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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.
What kinds of new understandings, and new questions, arise from thinking about phenomena related to the blind spot of the eye?
Another thing you might want to write about are any thoughts triggered by our conversation about Simon Levay's Haverford visit this week. If you weren't at the talk and want to see more directly what he had to say, there's an article, Sexual Orientation: The Science and its Social Impact, available on line.
As for where we are in the course, what are your reactions/thoughts/questions about the relation, as it has emerged so far, between the "picture on the retina" and the "picture in your head"?
some interesting questions arise as we take apart vision step-by-step. how do retina's detatch; how are they repaired? what about light sensitivity? nocturnal vision?
The other guess relates to corollary discharge (again). Let's think about a point light source that hits a single photoreceptor. When the photoreceptor detects the light, it enhence a signal that travels all the way to the visual cortex. In the brain, a particular part interprets the information sent from the single photoreceptor. At the same time, this part of the brain may send a corollary discharge signal (?) to the neighboring region, telling what kind of light the photoreceptor absorbed. Based on the corollary discharge signal, the brain expects what should be seen in the blind spot; the same image should be seen in the blind space and in the region right next to it. In our experiment with a dot and a cross, the dot disappeared because the reflected light from it fell on our blind spot. So, the brain "created" the image of a white paper, because the photoreceptors right outside of the the blank spot brought the sensory input of the white paper.
Why does the brain create an image to cover up the empty space? I understand that it would be very distracting to see blank spots all the time, but is there any evolutionary reason behind it?
Vandana mentioned the limbic system as being involved in the smell-memory association; I also encountered many references to the limbic system in my research, and was left feeling fairly confused about what it actually is. People have described it as a center that influences memory and emotions, but this definition seems very vague. (This is not meant as criticism of Vandana’s paper, by the way.) Interestingly, in my browsing I came across a researcher who totally rejected the limbic system model. He said he believed it was someone’s fabrication that served to simplify brain structure. And what does it mean when people refer to the limbic system as being a “primitive center” of the brain?
The results of Alan Hirsh’s study were surprising to me. I would think people exposed to good food smells throughout the day would experience increased hunger. Wouldn’t these smells suggest to the stomach that it should prepare itself for the arrival of something good? Interesting to learn this is not so. I’d like to know more about this mechanism.
I also found the idea of biofeedback mechanism very interesting. Does this mean that we can cure ourselves of diseases? I guess we don't have much control over outside influences, like viruses, but things like cancer or even simple things like headaches, can we will ourselves to not get them? So many questions...
I had always thought that headaches were caused by the constriction of blood vessels in the head (though I am by no means sure of this fact) and therefore was interested to read that with migraines it is the dilation (expansion) of blood vessels that then irritate nerve endings and cause the pain that is experienced...since it is a loss of serotonin that is at least in part responsible for this dilation, I wonder if SSRI (serotonin-reuptake inhibitors) used to treat depression would be helpful...it was a treatment not mentioned.
The eye is one of the most important senses and organs. Many of us even take vision for granted. Color Blindness is one of many diseases that effect the eye. What message is being sent or lack of that effect people with color blindness? We all are familiar with the color blindness test were we see color patterns and try to distinguish symbols in either blue and yellow or red and green. So a green object may appear brown. Color blindness is caused by abnormalities in the pigments of the retina’s cones. This disease is most always present from birth. And more males than females are color blind. And the condition can not be corrected, but it does get worse.
After searching the web some on the basic questions I had seemed to be answered. Color blindness is inherited. So if a color-blind man and a women who has no family history of color blindness have children, their kids will have normal vision. Their daughters will carry the gene for color blindness, and may pass it on to their children. Also if a woman whose father is colorblind and a man with normal vision have children, each of their sons has a fifty-fifty chance of inheriting the disorder. A little bit of genetics there, but it answered some questions as to why more men have this disorder than women do. But what’s really going on? I mean most colorblind people probably don’t even realize that their eyesight is defective. And if they confuse red and green for example they may only be able to tell traffic signals apart by their brightness. So most people probably stumble on the fact that they are colorblind. Behavior implications can cause problems, like the traffic light and just like all conditions I am sure there are restrictions, but how about the feelings and moods that individuals with color blindness have that are different than normal vision. What types of effects does this pose? When an individual lives in a black and white world (as some color blindness can be) as compared to a colorful one?
I had really not thought about how important smell is to survival. I guess that, like most other people apparently, I sort of took it for granted. But, reading this paper made me think about it in a different way and so now I see that it is critical to our functioning. I learned several new things about the sense of smell. That it is one of the oldest senses, for example. And that we have 1000 sensors that are able to distinguish between 10,000 odors (since each odor can be sensed by more than one sensor and each sensor can pick out multiple odors). Also, that smells go to several centers of the brain relating to taste, memory, and conscious thought. Finally, I was intrigued by Brown professor Trygg Engen's theory that one's designation of an odor as "good" or "bad" depends on a prior memory of that particular scent.
I guess if smell functions as an "index key" to accessing memories in a speedy manner for purposes of survival, it makes sense that it has evolved to be a powerful sense.
The first answer is that heat and temperature are not the same thing. Although the coals are at a TEMP of 1200 degrees, they don't conduct heat that well. Think about it this way: when you are baking someting at, say, 425 degrees, the metal pan the cake is in AND the air in the oven are both at this temperature. If you touch the pan, you will surely be burned. But when you reach into the oven, the air, which is just as hot, doesn't burn you. So a person couldn't walk over metal heated to this temperature since it conducts heat well, but could walk over the coals in firewalking, since the wood doesn't conduct heat well.
The second explanation was that when one walks on coals, they do it quickly so that only the bottom layer of sweat is evaporated. (There is a scientific name for the principle, but I forget it now). Some sites suggested that because of this, one needed to have fear (IE get sweaty feet) in order to keep from being burned. However, some sites had personal stories talking about standing on the coals and not being burned. It is an interesting possibility to consider.
It seemes, from what I found, that people don't in fact get burned when firewalking. The reason for this seems to be able to be explained by principles of physics and chemistry. In fact, one award-winning physics priofessor actually firewalks for his class to hel teach the difference between temperature and heat.
My other comment has do do with the brain "making stuff up". I am time and time again suprised about how much of our reality isn't the reality of our physical world. Signals starting in the middle of the box, getting only some sensory info that exists in the world, and our brain making up stuff convince me more and more that there is no actual reality and that everything IS the brain.
The second thing I wanted to comment on was the Music and neurobiology paper. I was thinking of doing a similar topic for some time because this is an area that fascinates me because I am a musician. The idea of a musicians brain being "more connected" and more interaction between hemispheres as opposed to those who just listen to music was really interesting. And then the fact that studies seem to suggest that musicians have more corollary discharge and corrolation in general between conscious and unconscious, emotional and mechanical centers would be a wonderful study to be involved with I think. I mean musicians are often characterized as being able to "feel more" and are in touch with art expression of emotions and such so if there are actual neurotransmitting connections between all sites involved then maybe there is a measure of truth. The comment that really got me was the one that related musicianship to intelligence I would be really interested in what studies they have done to work on this one.
The last thing I wanted to ask, which may be a silly question, but if vision and the function of the eye are such an integral part of the body and the brain then why do people get squeemish with contacts or dissection of the eye. Does this have to do with the conscious mind's perception of "eyes" being different than an internalized awareness in the unconscious mind?
Still, obviously, we do have eyes. And it seems to me that the fact that we do have eyes suggests that there IS an external world out there that provides a blueprint for the brain to fill in the details. So I take the existence of the eye (both human and other animals) to be evidence that there is some kind of external reality. However, what that is seems to be anyone’s guess. Again, we know that the light rays that enter the eye do so because there are appropriate photoreceptors on the retina. So, if we don’t have photoreceptors for certain light rays, no image (however imperfect) will be imprinted on the retina. Cats and snakes, for example, are able to “see” things that we cannot. Cats can see in the dark; snakes can see infrared rays. So we know that there is a lot out there that we are not “seeing”. But how can we explain why we all seem to see essentially the same world? If the brain makes such a large contribution to vision, why do all of our brains seem to see the same things?
Another issue that I have been thinking about is the neuriobiologist who came to Haverford to speak. The more and more I hear about him, the more and more I feel that I need to defend his studies. Although I was not present for the talk, after taking this course, it appears that people overlook the fundamental differences of being different. Indeed that is repetitive, but we can all agree that our brains work differently and that human brain activity constantly changes physically what our brains look like. We also can agree that we have trained our minds into a certain mold. I was told that plenty of humanities teachers have not been very accepting of this neurobiologist's theories in that it upsets them to think about homosexuals' brains as being shaped differently. Part of the discontent has to do with the fact that they never consciously connect the implications of homosexuality with a physical difference. As neurobio students, we are all right with saying that everyone's brains function differently and independent of others, but certain ways of thinking probably induce some similarites in size, shape etc on those people. In this sense, there can never be a norm to the structure of a brain, there can only be healthy brains. What I do recognize is that fact that these profs probably see this theory as being used for ammuninition in an anti- gay way as justifying that these type of people are biologically abnormal and different. Yes, that does complicate the matter because the fabricated norm does not really exist since no two brains are identical. But then how can we models of brains ever work since there is no standard? I believe it must be enforced from the start that every brain constantly changes- not just in the emotional sense or academic sense but physically as well.
On a side note, I personally am a philsophy student who argues tooth and nail for the validity of science and scientific process. However, there seemed to be a current of thought in class on thursday which indicated that empirical (natural) science was immune to the types of criticism that humanities or social sciences are vulnerable to. The general idea was that natural science somehow dealt in facts, and that a social science or humanities oriented critique of empirical biology was somehow missing the point, or at least belonged somewhere else. I certainly don't think that empirical science deserves any privilege, and that in the interest of honest and complete inquiry, that empirical science should also hold up against a wide variety of criticism both social and philosophical. Certainly scientists are not functioning apart from theri social settings. Certainly also, i have encountered alot of very unsound "scientific" conclusions from empirical scientists who i think could have benefited from a bit more philosophy. Just as much as i think philosophy of mind has benefitted from empirical discoveries in both neuro science, and computer science, Biology (especially neurobiology) could benefit from philosophy and social sciences.
I do think animals sense pain because of experience I have had with them. On a personal note, I had worked at a summer camp, where I had many excursions hiking and canoeing. On many of these trips, I met other hikers on the way who had dogs along with them. One pair of hikers who had a dog with them. tied the dog to a tree and went off somewhere else. I could tell the dog felt neglected since she looked in the direction that the people had walked off. Her eyes had a similar look of concern as one that a young child would have when left by an elder. Though I cannot speak for the dog, a friend and I approached her and tried to comfort her. She seemed to feel relieved that there were others there who noticed and cared.
I find it interesting that we as humans can often judge animals and say that they are not conscious or not able to reason and use language. It may be that their language is different from the one we use, but many animals are also social animals and many of them have survived much longer than humans (on an evolutionary time scale). I think it is quite impossible to say that animals are unable to sense pain, when we as humans who study them already have preconceived notions and judgements about them from the dominant view we have about ourselves as humans. It might be that it all depends on our definition of sensing pain. In that sense it all depends on the outlook of the person who is observing, considering that the person already has previous ideas from others or from the social setting he/she was exposed to.
So that leaves the question of what is reality? Reality seems to me to be a reflection of who we are, as humans. That is, we are not nocturnal, for example, so we lack the necessary receptors for clear night vision. Our eyes have clearly evolved to be most effective in the daytime and on land. Other animals have eyes that allow them to survive in much different environments. So who has the clearer picture of reality? The snake with infrared vision? The fish under water? It seems that reality is simply determined by the types of receptors a species has. When we "hallucinate", it seems to me that we are getting a glimpse of what of a reality we would experience if we didn't have the mediators in our eye, or the brain. But we can also see that people who hallucinate have difficulty operating in this world as humans. So the lateral inhibition network gives us a picture of reality that allows us to survive. This picture is more "real" to us than the information we're getting about it from our eye.
So we can say at least one thing about reality now, that it has things in it that are well-defined, for humans, by their edges, and that what is "filled in" by the brain is not a defining feature. The snake would say that reality is well-defined by the amount of heat coming off or not from another thing. So, again, I wonder, who (what animal) has the picture of reality that is most like actual reality? Can we know this? Our picture of reality seems to serve us well, but clearly we are missing a lot. What we are missing could be the missing links in answering the questions that have dogged us for centuries - everything from the nature of consciousness, to the existence of extraterrestrial life, to the possibility for world peace. Perhaps the most human trait of all is the desire to go beyond what evolution has given us to get a more complete picture of reality than what our limited senses can provide.
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