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Neurobiology and Behavior, Week 11

Paul Grobstein's picture

Welcome to the on-line forum associated with the Biology 202 at Bryn Mawr College. Its a way to keep conversations going between course meetings, and to do so in a way that makes our conversations available to other who may in turn have interesting thoughts to contribute to them. Leave whatever thoughts in progress you think might be useful to others, see what other people are thinking, and add thoughts that that in turn generates in you.

You're free to write about whatever came into your mind this week, but if you need something to get you started ... Our explorations of the sensory side of the nervous system have turned up evidence of significant motor motor involvement in perception, a lateral inhibition network, and  an unconscious part of the nervous system doing some significant filling in and guessing to create the picture in the head.  To what degree does this help or not help in our search for tools to go from neurons to behavior? What new questions does it raise?   


JJLopez's picture

Our eyes are like mini-cameras

I thought Thursdays class on our vision was really interesting.  I learned somewhere before that what we saw is upside-down or something like that and our brain sees it right-side-up.  I always thought of vision as an image going in through my pupils and bouncing back like a mirror somehow into my brain.  Apparently, we do have some type of "mirror" like function in the eye, but to me now vision works more like a camera taking snapshots of what it sees.  Now it makes sense to me why when I look into someone's eyes that is looking at me, their eyes are moving rapidly side to side up and down all over the place but still are looking at me just like I am looking at them.  Also, I thought it was interesting learning about nearsighted and farsighted vision.  I am nearsighted and wear glasses to see far away.  What I have noticed is that when I am not wearing my glasses I squint my eyes a lot, I guess now it makes sense that I do that because I am trying to focus my vision on the item I want to look at clearer.  It fascinates me how our eyes are able to adjust to wearing contacts.  The eye doesn't feel the contact in the eye and the eye uses the contacts exactly like it does regular glasses, most of the time I forget I have contacts on until they start to get dry and my eyesight starts getting blurrier.  How don't contacts get dry sooner, or move out of place more often, since our eyes are moving around so much and we are blinking all the time?


yml's picture

Can't trust my brain

I found McGurk effect, Blind Spot test, and Checkerboard exercises in this week’s classes very interesting and fun. Examples always make abstract ideas that can’t be examined by eyes more approachable and easier to understand. But in these examples, we could even do it to ourselves and see it happening and it was really fun and educational at the same time. However, at first they were just fun, but then I thought “I can’t trust my brain!” I want to see and things the way they are and don’t have them changed by the time those information reach my brain. I want to hear “dada” when he says dada, I want to see a black dot if it is on the paper, in front of me, and I want to see the two boxes on the Checkerboard as same colors when they are same colors. I always assumed “healthy” brain to be more “absolute” in receiving information, but in fact I feel very vulnerable to outside effect and can’t trust what I see or hear.


lfrontino's picture

Vision and Reality


From a physiological point of view, I really enjoyed learning about the eye and how the different parts function together to allow us to be able to see. Like with action potentials, this course is teaching me to appreciate all of the extremely complex mechanics that go into what we take for granted as simple actions such as seeing and vision.

The idea that our brain has a 'blind spot' has always sort of creeped me out. While I admit it is a useful evolutionary feature for our brains to fill in the missing pieces and make assumptions, I can't help but worry about what would happen if it were wrong? Could there be thing around us that we are not seeing at all? I wonder if this has anything to do with our incapacity to view things that are on different wavelengths. Our brains are just not equipped for all types of tasks.


egleichman's picture

Weird things the brain does

 I had surgery on my eyes this past summer to finally correct a long-lasting case of exotropia (lazy eye).  All my life I had convinced myself that if I just concentrated on not letting my eyes "wander," I could fix the problem and avoid surgery.  Imagine my surprise when the optometrist revealed that the problem had nothing to do with the eye muscles and everything to do with my brain -- especially when the surgery involved tightening the muscles behind my eyes.  Apparently, the brain sends a signal to the eye to wander.  As soon as the eye wanders, it goes blind; in other words, if my eye wandered up and left, I still wouldn't be able to see anything in my upper left visual field with that eye.  To correct the problem, they could, theoretically, fix that misguided brain signal -- but the easier fix, naturally, is with the eye muscles.  So the brain signal is still coming, but the muscles are tightened, restricting wandering.


When one of our eyes goes "blind" like mine did, our depth perception is compromised (Try going through a day with one eye closed).  Why, then, was I able to grab things in front of me, even when my eye "wandered"?  Why was I allowed to drive?  Where is the control center for our depth perception?



Schmeltz's picture

Fovea of the ear?

The discussion of the fovea kind of blew my mind on Thursday.  Throughout the day, I kept looking around myself and realizing that the picture I had in my head was mostly a construction of my brain since my eyes were limited to a very small distance of focus.  I began to imagine what life would be like if our brains did not have the capability of filling in the missing pieces. Basically it would be really boring I think, but also frustrating. How would we be able to exist in this world with ease if we could not create what feels like an instantaneous picture of our world? I know it is possible, and that the nervous system can make sense of the world through other senses, but I would imagine that it would be quite frustrating if we could not fill in these blind spots. I also began thinking that we are all visual artists in some way or another because we all have the ability to create these visual compositions of the world surrounding us.  I was showing a friend the cross/dot experiment we were doing in class and it blew his mind as well. He brought up a question that had not occurred to me: do our auditory systems do the same thing? Do we have a the equivalent of a fovea in the organization of our ears? From the bit of exploration I have been able to do, it seems like we do.  The pinnae is the area of the ear which is responsible for focusing on sound. Some animals, like dogs, have a movable pinnae that correlate to a wider range of sound detection.  So, it seems reasonable to think that our brains are not only visually composing the world around us, but constructing auditory compositions of the world as well.  So, everyone has their own auditory/visual compositions going on at any given moment. That is amazing to me. 

"Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth."

Marcus Aurelius 

Congwen Wang's picture

What we see is what we think we see

After our very interesting vision experiment, I was surprised at how sophisticated our brain is, and how we are all constantly "deceived" by ourselves.  After class, I did that cross and dot experiment again with a piece of paper full of text, and it turned out that my brain actually filled in some text at the blindspot. This reminds me that when I was little, I once wondered why we couldn't recall every detail of a picture even though we remembered the image.  Now it all make sense - we can't recall the details because we never really remembered them. Perhaps this is why our brains can process images so fast? I often play with Photoshop, and it sometimes frustrates me because the image files can be very space consuming. Apparently computer softwares don't use the same image saving mechanism as we do. I guess our brains must be very good at selectively storing certain parts of images, so we could have an outline of the scene but wouldn't be fatigued by those trivial details.

And the checkboard. I tried to drag the B square in and out of the board very slowly, and was amazed to see (at least I felt I did) the gradual change of color when it was passing through the grid. I think I can never look at my brain the same as I used to anymore.

Saba Ashraf's picture

Senses/filling in information

             In class I found it very interesting to learn about how certain senses are affected by different senses such as hearing being affected by sight. I always found it easier to understand what a person was saying as I saw them talk, but I never realized how much sight affected hearing until we saw the McGurk effect in class.  It was also interesting that while hearing the McGurk video without sound, the class unanimously had heard “ba ba.” However, when we saw and heard the video at the same time, some of the class had heard “ga ga” and others had heard “dha dha.” Also, the idea of different senses affecting each other does make sense if you take a look at other examples such as the smell of a food affecting the taste of it. I wonder if other senses have a strong relationship with one another besides sight and sound and smell and taste.

 I had also found the experiment with the cross and dot very fascinating because I wasn’t aware of the brain’s ability to fill in what’s missing. It was surprising to me that the brain knew exactly what to fill in and not fill in.   For instance, when we were shown the dot with the two lines through it, I would have guessed that you would see two separate lines, which happened to be false. The brain had the ability to remove the dot and create a small line connecting the lines that were originally there.  I wonder if all individual’s brains are filling in the same information for what’s missing or if there is difference in the way other’s brains are filling in certain information.   

natmackow's picture

Thinking in Pictures

    In class this week we discussed that while sensory signals constrain what you can experience, they don’t fully define it. The nervous system interprets what we see and how we see it. The brain constructs the world around us, given visual or auditory input. So how do we know that what we’re seeing is really true? Is there any “correct” way of seeing the world?
   Autistic individuals have been known to see or feel things differently, and more visually than other individuals. This does not mean that their eyes “see” differently, but rather that their brains interpret information differently and that this information is integrated into the brain with perhaps a greater connection to their thoughts. Temple Grandin, an autistic woman who has a Ph.D in animal science and works to design more humane methods of holding livestock, has described herself as a “visual thinker”. In her novel, Thinking in Pictures, she says,
    “Spatial words such as "over" and "under" had no meaning for me until I had a visual image to fix them in my memory. Even now, when I hear the word "under" by itself, I automatically picture myself getting under the cafeteria tables at school during an air-raid drill, a common occurrence on the East Coast during the early fifties. {…} Adverbs often trigger inappropriate images -- "quickly" reminds me of Nestlé’s Quik -- unless they are paired with a verb, which modifies my visual image. {…} As a child, I left out words such as "is," "the," and "it," because they had no meaning by themselves. Similarly, words like "of," and "an" made no sense. Eventually I learned how to use them properly, because my parents always spoke correct English and I mimicked their speech patterns. To this day certain verb conjugations, such as "to be," are absolutely meaningless to me.”
    Temple’s experience with visualizing words, concepts, memories, innovations, and in effect her entire world, is similar to many individuals with autism. They seem to understand better what they see (and the images their brains are capable of creating) than what they hear in conversation, or school (what we define as language). Perhaps the visual processing areas of the brain are fortified by stronger and vaster connections in autistic individuals and this leads them to rely on and think more using vision over language. There do seem to be certain advantages to thinking visually, as Temple is able to map her innovations in every possible situation, with different sizes of livestock and different variables. She can visualize mistakes in her designs and correct them, before finally writing them down on paper. She is very attuned to the behaviors of animals as well. But there are also advantages to being able to think with words, (for example, the ability to connect with other human beings). What causes the pictures seen by the eyes and interpreted by the brains of autistic individuals to be more vivid, more thoroughly integrated and more deeply relied upon in these individuals?

Here is a link to the first chapter of Temple Grandin’s book Thinking in Pictures.
Here's a link to the trailer for the movie they've made about her life. She is a fantastic woman and is considered a leader in animal welfare and autism rights campaigns.

cschoonover's picture

Vision Therapy

A few weeks ago I was reading an article about how vision therapy can help resolve behavioral problems in children. At first it was strange to me that such intense treatment of visual deficits can alter behavior. However, in conjunction with this class, it is beginning to make a lot more sense. The interconnectivity of our sophisticated nervous system implies that despite the large amount of visual input, it is worthless unless it can be integrated and understood by the rest of the nervous system. This dependency on visual input also means that once these processes start to deteriorate, the result can be devastating. For those with autism and autism spectrum disorders, this break down is the result of the confusion and fear created by visual impairment and is manifested in behavioral outputs: they become withdrawn from the world, are subject to nuances (such as “odd” walking patterns and postures, rocking, hand-flapping, etc.), and often experience hyperactivity. Vision therapists (also known as behavioral optometrists) support their practice with the notion that “vision isn’t just about eyes or eyesight but it is also something more holistic…how eyes work together and move together and process information and store information and do something with the information.” I think continuing our discussions about vision will lead to some insight as to how vision therapy can resolve some of the “problems” connected to children with behavioral “issues.” I am wondering if the processes involved in motion sickness can be applied here: if the visual input received by those with autism is not the same as what the brain expects to receive, does this mean the behavioral outputs are a mechanism to resolve the dissonance? I am not sure if they are quite the same, but it seems to me that they could be similar. I’m hoping we can delve deeper into the interconnectedness of vision and behavior.


For those who are interested, here is the link to the article I read:


rkirloskar's picture

Questions on Synesthesia

Synesthesia is a condition in which one perceives the world through the amalgamation of two different senses. For example, people are able to see a color when they hear a certain pitch. But would it be possible for the same person to hear a pitch when they see a certain color. Would this unusual perception change over time? For example, if a person heard a certain pitch and saw the color blue, would the same person see another color corresponding to the same pitch later  in life? If this were true, then synesthesia would be somewhat like a dream, which changes with our emotional state of mind.Since these neural connections in the brain causing synesthesia are random and illogical, would it be possible to undo these connections through the process of learning? If a repetitive activity is able to create a central pattern generation, which can be dismantled through lack of use, could the  neural connections causing synesthesia be dismantled?

Kwarlizzle's picture

A rose by any other name

in class we established that 'it matters greatly "what is connected to what in the nervous system' re the sensory side of this omnipotent system. We used synesthesia as an example and butressed our point by showig the McGurk effect: what we sense isn't only the function of one of our sense; it's a function of at the VERY least two of our senses working in tandem. So.....does this mean Shakespeare was wrong and that a rose by any other name wouldn't smell as sweet? (Because smell alone isn't implicated here....)

MEL's picture



I found our discussion this week about the sensory side of the nervous system very interesting. Being nearsighted, I have always wondered about how vision works and how it affects our sense of reality. I am still in awe of the blind spot test. Before our discussion I had never been conscious of my blind spot. The demonstration in class was remarkable; I can’t believe that my brain fills in the blind spot by guessing what is most likely there. I can’t help but wonder now what is and what isn’t a construction of my brain. What is reality? Although I understand why my brain must fill in my blind spot, I can’t help but feel a little bit betrayed by my brain because it is lying to me and making things up. I also found the McGurk effect very interesting. I had never realized how much of what we hear is a function of both what we see and what we hear.  


dvergara's picture

"The Doors of Perception"

Our conversations on perception are starting to remind me of when I read Aldous Huxley’s book, The Doors of Perception. Although I hated this book when I read it (I was 14 at the time) I now realize it’s relevance to my own life, and my own brain. In it, Huxley is basically writing while under the influence of drugs, and contemplating on how differently he sees the world. He was not in control of what he saw, or how he saw his surroundings because of the drugs (although I do remember his noting that if he started to think about sad things that would change his perception of things). But after our discussions, I realize that we may actually never be in control of our perception, we only assume we are.

When we heard the video in class, we assumed we knew exactly what the man was saying; however, when we saw the video, we realized our minds or perhaps our vision deceived us. (Either way, we never really figured out which was the reality) As the video showed, we don’t need to drugs to confuse our perception; our perception seems to be dependent on the mind. There is some unconscious part of the mind that meshing together all that we see or hear to give us a “reality,” leaving the I-function without access to the control panel of perception. However, why can’t we have access to this? Huxley actually gave an answer to this question, he theorized that the reason we can’t “see” everything (ie, the different things we see when under the influence of drugs) is that the unconscious purposefully discards ‘unessential’ information so as to allow us to live more efficiently; basically, if we were conscious of everything our brain did to mold a certain ‘reality’, we wouldn’t be able to function as well (or have enough time to) within that reality.


AndyMittelman's picture

I am very surprised by how

I am very surprised by how much of our perception is influenced by the unconscious factors we discussed this week. The McGurk Effect, in particular, demonstrated to me just how much of what I am seeing I am not actually “seeing.” As we discussed, when you see something it is actually the aggregation of many point sources of light. Then, our brain is taking in a series of snapshots and tying them together subconsciously. So this makes me wonder how this process actually occurs. If you imagined this from the perspective of a computer (or a camera for that matter), you would have to be continuously taking in images, sorting them based on where you had aimed the camera (where our eyes were looking), and then storing them in a short term memory. Then, you would have to be accessing this data and continually updating it, deleting the old memories and replacing them with new ones. Imagine you pan the camera around the room and then hold it still in one direction. The brain has to know to keep the older images of the surrounding area because it has not updated those views during the immobile period.

So imagine you’re in a very dynamic environment (like looking out the side window of a train). How does your brain process an entire frame of constantly changing image? In that situation, you can’t really focus on much for very long, but still you are able to perceive the intricate details of the landscape.

Our discussion made me think about those clocks that move a wand back and forth very quickly to display an image. (If you don’t know what I am talking about, check out They must work because our brain takes the images and stitches them together. If we didn’t normally store images and then reference it, we would just see single LED lights. Instead, we are able to stitch together a comprehensible image.

We don’t actually know what’s really going on in the world around us. Instead, we just perceive whatever our brain has constructed for us. Hence, there are really two ways that we could be affect what you see. First you could put on sunglasses, or look through a colored glass pane…this would affect what you see. But maybe you could also alter the way that your brain stitches together the images. If this alteration happened subconsciously (or without your awareness), is there any way you would know? Does this have anything to do with the way that drugs may affect our perception of the world? Imagine you unwittingly took a pill that caused hallucinations but didn’t affect consciousness. You wouldn’t know that you were hallucinating. If you’re hallucinating, your eyes are still inputting the same point sources of light. Despite this, you may actually see things that don’t exist. Hence, those hallucinations must be occurring in the processing of the visual input. Our brain might take in point source information from a lamp and see a monkey. I am curious to learn more about how that connection is made.

    Also, check out this video on synesthesia. He perceives numbers as having a sensory component!


molivares's picture

synesthesia and blindspots

I am still in awe of how much our perception of the world is processed and “manipulated” by the brain.  First we talked about synesthesia, or the condition in which one type of stimulation evokes the sensation of another.  When I first saw ‘synesthesia’ written in the course lecture/discussion notes, I actually did not think of synesthesia in science or biological terms. I actually recognized synesthesia first as a poetic device where the description of a sense impression (smell, touch, sound etc) is articulated in terms of another seemingly inappropriate sense (for example the phrase ‘deafening yellow’). But when we tested the McGurk effect, it really struck me how much our perception of what we were hearing changed when we only listened to the video versus when we listened and watched the video.  It makes me question how accurate our perception of the world actually is. Furthermore, the blindspot experiments that we discussed in class made me wonder even more how much our brain “fills in” our understanding and perception of the world. 

aeraeber's picture

The Evolving Senses

We were talking in class on Thursday about the fact that the human system for vision is not perfect, just a system that happens to work most of the time.  It’s strange to think that vision is more likely to not work well than to work well, but it does go a long way towards explaining why so many people need glasses, and most people end up needing them as they age. It reminded me of the argument for intelligent design, that something as complicated as the human eye could not have evolved without the influence of a creator. The fact that the human eye doesn’t work perfectly is good evidence for the fact that it is a product of evolution. Evolution simply favors what works, even if it isn't perfect. A "designer" wouldn't likely have created something that doesn't work perfectly, and certainly wouldn't have created something that doesn't work well much of the time.

The idea that an unconscious part of the nervous system fills in the gaps in your vision, along with the fact that even if you know about the gaps in your vision you can never actually see them, raises some interesting questions. To what degree does unconscious mind control behavior? How much of our unconscious behavior can we change if we become consciously aware of it? It’s also strange to think much of the information that is transmitted to our eyes is thrown away before it reaches the nervous system, and it just fills in the gaps. How much of the time is what our nervous system fills in different from what is actually there?


gloudon's picture

does the brain fill in reality... or what it wants?

 This is in response to Emily's comment about falsely accused convicts... I'm not sure whether I read this, or saw it on TV somewhere... however, there was a women who had be raped many years prior, and she had to identify her attacker in a line up.  She picked a man, and he was accused, and spent over ten years in prison for this crime.  It ended up that he didn't commit the crime, and was found innocent by DNA testing (i'm not sure what took them so long to do a DNA test).  However, when the women saw the man again, she was sure that he was the attacker even though he was proven innocent.  To me, this seems like a case where the woman was so insistent upon finding her attacker, that her brain manipulated his face too look like the falsely accused man in the line up.  In this case, the connection between this woman's brain and her eyes sent a man to jail for over a decade.  This case was dealt with by the law, but how many other things are there that don't end up in court where disagreements arise because peoples' brains perceive what they see differently. 

sophie b.'s picture

 It is really interesting- in

 It is really interesting- in a way it seems that we can change our own visual reality. There was a study published in 2006 in which participants were shown an ambiguous figure that could be interpreted as two separate outcomes and the study participants tended to assign the figure outcomes that would be most favorable to them, which suggested that we subconsciously include our own motivations in how we process visual stimuli.  

In the social sciences we often talk about the ways in which society is affected through prejudice that is taught to us from a very young age, that we may not recognize within ourselves. I wonder how this motivational impact on visual stimuli would connect to that? It seems as though our ability to somewhat alter what we perceive as fact (because we see it)  could have an extremely large impact on society (although we don't really know it) 

Serendip Visitor's picture

Vision and Reality

From a physiological point of view, I really enjoyed learning about the eye and how the different parts function together to allow us to be able to see. Like with action potentials, this course is teaching me to appreciate all of the extremely complex mechanics that go into what we take for granted as simple actions such as seeing and vision.

The idea that our brain has a 'blind spot' has always sort of creeped me out. While I admit it is a useful evolutionary feature for our brains to fill in the missing pieces and make assumptions, I can't help but worry about what would happen if it were wrong? Could there be thing around us that we are not seeing at all? I wonder if this has anything to do with our incapacity to view things that are on different wavelengths. Our brains are just not equipped for all types of tasks.

meroberts's picture

Lack of control & absence of reality

In light of our discussions this week about the visual system and the great deal of information that is actually constructed by the brain, it seems to me that humans actually have very limited control of our behaviors. We respond to stimuli, yes. But we are actually responding to stimuli that has been falsified in such a way as to make it easier for the human brain to understand it, process it, and create appropriate outputs for the inputs.

So what is the point of the I-function, then? Is it just to interpret the stimuli which have been processed and edited? Why can't the I-function discern what has been edited by the brain and what are in fact the raw details? Shouldn't there be some function that can reconcile the differences between the two realities?

Lauren McD's picture

What is reality?

I find it interesting that now we are discussing specific senses, such as sight, in class and how they are linked to the nervous system. 'Seeing' is something we all take for granted; we rarely think about the complicated processes that must occur in order for us to see. And even if we do think about these processes, we usually think about them in the simplistic way of information from the outside world being perceived by the eyes and sent to our brains for interpretation. However, as demonstrated in class this week, the information trail has many more twists and turns. There is a location on the retina that cannot receive any input because it is where the optical nerve connects to the eye. What we actually 'see' on this area of the retina is an image our brain creates for us. Instead of seeing a blank spot everywhere we look, our brain interprets the lack of information and fills it in for us. It figures that the most likely thing in that space is what is surrounding it. This may not be obvious in a normal setting because our eyes move so much that we truly do see the whole picture. But in experiments such as conducted in class, it is easy to discover that our brain really does fill in missing information in our vision with the most probable image: that of the background. There are advantages and disadvantages to this extraordinary function of our brain. For example, something truly important or dangerous could be undetected, leaving us vulnerable to it. On the other hand, the image we see makes more sense if there are no 'blank' areas. We would constantly move our eyes to try and discover what should be in the missing area. If our brain fills it in for us, we hardly notice that anything's missing at all.

This begs the question if what we perceive is truth. From the discussion in class, we discovered that sometimes our brain lies to us, distorting our vision from truth. Who's to know what is truly in our world if we can only interpret it through human eyes? It's a slightly far-out, but interesting thought that the world may be truly and completely different from what we perceive. Humans automatically think that what they perceive must be true. But perception is only one view of the world. For example, dogs don't see in color, but we do. Is their reality any less true than ours is? Some people may say 'yes,' that humans have the most accurate perception of the world and dogs are missing key information. But to dogs, their interpretation of the world is reality. Why are we any different? Unfortunately, we are left pondering ideas that we can never find the answer to.

kdilliplan's picture

Processing Details

            I’ve been wondering about the benefits of having our nervous systems make up information to fill in the gaps in our sensory inputs.  Is it faster to fill in the gaps in our vision automatically from pre-existing patterns or based on the rest of the image we are seeing?  Is it more efficient? I think it’s mostly beneficial that we’re only able to focus on a small area at a time while our nervous systems fill in the rest of the details.  I’d go crazy if I had to notice every detail of my surroundings at all times.  It would be too much information to process. For instance, as I’m typing this I’m sitting at my desk and there are sticky notes all over it, each a reminder of something else I need to get done. Right now I am very glad all I can see of them are their bright colors and not the words written on them.  I am similarly glad I can’t see what the people around me are writing in their notebooks in class. I can see them writing, and if I were to focus on their papers I could read them, but I don’t need to in order to write my own notes.  We’ve talked about how our senses can’t and don’t relay all possible information about all possible phenomena to our nervous systems and how that means our nervous systems are not perfect and are very limited.  It seems to me that our senses take in too much information at once and that it is in fact the rest of the nervous system that is not adequate to process it all.  

            I’ve also been wondering whether it’s easier to observe details or to ignore them when we don’t need them.  I’m assuming everyone has had the experience of having someone point out a detail that they hadn’t noticed before and subsequently not being able to un-see that detail.  The same thing happens with the other senses, too. I think the importance of details is determined by whether those details have become part of the I-function.  We’ve already pointed out how engaging the I-function can slow and limit the behavior of the rest of the nervous system, and I think this phenomenon is another example.   

mcurrie's picture

           Talking about

           Talking about vision and how the brain and the eye are used to show us what the brain believes the world is like, it made me think of the comment that it is hard to compare or make a determinate idea about how people react and see certain things. I have always wanted to look at something through someone else's eyes. Every time I'm in the car and seeing other people on the road with me I always wonder where their destination is? Why they're on the road? And what they are looking at, seeing, analyzing? If I was able to experience what they were seeing I would see what their brain is telling them is in their site, the guesses of the brain. The brain lying to you explains why you may believe that you are seeing things. Like after watching a scary movie I always think that the shadows are moving or that there is some creepy monster behind me. It is my brain lying to me due to seeing the movie and thinking that there could be something behind me. Is this the same for hearing? Is hearing something also a part of the brain lying to you or making guesses about the noise?

           What I also thought was interesting was that your retina is only telling the brain the boundaries of objects or the change in light intensities and with a checkerboard both black and white chips are seen as the same shade because they have the same light intensities. I'm hoping the talk about color will clear some things. Because I thought that we used the visible light and take in what is reflected back as a color to get an image, that color and light intensity went hand in hand. I guess light intensity helps with boundaries and color will come in to fill in the blanks.

mcchen's picture

Eyewitnesses and vision as a construction of the brain

This week we talked about how everything you see is a constructed best guess from our brains.  While I have heard this before, I do not quite know how to rationalize it.  If everything we see is our "guess" of the world, only from similar upbringings or culture surroundings would we be able to see the world in a similar fashion.  While our eyes all work the same, we are all different people who interpret situations differently.  This led me to think of the validity of eyewitnesses during murder trials or any other trial.  Based on what we learned this week, the eyewitnesses to certain crimes could have not seen the full crime at all but their brains filled in the blanks for them making them think they did.  Our brains are programmed at "filling-in-the-blanks", but that can have some serious consequences if the wrong person is put away in prison for 10 years.  When our brain fills in the blank, what is it based on? With the cross and dot illusion, our brain filled in the blank with the pattern behind it based on a pattern we had seen before. But in the case of seeing a crime, what do our brains draw from? Are there certain cultural pattern we are used to seeing? Or does the brain give the best "guess" at who we thought we saw commit the crime? 

meroberts's picture

False memories

Interesting point, Michelle. Not only are the eyewitness accounts faulty because of information that is edited out (or in) by the brain, but they are also faulty because of the time that elapses between seeing something and then being asked to recall it. Evidence shows that most eyewitness accounts are really just false memories conjured up by leading questions from the interviewers, as in the case of a study conducted by Dr. Elizabeth Loftus at University of California, Irvine:

Dr. Loftus wrote this paper quite a while ago describing how false memories sometimes are planted during therapy sessions, especially when hypnosis is involved:

The section in this paper titled "Impossible Memories" is very interesting to me because my aunt believes that she remembers being born and that's impossible.

emily's picture


 First of all, I am very excited we have been talking about vision! Vision has always fascinated me, especially the role the brain plays in what we perceive. The fact that our brain "lies" to us makes a lot of sense with respect to corollary discharge, which checks expected information with perceived information. Since we do not receive any input from the spot where our optic nerve goes back into our head, our brain has to make up what would be there based on what it expects. I like to think about how much we perceive and to what extent it is "real" or just what our brain is telling us. There is really no way to know. If you have never seen the Matrix before, now is probably a good time with the context of our class discussions and where they might lead. If our brain is pretty much guessing at what it sees, how can we know it is telling us the truth? A three dimensional world becomes a two dimensional retinal "image" that in turn becomes a three dimensional perception. How can we be sure that anything besides our own brain really exists, if our brain is what tells us what we perceive?

meroberts's picture

Willy Wonka

"A three dimensional world becomes a two dimensional retinal "image" that in turn becomes a three dimensional perception."

This depiction of visual imaging reminds me of that scene in Willy Wonka (the old school version) where the kid who wants to be a cowboy gets sucked into the tv. Then he becomes a smaller version of himself in the tv or something crazy like that.

This idea definitely makes you think about what information gets left out of the end result, or the picture in your head. It's interesting to consider what the brain deems as essential information- the information that remains intact in the final image in your head- and information that is extraneous- what's absent (or even filled in) from the image in your head.

Jeanette Bates's picture

Vision and Interpretation

Personally, I think that the fact that my brain literally “fills in the holes” is fascinating. Even when there is a spot that we aren’t able to see, our brain tries to make sense of things by lying to us. At the same time, however, it’s a bit concerning. It makes me realize that my brain may be lying to me about other things, and since this part of my brain is detached from my I-function, I can’t even know what those things are. How certain am I that I am perceiving the world correctly?


I also have to wonder if the way I see the world, visually speaking, can be dramatically different from the way other people see the world. My brain may tell me to perceive something one way, but it could tell someone else to perceive it in a completely different way. We may think that we’re seeing the same thing, but we’re actually seeing completely different things, and we wouldn't even know it. I don't know how dramatic the differences between humans can be, but I know that at the very least there are insects and fish and other creatures that are able to see colors that we can’t even begin to imagine. They are seeing the same world in a completely different way. This fact makes me realize that the way I see the world is just a simple interpretation and that I am very far from seeing the world in its entirety.