls personality? Maybe this is something I should look into more.
Subject: twins v. amputees
Date: 2003-04-01 03:37:57
Message Id: 5237
This may be unfounded or completely off base, but I have heard that often when one person in a set of twins gets hurt the other one will feel similar pain. If this is true, does it have any connection with the amputee phantom limb syndrome? I understand that corollary discharge from neurons causing an after effect, however, it seems that the brain plays a similar role in the two phenomena. I was wondering if the I function may play a part in not tangible pain. Perhaps when one twin gets hurt and then tells the other, the other remembers something that never actually happened in a way that could be linked to the incident. However, it seems that there may be a connection if both phenomenas hold true. I feel that I don't know enough about the twin-pain theory to discuss it without further investigation, but having thought about the two areas lacking substantial neural trauma makes me suspect a correlation.
Name: Cordelia Stearns
Subject: musical talent and limb pain
Date: 2003-04-01 08:14:13
Message Id: 5238
Marissa's discussion of genetic factors in musical talent is something I definitely think is valid. I transferred to Bryn Mawr from New England Conservatory, a music school in Boston. It was a fairly intense classical music program, and all of the instrumentalists had practiced since they were about 5 years old between 3 and 10 hours per day. In classical music, you are judged in 2 categories; technique and artistry. Technique, though it certainly involved speed, and other things that must have some genetic factors, is mostly something that can be learned. Technique is what comes from practicing. But artistry is just there - it cannot be taught. So many people that I knew at school were at a dead end because they just were not musical enough. They did not feel music in the way that makes people want to listen. I think that is something we are born with. You just cannot copy someone else's interpretation of music, there are no rules to follow, no magic hints to learn. You just have to be able to do it yourself. I'm not exactly certain where this hightened sensitivity fits in the brain; is it extra connections? More action in one part of the brain?
On a completely different topic I found Alex's comments on pain in phantom limbs interesting. Pain is supposedly one of the most difficult feelings to conjure up when it is not being experienced. So how can a pain, not triggered by sensory input, be the same as pain that is? Could it be some constantly relived nightmere of losing a part of the body, or is it the same type of pain that we feel on our attached limbs? It is interesting to note that there is a disorder where people cannot feel pain at all....the majority of people with this die young, not from the disorder itself, but from not noticing some sort of dangerous, painful thing that any of us would easily know to walk away from. Perhaps pain is such a valuable adaptation that it cannot easily stop happening when a limb is lost. Maybe proprioceptors that are aware of the limb being absent are somehow able to trigger pain??
Date: 2003-04-01 08:29:29
Message Id: 5239
As the model for the nervous system becomes increasingly complex, I begin to wonder how all the connections are made in the correct order that allows for the corollary discharge. One interesting article I recently read in USA Today (March 11 edition) is that in order for the nerve cells to recognize each other and form the right connections, a third 'matchmaker' is required. The matchmaker is able to organize the synapses. This added component to the nervous system, allows for yet another location where the signalling can be sent off track. As the model for the signalling within and to the nervous syustem is designed, I begin to wonder which outputs are a result of which variations in input and model design. How does corollary discharge adapt to changing circumstances?
Date: 2003-04-01 08:59:37
Message Id: 5240
I find it interesting that when a person loses a limb, they still feel that limb and even some pain in that area. I am curious as to why the nervous system does not register that it is missing part of its nervous system. Obviously there are some signals being sent to the brain. But how is that possible given that the limb no longer exists? Where does the signal come from?
Name: Stephanie Habelow
Subject: phantom limb & intelligence
Date: 2003-04-01 09:00:36
Message Id: 5241
In response to Alex's post about why people who experience the phantom limb phenomenon often feel pain ... I think it may be a psycho-somatic response. If a person has a finger amputated (or an arm, leg, etc.), they remember what it was that made that operation necessary, so when they look at where their finger should be, they may think, ouch, that must've hurt, or, that did hurt. Furthermore, I would imagine that having a limb removed is probably a rather traumatic event. In the aftermath, you have to deal both emotionally and physically with that loss and how you'll function without that part of your body. I think Alex may be right in suggesting that amputees who feel pain may be reacting to realization - to their realization that their limb is missing.
Also - there have been a number of posts about prodigies. This made me wonder about the difference between precocious people who show their talents early in life (like in middle school) and who, as a result, are called "gifted", and people who are less precocious, but show talent later (like in college) -- by talent, I'm mean something like being a talented writer. Is this just a matter of intellectual maurity ... like, your ability to think in a sophisticated way? I mean, I think genetics and just raw talent do have something to do with it ... but what about beyond that -- how much does one's intelligence have to do with genetics?
Date: 2003-04-01 09:42:09
Message Id: 5243
I was just wondering about the permanence of central pattern generators. It seems that some of the most complex tasks, once learned, can be performed forever, while the simplest ones, such as muscle movement, will atrophy if not in use. For the past few weeks, I have been unable to bend my leg, and I seem to have forgotten how to flex my quad. Only after several days of electric stimulation which forced my muscle to contract was it "re-educated," allowing me to move it on my own. I would understand if the muscle simply became less responsive from lack of use, but forgetting completely how to move it at all when I can contract my right leg so easily, really threw me. This is just what I was thinking about.
Date: 2003-04-01 12:43:48
Message Id: 5245
In response to the idea of the phantom limb that we've been talking about in class, one idea that helps me understand how people without a certain limb can feel its presence is the experience of one's hand or limb "falling asleep." I'm sure everyone has experienced this at one time- waking up in the middle of the night to find that you can't "feel" your arm because you've been sleeping on it. Yet at the same time, you still know that it's there and that it has a certain shape, but for some reason you're not receiving input as to its exact whereabouts or presence. It's a little different, but it sort of parallels what it might feel like to think that a body part is there even though you are not actually receiving sensory input from it. Also, in talking about the difference between boys and girls, it is important to consider that differences may be caused by their different personalities/brains that may be unrelated to their sex-- unless of course a commonality has been established within the sex.
Name: Elizabeth Damore
Subject: Sleeping Limbs
Date: 2003-04-02 21:27:21
Message Id: 5256
I think the discussion about not being able to feel your limbs while they have fallen asleep is interesting, although I don't quite agree with the description of it. When my feet or arms "fall asleep", they may seem numb to the touch, but I still have sensation in these limbs. Therefore, I don't think this phenomenon serves as a very good example of phantom neuron transmissions, although I agree with the logic behind the argument.
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