Biology 202 Neurobiology and Behavior Spring 2001

Neurons turns out to be input/output boxes which integrate (non-linearly) current flows resulting from permeabilities and permeability changes. As such, they are both remarkably simple and remarkably sophisticated. Does understanding the properties of neurons in fact change how one thinks about behavior? Are the smallest boxes "simple" enough so that one might entertain the idea of being able to make sense of behavior without mysticism? Are they sophisticated enough so that one can imagine how even the most sophisticated aspects of behavior might in principle be imagined to result from interconnected assemblies of these boxes?

So... additive passive current flow from all sorts of sensory neurons (possibly a thousand!) are coming into one interneuron through its dendrites and synaptic clefts... Though this interneuron uses them as additive current to decide when to fire itself, how does the brain eventually know where this impulse is coming from? How does the brain know that all these reactions are coming from the thorn in our finger, or the pebble in our shoe? If neurons only speak the language of action potentials, than what tags this information with the 'where' the multi-imput interneuron seems to know? Doesn't this all get tangled up from the sensory neuron through our narrow spinal collumn? How does the info come out to be so exact as to location?

Next, when we were hearing about inhibitory neurons, etc. I was just curious as to what level of the nervous system novicaine works, and what exactly it does.

and finally, though this is somewhat amusing, but in the spirit of 'thinking backwards', if a chicken runs around when its head is cut off because it is no longer inhibiting 'running around' then what does a human do when It has it's head cut off? Can this tell us something?

The more we learn, scientists as well as those of us in this class that don't have a degree, we can see this argument forming. The fact that some neurotransmitters have been tagged as 'pleasure' or that specific instances of memory can disappear with a simple removal of cells (and yet leave other portions of memory, even more specific than just long term or short term) is absolutely Fascinating. Not only that, but it takes us in the direction that yes, maybe the brain is a place where a little of this chemical and a little of that can make up the feeling you get when you look at your mother, father or even your child. There are so many options, so many places for variation in the biology of the brain alone, that yeah... we could be mapped out up there. Maybe I'm more cynical or logic based on this very topic, simply because a layer of my neocortex has a few shorter axons than someone elses does. That's Incredible. Utterly incredible.

Neurons turns out to be input/output boxes which integrate (non-linearly) current flows resulting from permeabilities and permeability changes. As such, they are both remarkably simple and remarkably sophisticated. Does understanding the properties of neurons in fact change how one thinks about behavior? Are the smallest boxes "simple" enough so that one might entertain the idea of being able to make sense of behavior without mysticism? Are they sophisticated enough so that one can imagine how even the most sophisticated aspects of behavior might in principle be imagined to result from interconnected assemblies of these boxes?

But I find it fascinating to know that the neuron has different neurotransmitters at the axon terminal that it is waiting to release and somehow it knows which ones to release when the signal comes down the axon. This has wide implications for behavior since releasing glutamate instead of norepinephrine can have very different consequences.

So I don't know if you can really resolve the question of whether the neuron is simple or a very advanced micro computer. On the one hand, like any other biological molecule it does what energy and ions tell it to do. It reads the DNA and produces the chemicals it needs. But it also is able to discern whether to release one neurotransmitter or the other. And differnt neurotransmitters bind to different sites which lead to the production of EPSP's or IPSP's post-synaptically.

It is possible, I suppose, to concede that brain and behavior are causally linked given the immense capacity of the nervous system. However to say that nervous system activity comprises the whole of the individual is far too simplistic. There are vast individual differences both biologically and environmentally that contribute to behavior, and to consider one or the other without factoring in the influence of the interaction between the two would be inaccurate.

It was interesting to consider that the nervous system in a large part is designed to inhibit extraneous behavior as opposed to initiating desired behavior. Prof. Grobstein was correct in his assumption that, as many times as I had learned the properties of action potentials, etc., I had never stopped to consider the extent of the inhibitory role played by the nervous system. I, for one, always assumed, incorrectly, that input resulted in behavior, not in the inhibition of behavior. That makes me think of the nervous system as being a lot "smarter" in itself, rather than just as a passive vehicle for whatever was deciding what action was useful at a given time.

I know that I still have plenty learn about brain and behavior, but I look forward to it. I think that as humans, we are curious creatures and maybe through learning about brain and behavior, we can learn why we are curious.

It seems as if we have stumbled upon another double-edged sword in the brain=behavior deabte. Or, perhaps, we never pulled ourselves off of it in the first place. Are neurons both simple and complex? Can we have our cake and eat it too? Seemingly, if the answer is 'yes' we could walk away knowing that neurons can indeed provide a solution. But are they a solid solution?

To address one of these characteristics, I do agree that neurons are the simplest way of thinking about behavior: the movement of electrical impulses thoughout the body, which can be correlated to our actions and reactions. Neurons have be "precison engineered" to allow for this. Prof. Grobstein poses the question of whether or not we can escape the mysticism involved when thinking about behavior. I think part of our desire to study the brain is wrapped up in the mysticism associated with behavior. Myth and mysticism allows us to propose and conjecture in an attempt to explain what we see around us. This is the foundation of science: trying to find explanations for the things humankind puzzles over. In the end, science is part of mysticism. And if that is what leads us to a better understanding of how the brain works, then I am all for the simple/complex issue not being enough, not solving the problem.

As a side-note, I found some interesting statistics in the march 2000 Scientific American. Jose Bueri of JM Ramas Mejia Hospita examined patients for 18 months and found that 39% of people who were brain-dead still had motor-movements up to 72 hours later. (the doctor determined the movements to be caused only by spinal reflexes) Just thought that was a nifty thing to remember when thinking about where the I-function's hiding...

This paper also made connections between how the brain has been thought of as a computer. After these new complex results were examined, the scientists now said our brain was able to receive and compute digital and analog pulses (much more than any computer). Because of this complexity, the neurons have been found to be able to compute time varying stimuli and react with an appropriate response (as studied on monkeys).

I believe that the mysticism behind the brain well never disappear because we will never truly know how the brain works. Even if we had conclusive data, people wouldn't want to believe it, because it is not in peoples' nature to believe everything that science tries to prove. I don't think people want to discover the power behind the complex systems, because we like mysteries. (Mysteries are never as fun, when they are solved!)

It got me thinking back to our whole discussion of action potentials and synapses and inhibitions. Maybe the node of the brain that codes for "carrot" overlaps with the one that codes for "six." Would that mean that those synapses excite eachother? Is that how this whole thing works? Why is it that 98% of people say one answer to that question? It makes me think that it has to be a neural processing thing because I'd hate to thisk we were all that unoriginal. I have to think that the reason relies on some common ground, mainly our neurons.

Another thought that my friend suggested was that "six" made us think of "sticks" and then "carrot sticks." She thought it was all some sort of inherent category representation thing imbedded in all of us. I guess that brings us back to the question of behavior shaping the brain. If I have no connection between "carrot" and "sticks or six" would I still have said "carrot?" hmmm.

So how is sophisticated behavior accounted for by such simple logic? I guess I am partial to the position that operations of the NS provide a template and that the specific quality of the input carves pathes which inevitably alter the balance of the system and thus influence multiple outputs. We know now that certain inputs (i.e. stress) can change the constitution of a box or a whole set of boxes. It follows that the output (behavior) will change, and referring back to our principle of balance, so will some complimentary aspect of the system or box. I think that these adjustments and responses adequately complicate things-- the old stimulus-response model is now convaluted enough to account for some of our sophisticated behaviors.

Another aspect of neurons that make them more complicated is the role they play in our though process. It seems hard to imagine that great works of literature and theories of quantum physics are the results of electrical impulse running down our neurons. To understand how we move physically or carry out basic--or even complex life processes through neurons is not nearly as bewildering as how we manage to reason and think abstractly with them. What neurotransmitters are being released when we produce works of art and push our minds to understand relativity? And why? The actions of neurons seem simple but they must be very complex to accommodate for what we put them through. We need only direct them to muse on themselves and help us to try to understand how it is possible for them to do all that they do.

I still think it is incredibly important to learn about and understand neuron activity in order to understand human behavior. However, when learning about the smallest piece it is hard to see the big picture of how behavior actually takes place. How does my brain tell my fingers to type? How does the neuronal connection work? How do the interneurons know to keep sending the action potential to my fingers? I know that axons vary in length and it is possible that there are axons reaching from my spine to my finger tips. But, it's still hard for me to see the big picture of how it all fits together.

Furthermore, even if behavior is fully controlled by the nervous system, as I believe it to be, there is still something mystical about the whole process. There are still questions beyond the scope of our scientific investigation that leave room for mysticism -- questions of purpose and origin. In other words, science and religion, if they remain suitably pliable and accepting, need not be opposed to each other, even if they historically have been.

Given the tendency of humans that I've observed (including myself) to want some measure of mysticism in the world, the realization that the two can coexist is significant. It allows the scientific explanation to be accepted without critically threatening that to which we are emotionally attached. In other words, yes, neurons can explain behavior, and yes, we can feel free to believe it.

If all those things don't change the results, then it's something interesting (and since psychology has relied on word association for a very long time, I'm sure the results are reasonably legitimate).

I am interested to learn how nerve cells differentiate and thus result in areas of the brain, each with a distinct purpose. Is any other organ as complex in the respect of having so many differentiated cells that are specific to a certain task? I am also curious to see how the brain differentiates into the two hemispheres.

The fact that neurons can decide what signals it wants to process and how to go about doing so is remarkable. But how do neurons decide when to alter or stop a signal? Could it be a random process? Impulses can also arise within the nervous system itself, without regard to the external environment. Is this what makes up behavior?

In addition, I was struck by the fact that there are many more inhibitory synapses than excitatory synapses. If the chicken gets its head cut off, it runs around. What are human impulses? What behaviors do our spinal cordss inhibit?

There is increasingly less doubt in my mind that it would be feasible for the work of the neurons to control even our most complex behavior, but I'm not sure if that is true. I admit that I want to maintain some mysticism, despite the fact that it intrinsically seems to me that brain MUST equal behavior, but I am finding it rather difficult to come up with situations that could possibly justify this stance. My initial hesitations had concerned the existence of God and the idea of infinity-- things that humans have obviously never experienced firsthand (ok, so the God example is debatable, but you get the general idea). In this sense, I wonder where the neurons fit in, as well as the I-function, and once again old Emily's views on the Brain vs. the sky. In discussion with friends, I was offered the explanation that humans had no other choice--> i.e. if they weren't controlling something, then someone else must be, and that if they couldn't see the end, then there must not be an end. These responses certainly make sense as even with these rationalizations available, humanity as a whole has certainly managed to maintain a certain level of frustration with the workings of the universe; the frustration felt by those who developped these theories and theologies must have been tremendous compared to our own. On a scientific level, it is possible that the paths used to explain regular, mundane cause-effect relationships were just applied in a slightly altered way. I'm still not sure if I am convinced by these solutions to our questions, but they are possible. I can imagine aspects of behavior forcing us to accept things we cannot experience, and I certainly don't feel that religion or God or mysticism is the answer--->there is something there, in our combinations of inhibitory and activating neurons that is capable of these concepts. Even if there is something more at work, in terms of the soul or true love, etc., I feel as if the brain is potentially complex enough to hold all of our behaviors within itself.

It is interesting that signals activate responses through a relay of depolarization reactions down the concentration gradient of nerve cells. The depolarization process involves amplification of a signal or a large enough stimulus to create an action potential, but what actually happens to the signals that don't become activated?

If we knew and could experience all of reality, we would be a sad people. Would we still be searching for the functions of the nervous system in order to understand that brain=behavior? Not knowing is in itself a challenge that brings excitement. I don't know if I would want to know everything there is to know about the nervous system. As Claire put it, "mysteries are never fun when they are solved." Maybe mysticism, like faith, should be accepted as valid...

Call this puzzle mysticism, God, an amine, a perinatal hormone, or an "intentional" collision of nerve endings. In the meantime, I think that we should all strive to integrate all possiblities and be willing to blemish whatever comfortable constructs we may have established thus far. I mean, if we can have silencing thunder and tears of joy, why can't we have simple complexities or even a mystical science?

the varios debates in the field of artificial intelligence, for me, have shed a lot of light on these difficult issues. for example, it's possible to create a neural net that can "learn" something simple over time. it's also quite easy to program a small robot that will successfully find its way through a maze, or to design a more complex one that will accurately deliver mail throughout a high-rise office building. the bottom line is: complex, "intelligent-like" behaviors can emerge from very basic programming and circuitry. does it really matter that the machine isn't "thinking" how we think we think inside our brains? if elementary school kids can work with a Lego Mindstorms set and build robots that perform simple, intelligent tasks, i think it's entirely possible that our inner neurological network is directly responsible for own complex behaviors.

it fascinates me how much/little of the world we experience through our senses and how much goes on that only other animals can perceive. we think of ourselves as the most evolved of animals, and yet the rattlesnake's vision allows them to see in the dark, while we remain stumbling around in confusion. i guess it's that the rattlesnake's survival is contingent upon its ability to prey on animals in the dark, while to us, it would merely be a convenience. has our ability to develop such gadgets as the flashlight hampered our evolution into more convenient beings? i wonder how much our brains make physical evolution unecessary and how much we have to think less about things because others of our species have developed computers and such to do it for us. it just seems as though our mind's capabilities really is guiding our behavior, despite our attempts to explain things at a neurological level.

The fact that proteins are tailored to respond to certain stimulus helps explain how feelings arise. There are different ways the proteins in the neurons of the skin allow the permeability to change, thus allowing APs to signal. For example, some neural membrane proteins change permiability due to pressure, temperature, pain, etc. This is a telling explanation for the neural mechanism. Still, this only explains one half of the nervous system. I still do not know how the neurons in the nervous system integrate these signals, gather information, and send signals back out..especially when those signals are influenced by actions and experiences of the past. How this works I still have to learn...but the possibility still clearly exists for the structure of the brain to equal behavior.

The carrot and six thing is an interesting issue. I have done this and also said carrot, but i'm pretty sure that if you just asked me to name a vegetable I would have said broccoli. We categorize information in a hierarchical model, so it makes sense to me that somehow "carrot" and "six" would fall under the same higher category, explaining their association with each other. I'm not sure how this categorizing plays into the interconected boxes idea, but it seems that there is rooms for complications to the model that we have not considered.

So yes, the key to understanding behavior lies in the study of the properties of neurons and particularly the sites at which nerve cells communicate.

I’m sure there is a way that the smallest boxes are capable of showing both simple and sophisticated aspects of behavior. It all depends on its particular duty and how it is identified and interpreted. I guess what I am trying to say is to imagine interpretation from all perspectives. There is no way a response to a particular reaction, which could be viewed as behavior can repeat itself in the same manner or maybe it can. This is another question that comes to mind.

One thing about neurophysiology that we didn't touch on, but I wrote in my notebook as a general question. Given the information we learned on Tues (2/13), how does the myelin sheath struture aid in the movement of an action potential? If some passive current flow is lost through the potentials movemnt in this structure, how then is a myelinated neuron a faster way to tranmit signals (as opposed to an unmyelinated neuron)?

I guess I will have to look that up on my own, huh? I hear others screaming against the "dry" stuff...

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