Before you begin this assignment, please go to the following site and read a couple of topical blog posts that were done by students last semester at : http://www.psychologicalscience.com/perception/2011/04/topical-blog-week-14-due-friday.html#comments
Next what I would like you to do is to find a topic from the chapter you read for Monday that you were interested in and search the internet for material on that topic. You might, for example, find people who are doing research on the topic, you might find web pages that discuss the topic, you might find youtube clips that demonstrate something related to the topic, etc. What you find and use is pretty much up to you at this point. But use at least 3 sources.
Once
you have completed your search and explorations, I would like you to
say what your topic is, how exactly it fits into the chapter, and why
you are interested in it. Next, I would like you to take the information
you found related to your topic, integrate/synthesize it, and then
write about it. At the end, please include working URLs for the three
websites.
Once you are done with your post make list of the terms and terminology you used in your post.
By integrating/synthesizing I mean to take what your read/experienced from the internet search (and from chapter 1 if you like) organize the information into the main themes, issues, info, examples, etc. about your topic and then write about the topic in your own words using that information. This is hard for some people to do - many students write what we refer to as "serial abstracts." They are tempted to talk about the websites rather than the topic proper. They will talk all about website #1, start a new paragraph and talk all about web site #2, start a new paragraph and talk all about web site #3, and then write some kind of conclusion. Serial means one after the other...This what you DON'T want to do!
At first it is a real challenge to get out of the habit of writing "serial abstracts," but I assure you once you get the hang of it it is much easier to write using the integration method. And besides this is the way researchers and scientists write their technical reports and findings - many of you will have to be able to do this for other classes and for jobs that you may eventually be hired for so now is a good time to learn this skill. At this point don't worry about a grade, worry about doing your best to have fun with the topic and then integrate it into your own words to share what you found and now know. We will work on citing the sources later....
Let me know if you have any questions.
I enjoyed reading about the anatomy and physiology of the eye, because I have always been interested in what our body parts are made up of, and I was even a Pre-Med/Biology major before switching to Pre-Law. I really like learning how each organ in our body functions, and what mechanisms make it function properly, and what problems make them function incorrectly. The book did a nice job explaining how the eye allows us to perceive the world around us, but I wanted more information so I found three websites that further explained the anatomy and physiology of the eye.
I found some videos with narration giving the viewer a visual and auditory explanation of the anatomy of the eye. I liked the video explanations because it was easier for me to fully understand the process than just reading about how the eye functions. In one video, the viewer takes the role of light entering the eyeball, first passing through the tough transparent tissue that covers the eye called the cornea. The cornea is composed of multiple levels of fibers, and protects the iris and other delicate components, while it focuses light on the lens. Inside the aqueous body, the viewer (light) looks through the lens into the vitreous chamber. A clear, thick jelly fills the vitreous chamber. Passing through the vitreous chamber, we see blood vessels that carry nutrients to the components of the eye. Behind the blood vessels is a small disc that is called the optic disc, or the blind spot. This is where the retinal blood vessels pass through the back of the eye. The retinal blood vessels nourish the inner layers of the retina. To the left of the blind spot is a dark red spot that is called the macula. The macula contains a high concentration of photoreceptor cells which convert light into nerve signals. This portion of the retina has the sharpest vision. And at the very center of the macula is the fovea, the site of our sharpest vision.
Because the macula is the portion of the eye that has the sharpest vision, I wanted to learn more about macular degeneration. In a healthy retina the tips of photoreceptor cells are constantly being shed and then absorbed by the neighboring pigmented retina. In contrast, with dry macular degeneration the pigmented retina becomes less able to absorb the photoreceptor cell tips. As a result, “drusen” (the poorly digested cell tips) accumulates under the pigmented retina. This leads to the photoreceptor cells over the area of the drusen begin to atrophy. Overtime, these photoreceptors will die, leading to a gradual loss in vision in the macula. People suffering from Macular Degeneration see dark spots in their vision not allowing them to see the world around them completely. Some people see straight lines as wavy lines because the retina is not smooth anymore. I know of some elderly people that suffer from Macular Degeneration, and I think it would be a horrible experience.
I enjoyed looking up more information on this topic because I feel like I have a better understanding of the anatomy and physiology of the eye now.
http://iknow.net/player_window.html?url=media/fly_to_retina_auto.swf&width=360&height=317
http://iknow.net/player_window.html?url=media/dry_amd_auto.swf&width=360&height=317
http://iknow.net/phys_eye_education.html#_nogo
Terms: cornea, iris, fibers, lens, aqueous body, vitreous chamber, optic disc, blind spot, retinal blood vessels, retina, macula, photoreceptor cells, nerve signals, fovea, Macular Degeneration, pigmented retina, drusen
Good post. Definitely a lot to learn about the basics and physiology.
I decided to learn more about the photic sneeze reflex (PSR). I wanted to learn more because the book told us that there isn't a logical reason why this happens. A PSR is when you go from a dark room, say a movie theater, and you walk outside into the sunlight and sneeze! It's harmful, really, which is why it hasn't been on the top of researchers list to research. I found it interesting that we haven't found a reason why it happens yet, after people have been aware of it since Aristotle days!
Aristotle thought it happened because one sneezed because the heat of the sun, but some years later, Francis Bacon came along and proved him wrong. He noted that if you walk outside in the same setting, with your eyes closed, you do not sneeze! Bacon thought it was from your eyes watering, which made one sneeze, but this was also poo-poo-ed because eyes watering does not make one sneeze, which we now know from our neurological knowledge.
So what do we know? We know that not everyone has this reflex. Scientist believe it is a biologically based thing, passed down from family members. They think that when one walks out into the sun from the dark, the neurotransmittersne that the optic nerve signals to the eyes to constrict the pupils actually crosses paths with the nerve that senses facial sensations and motor control (trigeminal nerve) and is mistaken to sneeze. This sounds pretty logical to me!
The only research I could find being done is at the University of California, San Francisco. They believe it is one gene that makes this reflex happen. They are collecting blood samples from families who want to participate, and are researching to find similar genes that would create the reflex.
With little research conducted we don't know for sure how many people have this reflex, but with the little research that has been conducted, they believe that 10-35% of people have this.
http://www.scientificamerican.com/article.cfm?id=looking-at-the-sun-can-trigger-a-sneeze
http://www.neugenes.org/photic_sneeze_reflex.htm
http://www.experienceproject.com/groups/Have-The-Photic-Sneeze-Reflex/61993 -- this one is simply interesting to hear people's thoughts who do have the reflex, since we do not know a whole lot about it yet.
http://www.youtube.com/watch?v=fiu8Eu6RRvo -- This is just pretty funny.
Terms: photic sneeze reflex, optic nerve, trigeminal nerve, neurotransmitters, pupil.
I've heard of people with chronic coughing and sneezing who actually rupture an artery eventually that can lead to sub-acute infarcts in the brain, which is bad.
I thought it was very interesting that we all have a blind spot in our vision. This fits in to the chapter because it has to do with how our eyes work . It has been found that brain can fill in missing information to supplement for our blind spots in our vision when both of our eyes are open. But when one eye is closed and you work carefully it can be demonstrated that that there is a blind spot in our perception. In one spot in the retina of each eye there are no photoreceptors, which causes us to have a blind spot in our vision. It is just due to the anatomy of our eyes.
Our eyes actually can make up information where our blind spot lies. Many different studies have been done with blind spots. Some of the more simple ones include a dot and a cross that you look at and move them closer to your face. When covering one eye the dot will disappear at a certain point. When the space is divided in half (one half green, the other yellow) and the dot is in our blind spot, our eyes fill in the dot with yellow. Our brain is actually making that information up, it just assumes it is yellow space so that is what it puts there, which is pretty cool! This is remarkable to me that our brains can make us see something that is not actually there.
Similarly, when the half of the space with the dot in it is filled with red dots with one yellow dot in the middle (and the yellow spot falls in our blind spot) our brain fills in the blind spot with a red dot. This can be done with any pattern, a spinning shape, anything, it is really consistent.
Similarly Maus found in his 2008 research, when a moving line enters the blind spot it disappears from our site and our brain fills in the information with the background. It appears that the moving line just disappears until it gets out of our blind spots.
This is not the only thing that can happen when something enters our blind spots though. Sometimes our minds make up what we think is there. For example in Araragi, Yukyu’s 2008 research it was found that when individuals were shown 2 and 3 disks then they were moved into their blind spots (the disks had to be large enough to be counted) their blind spots actually compensated for that by showing 3 and 4 disks when there were actually only 2 and 3 there. It is remarkable that our brains can make up information like that.
Terms: Blind spot, photoreceptors, retina,
http://serendip.brynmawr.edu/bb/blindspot1.html
http://www.perceptionweb.com.proxy.lib.uni.edu/abstract.cgi?id=p4003rvw
http://web.ebscohost.com.proxy.lib.uni.edu/ehost/detail?vid=6&hid=11&sid=cf48eccd-5641-4ebf-9ed0-efeb2187772f%40sessionmgr4&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=psyh&AN=2008-18156-006
http://web.ebscohost.com.proxy.lib.uni.edu/ehost/detail?vid=6&hid=11&sid=cf48eccd-5641-4ebf-9ed0-efeb2187772f%40sessionmgr4&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=psyh&AN=2008-14710-016
It is efficient that the brain can fill in information based on other input present. It seems to be very probabilistic and beneficial to us. It also shows you that we don't get all of the visual world represented, which in theory means there are a great deal things we could be missing from our external world.
I found the subject of light and dark adaptation interesting from Chapter 2. It fits into the chapter because it was talked about in the book and we extensively discussed it in class on Tuesday. Topically speaking, adaptation is a branch of ocular physiology in which the ability of the eye to adjust to various levels of darkness and light is studied. The efficacy of the eye to the adjustment to light and dark is very intriguing. It takes the eye approximately 20-30 minutes to fully adapt and adjust from bright sunlight to complete darkness. In this same process, the eyes perception of color changes as well. It takes the eye approximately 5 minutes for the eye to adapt to bright sunlight coming from absolute darkness. According to Wikipedia this is due to “cones obtaining more sensitivity when first entering the dark for the first five minutes but the rods take over after five or more minutes.”
Dark adaptation has to mostly be associated with the rods mechanisms. Rods essentially provide what is called scotopic or night vision. There are different factors that inhibit quick dark adaptation to occur. Depending on how long one stays in a laminated area, inhibits and slows rods threshold. Dark adaption also depends on something called photopigment bleaching. In an experiment involving retinal densitometry, which is measuring the light reflected from the fundus of the eye, it was found that the time it took for dark adaptation and rhodopsin regeneration was the same.
Light adaption has to mostly be associated with cone mechanisms. When leaving a very dark room and stepping into a lit room, all we see is white light. This is because the sensitivity of the receptors is set to dim light. Both rods and cones are very sensitive to light and are stimulated very easily by large amounts of photopigments. When these photopigments are broken down so quickly, it produces a rapid flood of signals resulting in what known as glare. Adaption occurs in two ways; when the sensitivity of the retina decreases substantially, and when retinal neurons undergo rapid adaptation inhibiting rod function and favouring the cone system. Essentially after one minute of exposure to light, the cones are sufficiently stimulated and visual accuracy and color improve over the next ten minutes. During light adaption, retinal sensitivity is fully dysfunctional.
TERMS: Dark adaptation, light adaptation, ocular physiology, cones, rods, photopigment, scotopic, retinal densitometry, fundus,
http://www.chm.bris.ac.uk/webprojects2003/white/light_and_dark_adaptation.htm
http://en.wikipedia.org/wiki/Adaptation_%28eye%29
http://webvision.med.utah.edu/book/part-viii-gabac-receptors/light-and-dark-adaptation/
Interesting stuff. Dark adaptation is an interesting experience because after a while you start to be able to resolve things in your environment. Try this next time you wake up in the middle of the night to go get a drink of water. If there are no lights on and it is really dark, it will take a while to find your way around, but you'll eventually become really efficient at it. Plus, if you turn the lights on at night it's as if the brain is being told, "well it must be time to be awake now," which is something you want to avoid if it is only 3 am and you don't have to wake for a while.
I think the most fascinating to me that I read about in chapter 2 of the textbook was about the rod and cone photoreceptors. Initially that is what I tried to find sources on, especially the possible third photoreceptor that the book talked about. I didn't have much luck with this subject, so I ended up looking up a subject that is very related to rods and cones, but not about them exclusively. I ended up looking up color blindness, which became a rather eye opening experience ( Haha, Pun totally intended).
Before I start describing Color Blindness lets reword it. From this point on Color Blindness is no longer going to be referred to as Color Blindness. It will be called a Color Vision Defect. This is because calling it Color Blindness is a misnomer because most people assume this means that people who are color blind cannot see color period, even though complete 100% color blindness is very rare. Another thing that most people do not know is that there are several different types of Color Vision Defects. Color Vision Defects can be both inherited and acquired, but most of them are inherited. Colors are only received by one of the two photoreceptors, the cones. The cones come in three different types Long Wave Length Cones, Medium Wave Length Cones, and Short Wave Length Cones. These different Cones receive a specific color based on the wavelength of that color. In Color Vision Defects that are inherited the defect can be caused by one of two things. Either lack of a specific type of cone altogether, or a lack in the needed pigment for that cone to work.
One of the rarest types of Color Vision Defect, is Monochromacy. This is a complete inability to see any color. This is what most people think of when they hear the phrase Color Blind. In most cases of Monochromacy the person can either not have any cones or none that function properly which is called, Rod Monochromacy. People who have Rod Monochromacy suffer from other issues, besides not being able to see color, because they do not benefit from the other functions cones have other than color reception. An example of this is, Photophobia, which is abnormal sensitivity to light. This is because Rods do not function at high light levels, which is what the cones do. The other type of Monochromacy is Cone Monochromacy. This is when the cones exist and function they just lack the pigment needed to receive color. People with this Color Vision Defect still benefit from the other functions of the cones. Rod Monochromacy is especially rare as the trait for it needs to be inherited from both parents. This means that only about 1 in 30,000 people have this Color Vision Defect.
The most common type of Color Vision Defect is called Dichromacy. Dichromacy means that a person can distinguish certain colors from each other, but others they have a hard time differentiating. Dichromacy is divided into three categories for the reason above. The least common type of Dichromacy is called Hereditary Tritanopia. This is also the rarest form of Color Vision Defect. This Color Vision Defect can only be inherited, as denoted in its title. This is a yellow-blue defect. People who have this defect have a hard time distinguishing between blues and yellows. The next two types of dichromacy go hand in hand. They are Protanopia and Deuteranopia. Both of these Color Vision Defects have to do with an inability to distinguish reds, greens, and yellows, but they have no problem distinguishing yellows from blues. Protanopia is an inability to receive red, and Deuteranopia is an inability to receive green. These two forms of Color Vision Defects are the most common types of Color Vision Defects.
The last type of Color Vision Defect is called Anolamous Trichromacy. This is not characterized by a complete inability to see certain colors, but a desensitization to certain colors. Anolamous Trichromacy is divided into three types as well. Tritanomaly which is decreased sensitivity to blue, Protanomaly which is decreased sensitivity to red, and Deuteranomaly which is decreased sensitivity to green. These three Color Vision Defects vary in severity and can be so mild that most people who have them go through life without noticing they have them.
There are two main tests for checking for Color Vision Defects. The first is the most common way to detect Color Vision Defects. It was invented by an Opthalmologist named Shinobu Ishihara. The test is often referred to as the Ishihara Color Test. It takes what looks like plates made up of dots varying in size and color. The task is to see if you can identify the number or object drawn with the colored dots within in the plates. The objects are drawn with specific colors to test for Color Vision Defects. For instance if there is a number in the plate made up of red and green dots, but you can't distinguish it then you might have either protanopia or deuteranopia. The next test is a color arrangement test. This test can give you an idea of possible Color Vision Defects but it does a better job of telling you what color hues you have a hard time distinguishing. If you take one thing away from this take the alternative word usage for color Blindness, Color Vision Defect.
Key Terms:Photoreceptors, Rods, Cones, Color Blindness, Color Vision Defect, Inherited, Acquired, Wave Length, Monochromacy, Photophobia, Sensitivity, Pigment, Dichromacy, Protanopia, Deuteranopia, Anolamous Trichromacy, Tritanomaly, Protanomaly, Deuteranomaly, Opthalmologist, Shinobu Ishihara, Ishihara Color Test, Color Arrangement Test
These are links to the two types of tests I described if you would like to test yourself.
http://www.colour-blindness.com/colour-blindness-tests/ishihara-colour-test-plates/
http://www.colblindor.com/color-arrangement-test/
These are my sources
http://www.uic.edu/com/eye/LearningAboutVision/EyeFacts/ColorBlindness.shtml
http://www.colour-blindness.com/variations/total/
http://www.archimedes-lab.org/colorblindnesstest.html#visione
Good points about the definition of color deficiencies versus full on color blindness. All the photopigment types that can be missing from genetic color deficits are pretty interesting as well. There are a bunch of color tests that you can use. The Munsell color palates are all isoluminant little black pieces with colors on them and you line them up according to hue similarity. It's actually kind of hard to do, but this can tell if you can differentiate between certain hue types indicative of either protonopia or deuteronopia or the rarest yet, tritanopia (lacking S-cones, which are already in short supply if you look at images of the retinal mosaic).
Cool post.
As stated in class, about the only thing I found remotely interesting about the chapter that we read, were the eye problems. Did you know that migraine headaches fall under the category of vision problems? Sure, when you have a migraine you do become sensitive to light and sometimes you do see zigzag lines, but I never would have considered it a vision problem. There are the vision problems the book talked about such as: cataracts, myopia, hyperopia, floaters, night blindness, blind spots and many more. One I was not familiar with is diabetic retinopathy. As if diabetics don't already have enough problems, they can also have bleeding in the retina which can lead to blindness. One website I found listed 25 different kinds of eye problems. Just looking through them and looking at the pictures made me eyes hurt. My eyes are very sensitive. Acanthamoeba was another interesting vision problem. This one has to do with your contact lenses and the cornea. It was a very uncommon problem, but studies show that it is slightly increasing. The cause is using tap water to clean your contact lenses and also swimming with them in. If it does become bad, it threatens eye vision.
Our brain is largely dedicated to our vision, way over any of the other senses. We take our good eyesight for granted, but as soon as something goes wrong we are quick to fix it. Errors of refraction are the most common vision problems. This is when the light rays are focused inside the eye so that the images can be transmitted to the brain. These are easily cured though through glasses, contact lenses, surgery and other options.
The prevention of vision problems was another thing that surprised me. Wearing glasses is a common sense one, but the fact that you should stop smoking, limit how much alcohol you consume and eat green vegetables are surprising factors that contribute to vision problems. There are also three different kinds of people who are helpful with vision problems. For example, an optician only despenses glasses and does not diagnose eye problems. Optometrists are the ones we are most familiar with. They are the ones that do the eye exams and can treat eye problems if needed. An Ophthalmologists are the ones who diagnose and treat eye infections and they do the surgery.
Sources:
http://www.nlm.nih.gov/medlineplus/ency/article/003029.htm
http://www.psychologicalscience.com/perception/2012/01/topical-blog-week-3-due-thursday.html#_login
http://www.webmd.com/eye-health/understanding-vision-problems-basics
http://www.webmd.com/eye-health/understanding-vision-problems-basics
Terms: cataracts, myopia, hyperopia, floaters, blind spots, diabetic retinopathy, cornea, refraction, light rays.
There's actually some really interesting research from Arnold Wilkins lab in the UK, about visual discomfort. He gave a couple talks here at UNR and he showed mid-spatial frequencies which gave people prone to migraines a great deal of discomfort. My friend's who suffer from migraines were at this talk and reported that the mid-spatial frequencies (so actually some kinds of text fonts on computers, etc.) caused a sensation close to producing the onset of an actual migraine. There is some interesting research going on out there about this stuff. You can check out his research if you're interested.
The photic sneeze reflex was something that I found very interesting from the chapter. It is something that I had never heard of or been aware of. The photic sneeze reflex is you body sneezing after suddenly being exposed to an intense bright light. This could happen when a person walks out a movie theater or when they walk outside from a dark room. This causes the body to sneeze once or as many as 40 times. This condition effects 18-35% of the world's population. This condition is a genetic disorder. It is passed on by a autosomal-dominate gene from parents to their children. This means that if one of the parents has the photic sneeze reflex, that about 50% of their children will have it aswell. It is thought that this condition happens when the optic nerve becomes over stimulated by the intense light. This over stimulation of the optic nerve triggers the trigeminal nerve, which is the nerve in the brain responsible for sneezing. Although this disorder seems relatively harmless and possible embarrising, it can be a potential danger for people driving vechicles out of tunnels or pilots flying out of the clouds.
This condition also exists in cats and dogs. The reflex is a useful way for cats and dogs, who sneeze though their noses, to clean out their nasal cavities.
Terms: optic nerve, photic sneeze reflex,
http://en.wikipedia.org/wiki/Photic_sneeze_reflex
http://www.medscape.com/viewarticle/714420_6
http://www.scientificamerican.com/article.cfm?id=looking-at-the-sun-can-trigger-a-sneeze
This stuff shows you how all the nerves and reflexes we have are all connected to our sensation of external stimuli. Pretty interesting how this all happens and works in concert.
I wanted to look at bipolar cells. I am currently thinking of them as tiny secretaries or administrative assistance if you prefer that term better. These little cells get the information from the photoreceptors (the workers) and then send it to the inside where it is processed (by the boss or ganglion cells). Without the bipolar cells everything would get all mixed up and disorganized and important signals that could protect you from a dangerous situation might get lost forever.
What I discovered on the internet about bipolar cells was very interesting. I found some really good pictures that show how they light up when information starts coming in and causes them to react and send the message on to the ganglion cells receptive field and the differences between how they work with the rods and cones. Another really cooI fact that I learned that baffled me for some reason is that the MORE bipolar cells a person has the less fine detail you can see the less bipolar cells that are connected to the ganglion cells the more fine detail you can see. This is so counterintuitive. Is everyone one born with different amounts or do we lose or gain them as we grow older? How strange. I began searching to answer this question but I could not find it. This is really fascinating because I understand how it relates to the fovea and visual acuity now. I feel so smart! Did you know that lots of research done about bipolar cells is done on goldfish? You may have but I did not, this is a little odd.
I also learned about the retina and that some scientists consider it to be a part of the brain that exists outside the brain. This is a crazy concept to me! They believe this because the retina begins processing the image even before it goes into the brain. The bipolar neurons help this process move along. On a side note I also learned about the vestibulocochlear nerve because apparently bipolar neurons are part of many of the sensory systems within the body THIS is a pretty important distinction to make when it comes to speaking as an expert about this topic. I am hoping we learn about this term later when we learn about the auditory system. I thought this term was interesting because it is responsible for the balance within the auditory system. I had never thought about how important this really is. What if I was in the library right now and the only thing I could hear was the printer and there was no balance, which would be very bothersome.
Bipolar cells, bipolar neurons, photoreceptors, ganglion cells, receptor fields, rods, cones, fovea, visual acuity, vestibulocochlear nerve, and auditory system
http://thebrain.mcgill.ca/flash/d/d_02/d_02_cl/d_02_cl_vis/d_02_cl_vis.html
http://en.wikipedia.org/wiki/Vestibulocochlear_nerve
http://www.youtube.com/watch?v=ePSz6oQ2cuk&feature=related
http://www.neuinfo.org/nif/nifgwt.html?query=%22Retinal%20Bipolar%20Cell%22
It is cool you dug deeper into the cellular level of the eye. Most people avoid this kind of stuff. A couple of my friends who are grad students in vision science were at a trivia night trying to win free beer for winning rounds of trivia and one of the questions was, "other than the cerebrum and spinal cord, what part of the human body is part of the Central Nervous System?" And much to their disappointment and ridicule from people like me later on, they did not know that the answer was the retina! They were like, "oh yeah, now I remember" after the fact, but alas it was too late. Anyway, most people don't think of it as part of the brain, but if you think about it, there is neural tissue in the form of the ganglion cells, etc., so the classification is actually quite appropriate.
After reading chapter 2, I decided I wanted to know more about rods and cones. While going through school, I’ve always had an interest in how the body functions. I would say if I wasn’t a psychology major that biology or something like that would be my next choice. Learning about the eyes was really cool. I had no idea so much occurred just in the eye. It’s like our eyes are mini brains that do most of the work before an image even gets to our brain. I was very interested in rods and cones from this chapter. I was intrigued on how we use rods and cones in dark and light situations. So my main objective in this topical blog is to understand how some animals can see nocturnally and compare that to human sight.
As the book points out, Rods are photoreceptors used for night vision. Cones are photoreceptors that we use for day light vision, fine visual acuity, and color. Rods and Cones both convert light energy into neural signals but there difference is the visual pigments that are involved. In our retina, there are about 120 million rods and 6 million cones. It may not seem like the cone to rod ratio is very unbalanced, but most animals only have a few cones while many more rods. This is also why many animals have only black and white vision. Since most nocturnal animals have few cones, they don’t have the right photoreceptors to interrupt color.
After doing a lot of reading, I found that a main reason why animals have such better night vision than humans was because humans lack the tapetum lucidum. The tapetum lucidum is a layer of tissue behind or within the retina in animals. Its purpose is to reflect visible light back through the retina which increases the light available to the photoreceptors. This improves animal’s low-light vision. A cool way of knowing if an animal has a tapetum lucidum is when at night if you can see a pair of glowing eyes reflect back some sort of light that is shown on the animal.
Another thing I wanted to look at was if there was any way for humans to have nocturnal vision like animals. I really couldn’t find much information on humans having nocturnal vision. The main way for humans to see in the dark is though a night vision device. There are two ways of doing this, which consist of Image enhancement and thermal imaging. Image enhancement works by collecting tiny amounts of light, even light that comes from the lower portion of the infrared light spectrum, and amplifying it to the point in which we can see an image. Thermal imaging, on the other hand, happens by capturing the upper portion of the light spectrum (heat). With a heat signal, a person will be able to tell if a living creature is in their vision because their body will show up hotter (more red) than the surrounding objects. Image enhancement is more what animals do. With the help of the tapetum lucidum, animals are able to pick tiny light sources in a similar way as image enhancement devices do. I found that to be very interesting because I never knew how night vision worked.
Terms:rods, cones, photoreceptor, retina,tapetum lucidum.
http://www.pbs.org/wgbh/nova/kalahari/nocturnaleye.html
http://www.ehow.com/list_6935082_differences-between-rods-cones.html
http://www.ncbi.nlm.nih.gov/books/NBK10850/
http://en.wikipedia.org/wiki/Night_vision
http://en.wikipedia.org/wiki/Tapetum_lucidum
http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/nightvision.htm
Cool post. Glad to hear you learned more about the topic you were interested in. I once dissected a cow eye, which was pretty intense. There is a lot of tissue and muscle surrounding the eye, but the cool thing was the way the pigment epiphelium looked (kind of this shiny turquoise oil on glass kind of visual experience) and the way the lens felt. The lens is this crystalline like structure that just kind of disintegrates as you rub it between your fingers. Pretty strange, but educational experience. See if MacLin knows anybody with access to cow eyes.
In chapter two we were dealing with the eye and all that are involved with seeing and how we see. It came to my attention that though this is the normal average vision of a person, what was happening with people that are color blind. So that was my choice of topical blog this week.
Colorblindness is the inability or decreased ability to see color or perceive the differences in colors and hues while under conditions when color vision is not normally impaired. The name itself is rather miss-leading as people that are color blind aren’t actually so; the more accurate terminology would be color vision deficiency. And it has been found that color blindness is a sex-linked condition; the gene for color blindness as it were is carried on an X chromosome. That means that 1 out of 1o men are that much more likely than females to have this condition, as one of two X’s would be enough to make the pigments needed; in some cases woman still receive the gene and have the deficiency. Then there are that cases where injury or trauma to the head would cause a case of colorblindness which may or may not get better depending on the injury sustained.
Where the issue is with colorblindness is within the cones of the eye, where they dwell within the retina of the eye itself. Cones are the photoreceptors specialized for daylight vision, fine visual acuity, and color. The visual pigment, the molecules within an actually has three different types of pigments within the cones. A cone can only have one of the three within it, each pigment dealing with short, medium or long wavelengths. When a cone is lacking one of these three pigments, this is where colorblindness comes in and there in lays the type. There are actually two general types of color blindness; red-green blindness and blue-yellow blindness. Red-green deficiencies cause the person to have a difficult time distinguishing between red and green colors. It is found that this is the most common form of color vision deficiency. Blue-yellow deficiencies are where a person has difficulty distinguishing between blue and yellow colors; this is a mutation rather than genetically transmitted. Usually with blue-yellow deficiencies a person with have some red-green issues as well and is c. The severest case of colorblindness is called achromatopsia, which there are in fact no pigments within the cones and a person sees no color at all; appearing more as shades of gray. There are more types of deficiencies as well with some of these greater categories.
These color visions deficiencies have some impact on the individuals that have it, more so if it from a injury or illness like RP. However, no other problems come from such a condition and people are able to function relatively well with their colorblindness. However, when dealing with certain jobs that they are not allowed performing. Pilots in the air force is one of common knowledge, but also public transportation and machinery that deals with a lots of colors lights are a challenge and they won’t be allowed the job. Difficult to manage it’s not impossible to do so. There is a battery of tests that can be taken to check for color blindness that an eye doctor can perform. The Ishihara color test, consists of a series of pictures of colored spots, is the test most often used to diagnose red–green color deficiencies; I actually remember taking this test way back finding it strange at the time. A figure of numbers most commonly used is embedded in the picture using slightly different colors. These can be seen easily with normal colored vision, but with a color vision defect it’s either a challenge or they will not see it at all.
Terms: retina, cone, retinitis pigmentosa, visual pigment, photoreptor
http://en.wikipedia.org/wiki/Red-green_color_blindness#Total_color_blindness
http://www.tree.com/health/eye-problems-color-blindness.aspx
http://www.medicinenet.com/color_blindness/article.htm
Good points about color blindness or deficiency. Also, what is interesting is the natural variability between the spectral sensitivity functions for different people. Each person's photopigment for each cone type is variable genetically, so for person A, their M-cones might be maximally tuned or sensitive to detecting light in the 540 nm range, but someone else's M-cones could be tuned to 550. This means their subjective (qualia) experiences of the same external color (say a greenish color) could be different. Seems to explain why two people deciding what color to paint a room would have differences in opinion about the perception of how well that color works with that room, etc. Kind of funny when you think about it. Your perception isn't any better than mine, or vice-versa. We simply have slightly different genetic variations an opsin that codes for a specific photopigment molecule associated with a cone type and there you have it, we see the world differently. Amazing.
After reading chapter 2 I found retinitis pigmentosa to be interesting. This I probably because as we discussed in class, like most other students I am fascinated by what went wrong, not the normal things. This topic relates to the chapter because it was discussed at the end of the chapter. It is a hereditary disease that is in the eye(the retina) and can cause blindness, and chapter 2 was based off the eye. This disease does not happen right away and many times it slowly develops. In most cases total blindness doesn’t happen until the 40’s or 50’s. This disease is an abnormality in the photoreceptors, it usually begins at night with night vision or the rods, it becomes harder for them to see at night and they develop tunnel vision, from there on it slowly becomes worse. It also reduces their peripheral vision and it will become harder for them to see.
The main reason this is interesting to me is because there is no cure for the disease. It is known that it is hereditary,passed through the genes, but they cannot find a cure. It has also been discovered it is develops more in men then in women. Even though there is no real treatment for people who have the disease it has been said that by taking Vitamin A supplements and wearing sunglasses to protect the retina from UV rays it can slow the process down. I found one study that used gene therapy on dogs to see if the disease could be stopped or cured. Although the study was mainly done on blindness, they did find that gene therapy worked for the dogs in curing the blindness. The type of blindness that was in the dogs is known as “X linked” retinitis pigmentosa in humans, it is called “X linked because the abnormal gene is on the X chromosome. I believe as we find out more about the disease eventually a cure can be found.
To me this would be a difficult disease to deal with because your vision will be fine up until early adulthood, and then you would know by your night vision and you peripheral vision slowly declining that you were beginning to go blind. I could not imagine having your sight one day and losing it the next. After learning about this disease I will not take my sight for granted.
Terms: retinitis pigmentosa, retina, night vision, rods, tunnel vision, gene therapy, peripheral vision
http://articles.philly.com/2012-01-25/news/30663366_1_corrective-genes-gene-therapy-healthy-genes
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002024/
http://en.wikipedia.org/wiki/Retinitis_pigmentosa
Truly something you hope you never have to experience. I think your point about taking our sensory capabilities for granted is a good one. We often get caught up on the little things in life (e.g., why is my internet slow today), but reading about these disorders and degenerative conditions really reminds you how quickly your portal into everything you like to see, hear, touch, etc. could be quickly ameliorated by either degeneration of some disease or injury to the brain. Be careful out there, and take care of yourself and your brain is the message I always tell people, without trying to sound too authoritarian.
After reading the chapter and participating in the discussion in class, I have decided that peripheral vision is very interesting to me. I am intrigued by the concept of seeing but not really “seeing”. I am curious to see what happens when the peripheral vision is dysfunctional in the visual system and how this would affect a person on a daily basis. After researching, I have found that there is a name for this condition known as kalnienk vision, or tunnel vision. Tunnel vision occurs when peripheral vision is lost, and therefore the visual focus in on central vision. When the visual system relies solely on the central vision, it creates a restricted field of vision, or a ‘circular tunnel’ way of viewing the world. The peripheral vision has a large concentration of rods, which are photoreceptors within the eye, which are useful for seeing at night. A common example of tunnel vision occurs in people who wear eyeglasses. They can see clearly out of their central vision because this is where the glasses are, but their peripheral vision is blurry; which is when tunnel vision is experienced.
There is a plethora of medical causes of this disorder such as blood loss, glaucoma, and high levels of adrenaline. Tunnel vision can also be caused by behaviors such as alcohol consumption, drug use, or even a snake bite.
With these causes being said, there is new research that is looking into the study of how tunnel vision affects college students. A study by Eric Rassin looks at this in more depth. He tested to see how tunnel vision affected decisiveness among college students. After having students complete a series of questions involved with decision making and he concluded that tunnel vision had a significant impact on a student’s ability to make a decision as well as gathering information.
This does not only affect college students, however. People who are deaf and also stuffer from tunnel vision have a different way of using American Sign Language. The difference is that they tend to sign closer to their face, meaning in the field of their central visual system. Because there is an array of different causes of tunnel vision, treatments vary greatly from situation to situation.
Researching tunnel vision is applicable to sensation and perception because it gives perspective on the importance of peripheral vision and how crucial it is to our daily functioning.
Sources:
http://web.ebscohost.com/ehost/detail?vid=4&hid=108&sid=6906eb49-2976-47fd-bb2d-7a441e78a8f6%40sessionmgr104&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=psyh&AN=2008-18472-006
http://en.wikipedia.org/wiki/Tunnel_vision
http://web.ebscohost.com/ehost/detail?vid=4&hid=108&sid=6906eb49-2976-47fd-bb2d-7a441e78a8f6%40sessionmgr104&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=psyh&AN=2008-05779-017
Terms: Tunnel vision, peripheral vision, visual system, central vision, rods, photoreceptors.
Interesting, I didn't know that deaf people's ability to communicate was altered by this visual issue. It shows you how integrated these sensory capabilities are. Good post.
For my blog this week, I chose to do extended research on the photic sneeze reflex. I have been aware that I had this condition since I was a child, but for a long time I thought it was a natural reflex shared by everyone! In fact, I have always considered it to be an extremely logical mechanism. You would not want to stare at a bright light such as the sun for very long lest you damage your eyesight, so what better way to prevent self-induced blindness than an abortive sneeze reflex?
The condition has sometimes been half-jokingly referenced as “Autosomal-dominant Compelling Helioophthalmic Outburst Syndrome,” or “ACHOO” Syndrome. Approximately 18-35 percent of the population is estimated to have this strange condition. The trait has been found to be autosomal dominant, which means that it only needs to be passed on by one parent for it to be received by a child. The first known mention of the disorder was made back in Ancient Greece by the philosopher Aristotle, who wrote, “Why does the heat of the sun on the nose provoke sneezing?” Several centuries later, we are still trying to figure out the mechanism that causes this strange reflex.
Sneezes are normally triggered by an irritation in the nose that is detected by the trigeminal nerve. This nerve is rather close to the optic nerve, which senses visual stimuli such as a sudden burst of light from the sun. Scientists believe the most likely explanation for PSR is that when the optic nerve sends an impulse telling the brain to close the eyelids due to bright light, some of the electrical signal is picked up by the trigeminal nerve and mistaken for nasal irritation. This has previously been compared to the odd association between urination and the shivering reflex, another phenomenon with which I am all too familiar.
http://pmj.bmj.com/content/66/781/892
http://www.scientificamerican.com/article.cfm?id=looking-at-the-sun-can-trigger-a-sneeze
http://www.scientificamerican.com/article.cfm?id=why-does-bright-light-cau
http://en.wikipedia.org/wiki/Photic_sneeze_reflex
Interesting "technical" abbreviation for the phenomenon. Interesting how all of these reflexes and sensory components are intricately inter-weaved.
Terms: photic sneeze reflex, autosomal dominant, trigeminal nerve, optic nerve
I chose the specific topic of myopia or nearsightedness and how to correct it surgically. Myopia is a condition where the light focuses on in front of the retina making objects at a distance blurry while objects up close stay clear. Although many people may say “I’m blind without my glasses!” they are not actually blind. Colors can still be seen and recognized but every line goes away leaving the world in colory blobs. I chose this topic for some relatively personal reasons: 1) I have myopia (I mentioned this in my Monday Blog) and just wanted to know more about it and how to correct it, 2) I have family who has had it corrected, 3) I might have to have mine corrected. I won’t know until Friday after I go to the eye doctor so I’m a little nervous. It’s for a good reason though, not just because I don’t want to wear contacts anymore. To be a police officer in the state of Iowa, uncorrected vision must not be less than 20/100. I don’t know what my sight is now without corrective lenses but I will soon find out. Anyway, on to the research!
The book has an understandable definition about myopia but then it moves onto other sight problems. I usually don’t use Wikipedia as a source for an assignment because some teachers don’t like the site or accept it for their assignments. But it was able to give me a condensed background of refractive surgery. Refractive surgery or more commonly known as LASIK (Laser Assisted In-Situ Keratomileusis) is the surgical procedure that is used to correct vision problems. This procedure includes cutting a flap in the cornea to expose the cornea bed and then using an excimer laser to reshape the cornea so that vision is corrected (Wikipedia website information). After a quick Google search I found the FDA’s website for LASIK surgery. A lot of important information was displayed to three ways; (1) they gave a descriptions of the procedure and what to expect, (2) timelines of don’t before surgery and what to expect afterwards, and (3) video demonstrations of what the procedure looks like. It was very informative but they seemed really heavy on the ‘caution’ and ‘what to expect discomfort’. I can’t believe my grandmother went through all of that and didn’t complain, she was very happy with her results though. The FDA’s website had some warning information about ‘discount deal’ that some places would charge for LASIK. But that just raised a question: how much does LASIK coast? It is a surgery so it can’t be cheap but just how deep do your pockets need to be for corrected vision? USA Eyes priced the average coast of LASIK at $1,350 PER EYE. But they also said that the price could also range from $1,400 to $3,600 PER EYE depending on the surgeon and the technology used during surgery.
http://en.wikipedia.org/wiki/Refractive_surgery
http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/SurgeryandLifeSupport/LASIK/default.htm
http://www.usaeyes.org/lasik/faq/lasik-cost-price.htm
Terms: myopia, retina, contacts, refractive surgery, LASIK (Laser Assisted In-Situ Keratomileusis), cornea, and excimer laser.
Interesting. You took something you were interested in and dug deeper into learning more about it. Its pretty interesting stuff. I'm glad there are standards of visual acuity to become a law enforcement official. I wouldn't want a person's visual deficits to become an issue in important situations. Also, take what you learn from this class and apply it and remember it when you become a police officer. I feel like so many stereotypes exist about cops which are inaccurate, but you could change the mold by applying what you learn in this class to the criminal justice system!!
I chose to do further research on the retina because of its importance to vision. Although it’s not the largest part of the eye, it is the place where light finally gets interpreted. It is through a transduction or conversion of light into electrical energy that messages get sent from here to the brain and that is something that is really interesting to me.
One thing that the retina does as an image is being processed and interpreted is what is referred to as edge detection. Edge detection is when the retina enhances the edges of objects in the visual field in order to basically draw the clearest possible conclusion on what is being seen. Another thing that has to be done the retina is some spatial encoding. There are more photoreceptors present than there are ganglion cells so in order for incoming images to be passed on the image must be compressed.
Besides all of the great things that go on in the retina there are cases where problems arise. Retinitis pigmentosa is a disease that causes degeneration of the retina it first starts with issues in ones night vision and may lead to potential blindness. There has however been great strides taken to try and help those with retinitis pigmentosa see. Some very small scale ways to try and slow this degeneration are by wearing sunglasses, and taking high doses of vitamin A. On a larger scales research is being done to and to some success to create retinal prosthesis. These prosthesis are implanted in the retina and are microelectronic. The device takes the light and directly stimulates the retina. It helps individuals to have partial eyesight by seeing shapes.
As much as I struggle with understanding the complexities of the eye, I really enjoyed learning about the retina. I also enjoyed watching videos about retinal prosthesis.
http://en.wikipedia.org/wiki/Retina
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002024/
http://singularityhub.com/2011/03/08/artificial-retina-that-lets-the-blind-see-again-more-great-videos-of-the-argus/
Key terms: Retina, retinitis pigmentosa, photoreceptors
It is a really intricate design based on the space limitations. The cool thing is that even though there's limited real estate in the retina, the design allows for multiple photoreceptors to converge on a single ganglion cells to save space when acuity is not needed (periphery) but then the one-one ratio is present in the fovea where acuity is important.
My topic that I find interesting is the actual diseases of the eye. In this case I found retinitis pigmentosa fascinating. This fits in our chapter by being described as the “man who could not see stars”. The reason why I am so interested in it is because I have taken some anatomy courses before so I’ve been through the actual anatomy of the eye so learning abnormalities is more interesting to me now. Another reason why I find actual diseases of the eye fascinating is because I work at a financial institution and during a meeting we had a geriatric coordinator come in to speak to us about dealing with our elderly community. She brought with her a little experiment. This experiment involved special glasses that she has us try on to let us see what it was like having certain diseases. One of the glasses were suppose to represent having retinitis pigmentosa. It was such an eye opener to realize how other people may see things. It made me really thankful that I currently have very good vision.
Retinitis pigmentosa is a progressive disease that affects the pigment epithelium and the photoreceptors. It affects the rods, which are responsible for night vision the most; however it has been reported to affect the cones as well. Unfortunately it progresses to the point where peripheral and central vision will be lost. This disease is not something that can be prevented because it is inherited. Most people find out they have this disease due to their night vision becoming weaker. As of right now there is not any known cure however many patients who have this disease are advised to wear sunglasses to protect from any UV rays. Currently there are undergoing research projects regarding high amounts of vitamin A; however an excess amount of vitamin A may cause liver failure. Other research includes inserting a microchip into the retina acting as a microscope in the early stages of the disease. Hopefully a cure can be found soon because other side effects like cataracts and the swelling of the retina are also common with retinitis pigmentosa.
http://www.youtube.com/watch?v=aeD7e0QfD2c
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002024/
http://en.wikipedia.org/wiki/Retinitis_pigmentosa
Terms: Retinitis pigmentosa, pigment epithelium, peripheral, retina, cataracts, rods, cones, photoreceptors.
There is a lot of cool research being done to try to fix some of these issues. There are people who put a micro-electrode strip in the retina of a dog who lost its vision and the dog regained some edge detection/low level vision as a result. Really cool stuff.
The topic that I expressed some interest in was presbyopia. Presbyopia according to Wiki is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Presbyopia fits into the chapter, because it involves a condition of the eye, and the way it functions. I thought this was an interesting topic for the simple reasoning that I have never heard of it before, so naturally it struck my curiosity.
The exact cause of presbyopia is not exactly known, but researchers suspect that, due to some evidence, that it is due to the eye losing the elasticity of the crystalline lens over the years. They also had another possible cause that the change in the curve of the lens from growth, and loss of power in the ciliary muscles may cause presbyopia. Presbyopia occurs slowly over the years, most noticed between ages of 40 and 50, and tends to be in full effect by the age of 60.Presbyopia cannot be prevented, but there are treatments to correct your vision. Presbyopia symptoms are noticed mostly when you are reading. People with presbyopia have a hard time reading in dim lighting because it is straining on their eyes. I thought it was kind of funny that a common complaint from people with presbyopia is that they say that their arms have become too short, because they can’t hold their reading material at a comfortable enough distance to read it.
There are a few treatments that have been discovered for the correction of presbyopia. Presbyopia can be treated with corrective lenses, as well as corrective contact lens. This helps them see without eye strain, and having to hold their reading material a far away from themselves. There also has been many advancements in surgical procedures, such as implanting accommodative intraocular lenses, reshaping the cornea, laser procedures, and various other procedures as well, some working better than others. There has also been another treatment used to correct presbyopia, that raised some controversy, which is eye exercises. I couldn’t find too much on it, but wiki said eye exercises have been touted as a way to delay the onset of presbyopia. The biggest complaint of this is that there is no medical evidence that supports its effectiveness.
http://en.wikipedia.org/wiki/Presbyopia
http://www.allaboutvision.com/conditions/presbyopia.htm
http://www.aoa.org/x4697.xml
Terms- Presbyopia, crystalline lens, ciliary muscles, intraocular len
Empirically based evidence and treatment based on that evidence is important, but sometimes it becomes a "whatever works" mentality, especially for people who have tried a bunch of different ways to either prevent or live with a certain condition/disorder. Definitely interesting in the number of ways that your vision can be altered by one piece of the puzzle being removed (so to speak).
One of the most interesting things I found from chapter two dealing with the eye was the disease of retinitis pigmentosa. Naturally any disease is terrible for anybody to acquire, but the concept of how this particular disease takes effect and its course of action that leads to blindness interests me because of the rarity of the condition as well. Retinitis pigmentosa is an eye disease that is hereditarily contracted and degenerate the retina, which ultimately harms peripheral vision as well as night time vision. This particular disease varies amongst individuals and does not always take the same length of vision impairment. In some cases it may affect children at a young age, while in others takes years, where vision becomes less clear over time and may be as late as their 50s. The retina is one of the most important pieces that help the eye see. Dystrophies of the retina lead to eventual vision loss. Visual testing and ERG’s will show photoreceptor loss during the diagnosis of retinitis pigmentosa. Retinal damage and the association with retinitis pigmentosa strongly relate to the chapter because it involves the functions of the eye that allow visual perceptions. Retinitis pigmentosa is also affected due to the loss of peripheral and night vision. As far as retinal degenerations in the form of hereditary disease go, this is probably the most common. Another catastrophic part of retinitis pigmentosa is the damage of the photoreceptors rods and cones. The rods are the primary part of damage because of the gradual loss of night time vision, which appears to be the first noticeable sign of the disease. Cones also play another important role in the degeneration of the eye. Unlike the rods, cones contribute to the light vision of the eye, and contains photopigments. Together these two parts make a duplex referring to the retina. This disease proves to be very serious in the damage of sensation and perception for individuals. Around 75,000 Americans are affected due to this condition. The likelihood of both eyes becoming affected by the diseases is also very high. There are also signs that are associated with the loss of hearing and this particular disease. I believe, while as terrible as it is, this disease shows a lot of insight toward how the functions of vision can become damaged and change the perspective of how we view and perceive sensation and perspective concepts.
Terms: retinitis pigmentosa, retina, rods, cones, photoreceptors
http://en.wikipedia.org/wiki/Retinitis_pigmentosa
http://emedicine.medscape.com/article/1227488-overview
http://www.medicinenet.com/retinitis_pigmentosa/article.htm
Good post that seems to synthesize the information you learned into a coherent post. The RP is a bad disease and I think that people are doing some great research out there currently to either take preventative/screening measures to help people predict if/when it will happen and also ways to help people who have suffered from the effects of RP and possibly regain some retinal functioning.
My topic of interest is the evolution of sight, or more specifically, the reasoning behind why humans can't detect infrared or ultraviolet light. The eye has gone through many changes throughout time.
Evolution has altered simple light receptors into the complex duplex system humans have presently. The most drastic change the eye has undergone was through the evolution of vertebrates from invertebrates; and more recently, the evolution of mammals from reptiles.
Most people assume that homo sapiens are the pinnacle of evolution, and thus should have the best sensory organs; including night vision. However, this is not the case. Organisms evolve from the mold that the environment creates. The most successful environment for primates to exist was during the daytime. Therefore it was unnecessary to adapt to a nocturnal life. Nocturnal organisms have developed a tapetum lucidum, which (as discussed in class) reflects reflects photons to create more out of less.
As for the inability to detect ultraviolet and infrared light, the short answer is that mammals never had to. The visual system that was used was sufficient. Hypothetically, there could have been some mammalian mutants that were able to detect ultraviolet or infrared; however, the genetic malformation could have hindered "normal" visual processing (blue to red), or if the mutation was successful, that the offspring had the same advantages as normal offspring, and so the mutated genes would be just a drop in the oceanic gene pool.
Terms: evolution of sight, duplex system, tapetum lucidum
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
https://en.wikipedia.org/wiki/Evolution_of_the_eye
https://en.wikipedia.org/wiki/Night_vision
https://en.wikipedia.org/wiki/Tapetum_lucidum
My topic of interest is the evolution of sight, or more specifically, the reasoning behind why humans can't detect infrared or ultraviolet light. The eye has gone through many changes throughout time.
Evolution has altered simple light receptors into the complex duplex system humans have presently. The most drastic change the eye has undergone was through the evolution of vertebrates from invertebrates; and more recently, the evolution of mammals from reptiles.
Most people assume that homo sapiens are the pinnacle of evolution, and thus should have the best sensory organs; including night vision. However, this is not the case. Organisms evolve from the mold that the environment creates. The most successful environment for primates to exist was during the daytime. Therefore it was unnecessary to adapt to a nocturnal life. Nocturnal organisms have developed a tapetum lucidum, which (as discussed in class) reflects reflects photons to create more out of less.
As for the inability to detect ultraviolet and infrared light, the short answer is that mammals never had to. The visual system that was used was sufficient. Hypothetically, there could have been some mammalian mutants that were able to detect ultraviolet or infrared; however, the genetic malformation could have hindered "normal" visual processing (blue to red), or if the mutation was successful, that the offspring had the same advantages as normal offspring, and so the mutated genes would be just a drop in the oceanic gene pool.
Terms: evolution of sight, duplex system, tapetum lucidum
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
https://en.wikipedia.org/wiki/Evolution_of_the_eye
https://en.wikipedia.org/wiki/Night_vision
https://en.wikipedia.org/wiki/Tapetum_lucidum
There's also some evidence to suggest that the species that we evolved from (millions of years ago) used to be nocturnal and use four legs, etc. You're right that the environment produces the need to modify the genes to perform some function in the face of new environmental changes/challenges. Pretty interesting stuff. I can point you to some more articles about the evolution of color vision if you want to email me.
Topical Blog #3
I chose to focus my research topic on facial recognition in the brain and software.
- When the brain identifies faces there are certain parts of the brain that are triggered to clearly recognize people that you have met before. The research I found in a science magazine states that the temporal lobe activates with humans look at other people, but one can not fully say that the temporal lobe is the only part of the brain to recognize faces. There is evidence that neurons in the temporal lobe helps recognize faces but only that, and not the body of other humans or other objects. I found this research to be interesting because according to the book, they did not state whether a person’s perception of other objects would be in the temporal lobe as well. Signals in the brain are fired to recognize and be stored in the memory. Also, this may play a factor in attractiveness, and what people find to be attractive or ugly.
http://news.sciencemag.org/sciencenow/2012/10/identifying-the-brains-own-facia.html
-Another research project from Georgetown University also says that the brain is very important to process facial recognition to spot differences in individuals faces. The research then goes on to say that is why autistic individuals have a hard time perceiving faces because the neurons are not fully firing in this part of the brain which allows facial recognition. The theme of this research focuses on how the brain interprets the difference between faces, because it would be hard if the neurons could not tell the different faces apart due to not knowing who we were talking to, or understand the facial expressions in other people!
http://www.georgetown.edu/news/autism-facial-recognition-research.html
-Lastly, I research about Google Glasses, because in today’s society technology is changing on a daily basis, and these glasses can recognize faces for you. This youtube video shows how the google glasses are constructed to perceive faces. The glasses will have a picture of a person and then when you see that person again it will tell you their name and other things searched on google about them. Facial recognition is important, but do we need this advanced technology if our brain can already process this information? I feel that the facial recognition in software and robotics is useful for forensics and maybe even to help those with autism. The facial recognition process in technology is similar to the brain, but does not come naturally.
http://www.youtube.com/watch?v=1t6DBGY0TI0 vocab= facial recognition, neurons, temporal lobe
This week, I chose to do my topical blog on astigmatism. I thought that this topic was interesting to look into because I have bad astigmatism and the book wasn't real clear on how it works.
First I decided to go straight to the source: the American Optometric Association. I got a rough definition as to what astigmatism truly is. Here, they define the disease as an irregular shape in the cornea or lens. I found it interesting that there are several different causes for one disease. The AOA says that astigmatism is very common, especially in people who have nearsightedness and farsightedness. I know that I am near sighted and originally, I thought that is what astigmatism was, so it was cool to learn that it can be for farsightedness as well.
http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/astigmatism?sso=y
Because the American Optometric Association website mentioned that there were 3 types of astigmatism, I was curious to learn more about each type. So I looked on the All About Vision website. The three types are myopic (nearsighted), hyperoptic (farsighted) and mixed (both nearsighted and farsighted). I found that astigmatism can be classified as regular or irregular. Since it is such a common disease, most people have regular astigmatism, but those who have irregular astigmatism need to have surgery because contacts cannot correct their vision.
http://www.allaboutvision.com/conditions/astigmatism.htm
Since I really enjoyed the test for astigmatism in the book, I decided to find a website that could give me more input on how the tests work and maybe even take some more! Basically, I found out that astigmatism is detected during a yearly eye exam almost 99% of the time, usually without the subject knowing they had that terrible of eyes. I thought it was cool that astigmatism is found by just shining a light into your eyes to determine how severe it is. I figured they could tell you had astigmatism when they place that appliance on your head to see what your vision is, not just by looking. It's cool that it can be detected just by looking. The Acuvue website actually gave some awesome input as to what astigmatism looks like and had some additional tests as well (in which I failed all of them).
http://www.acuvue.ie/astigmatism