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An ongoing conversation on brain and behavior, associated with Biology 202, spring, 2000, at Bryn Mawr College. Student responses to weekly lecture/discussions and topics.


TOPIC 3:

The nervous system is an input-output box consisting of interconnected input-output boxes themselves consisting of .... its boxes all the way down ... lots and lots of boxes ... and they're pretty much the same boxes everywhere". Is that a useful way to think about the nervous system? Does it help to make better sense of behavior? Of any particular behaviors?


Name: Richard Cruz
Username: rcruz@haverford.edu
Subject: I felt like it!
Date: Thu Feb 3 22:54:11 EST 2000
Comments:
In the first class Prof. Grobstein raised the issue of how we sometimes do things because we "feel like it" - that is, without any apparent input or output. In our (admittedly simplistic) model, this is a problem, because we can't explain an output without an input.

Well here goes. We learned today that we have 10^12 neurons in the central nervous system, 99.9999% of which are interneurons, each of which typically is connected to 10^3 other neurons. It would be easy to 'lose track' of an input's relation to a later output with such an unconceivably complex cloud of neurons. Thoughts and ideas could be bouncing around from neuron to neuron for weeks before a signal ends as an observable output.

And another thought: do these truly astronomical numbers make it any easier to accept the implications that the statement "there is only the brain" has for the concepts of "self" or "soul"?


Name: Paul Grobstein
Username: pgrobste@brynmawr.edu
Subject: Week 3
Date: Fri Feb 4 11:20:19 EST 2000
Comments:
Hah, so Richard snuck in this week before I could get here, "felt like it". So be it; like the enthusiasm/spontaneity (what is THAT in terms of boxes?). Anyhow, a topic for this week? Needs, I guess, to be one that fits Richard's comment. Remember, though, that its just a topic to get you started if you need one; you're free, as always, to write about anything that this week's classes brought to mind. How about:

"The nervous system is an input-output box consisting of interconnected input-output boxes themselves consisting of .... its boxes all the way down ... lots and lots of boxes ... and they're pretty much the same boxes everywhere". Is that a useful way to think about the nervous system? Does it help to make better sense of behavior? Of any particular behaviors?


Name: Anna Arnaudo
Username: aarnaudo@brynmawr.edu
Subject: Underlying Complexity
Date: Fri Feb 4 14:11:30 EST 2000
Comments:
I did not find it all that surprising that all the complex of the nervous system was based on a single fundamental building block- neurons. I guess I did not find it surprising because most of the building blocks of life in and of themselves are not all that complicated- just a few elements. The huge number of neurons lends itself to the idea that neurons are a building block; there are so many ways in which that many neurons can arrange to make the various structures of the nervous system. This does not even take into account that neurons differ among themselves; the possibility for complexity is astounding. Leaving neurons as the smallest box seems a substantial way to describe the nervous system.

The estimate that 99.999% of the neurons are inside the nervous system was surprising; I thought that motor and sensory neurons accounted for more than that. This means that very little of our brain power is used on anything exterior to the nervous system. Under the assertion that the brain is behavior (which I still have my reservations about), this means that pretty much all of our behavior is inside of our nervous system. Perhaps the most amazing part of all of this is that if our nervous system only uses 0.001% of itself to comprise all external “behavior,” imagine the complexity of the behavior that is being performed by the other 99.999% of our nervous system. To me this just shows how complex behavior really is- it actually augments the problem of understanding behavior. If a majority of it is hidden within the nervous system and it is being dictated by a system almost a hundred times larger than our external behavior- How could we possibly understand behavior completely?


Name: Stephanie
Username: stephmd@hotmail.com
Subject: percentages
Date: Fri Feb 4 15:58:54 EST 2000
Comments:
I think that our model of the nervous system as an input-output box consisting of interconnected input-output boxes which in turn consist of boxes, etc. is a useful beginning in thinking about the nervous system and behavior. But I think it raises more questions than it answers. At the most basic level, we are saying that these “boxes” are all the same (composed of neurons). Yet the boxes do very different things. Perhaps this discrepancy can be explained by the many different shapes and sizes of neurons and by the nature of the signals passing between them. But that somehow doesn’t seem very satisfying to me. Isn’t there “something else”? Just neurons?

If the brain equals behavior and if 99.9999% of the boxes in the brain are composed of interneurons (and thus do not “talk” to the outside world), what does this mean about behavior? My first reaction is to say that most of behavior (99.9999%) DOES equal the brain. It appears that receiving input from the outside world is a very small part of what the brain does. Therefore, perhaps the outside world has very little to do with our behavior. I don’t agree with this last statement, in spite of the numbers.

I am reminded that we, as a class, have not defined “behavior.” In my previous essay, I defined behavior as observable actions/reactions. Using this definition, I don’t think we can say that what happens in 99.9999% of the boxes counts as “behavior”. We can’t see it! We can observe the inputs and outputs of sensory and motor neurons. But how can we talk about the input and output of interneurons? (I know we said that the inputs of interneurons are the outputs of other neurons, but this doesn’t explain what that input/output is.) I guess I’m saying that, while close to 100% of the neurons in the body do not communicate with the outside world, I’m not sure if we can call what these neurons are doing “behavior”.

Maybe I’m getting lost in the semantics here. But I do believe that the relative significance of the <<0.0001 % of neurons that are sensory and motor neurons is much greater than their numbers would suggest. They are the “bookends” of the system; they depend on the interneurons to translate inputs into outputs. But it is what comes in and goes out that counts (as behavior). What I want to know is how do the interneurons translate the inputs to outputs? Can interneurons themselves generate a chemical signal that results in an output to a motor neuron? Can they change a signal received from a sensory neuron? If so, does this count as behavior (even though it can’t be observed)?


Name: hillary bobys
Username: hbobys@haverford.edu
Subject: boxes and boxes
Date: Sat Feb 5 14:59:31 EST 2000
Comments:
this model holds serious problems for my understanding of the brain. the boxes withn boxes within boxes (or, turtles all the way down) explanation helps with ideas concerning complex behaviors like learning, but seeing the larger picture with this model is confusing. i feel as though i am looking down a well with no end using the box logic. it runs counter to my other education of neuroscience where stuctures are taught fairly independent of one another at first and then connections are shown. the box model clouds the picture before i can even grasp the elementary concepts. is any one else feeling this way?

for the behavior of learning, however, the model does give some logic to my understanding. learning is such a complex interweaving of various connections that endless sub-boxes acually begin to make sense. yet, the questions arise of where the input for learning comes in and in what ways it manifests itself. why do we use 99.9999% of our resources within ourselves/brain? what is the purpose, if there is one? i agree with stephanie that much gets confused in the semantics of this discussion. is there a way to lessen this confusion or will i (we?) continue to lose sight of the goal because of wording?


Name: Mridula Shrestha
Username: mshresth@brynmawr.edu
Subject: more than just turtles
Date: Sat Feb 5 17:41:44 EST 2000
Comments:
It comes as no surprise that a complex system such as our nervous system is comprised of a hierarchical series of subunits--we see this trend in almost every science relevant to life--from the cells of biology to the atoms of chemistry(we can keep breaking these units down to smaller subunits of course). This does not, in any way, however, impose any idea that the system is made of homogeneous subunits, or that it is therefore a simple summation of those subunits. As is clear from our own experience, the whole is indeed greater than the sum of its parts, and therein lies the mystery and magnificence of life.

It seems an oversimplification to claim something to the effect of "the nervous system is turtles all the way down." We must account for questions like, what colors are the turtles? How old are they? Are they of the same species? Do they behave the same ways? Who do they associate with? What postion does each assume in relation to the others? It is important that we probe further into the neurons themselves--we have already learned that there are sensory neurons, motor neurons, and interneurons--there must be other such distinctions that might deter us form dismissing them all as one and the same. Just as different atoms combine to form a vast array of molecules, and just as they have different interactions and properties, so too must the different neurons be capable of forming various functional systems, engaging in different interactions and exhibiting different properties.

It is not my primary objective to try to complicate everything, but I do think that we might run into problems if we ignore the inconsistencies that may make our basic buliding blocks significantly different from one another. I just don't want us to be mixing apples with oranges, that's all. But if we acknowledge these differences explicitly and also recognize the great(er) simililarities, then we can probably use the units as useful building blocks of our known to be imperfect models.


Name: Sangeeta
Username: siyer@brynmawr.edu
Subject: Input/Output Boxes
Date: Sat Feb 5 17:58:43 EST 2000
Comments:
I think that the input-output boxes are a reasonable way to think of the nervous system because the term input usually suggests output but not immediate and the term output suggests a processed input, which is exactly what the brain does to incoming messages, process it. I see the nervous system as a highway almost, where you can enter anywhere really and then just travel down, exiting only to enter another interstate.

To what stephanie was asking before about whether the interneurons can change an input or generate one, I think they can. I mean, as messages are being passed, I don't think that it can remain totally intact. We talked about in class how we did not think that one input led to one output. Well, I think that sometimes, many inputs can result in one output. This would change that preliminary input because it is not being affected by others. As to the question of whether the passage of signals from one neuron to another is behavior, well, that is rather vague. I mean, your defination of behavior was "observable actions/reactions". And at a microscopic level, the neuron is reacting to the message given to it by the neurotransmitters that it receives from it's dendrites. The depolarization wave, the charge developed, all these are reactions to the message being received and sent. So by that defination, this is a form of behavior for the neuron.

I, as hillary, would like to know if there is an end to this boxes theory. Would it be the molecules that make up the every piece of the cell? Where does it end? They can't all be the same boxes because messages need to reach different places, therefore, there must be different boxes that set them on the correct pathway.

These are just some quick thoughts I had. Although the input-output box theory explains behavior rather well on the physiological sense, I just feel that it is rather cold. To describe behavior as pathlike and logical.


Name: Laura
Username: lchivers@brynmawr.edu
Subject: Boxes
Date: Sat Feb 5 18:15:08 EST 2000
Comments:
I don't feel that we were saying that the boxes are all the same because they are composed of neurons, but that neurons themselves ARE boxes. And these boxes, neurons, are in essence the same. Which would then imply that as we move back up the hierarchy of boxes that the larger boxes are also essentially the same. But there are differences in them. Perhaps these differences can be accuounted for through even smaller boxes in the neurons. I know that Prof. Grobstein said that the neuron is the smallest box we will look at in this class, but it is reassuring to me (and I hope to Stephanie) to remember that there are indeed smaller boxes that do have differences-that make the neurons slightly different. Thus there is more than just neurons, but this something is just smaller boxes.

I see differences in function at this smaller box leve as possibly stemming from two things. The first is the way in which one neuron communicates with other neurons. Although we have not talked about them, neurotransmitters and receptors are for me smaller boxes in boxes. A neuron that is releasing dopamine into its synapse cannot relay a message that serotonin must transmit to the neuron across the synaptic cleft, no matter how often it fires or how strong the input from the signal is in the nervous system. Thus different neurons could be specialized by the kind of small, neurotransmitter- production boxes that they contain. Accordingly, even if the first neuron was able to release the serotonin needed for the message, if the neuron across the cleft didn't have the receptors to receive the message, the message would not continue on along the path. Thus receptors seem also important for function. If a whole bunch of one type of neurotransmitter production neuron or specific receptor neuron made up one of the larger boxes, then it seems to follow that that larger box would only be able to perform the functions that its individual cells could do.

Another possibility regarding differences in funtion could be the actual messages that each part receives. Although we learned in class that each neuron communicates with 10^3 other neurons thus resulting in an unbelievable web of neurons in the brain, some signals may be not received or not as strong in some of the boxes as in others. For instance, maybe the way that the neurons are connected from the retinas, the visual cortex is "wired" to receive the signal, and gets it strongly. Maybe the auditory cortex gets this messgae as well, but it is much weaker than the information that it is receiving from the ears. If the function of boxes is related to the strenghth of the messages that they receive, then differences in function could be explained by this difference in strength.


Name: Ann Mitchell
Username: amitchel@haverford.edu
Subject: response3
Date: Sun Feb 6 01:17:35 EST 2000
Comments:
Is this a useful way to think about the nervous system? Sure, it’s what the nervous system is, on an organizational level. If we are just talking about structural level, this explanation serves a purpose. However, if we are talking about the function of the nervous system in it’s entirety, this explanation leaves certain things to be desired. For instance, the role of different chemicals in the brain. If every neuron/nerve is a box, and the boxes are “pretty much the same” everywhere, and the chemicals were all the same, there wouldn’t be much differentiation between structures or function(on a purely theoretical level). But because each neuron has a selectively permeable membrane with different concentration gradients, there are different structures and systems in the nervous system. (What the class might refer to as boxes within a box).

On the same note as chemicals or environment, I can not conceive of a working nervous system without an action potential, which has to begin somewhere. The action potential is maintained by receptors and chemicals at the synapse, thus this chemical environment is imperative for nervous system function. Without it, we would have a bunch of useless boxes , or perhaps no boxes at all. Certain neurons contain growth factors for other neurons in nervous system development, and without these neurons, entire organizations of tissue and organs would not exist.

Maybe some of this sounds like a boring to review to some of you, but I say it to remind everyone that even though we are approaching the nervous system from a very theoretical level, we shouldn’t forget some of the basic biological principles that still have to apply in our theory. It’s like trying to play a game without remembering what the rules are. For instance, one person made the comment at the end of last Thursday’s class that if the organization of the nervous system really were interconnected boxes, then one box that didn’t work would screw up the whole system. Someone else responded that since there were so many other neurons/nerves in the system, it wouldn’t be that big of a deal because that neuron could get “bypassed”. I’m not exactly sure what “bypassed” meant in this context, but it is my hope that others in the class remind themselves of another basic biological principles before they start thinking about the exact implications of structure-homeostasis. One of the most fascinating things about living organisms is their ability to heal themselves, which is largely due to homeostasis. Homeostasis, just like our theoretical model, also occurs at the smallest possible box in the form of receptor regulation. People with Parkinson’s disease don’t manifest symptoms until 80% of the structure responsible is gone because of homeostasis at the level of dopamine receptors.

Another important effect of these chemicals on the nervous system is that through receptors and receptor regulation, they can change cyclic amp cycles, get into the membrane of the nucleus of the cell,change mrna transcription, and alter gene expression, all in a matter of seconds. These chemicals have a powerful effect- so how does this effect behavior? Psychotherapy has been shown to change receptor regulation at the level of the synapse. Therefore, this is an instance of the outputs of your nervous system being changed as a result of environment. What about the fact that somatosensory neurons may as well not exist statistically in comparison to interneurons? Does this change their importance in the way our behavior is effected? Does this change the way they are connected to neurons, or the importance of their role? It does not make sense to me that we should dismiss the role of the function of the nerves that are not interneurons simply because interneurons are so much more abundant. The point is, somatosesory neurons still exist. They are still important as a bridge between our external and internal environments. For this reason, and because of the role of the internal chemical environment in the nervous system, I am not comfortable with the conclusion that just because more interneurons exist, and they are located in the CNS, this serves as more evidence that the brain is behavior. There are still strong environmental forces(internally and externally) that exist.


Name: Maria Vasiliadis
Username: mvasilia@brynmawr.edu
Subject: Brain = Behavior
Date: Sun Feb 6 15:35:34 EST 2000
Comments:
One of the concepts that struck me most in class on Thursday was the idea that if brain equaled behavior, then behavior may be less dependent on the outside world. The notion that receiving input from the outside world is a relatively small part of the nervous system and a relatively small part of what behavior is.

The idea and definition of behavior that I have formulated is that behavior is the way human beings and other organisms, (Lets not forget are friends the frogs) act. There is an entire science dedicated to behavior, psychology. Psychologists regard behavior as any activity of a person or other living thing. Human behavior includes a person’s emotions and thoughts, and the responses of glands and muscles. Behavior itself can be broken down into two different parts: voluntary and involuntary. For example speaking up in class is a voluntary behavior, and breathing heavily after running is involuntary behavior. Both types of behavior may occur as a response to environmental stimuli. On the other hand, some voluntary behavior is self-determined. It takes place simply because a person chooses to act in a certain way, with no apparent outside stimulus. I think human behavior is determined partly by hereditary and partly by environment. But, most importantly it can be modified through learning.

Hereditary, determined by our genes. Environment, consists of those conditions and forces that surround and influence an organism. Learning, which I consider to be the most important, is the process by which behavior changes as a result of experience or practice. A person learns many behaviors through experience in situations that involve some type of motivation, such as a reward or punishment. The motivating factor stimulates the individual to behave in a certain way.

At one point my skepticism was fading, and the idea of brain and behavior being the same thing was beginning to become clear. This new approach that we have been discussing has halted my thinking. I don’t seem to understand the relationship we are making with behavior being less dependent on the outside world. The following paragraph has just explained how I view behavior and how behavior is impacted by other external factors, I know we are not disregarding these factors but where exactly do these ideas fight in our puzzle?


Name: anonymous
Username: sito@haverford.edu
Subject: 99.9999%
Date: Sun Feb 6 19:02:55 EST 2000
Comments:
I agree with Stephanie that 99.999999% of the behavior is the brain. It really struck me in class to know that such an overwhelming percentage of our neurons are interneurons. From the enormous number of interneurons in comparison to sensory and motor neurons I think that the box is much more complex and thus interneurons have much more of a role in how we behave. Of course I am not saying that the outside environment does not have any effect on how we act, but I am saying that our interneurons (brain) effects how we interpret that input.

I don't really know if it helps us understand the nervous system or our behavior by saying that its boxes all the way down and they're pretty much the same boxes anywhere. I feel this way because you could really say that about anything. If you brake things down to a certain extent all things will be the same. But it really does not help us understand the why, and how it works etc. And the how and the whys are the key to understanding behavior and the nervous system (or at least I think so).

About the turtles..... Well well the ultimate question is what does the last turtle stand on???? The thing is for this analogy it is possible to say it is turtles all the way down. But for neurons? after a while the boxes are no longer boxes. If you go down too far they will no longer be neurons, or be something with a specific function. Right? or can you say it really is boxes all the way down?


Name: chrissy
Username: cpili@haverford.edu
Subject: turtles and boxes
Date: Sun Feb 6 19:49:44 EST 2000
Comments:
First, I am not completely sure what I am supposed to make of this turtle analogy. I couldn't help thinking that I misunderstood the punchline or if I heard it incorrectly. But after reading some comments, the turtle analogy is just as complex as explaining what these boxes mean...in other words, I think I have a semester to figure out this analogy.

When we learned that most neurons are also interneurons, this didn't seem to affect my opinion on if the brain equates, or rather is the primary influence on behavior. I agree with what Ann said earlier- our bodies are capable of maintaining homeostasis and so if one neuron malfunctions, our whole body does not falter. Along those lines, regardless if most neurons are interneurons, this just proves that our bodies are constructed of several intricate systems, some of which might not have been uncovered by scientists. But to say on the most basic level that these interneurons are so similar would be like saying that my foot has the same function as my eye. Some kind of distinction must be made. It might be more safe to say, something along the lines of.. the structure and physical function of these boxes are similar, but the ultimate operation and goal of these interneurons differs a great deal.

So, since there are what seems like an infinite number of interneurons in our system, how can we ever be sure that we have successfully found the necessary pathways of the inputs and outputs through these boxes? Have we just uncovered the shortest, but not necessarily the most effective pathway? This though leads me to my next point, because there are so many different available pathways, to say that behavior is generated somewhere WITHIN these routes would force me to doubt God and the outside world..which is frankly why this speculation (brain = behavior) seems too simple. If I think about the outside world purely in terms of its physical aspects, I would say this has a profound effect on me. Just think of a beautiful spring day where the birds are chirping and the sun is beaming on your face. I have not had any "emotional or spiritual" contact with the birds or the sun, yet they only help my mood. Now, if I walked out of my dorm and it was dark as night at 10 am, I don't think I would be able to smile so readily. The physical world has too much of an effect to assume that our behavior comes solely from within us.


Name: Hiro
Username: htakahas@haverford.edu
Subject: boxes and alarm clocks
Date: Sun Feb 6 20:52:28 EST 2000
Comments:
I agree that the nervous system is "boxes all the way down." I also believe that there are smaller boxes within neurons, too, each having input and output cables. Here, I want to focus on our smallest boxes, neurons. My question is: if each neuron is connected to 1000 other neurons, how does a signal (input) know which way to go?

My guess is that the inputs can be transmitted through only certain neurons. Some postsynaptic cells might have receptors which do not correspond to the input (neurotransmitters) sent from the presynaptic cell. So, I believe that the boxes are different although they all have similar basic structures.

My another point. As Maria, I also think that the behaviors are pretty much independent from outside inputs because of the tiny percentage of sensory neurons. Like the cricket's song, the foundations of behaviors are already set in the brain early in the embryonic development stage. I have mentioned before that brains consist of a network of input-output cables with some alarm clocks attached within a box. What I mean by alarm clocks is that some information of animal behaviors are set and "wake up" as the time comes - like the cricket which already has the information of its singing pattern early in its life but can only sing after the final molt.


Name: Soo Yi
Username: syi@brynmawr.edu
Subject: Weekly Essay #3
Date: Sun Feb 6 21:18:25 EST 2000
Comments:
To me, thinking of the NS as "boxes all the way down" doesn't seem like an oversimplication. It just means that our fundamental basis of thinking and behaving is dependent on boxes with the same structures. That does not somehow simplify things for me by any means.

Just think of things like codons which are comprised of 3 bases each -- just 4 different bases in different combinations has the ability to encode for 64 a.a.'s.

Now think of how many neurons ("boxes") we have -- I think Dr. Grobstein said 10^12. I can't even begin to comprehend all the different combinations that can be made with that massive number especially since a typical neuron receives inputs from 10^3 other neurons and also transmits outputs to 10^3 other different neurons. And that's not the end of it.

There are all those different neurotransmitters that can bring about different outputs. In one of our readings, Neuropeptides, Bloom gives an example of how injecting different species with angiotensin II brought about a drinking behavior despite a salt/water balance. Also, injecting rats with LHRH (luteinizing hormone releasing hormone) evokes the posture required for copulation.

I find it unbelievably amazing how the combo of the innumerable amounts of neurons and the different hormones/neurotransmitters can bring about such outputs. The individual "boxes" themselves may seem simple but the interactions between the whole lot them are anything but simple and I like to think that, that is the beauty of nature.


Name: melissa
Username: mwachter@haverford.edu
Subject: response3
Date: Sun Feb 6 21:50:09 EST 2000
Comments:
Wow- i got to the forum a little later this weekend, and there is such a wealth of dialogue going on. From the theoretical approach taken by some to the more "back to the biological principles" approach taken by others (the posting coming to mind is Ann Mitchell's) there is a lot to digest. What had formed in my head prior to reading other postings has been influenced by others' postings...

People seem uncomfortable with the idea (and implications) that somatosensory and motor neurons only account for .001% of our total neurons...the statistic surprised me as well, but I do not think that it necessitates a change in our view of everything we had come to believe about people and the importance of the exterior world ( Grobstein and others may well challenge me on this!) First of all .001 multiplied by 10^12 neurons is still a whole heck of a lot of neurons which allows for a very real neural connection with the outside world. I feel like one key thing to remember is that while interneurons are connected to lots of other interneurons, eventually, this string of interneurons is connected to an interneuron that is connected to either a sensory neuron (which connects with the outside world) or a motor neuron (which connects with the outside world....so although the connection may not be direct, it is nonetheless there and plays a central role in both the overall input and output (behavior) pathways...as far as I understand the neuroanatomy of the system this is true of all interneurons...so it is not as if there is this isolated system of interneurons within the central nervous system which is not affected and does not effect the outside world. Chrissy concludes her posting by saying that "The physical world has too much of an effect to assume that our behavior comes solely from within us" and I agree with her that I think that the physical world (environment) has a major impact on us. However, I don't think that the fact that 99.999% of our neurons are interneurons means that "our behavior comes solely from within us"...instead I would argue that it is precisely because of the complex interworkings of the nervous system that the outside world can have such a, as Chrissy writes, "profound effect on [us]"....

I realize that the following writing is very theoretical (and does not use the biological lingo]...If Ann is reading this, she is probably going to cringe...but my thinking is that the "profound effect" that the outside world has on our behavior and the amazing complexity with which our behavior unfolds arises out of the interworkings of the interneurons link the external ( to the body) input and internal output (behavior)...why should it make us feel that the importance of the environmental input in dictating person/situation specific behavior is diminished by the fact that it is processed by millions upon millions of neurons...if space aliens were told about our nervous systems, wouldn't it appear that info that got that much of attention before a motor output was spit out was incredibly important information.


Name: Jennifer Webster
Username: jwebster
Subject: Response 3
Date: Sun Feb 6 22:09:07 EST 2000
Comments:
I see no reason why the notion that the entire nervous system is made of intrinsically similar "blocks" should be difficult to deal with, especially considering the other examples we see in nature. All matter is made of atoms, which are intrinsically similar "blocks" that have slight variations which affect their properties. All living things are made of cells that have simply adapted and specialized to best serve the organism they are a part of. It therefore makes complete sense that the nervous system would be made of intrinsically similar cells with slight variations depending on their specific purpose. From an evolutionary standpoint, this is a much more efficient way of organizing things, rather than many different types of cells developing to serve essentially the same purpose. I think the idea is actually very elegant.

I did find the notion that every neuron receives input and gives output to a thousand other neurons really surprising. But considering the consequences of neurons misfiring (seizures, etc.) it makes sense that there would be a web of neurons as opposed to a chain of neurons for every action. That way if one neuron does get damaged, the being may not necessarily be affected.


Name: Susan Lee
Username: sslee@aol.com
Subject: Week 3
Date: Sun Feb 6 22:27:13 EST 2000
Comments:
I was very amazed to find out that external sensory neurons comprise only .0001% of the total number of neurons. However, for me this doesn't diminish the effects of external stimuli/inputs. .0001% may sound like a small percentage, but given the fact that the nervous system is composed of 10^12 neurons .0001% is still a very large number.

I think that the external environment has a greater effect on behavior than the .0001% would have us believe. There are probably internal factors that will predisposition us to behave in a certain manner; however, whether these behaviors manifest themselves is dependent upon the external environment.

The numbers discussed in class opened my eyes to the fact that internal processes make up a greater portion of our brains' functions. Currently I don't believe that I am fully aware of the implications of this. I am interested to see how this topic will progress in class discussions


Name: Sunny Park
Username: spark@brynmawr.edu
Subject: Weekly Essay 3
Date: Mon Feb 7 10:24:14 EST 2000
Comments:
Since I don't have much knowledge in the field of science, the way Professor Grobstein explained the nervous system as these countless boxes helped me understand it better, I guess as someone has commented, from an "oversimplified" perspective. At the same time, I feel as if there is a great number of intricate details that need to be learned or discovered to see that the brain and behavior are the same and that there is nothing else. Also, if 99.999% of our nervous system consists of interneurons, and if each neuron transmits and receives thousands of inputs and outputs, our model seems to be too simple, and that worries me to see that there is so much to learn about this simple yet highly sophisticated system.
Name: Laurel Edmundson
Username: ledmunds@brynmawr.edu
Subject: Hidden Genius
Date: Mon Feb 7 13:09:45 EST 2000
Comments:
When I wrote my first forum entry, I had the mistaken impression that "the brain is all there is" excluded the outside world—that the birds and sun and the Wawas were all created by our brains and not actually there. This idea disturbed me and prevented my acceptance of the above statement. However, once this misunderstanding was corrected, I had no remaining objections to the brain=behavior hypothesis. As I said earlier, I do think we create much of our own realities. So our discussion about the approximate number of interneurons in our nervous system did not change my opinion; it further supported it. If 99.999% of our neurons have nothing to do with processing input from or sending output to the exterior, they certainly must be occupied with something!

The interneuronal line of thought goes along nicely with a piece of trivia I heard somewhere— that we humans use only a fraction of our brains during our lives…something like 1/9. If that’s true, think of all the untapped intelligence and power to control our lives we possess! That’s probably enough to will ourselves to fly over the mountaintops if we wanted to, which incidentally is a childhood dream of mine. But is it possible to learn to use the other 8/9? Maybe the geniuses and prodigies among us have already learned or possess the innate ability to tap into that reserve. For the rest of us, I wonder what’s happening in the unused portion. Does it constitute our subconscious? Or is it lazy brain mass that lies around waiting to be discovered?


Name: Andrew Hollander
Username: aholland@haverford.edu
Subject: Response 3
Date: Mon Feb 7 14:42:01 EST 2000
Comments:
The analogy of the nervous system as a box within a box all the way down is very interesting, but is it really valid? There has to be some final box. Just something I've been thinking about.

I agree with what many people wrote in the forum this week about the implications of the interneurons accounting for 99.999%. I do not think that the relatively small number of sensory and motor neurons should effect the relationship of the nervous system = behavior. That 0.0001% is still a very large number. It just illustrates how complex behavior really is and how much of an effect the outside world has on it- especially if the 99.999% of neurons are needed to process the effects of the outside world. What else do interneurons do besides process information from the outside? Chrissy mentioned mood. I was wondering what actually accounts for mood? You would have different reactions to the same inputs depending on your mood. Do the interneurons have to do with the development of mood?


Name: Elisa Braitman
Username: ebraitma@brynmawr.edu
Subject: Boxes
Date: Mon Feb 7 17:19:08 EST 2000
Comments:
Like Sunny, I feel a bit overwhelmed by how much we, as a class, have yet to learn about the nervous system. And, no doubt, there is a lot that no one really understands at this point.

I had learned a bit about the nervous system in other biology courses but I hadn't learned or thought about the 10^12 neurons in the CNS. And a few people made the interesting point that .0001% of that number is still a lot.

As for the idea that the nervous system is made up of many interconnected boxes, that sounds like a reasonable way of describing it (since the nervous system is made up of neurons and each one has inputs and outputs). Another thing I had never learned before was that each neuron receives input from and gives output to 10^3 other neurons. I mean, I'd figured it was a lot but I had never thought about just how many. The picture that comes to mind of 10^12 points with many branches coming out of each one seems very complicated and a bit disorderly but the boxes idea certainly fits that picture. Still, I agree with those who said that this model is oversimplified and ignores a lot of other issues.

As far as the ongoing "Is the brain equal to behavior" question, I still don't feel able to agree with it completely. It is sounding more reasonable but I guess I need more proof.
Name: Cameron
Username: cbraswel@brynmawr.edu
Subject: The rest of the brain
Date: Mon Feb 7 20:03:55 EST 2000
Comments:
I too have always wondered what we do with the other portion of our brains that we dont use...and do all living things with brains not use just as much comparatively. I would assume that the part we dont use is part of the 99.99% which was a surprising number. Is there a way to use it and why havent we figured it out yet. It must be terribly complex seeing as the part of interneurons we do use do some pretty amazing things the further down the evolutionary line you go. It would appear that since so much of the neurons devoted to synapses and relays are interneurons behavior does have its pick and can use as much of the "brain" as it wants. But I too was wondering if the outward "behavior" that we as people express comes from the motor neuron synapses or from messages to the motor neurons from the interneurons and is, of course, therefore, a function of the brain,supporting the current theme.

One reaction I had at the very end of class when we were discussing the shear numbers of neurons involved in every process great or small was that there is no room for spontaneity. The neurons have to be so coordinated and so in charge of every transmission that the interconnection leaves no room for chance. There therefore has to be a predefined set of purposes and pathways that are already known and then just traveled at the right time. Its like all the dancers know the dances ahead of time and just follow the right steps when the number is called. In that case is there really such things as spontineity within humans? Its interesting to thing that behavior might not be as spontaneous as it seems to us sometimes if brain is behavior. Maybe the other part of our brain is just storing the dance steps in a box marked spontaneity.


Name: Sarah S Kim
Username: sskim@brynmawr.edu
Subject: weekly essay #3
Date: Mon Feb 7 20:51:05 EST 2000
Comments:
I feel like I don't know enough biology to see how the "box within box" theory connects with how the nervous system biologically works. However, from what we have discussed in class, the nervous system as interconnected box within box does give me a better sense of behaviour. First of all, the box within box theory explains the complexity of behaviour in certain organism. Human behaviour is the most complex out of all living organisms. We have so many different ways to act -- we can run, walk, smile, feel, touch -- do many things that other organisms can not do. Because of our wide range of behaviour options, humans have the most complicated brain -- we have the most boxes within boxes. Dogs on the other hand don't have as wide range of behaviour options as humans and thus won't have as many boxes within boxes. The box within box theory also explains how different organisms process things differently within the brain. Each box has an option of stimulating the inside box, or generating an output from the box and not going any further within the box. For example, if a mouse's input was a seeing cat, then it would most likely process an output to run. But if the dog saw the same input as the mouse -- the cat, it would generate a different output because it would either go further within it's boxes or not as far to go and eat the mouse as bait. What does the question mean by "they're pretty much the same boxes?" Obiviously it can not be by size because they are all within each other. Is it by processing things?
Name: Anjali Patel
Username: apatel@brynmawr.edu
Subject:
Date: Mon Feb 7 22:12:24 EST 2000
Comments:
I was very surprised to learn that 99.999% of the neurons in our body are interneurons....actually I'm still trying to comprehend it all. I'm not sure if the box analogy is useful in trying to understand the brain...it seems too simplified for such a complex matter. All the interneurons work together to process information but as someone mentioned earlier what happens if one of the boxes fails? How does that interneuron get bypassed and how does the input/output know where to go? Like Laurel I wonder what our unused portion of our brain does. Will we ever find a way to use our entire brain? I admit that I'm still not convinced like the others that brain does equal behavior.
Name: Hajira Amjad
Username: hamjad@brynmawr.edu
Subject:
Date: Mon Feb 7 22:39:37 EST 2000
Comments:
If 99.999% of the 10^12 neurons in the nervous system consist of interneurons, it is supportive of the statement that the brain is behavior. Although these numbers are supportive of the brain is behavior theory, I still find it difficult to accept. In actually observing behavior of individuals, it seems that environment and society play a much a greater role in shaping a person than does the individual's nervous system.

From the day a person is born, his or her ideas, values, beliefs and outlook on life are strongly influenced by outside factors. Parents are strong influential factors in molding the behavior of their small children. In observing small children it is interesting to note how they pattern their behavior after their parents. It has also been shown that many adults inadvertently exhibit behavior similar to that of their parents.

Peers and society in general also have an effect on an individual's behavior. "Everyone else does it" is a common explanation cited by many teens to explain their choices. The outbursts of school violence in the past few years has been blamed on the excessive violence portrayed in the media.

I find it hard to believe that of the 10^12 neurons found in the nervous system less than 0.0001% of the neurons are responsible for input from the outside. Although 0.0001% of the 10^12 neurons is still a very large number, I find it difficult to accept that there is less input from the outside world than from within the brain itself.


Name: anonymous
Username:
Subject: week 3
Date: Tue Feb 8 08:47:37 EST 2000
Comments:

Name: rebecca
Username: rjones@brynmawr.edu
Subject:
Date: Tue Feb 8 09:00:15 EST 2000
Comments:
10^12 nerons is a lot. Having that many makes sense if you look at all teh various behaviors we have. I am not sure that brain does equal behavior but, it does seem possible. Of the interneurons it would be interesting to see how many of them are just connectors between different cells and how many process information. I also wonder how many cells it takes to store a memory: if cells can store parts of multiple memories.

From different sources i have heard widely varing sayings as to how much of the human brain is used and how much wasted. I wonder how much of that is made up, if it is at all possible to say "well gee this part doesnt seem to be doing anything". Even if a part were removed and personality did not seem to change and organ function did not seem to change the internal personality could have changed and since it changed teh internal person not being the same might not be able to tell other people this.


Name: Shana
Username: shutchis@brynmawr.eduI
Subject:
Date: Tue Feb 8 09:23:14 EST 2000
Comments:
I think that a box is a useful way to think of the nervous system for now, but the features and types of boxes must eventually be defined. The nervous system is highly complex and just stating that it is boxes all the way down does not clearly define it or explain it. There have been interesting points raised in previous comments about the types of boxes and if the input output system is a true way of passing on information, ie is what originally came in what really arrives. I'm sure everyone played telephone as a child and as we all know the message we start with is not the one we end up with. Consider all the people in the chain a box, we recieve an imput, we give an output in accordence with the imput- as we percived it at the time of reception. Is our output the same as the imout we recieved? Generally not. This can also apply to behavior, if we are all considered to be boxes with our own series of boxes all teh way down. When a group of people recieve a stimulus do they all act exactly the same? Generally no. So are some peoples boxes different? And if so, how so? Are the boxes the same but the connections different? How can differences be accounted for?
Name: amse hammershaimb
Username: dramatraumaqueen@hotmail.com
Subject: well ...
Date: Wed Feb 9 01:46:32 EST 2000
Comments:
i, personally, found the "boxes" confusing. please forgive my snobbery, but i came into the class rearing to go with the neurons and transmitters and whatnot. instead, we talked about boxes and simplistic philosophical introductions to the nervous system. that's fine. i think that the tecnique would have served me well in my earlier exposure tot he nervous system.

i know it's boxes all the way down. all of my forum comments have been tainted with my pre-exposure. i'm afraid that this makes my comments dull. i am interested in knowing how the trail betwen boxes and beginning in boxes, etc. affects behavior. i want to know the neurological process behind my mood swings, muscle aches that emerge from nowhere, and why my torn rotator cuff - though supposedly recovered - hurts like the sun when i laugh. i want my neurological map! and i want to be the one charting it! i want to find out why the undiscovered territories are undiscovered. maybe i won't get that out of this course, but i and my measely gpa will go down trying. for now, i know it's all boxes. what starts the charge? those whims that we cannot explain? how does each box start a pathway of its own?

on a very different note, would any one like to meet up to brainstorm about paper topics and web sources, and whatnot? as most can probably tell, i just like to hear myself 'storm and thought maybe some one else would like to collaborate. i ifnd such taks help to refine paper topic ideas and provide a little more direction. extra input into the paper output box. ha ha ha. sorry.

has anyone seen animaniacs? the mindy and buttons sketches? why. why why? does any one else hope these boxes will answer?


Name: amse hammershaimb
Username: dramatraumaqueen@hotmail.com
Subject: waste only bin
Date: Wed Feb 9 01:56:14 EST 2000
Comments:
reading over the other comments after i have posted my main comment, i feel the need ot add that the brain space is wasted bit is supported by my book writers and motivationalists. personally, i think it is a myth perpetuating through those that "buy the hype." as a smal child, i remember watching the cosby show wherein theo was reading a book about how brain space he was not using. this led him to believe he could tap into that area and weild telepathhic and telekinetic powers. i held onto the same myth for years after seeing that episode (i was not the most intelligent child) until one day in the shower, i realized that we must use all of our brain space. we store memory there, we continually operate our bodies from there - how can we not use the whole thing up in a lifetime? from a series of illnesses, i know that my brain does stuff without my lawful consentwhen i am not looking. i think that the real question is, how much of our brain space and activity is used in conscious thought and operations, short term memory, sub-conscious, and whatnot?
Name: Vandana Mathrani
Username: vandnam@yahoo.com
Subject:
Date: Thu Feb 10 23:51:09 EST 2000
Comments:
I agree with Amse about the "boxes", though I think that the boxes were useful as a start. I like the fact that now, we are speaking of neurons and not boxes. I find it amazing that the human body is able to maintain the right conditions so that we are able to do some of the simplest things. But, I guess those things are not really as simple when we look at it at the cellular level. The charged fields or batteries inside are somethings that I often take for granted. Similar to the metaphor that batteries are the concentrations of charged particles, I liked how the Sci. Amer. article on muscle contraction explained that human physiology is similar to how a car works. I also had no previous knowledge that there are no sense organs in our eyes that tell us which way our eyes are pointing. I also think that the sayings, that we use only a certain percentage of our brain and not all of it, are rooted from the idea that when we think about what to do and when we do what we do, we sometimes tend to think that we have to save some space for later. It sometimes seems that our brains are finite and therefore the brain cannot "be wider than the sky", can it?


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