FINAL BLOG

 

 

 

I have always been deeply interested in the relationship between diabetes and blindness because one of my uncles currently has diabetes. His eyesight is becoming worse and worse due to its complications. Because we spent so much time on vision, I thought it was appropriate to do some research on the blindness caused by the complications of diabetes. There are various types of diabetic eye diseases: diabetic retinopathy, cataract, and glaucoma. Diabetic retinopathy involves damage to the blood vessels in the retina. Cataract, which occurs at an earlier age for people with diabetes, occurs when the eye’s lens clouds. Glaucoma occurs when the optic nerve is damaged due to the increase in fluid pressure inside the eye. It eventually leads to loss of vision. People with diabetes are twice more likely to get it. It has been known that “diabetic retinopathy is the most common complication of diabetes and a leading cause of blindness among working-age adults.” My uncle has diabetic retinopathy and every now and then, blood vessels of his eyes break. There are four stages of diabetic retinopathy. First stage is called mild nonproliferative retinopathy. The blood vessels begin to swell. As the disease gets worse, it moves into the second stage, moderate nonproliferative retinopathy. Some of the vessels that provide nutrients to the retina are getting blocked. As the disease gets even worse, the third stage called severe nonproliferative retnopathy kicks in. More blood vessels are blocked thereby not being able to provide enough nutrients to certain parts of retina. In order to provide sufficient nutrients, the eye builds new blood vessels that are very fragile. These vessels can easily break and leak blood within the eye. This leakage of blood would result in a possible vision loss. This last stage is claeed prliferative retinopathy. I think my uncles’ diabetic retinopathy is moving slowly into the proliferative retinopathy. It is extremely devastating for people like my uncle because they can no longer drive. Because my uncle had a good vision before, it is harder for him to adjust to it. He lost his job because he could not see clearly. Most importantly, he has trouble going to work by himself. He has received numerous laser treatments. I was able to learn how it was done from him. Many laser burns are placed away from the macula of your eye. They result in loss of some of the peripheral vision; however, they can save the eye from becoming completely blind. The cause of the damage to the vision occurs, when the blood vessel breaks and leak blood. Then, the vision becomes very blurry. As you can see in the picture, black spots develop on top of the blurry vision. Another way that retinopathy could cause vision loss is by leakage of fluid into the center of the macula. It is called macular edma and people with this condition lose acuity. The laser surgeries did not work well for my uncle because his blood vessels already have leakage. They do not cure proliferative retnopathy. As a result, my uncle will eventually lose his eyesight. I believe that diabetes retinopathy should receive more attention as it affects so many people.

 

 

http://www.nei.nih.gov/health/diabetic/retinopathy.asp

http://www.springerlink.com/content/43250105433377l2/fulltext.pdf

Giotto’s mistake!

1. Pre-renaissance artists had trouble with depicting depth in their paintings. Can you find some examples of this? How did their paintings fail to depict depth? What aspects of a painting give it depth?

 

            The topic of depth perception was very intriguing to me in many ways. Out of many interesting examples of use in depth perception, I found depth perception used in paintings as most fascinating. As a grandson of an oriental painter, I have always been deeply interested in paintings. When I came across the depth perception used as a method in paintings, I could not overlook them. After all, it would be quite hard to portray three dimensional world on a two dimensional canvas. I have tried it as well, but I was not successful as I am not that artistic. It was not until after pre-renaissance era that the depth perception was incorporated into the paintings. Until then, the pre-renaissance paintings often failed to lucidly represent the world on a canvas. There are numerous depth cues that shape the depth perception. Cues that could be used in paintings are occlusion, linear perspective, texture gradient, size, and shading. Many of the pre-renaissance paintings lacked these cues. It is quite obvious that some paintings contained some of the depth cues but they were not sufficient to make the drawing into three dimensional.

 

            There are several paintings that I have scrutinized to find which depth cues were used and whether or not the painters were successful with utilizing the depth cues. I looked at the painting by Giotto di Bondone. He used linear perspective on the roof, windows, and the walls. The walls and the windows converge toward the back a little, trying to indicate that twelve disciples are located in front of the wall and that the windows are located in the far back. Even though it could have worked if he was more careful with applying linear perspective in all the details of the drawing, this attempt fails utterly. Giotto failed to recognize that the front door and the wall in front of the disciples should contain some details of linear perspective as well. That wall merely looks like a thin piece of sheet without any width. He tried to show the linear perspective by positioning the disciples in somewhat of a triangle, its base towards the front. Nevertheless, he failed to recognize the size. The heads of the two people in front of the disciples are actually smaller than the disciples located in the back. When I disregard the background and simply compare the people, I would most likely see the disciples as located closer to me than the two in the front. This explanation is kind of a stretch because Giotto used occlusion to show that the disciples are actually behind the wall containing the door.  In addition, the paining does not contain any sort of shading to indicate the positions. Lack of shading clearly diminished the affect of the occlusion because occlusion works almost in parallel with shading. It was hard to see the texture gradient because the painting itself was old. Some of the details were smudged out due to the age of the paining, regardless of depth perception.

            After closely dissecting this paining by Giotto, I could do nothing but be grateful that the contemporary artists can utilize the depth cues very well. The appreciation for art would have been much less if there was no depth perception incorporated in paintings.

 

reference:

perception textbook

http://upload.wikimedia.org/wikipedia/commons/6/62/Giotto_di_Bondone_088.jpg

 

Nature vs. Nurture

           

The nature versus nurture debate has been going on for a long time and it has remained as a stalemate. It seems like it would take some significant time to come up with a solid answer. Would there really be a clear answer? Since we have been learning about visual system in the class, I decided to do some research on this debate involving visual system. Neuroscientists especially are deeply engaged in search for an answer to this debate. Would the development of a normal visual system more affected by nature or nurture? With this question in mind, I spent time studying a paper published by David Ferster. Surprisingly, according to Ferster, “the most intensely studied model of environmentally driven neural plasticity is that of ocular dominance columns in the developing mammalian visual cortex.” This paper describes an “activity-driven adaptation of the mammalian visual cortex to incoming stimuli during early post natal life.” The incoming stimuli producing synaptic inputs from thalamic relay cells from one eye are combined in the visual cortex into columns, alternating with columns containing synaptic inputs from the other eye. The thalamic inputs to the visual cortex are merged at the time of the birth; however, in the next months, the inputs are separated. This separation process is related to visual experience. If the baby uses one eye distinctively more than the other eye after the birth, the occular dominance band for that eye become greater, while that of the unused eye become smaller. As a result, the visual cortex for the eye that has been used much more become greater. This effect can be explained by hebb rules in the visual cortex. Since the synaptic input that activates a cortical neuron greater wins the competition over the other synaptic input that activates a cortical neuron less. Consequently, “the stronger get stronger and the weak get weaker.” “The closed eye’s inputs are reduced in activity and can no longer compete effectively with their counterparts from the other eye.” This particular study also fails to come up with a solid answer to the debate. After reading this paper, I was more convinced that there cannot be a solid answer to this debate. The closing sentence of this paper explains all; “Ultimately, we may indeed learn not only how genes shape behavior directly, but also how the environment shapes behavior through its effect on gene expression.” Applying this to my life, I could understand it better. My left and right eyes have very different eye-sights. My left eye is significantly worse than my right eye. According to my mother, I tended to use my right eye more when I was a baby. I think my current eye-sights have a lot to do with it. However, both of my parents do not have such distinguishable eye-sights between left and right eyes. It is more likely that both nature and nurture are working right next to one another in development of visual system as well as in development of everything else.

 

 

http://www.sciencemag.org/cgi/content/full/303/5664/1619?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=nature+vs.+nurture%2C+development+of+visual+system&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT

What causes Change Blindness?

             Until now, I have never really paid much attention to topics such as change blindness or inattentional blindness. Honestly, they did not seem significant or crucial in visual perception. Nevertheless, my attitude toward these topics quickly changed after I watched the movie clips posted online. The second movie clip (grass field with a barn) especially surprised me because I could not find any conspicuous change even after watching it five times. I finally discovered what was different only after I compared the last scene with the beginning scene separately. The grass getting cut near the right side of the screen was the change being made to the scene. It was then I realized that change blindness could affect our lives greatly. (I will only discuss change blindness in this journal entry.) To determine the cause of change blindness, I turned to Daniel J. Simon’s article. Simon describes change blindness as an “inability to spot changes as observers fail to detect substantial changes to the visual details of objects and scenes.” He lays out several possible explanations for change blindness. The first one is “overwriting.” “The initial representation is simply overwritten or replaced by the blank interval or by the subsequent image.” To me, this explanation seemed most plausible because it is most intuitive. The image of the first scene remains as a simple abstract while the new scene replaces the old image. This new image is understood as the initial image that I first saw. The second one is “first impression.” The observer does not see the final image but is only be able to obtain the initial image. I did not particularly agree with this one because I tend to put more emphasis on the last scene or image. Therefore, it is more likely that I would understand the last impression as the one that remained intact throughout the movie clip or the situation. The third one is that “nothing is stored.” It argues that simply nothing in the visual world is stored internally that an observer does not store anything that goes on in the movie clip. This hypothesis was the one that I had the most trouble understanding because after watching the movie clip, I could recall most of the details of the image. The fourth one is that “everything is stored but nothing is compared.” This one clearly contradicts the third explanation that everything is stored. However, it contains one unique detail. Both the details of the initial image and the details of the final image are stored internally but they are not compared. Therefore, the observer cannot find the differences between the initial and the final images. The final explanation is “feature combination.” The details of the initial image and that of the final image are combined within the observer’s brain so that he or she fails to come up with a conclusion that the image has changed during a certain period of time.              These explanations account for part of why change blindness occurs but they cannot be accounted for everything. Few explanations seem farfetched. The overwriting explanation seemed the best one out of the five. I have experienced this change blindness when I was driving. Waiting at the intersection for the traffic light to change, I was looking at a Porche on the other side of the lane. Soon, the light turned green, but I could not see the change. It was not until the cars behind me honked loudly that I realized that the light had changed. The change blindness is occurring in everyday life and it is not something that could be overlooked.References:

http://schneider.lrdc.pitt.edu/P2465/Readings/simons_viscog.pdf

Perception textbook

The Oblique Effect

                  The oblique effect is defined as a decrease in visibility of obliquely oriented patterns as compared to horizontal or vertical patterns. In order to find out more about this topic, I began researching it from a few scientific journals. First, I set out to find out the types of experiments used to discover the oblique effect. From the nature neuroscience journal, I could locate few studies performed to verify that the oblique effect is indeed accurate. Furmanski and Engel performed fMRI “to measure an asymmetry in the responses of human primary visual cortex (V1) to oriented stimuli.” As I had expected, human primary visual cortex (V1) showed a reliable increase in metabolic rate, meaning increase in neural activity. From this fMRI measurement, they found out that the humans show a greater sensitivity towards the horizontal and vertical orientations than the oblique (45/135 degrees) stimuli. V1 generates more response to horizontal/vertical stimuli than oblique stimuli. Nevertheless, this effect was not shown in V2, or VP, which might indicate that the oblique effect is only possible in V1 region. In addition to fMRI results, data from single-neuron electrophysiology and evoked-potential studies helped to maintain the claim that the oblique effect exists. It was very surprising that V2 and VP regions of the brain did not show the oblique effect. If a person has a small lesion in V1 region, not affecting other functions, he or she might not be vulnerable to the oblique effect after all.           

             After learning the basis of the oblique effect, I wanted to learn more about it. Reading through a journal, I found an interesting topic. “The oblique effect is determined by the perceived, rather than physical, orientation or direction.” Meng and Qian used tilt illusion in numerous experiments to produce perceptually different orientations of the same grating by varying the orientations of the grating surrounding the inner same grating. By applying the psychometric curves, they could discover that the oblique effect is determined by the perceived. The slopes of the psychometric curves were steeper “when perceiving target gratings near vertically as opposed to more obliquely.” Combining all the data from their experiments, they concluded that “when the perceived orientation or direction differs from the physical orientation or direction, the oblique effect depends on perceived, rather than physical, orientation or direction.” I believed that the oblique effect should be determined by the physical, orientation or direction because the oblique effect being determined by the perceived merely seemed non-scientific. It was very intriguing to learn about something that I had not expected. I also learned that reading scientific journals provide much more in depth knowledge, and provoke a greater fervor for the subject.     

References:http://www.journalofvision.org/3/3/4/McMahon-2003-jov-3-3-4.pdfhttp://www.nature.com/neuro/journal/v3/n6/pdf/nn0600_535.pdfhttp://brahms.cpmc.columbia.edu/publications/oblique2.pdf

The eye

Throughout the course so far, I learned various types of senses. From this list, I believe that I consider vision as the most important type of sense available to me. I tend to trust the ability of the vision more heavily than other senses; therefore, I expected the vision to be error free. As I learned more about vision, I became aware of the fact that vision is not an error-free sense. What Roger Carpenter meant by this quote was probably this: Although eye is the most powerful tool, it often fails to live up to its expectations. A pair of eyes, a tool for vision, allows me “to detect and recognize objects that make no sounds.” eyes give me knowledge about the shape and color of such an object therefore, I have control over what I am about to touch, grab, or hold. Shapes and colors describe much about an object. For example, by relying on smell only, a person might try to grab a good smelling rose stem with bare hands. This person will surely end up with bleeding fingers. In addition, merely by looking at the color of an object, a person can determine whether or not such food is in edible condition. From these examples, I can easily discern that the eye is once the master of the vision. However, these useful pair of eyes can pose various problems. Because I believe that the eye is the master of vision, I often overlook the fact that I rely too heavily on it, although it is not error-free. I become slave of the vision because I tend to believe that the eye is accurate all the time. Rather, eyes can have many problems such as myopia, hyperopia, astigmatism, and various defects. With these problems, sometimes the shape and color of an object might be altered but I end up trusting the visual information that the eye obtains.    Reference: Perception textbook

How do conatact lenses work?

 

I have been wearing glasses since I was 12 because I have both myopia and astigmatism. So, the question of “how do contact lenses work?” brought my immediate attention. I did some research to find out an answer to it. First, I will define myopia. Myopia is defined as a vision condition in which objects in the far distance are not seen focused while objects in the near distance are seen focused. It is due to the fact that the eyeball is longer than normal or the cornea has too much curvature, causing the light to be focused  in front of the retina instead of being focused right on it. Contacts lenses stay in place by the natural tears produced by the eyes and add a thin concave, in the case of myopia, layer over the cornea to refocus the light so that the light can focus closer on the retina itself. In the past years, contact lenses created a huge problem because they prevented the necessary oxygen flow to the eyes but nowadays, most lenses are somewhat permeable to the oxygen flow. Astigmatism is a more complicated vision condition and it is due to irregular shape of a cornea. Astigmatism occurs “when an optical system has different foci for rays that propagate in two perpendicular planes.” The irregular shape does not allow light to be focused on the retina causing a blurred vision. In the past years, astigmatism could not be corrected with lenses. Due to the improvement in the lens industry, astigmatism can now be corrected with lenses. These lenses refocus the light distorted by the irregular shape of the cornea directly on the retina. Hard lenses are better for astigmatism because they do not mold to the shape of the cornea. It is fair to say that the development of contact lenses is quite impressive after learning how they work and about the fact that it allows people to play sports without the hassle of wearing a pair of glasses. However, from my experience, I believe that they are still not at all perfect. I have bad astigmatism and I often struggle with eye infections. I could never be able to get used to contact lenses. They do not allow much oxygen flow and the astigmatism cannot be corrected perfectly with lenses. Every time I wore them, they made my eyes too dry and irritated them. Therefore, I still wear glasses instead of lenses. Maybe in the future, there will be a contact lens that I could wear without any problems.  

  

http://www.aoa.org/x4688.xml

http://www.aoa.org/x4698.xml

http://www.medopedia.com/vision/contact-lenses

http://en.wikipedia.org/wiki/Astigmatism

 

Hearing as a survival tool

             Hearing is one of the most crucial senses in our lives. Unlike touch and vision, hearing does not require a direct contact with the stimuli. Therefore, it can attend to a broad range of stimuli. In evolutionary sense, hearing is the most integral senses in surviving. Because we only have two eyes that can look in one direction only, we cannot rely on vision so much. If a predator is coming from the back, without hearing abilities, there is no chance of noticing and avoiding it. However, with hearing abilities, a slight movement of the grass would be able to tell us that there is a predator coming behind us. Nowadays, we do not need to worry about getting killed by a predator. Nevertheless, with the development of the technologies, hearing abilities are more important than ever before. Everyday life, we encounter the use of various machines and technologies. While they are mostly beneficial to everyday life, they all possess some possibilities of danger. One of the clearest examples is apparent when we cross streets. If we rely only on vision and touch, it would be impossible to know what is coming from our side or back. We would be very much limited to small area in which we can see and touch. Most of the times, we would end up getting hit by a car. Hearing allows us to break the limits. With hearing abilities, we can easily listen and recognize the cars coming near us. We would then be able to avoid them. It seems very easy to overlook hearing in this sense because often times we associate it with pleasure related activities only. In terms of survival, hearing is the most important senses.

taste experiment (12:00PM 02/08/08)

            First, I performed the same experiment mentioned in the text with a small modification. Beginning from a cup with pure water, I gradually increased the concentrations of the next three cups by three drops of orange juice (0 drops for the first cup, 3 for the second, 6 for the third, 9 for the fourth). I tried to taste the second cup with three drops of orange juice. Sure enough, I could easily discern the sour taste. Next, I tasted the third cup and compared with the first cup. It was much easier to tell the difference in sourness. Then, I kept the solution from the fourth cup in my mouth for about a minute. It was quite amazing to find out that I could not taste the difference between the first and the second cup due to the adaptation. Since I am a very doubtful person, I performed another experiment with different type of taste. I used drops of hot sauce instead of the drops of orange juice. I used the same concentrations for this experiment. When I tried it myself, it was hard to differentiate between the different concentrations. Therefore, in order to make an unbiased experiment, I asked my friend to participate in my experiment. As I had expected, his result was somewhat different from mine. He could differentiate between the second and third cup much better than I was able to do it. I concluded that since I was more exposed to the hot/spicy taste (Korean cuisine has many spicy foods), my tongue was more adapted to the spicy taste than my friend’s tongue was. When my friend and I both tried to adapt our tongues for a minute with the fourth cup (9 drops of hot sauce), out of ten tries, he could differentiate the concentration 30% better than I could. This phenomenon occurs when I eat something right after brushing my teeth. My tongue becomes adapted to the taste of toothpaste and eventually blocks some of the taste that I could have acquired. From this experiment, I could learn that all of my senses behave in a similar way. They can all become adapted to certain level resulting in an inaccurate sensitivity.

Commercialization of smell (10:15 2/2/2008)

            Smell and taste are closely related to one another. They are crucial senses in our everyday life. From the foods that we eat to the fragrance that people put on to attract others, the importance of smell is clearly apparent in our lives. Smell and taste can enhance our appetite and attract another person. It seems that if there is a way to commercialize smell, people can make a great fortune out of it. However, it is quite intriguing that the level of activity of “venture investment and commercial innovation we have come to expect in other fields” is very low. In order to find an answer to this question, I did some research on it. According to the review written by Gilbert and Firestein, the lack of the activity is due to the fact that olfaction utilizes multitude of receptors that distinguish numerous chemical compounds. There are simply too many combinations to look for. The research would require a tremendous amount of funding, while being high risk. In addition, another reason that the commercialization has hit the wall is because of “the tremendous amount of inter-individual variability in sensitivity and the variation at the ethnic and geographical levels.” Because smell is a “muted” sense, there is not an easy way to standardize certain smell.           

           Aside from the difficulties, there are some ways in commercializing smell. “Odor modulation technologies” show quite a promise. Below is the example of possible odor modulation technologies:

This method immediately grabbed my attention because it utilizes perception, which is closely related to this class. By either enhancing or suppressing the levels of perception, people could come up with various ways that could improve one’s health. For example, my grandmother lost her sense of smell after she got into a car accident. She lost her appetite along with her smell.  It was a devastating loss for an elder person because she could not obtain all the nutrients that she needed. After reading this review, I was relieved that a product that improves perception could enhance my grandmother’s appetite and greatly improve her health. I only thought about commercialization of smell along the lines of fragrance. This research broadened my knowledge and greatly enhanced my interest in the field of perception.

Reference: http://www.nature.com/neuro/journal/v5/n11s/pdf/nn937.pdf