Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!

Remote Ready Biology Learning Activities

Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.

From Serendip

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?

Name: Paul Grobstein
Subject: week 10
Date: Fri Apr 7 14:38:24 EDT 2000
Your second web papers (at least most of them) are now posted. There is an impressive diversity of topics; have a look. And if you feel like commenting on one or another (probably not your own) in the forum area this week, that would be fine.

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"?

Name: hillary bobys
Subject: perception vs. sensation
Date: Sat Apr 8 09:44:30 EDT 2000
i am very interested in ideas of perception and how this seemingly higher order behavior relates to sensation. sensation is the detection of stimuli in the environment. perception is the recognition, integration, and interpretation of these sensations, and there for takes place in one particular part of the brain, the association cortex. however, these two processes can take place one without the other. for example, general anasthesia (pardon the spelling) closes down perception, but sensory neurons are still firing. and perception occurs without sensation in phanton limb. (speaking of which i found a website on phanton limb some of you may be interested in at in the previous journal). do you all have any thoughts on this?

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?

Name: hiro
Subject: filling the blind spots
Date: Sat Apr 8 23:44:50 EDT 2000
Why don't we "see" a blank spot even though the image on the retina has a blind spot? I have two guesses. For the first guess, I think that the lateral transmission by horizontal, bipolar and amacrine cells plays a key role. Horizontal cells recieve action potential from several different photoreceptor cells and transmit the signal to some bipolar cells. Then, the bipolar cells synapse to several different amacrine cells, which transmit the information to the ganglion cells. From the ganglion cells, the action potential moves through the optic nerve to be finally integrated by visual cortex in the brain. Because of the network between the photoreceptors and ganglion cells, the information sent by a single photoreceptor ends up in several different ganglion cells. It is not like one ganglion for a specific photoreceptor. Also, the signal issued by neighboring photoreceptors may reach the same ganglion cell and hence, "blends" with each other. I am thinking that this "blending" caused by the lateral transmission may be able to "cover up" the blind spot in our brain. The information sent by the photoreceptors around the blind spot may interact with each other through the network and generate a blending image that fills the empty space.

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?

Name: laurel edmundson
Date: Sun Apr 9 20:02:45 EDT 2000
Vandana’s paper on scent and memory was intriguing to me. More than any other sense, olfaction really does seem to have transcending powers. For me, odors mostly provide positive associations…or at least not negative. There have also been times when I haven’t been able to identify what I was remembering.

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.

Name: Soo Yi
Subject: Weekly Essay #9
Date: Sun Apr 9 22:35:20 EDT 2000
I just read over Yun-Wen's paper on firewalking and found it fairly interesting that these people can stand to walk over 1200-degree coals. I mean, I can understand that they are changing their set points and, in a way, "controlling" their minds to not feel the pain but nevertheless, aren't they charring their skin? No matter how much control you have over your mind and body, you can't control the physical things around you -- 1200-degrees of heat is going to burn you no matter how good you are with controlling your set points. When these firewalkers are said to walk over the coals "successfully", does that mean that they didn't get burned or that they were able to control the perception of pain?

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...

Name: Melissa
Subject: migraines
Date: Sun Apr 9 23:26:13 EDT 2000
I just read the paper on migraines and was really fascinated by it. I had a personal interest in the topic because my dad has, since I was young, had these really terrible headaches that debilitate him for the entire day...the two things that 99% of the time trigger these particularly awful brand of headaches are 1) if he sleeps in on the weekends past 9 am, regardless of what time he went to bed...if he went to bed at 5 am and woke up at 9:30, he would be debilitated all day... and 2)if he drinks wine (either red or white)..even just 1/4 of a glass. So i was so interested to read both of these things on the list of possible triggers...I definitely agree that from experiential knowledge, these are genetic...and I think even the nature of which triggers cause the migraines might be genetic as I find myself occassionally getting hints of the headaches if I sleep in late (though of course that could be the power of suggestion!)

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 was a treatment not mentioned.

Name: Maria
Subject: Vision
Date: Sun Apr 9 23:33:57 EDT 2000
The idea that the eye does not actually see objects, but instead it sees the light they reflect or give off is intriguing and can pose many questions. We experience it everyday. We are not blind because we can’t see in the dark. Rather the eye can see in bright light and in dim light, but it can not see in no light at all.

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?

Name: Elissa Braitman
Subject: Smells...
Date: Mon Apr 10 12:40:50 EDT 2000
Interested in learning more about how smells trigger memories, I read Shigeyuki Ito's paper "Smell and Memory."

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.

Name: Laura
Subject: firewalking; reality
Date: Mon Apr 10 14:02:40 EDT 2000
I first wanted to respond to the question about whether or not peoplle get burned when firewalking. I was interested in writing my web paper on this topic and did some reasearch, most of which explainned the answer to this question.

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.

Name: Andrew
Subject: vision
Date: Mon Apr 10 17:18:55 EDT 2000
I found the experiment with the dot and cross very interesting. I am wondering how much the brain is able to actually "make up." If the optic nerve were larger, and there was a larger blind spot, would the brain be able to fill that in? When people get older, their vision becomes worse; often, this worsened vision stems from patches of blindness, I suppose that they are similar to the optic nerve blind spot. For these people, does the brain fill in the missing parts? Is it possible that a person will not recognize how severe the blindness is because of the brain? I am also wondering about laser eye surgery. I think that it corrects vision by reshaping the cornea so that the light rays are reflected on the retina in the correct place. A possible side effect following this procedure is night glare. Why does night glare occur? Is it because the cornea has been changed and the brain needs to adjust to the new vision, or maybe, after the procedure, a different amount of light enters the eye?
Name: amse hammershaimb
Subject: the sistine chapel
Date: Mon Apr 10 21:14:24 EDT 2000
i have always known that the brain makes up images (i noticed this particularly when i started driving and knew what the signs said from a distance i could not possibly see from). i was surprised to learn that the retina has a blind spot - the optic nerve. this fact greatly disturbs me. i have always been obsessed with studying art and came to bryn mawr specifically to study art history. i have always spent my spare time looking at paintings and prints - buying magazines and books just for the pictures. i consider a bad movie worth paying 7.50 for because i saw a particular color i liked in the commercial for the film. i didn't look at clouds to find shapes as a child, i looked for various artists' brushstroke styles. i admit, the idea of a retinal blind spot somewhat panics me. what am i missing out on? has all my studying been pointless? i can't stand the idea of anyone loosing his/her eyesight. it is the one sense i could never do without. i am choking as i write this. what would your lives be ike without visual indulgences? the whole thing reminds me of the sistine chapel. when it was covered with varnish and was "dark" and dirty, michaelangelo's work was examined by art historians world wide. the very nature percieved of the man was based on these dark colors. when the chapel was cleaned, art historians the world over felt that the chapel was "truer" to it's message before it was cleaned. They were enraged at the vivid, venetian colors michaelangelo truly used. how would our persepctive of the world change if we didn't have the blind spot at the optic nerve head? since class, i cannot shake the panicked question : "what am i missing?" as usual, i will jump ahead of myself. what happens in the retina and the brain to cause color blindness, dyslexia, and hallucinations (drug induced or otherwise)?
Name: Cammie
Subject: Miscellaneous
Date: Mon Apr 10 21:20:27 EDT 2000
First off in response to Melissa yes SSRI's are being tested for their effects on ridding people of migraines and so far the results look promising. I did not include this in my paper a) becuase I found the site after I had basically finished my paper and b)because I didnt want to laundry list. But you are absolutely right.

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?

Name: anonymous
Subject: back to seeing thunder
Date: Mon Apr 10 21:53:44 EDT 2000
All this talk about the eye takes me back to the time we talked about the crossing of the optic and auditory nerves--that whole see thunder, hear lightning thing. Doesn't it seem a little bizarre that we have such a specialized, intricate apparatus for vision but we could also "see" with our ears if only our signals went somewhere else? It just seems weird that we have such complex machines like eyes and ears that discriminate so well between the subtle differences in visual and auditory inputs respectively, if one system do the other's job even if only in theory. That thought is counterintuitive for me, and i'm still struggling with it. If seeing is so much of just action potentials going to a visual cortex vs some other sensory cortex, why is it so consistent from one species to another? The way the whole optic nerve and auditory nerve crossing argument was presented made it seem so arbitrary, and perhaps it is, but i wonder why we don't see more variation in that regard. Maybe i am simply ignorant though--are there any animals that see sound waves and hear light waves? Might not there be some good reason why we see what we see, and most of us use our sensory organs to translate similar forms of energy into similar sensory information? Of course I'm implying that what naturally and consistently exists is the good or best way to be, and that isn't necessarily true.
Name: Stephanie Wall
Subject: the eye and reality
Date: Mon Apr 10 21:56:56 EDT 2000
I am surprised to learn how much contribution the brain itself makes to vision. Most of what we see seems due to what the brain makes up in relation to the picture on the retina, not the picture on the retina itself. So “seeing” has at least as much to do with the brain as with the eye. And seeing (as done by both the brain and the eye) may not have much to do with what is out in the “external” world. If we can’t trust what we see to be reality, then how do we know what reality is? Why do we have an eye if the brain fills in much of what we “see”? The anatomy of the eye leads me to believe that there is a relatively large margin for error (in terms of focus, for example), versus say the margin for error in other organs such as the kidneys. Seeing an object clearly depends on rays of light being refracted by the lens and cornea so that they converge on the retina at the same place. If a ray of light is not bent enough (or too much), then our vision is blurry. A lot of people wear or need glasses in this world! And what is the evolutionary reason for having a “blind spot” on the retina (where there are no photoreceptors)?

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?

Name: Jennifer
Subject: perception
Date: Tue Apr 11 00:02:35 EDT 2000
As we talk more and more about the connection between the "picture on the retina" and the "picture in my head," I keep coming back to a somewhat alarming conclusion. There is no direct connection from our brain to the outside world. Every sensory imput is somehow filtered or changed to the point that we don't even know if what we are seeing, tasting, smelling, etc. is actually what exists. We assume that it is, because that is the simplest conclusion. However, we have no definite proof of the existence of anything around us, including our own bodies. Although the chance is slight, we could simply exist as a "brain in a vat" as philosphers say, with no physical body or interaction with our envirionment, living solely in a world that our brain has perceived. The thought both scares and exictes me. I think we almost have to assume that that is not the case though, or the study of science in general is useless. Science is based on observation, and if we cannot trust our observations, then we cannot trust the conclusions of science.
Name: christina
Subject: retina probs
Date: Tue Apr 11 01:44:10 EDT 2000
I was recently diagnosed with a convergence deficiency. The problems with my eyes began in my first year of college. I experience a great deal of eye strain and I constantly end up reading the same line of the text. After receiving a very light presecription for my glasses that seemed to magnify the words, I became once again extremely uncomfortable while reading. So, after several tests, my optomoetrist concluded that I have a convergence deficiency. I've been trying to develop the mechanic of this problem. When he explained what was wrong, I understood that problem dealt with the coodination of my two eyes. He told me that exercising my eyes would help me. One exercise included what we did in class which was hold a pen near our noses and then focus on an object in the distance and then focus back on the pen. I suppose I am trying to make sense of how this will help the images forming at the back of my retina. The way I understand the retiina is that is possible for the image to be formed on one receptor cell composed of different converging images that eventually land on this one receptor. Is my problem occuring in the process of forming one picture onto the recceptor cell? It seems though that is this were the case, how come the world is nevery blurry and I can see clearly at most distances? But even more confusing is the fact that I am more comfortable using one eye while I read than both when I do not have my glasses. Does this mean that my brain is more ocnfused when I use both eyes and cannot form one picture?

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.

Name: Andrew Jordan
Subject: Science...
Date: Wed Apr 12 02:48:03 EDT 2000
I think it is interesting that the fact that our brain fills in some detail is the cause for worry about objectivity in neuro biology, while in philosophy, the fact that the brain fills in sensations is not the reason that we should be concerned about losing some sort of sacred contact with the world, as sensations are strictly caused, and therefore figure into the natural (as opposed to the rational) world. The philosophical concern is that our use of linguistic concepts somehow have no bearing on the world, and that therefore our claims (yes even rigorous scientific ones) are somehow not justified or have no bearing on an external reality. That said, i don't think the form of skepticism that says that for any given perceptual "fact" our brains could be making it up, should really be a worry. It would be more troubling, if somehow our brains were making everything up, as in the brain in the vat scenario, but that also shouldn't be a particularly troubling form of skepticism, because to the skeptic we can always reply, that yes, we may be brains in vats, but we might not be. there is no necessity to the argument that we can't get things right, whether our perceptions are real or made up is simply a matter of a particular situation in which we are living. Basically even extreme forms of this kind of skepticism (such as brain in vat fears) leave us where we already should know we are, that is, in a situation where we cannot be certain about any empirical claims. The more extreme form of skepticism, which i think does give us cause to worry is the one that says, even if everything goes right (i.e. we aren't brains in vats) we still can't get things right, as getting things right is somehow impossible by virtue of a gap between linguistic utterances and the way things actually are.

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.

Name: Vandana
Subject: sense of pain
Date: Thu Apr 13 20:38:13 EDT 2000
I found Andrew Jordan's paper on Pain Without 'Pain' interesting. Though I am not well educated in the field of philosophy, I had studied some of Kant's work in a humanities class in my first year of college.

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.

Name: Stephanie Wall
Subject: who's reality
Date: Sat Apr 15 23:56:15 EDT 2000
I am intrigued by what we are learning about the eye, particularly about the relation between what the information the eye takes in and "reality". Not only do we have a blind spot, but we see only the points of light contrast in the world, the edges (between dark and light) of the world. The brain fills in the majority of what we see. It makes sense that this phenomenon called "lateral inhibition" gives us a more stable sense of reality. As we said in class, if the ganglion cells reported light intensity to the brain, the world that we would see would be constantly changing to the point of chaos. The lateral inhibition network gives us a stable sense of reality. A "sense", that is.

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.

| Course Home Page | Back to Brain and Behavior | Back to Serendip |

Send us your comments at

© by Serendip '96 - Last Modified: Wednesday, 02-May-2018 10:53:15 CDT