Nervous system architecture: from the output side

On the topic of the existence of a conductor, I agree with what one person said in class, which was that maybe there is an initial conductor which gets taken away as the activty is picked up.

It seems that a conductor is only needed to start the pace of an activity such as the clappingin unison however once it got started the conductor was necessary.

This conductor may not necessarily be a specific person and could just be that eveyone is conducting themselves based on the auditory feedback, and adjustments of whether they should clap faster or slower.

Earlier in the forum a lot of people were discussing phantom limbs. There was actually a very recent article in the BBC regarding treatment for phantom limb pain ( http://news.bbc.co.uk/2/hi/health/7305207.stm ), which basically stated that, in conjuncture with the mirror box treatments, watching someone else rub their hands together can also help relieve the phantom pains. They seem to think that this might be due to mirror neurons firing when the patient watches another's actions. An excerpt from the article explains mirror neurons:

 

"Mirror neurons in the brain fire up when a person performs an intentional action, such as waving, and also when they observe someone else performing the same action.

They are thought to help predict the intentions of others by simulating the action in the mind.

Similar cells exist for touch, and become active both when a person is being touched and when they watch someone else being touched.

Researchers at the University of California, San Diego, say the reason people do not constantly feel what they observe happening to others is that a person's sensory cells do not give the right signals, so they know it is not happening to them."

These researchers argue that, since, the amputated arm is not giving these signals to the brain that the rubbing is not actually being felt, the brain does not receive the feedback that their arm is not actually being rubbed.

Reading this article made me think beyond phantom limbs to mirror neurons. I recall talking about mirror cells when learning about language acquisition in young children. In fact, it is thought that mirror neurons are whant enable us to learn how to move our mouth in ways to make specific sounds. Also, when you make faces at a young infant, they will mimmic your expression, also presumably due to mirror neurons. Yet, when children grow older, they no longer automatically mimmic expressions. This lead me to wonder whether we are just controlling ourselves from mimicking others as adults through feedback or whether the feedback system between the child's brain and their muscles is not yet strong enough.

 

In any case, it seems we have another little sub-symphony going on here between mirror neurons and sensory neurons to determine behavior.

I really hope we come back to the topic of mirror neurons as I find them so interesting!

If anyone is interested, I came across an interesting article on CDs and auditory hallucinations in schizophrenic patients...

http://archpsyc.ama-assn.org/cgi/content/full/64/3/286

 

I am really interested in our class' evolving discussion about phantom limb pain (and pleasure). It is an interesting concept that I have not thought about much until now, but increased attention to treatment options seems to be a growing concern. To understand this topic a little better, i thought I might look up some articles online, and I missed class on thursday so I might be repeating some things, but I found a lot of interesting. One article by TOni Ray explains that "When a body part is lost the corresponding part of the brain is not able to handle the loss and rewires its circuitry to make up for the signals it was no longer receiving from the missing digit...Perhaps nerve impulses in the sensory cortex begin to course down previously untraveled pathways. The second theory is that neighboring neurons in the cortex may actually invade the territory left fallow because sensations are no longer received from the missing limb." I don't really understand why the implications for the second theory would cause a phantom sensation or why our brains would find this adaptation useful.

Next, i found an interesting discussion on cultural differences of phantom limb sensation experience. Nicola Diamond discusses several drawbacks to the western perspective regarding this subject, and i found this slightly intriguing because i had never before analyzed the perspectives used to explain this phenomenon. For example, she mentions that in some african societies, "phantoms of the body –affects/sensations and images –are not set up in contradistinction to the actual body, but are taken as bodily because they are lived as such and there is a fluidity between bodily attributions and actual bodily states. Belief that the spirit is possessing the body is fluid with images of the body, to that of trance states and muscle and nervous activity ect." http://www.artbrain.org/phantomlimb/diamond.html This is a very distinct way of thinking as compared with our own, and I believe it stems from a presence of different types of warcraft and religious beliefs. its a wonder that such societies perceive limb loss not as a loss but as an intangible extension of the self.

In class the other day, we were asked to clap syncronously without someone directing us. I found it was intriuging that it was an everyday thing that we can do without really thinking about. Also it made me wonder what other interactions our bodies can do with one another without a "conductor" or IS there a conductor, just that we can't see it or isn't the same definition as we think it is. Is it possible for a higher order in our system, that controls these things?

I really enjoy the questions that have been brought up by Angel, EB and Jenn. There are so many questions that have yet to be answered that it seems almost asinine to assume that we found the big picture in regards to behavior. Like obviously, as brought up that experiment in Jenn's post, some behavior is in fact genetic and influenced by outside factors. The brain is different for everybody so what really accounts for the uniform behaviors that all of us, fofor the most part, have like walking, talking, etc. To what extent are our behaviors influenced by genetics, actually neurology and all of that craziness? How and why to they influence/define our behaviors only to the extent that they do?

I had to leave a few minutes early on Thursday, so if I am asking something that was talked about, someone please fill me in!

I have been thinking about central pattern generators and would it not make sense that if they are thought to be responsible for many behaviors: walking, breathing, swallowing, that these CPG’s would be found in the parts of the brain such as the brain stem for breathing or swallowing that we know control these functions, just as the CPG for walking is found in the spinal cord?

I am a bit lost and need help with the connection of the RA loop and CPG’s…can the RA Loop initially generate a CPG and once stored, then a CPG no longer needs the RA loop? Or are we born with the CPG’s? And if we are born with these CPG’s, do they have the ability to be inherited? Have you ever noticed two family members who have a very similar gait? And you definitely know they come from the same family? Is this learned or is it already built into our storage system within the CPG?

And if CPG’s have to do with storage and memory, it seems to me that the “I” function and CPG’s have a lot to do with one another…thinking about OCD and other similar disorders, I wonder if CPG’s play a part in the repetitive nature of handwashing, etc…

I am increasingly interested in the idea of neuronal arrangements being the distinguishing factor among people. I wonder if it is too easy to buy into the idea that arrangements have the final say in behavior. How does that account for similarities among people (is it that some of the arrangements are similar and others different) or that tastes change (behavior influencing arrangements?) It's true that probability wise there are many, many different arrangements that can occur to account for why everyone is different...but in the span of thousands of years of human history, is there no overlap at all? And if there is, how is it that someone from the present time could act similarly to a person from an ancient civilization based only on groups of neurons alone? I guess this ties into the ideas presented by jwong etc....

The idea of reafferent loops at first was counter-intuitive, however, when I left class this week thinking about how an output could also be an input, I thought about it and how when we move our hand, there is a whole new set of sensory inputs that need to account for the change in location of your hand. This need for accounting is important especially when considering a fear response. Let’s say that you burn yourself, your nervous system quickly gets the sensory input to move your hand, and produces an output to move your hand, but without the reafferent loop, the nervous system would not know whether the hand needs to be moved more or if the hand was safe.

Central pattern generation (CPG) is a genetic or learned behavior that requires coordination of various parts of the nervous system, and this coordination would not be capable if it were not for reafferent loops. In the example that Prof. Grobstein gave in class, the crayfish has a nervous system produces swimming behaviors, which requires the coordination of movement of many legs. Reafferent behavior feeds into this because before CPG can occur to tell another leg to begin its swimming movement, the sensory neuron sends a signal back to the nervous system informing it of the leg’s new location. Once this information is received, the next leg moves and allows for coordination to occur.

I am now able to understand how the coordination of the nervous system translates into the coordination of the organism, but how does the nervous system establish CPGs? Is it like conditioning, where once a behavior is reinforced enough the neurons become connected to produce the behavior without thought?

I have found our class discussions this week about central pattern generators in the nervous system quite fascinating. We can apply such a topic to everyday tasks such as picking up a coffee mug, or somewhat less common practices, such as playing the piano. I mentioned in class that I can now view my experiences from playing the piano in a more scientific context. I mentioned that, in the past, I have played innumerable songs infinite times, and that I could cut off certain sensory 'inputs' (visual and/or auditory) and still play the exact song with reasonable accuracy. such as visual and/or auditory. I realize that the idea of 'muscle memory' is quite a hot topic in the forum, and I cannot really say whether my ability to have this specific experience is a result of nature or nurture (both my father and my brother play, and we all share this experience). I may do some additional research on this topic at some point...

I am also beginning to think that while the nervous system has multiple ways of performing some function, it definitely contains some element of selectivity with respect to its performance of these functions. For example, in high school I began practicing and working on a difficult piano piece by George Gershwin 1.5 years in advance for a school talent show. I practiced this song daily until the show. In the later portion of this 1.5 year committment, I had pretty much memorized the song for its sound (auditory), for its presence on a score of music (visual), and for the way that this song felt on the piano keys (tactile). I could do any combination with these three inputs to generate a very respectable performance of the song, and it became so easy that I didn't even have to think about it...but only when I practiced at HOME!

However, when I attended practices at school (change in environment and audience), and even the real event itself...I found that these multiple well-established 'patterns' of playing the song would temporarily disappear or 'malfunction'. My muscle memory would fade somewhat, I found that my eyes would jump from the keys to the music in confusion, and that I was not as quick to fix/realize any mistakes that I heard. While this may be explained most simply as a classic case of pre-performance nervousness or anxiety...it is really very interesting. It always used to annoy me that I could return home the night of a show or concert and that my central pattern generator would function perfectly.

If I practiced in front of large audiences more often, would I be training my nervous system to balance/compromise its functions differently? Probably. My anxiety would likely decrease, and then maybe my pattern generator functions would not temporarily malfunction? In this case, would I be influencing my central pattern generator? Is this even possible?

If the nervous system, through its complex network of boxes and connectivity assimilates information both from within the system (the nervous system) and without the system (the environment), as the corollary discharge signals and central pattern generators work in tandem, how might the corollary discharge signal reconcile external input that is in conflict with the signal it is receiving from within the nervous system that is not strictly sensory information? This issue makes sense as we explored in class using the two different eye experiments, one poking our eyes and the other closing one eye and following a finger. Does this, however, account for messages that we send ourselves, so-called “self-talk?” For example, someone with an eating disorder, who may be visibly emaciated to outside observers, but “believes” herself and may even “see” herself as being overweight. And what about people with schizophrenia who have more than one “voice” in their heads? Which signals are enhanced or inhibited that may lead to this?

Like Skye, I also had some questions about the I-function. How does the I-function come into play in terms of interpretation or signals, or is the I-function merely an audience to the symphony?

In class we decided that no one part of the nervous system is “in charge,” but rather, all the different boxes communicate with each other via corollary discharge signals. I suppose having a central control box that signals were sent to would add another step and decrease efficiency, but I wonder what we consider the I-function? Have we not been describing it as some sort of control module? Maybe, though, like all boxes, it just gets information from all the other parts of the nervous system, but it does more with the information it receives… does that make sense?

mcrepeau, that’s a really interesting question about vestigial flight patterns. I wonder what kind of CPGs are genetically transmitted and how they come to be genetically transmitted. We talked a little bit about human walking, but what about swimming? It seems less natural, but is still a skill that many people have- if there’s a culture in which swimming is important and necessary, can that ever become incorporated into the genetic code? How, and how long does it take?

The discussion of the brain being a structure of many different neurons makes the explanation of our minds and souls being results of different combinations of chemical functions and physical functions a more probable hypothesis.

Not only are there so many different kinds of neurons and different ways to extract a specific output from one neuron, combining those individual combinations and multiplying those combinations by the numerous ways that these enurons can function as a whole just adds more and more infinite explanations to explain the variety of human behavior.

Yes, we do have the ability to trigger the same output with the same brain everytime, however, there may be many different ways to trigger one output. Also, maybe the reason why humans are so likely to make mistakes may also be due to the fact that as much as there are many ways to produce one output, there are so many ways to mess up and backfire, causing an output that was not initially intended.

And for muscle memory and memory "scores" with the neurons acting as an orchestra, there may be an original song, then a remix, a variation, etc. WHich is why, those who are more familiar with certain patterns of action can adapt easier to certain actions, such as dancers, pick up on choreography easier than those who have never danced before.

I was intrigued to learn more about phantom limbs after class on Thursday. I have heard of the term in other psychology classes that I have taken, but have not had the opportunity to explore the issue more fully. Not only do those who have had a limb amputated feel sensations in their phantom limb, but also children who are born without a limb at all. This suggests “that perception of our limbs is ‘hard-wired’ into our brain” (Cole, Jonathon. “Phantom Limb Pain” The Welcome Trust. http://www.wellcome.ac.uk/en/pain/microsite/medicine2.html). Therefore, it is probable that our brain is the cause of the phantom limb because it is still receiving signals from the area around the limb. People continue to feel and perceive the missing limb, and often feel strong pain that must be treated with prescription pain killers. The most difficult thing about losing the limb is usually not in dealing with the reduced quality of life, immobility, or feelings of low self-esteem, but rather the pain itself.

In order to reduce the pain suffered by those with a missing limb, neurologists Ramachandran and Rogers-Ramachandran created a device called the mirror box. (http://www.23nlpeople.com/brain/Phantom.html)
Essentially, the patient looks at the side of the mirror with his good limb and sees a reflection. Thereby in his/her mind, they have two good limbs because of what they see in the reflection. When the patient moved their good limb, they were “fooled” into believing that it was their amputated arm that had moved, which seemed to have reduced the pain in many patients. It has been suggested that attempts like these to link “the visual and motor systems might be helping patients recreate a coherent body image, and so reduce pain as a result of reduced and disordered input”. (http://www.wellcome.ac.uk/en/pain/microsite/medicine2.html). The brain must be re-trained in order to alleviate the pain felt by these patients, and has therefore become the main source of looking for treatment.

From our discussion on Tuesday about inputs being a result of outputs, I began to think about these central pattern generators and the analogy that they resemble an orchestra, creating a “motor symphony” of movement, a pattern of action potentials that are based on memory. This idea of a prewritten score was very interesting to me because of the visual that I got from it; from it I began thinking back to when we described the brain as a computer with preprogrammed programs already existing inside of it. By equating behavior with a “motor symphony,” we assume each motor neuron produces different patterns and the mixture of these patterns constitutes behavior. These motor neurons derive instructions from the central nervous system, where sensory organs contain specific sensory neurons called receptors. The receptors then continue on to translate information from the nervous system to different parts of the body in the form of nerve impulses. Seeing such a mechanism made me wonder about how such a complex system could be initiated by experience or whether or not it was a result of genetics. In some readings I found online, I learned that CPGs are actually developed during early embryonic maturity, where efficient motor patterns are initially developed by neural circuitry. An example of this “learning” is demonstrated in the instance of a young bird learning to fly; in the particular experiment, the newborn birds were constrained in straight jackets. After the period of time during which a bird would normally learn how to fly, the jacket was removed and the young birds still had the ability to fly. Thus the motor patterning that determines this characteristic of birds was proven to be of a genetic factor, and that such patterns are not necessarily learned patterns.