What I would like you to do is to find a topic from chapter 5 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.
By now you all should be skilled at synthesizing the topical material you have obtained from the various web sites you visited. If you need a refresher please let me know.
Include a list of the terms and concepts you used in your post. (example - Terms: positive reinforcer, extinction, reinforcer, discriminative stimulus...)
Thanks,
--Dr. M
Chapter 5 has been the most interesting and understandable to me so far, so for my topical blog I chose to further my interest on achromatopsia since I wanted to learn more in depth about this topic in class. Achromatopsia is the inability to perceive colors that are caused by damage to the central nervous system. One possibility is someone who has had brain damage, indicating damage to pieces of the cortex that are important to our perception of color. Two primary forms of congenital achromatopsia: rod monochromatism and blue cone monochromatism. Both conditions impair the cones receptors in the retina. There are three basic rods and cone function. These being phopic (all bright lighting situations) vision, mesopic (mildly dark area where you can still see colors) and scotopic vision (dark, like a moonless night). Loss of cone receptors impairs color vision, reduces acuity and debilitates glare which is know as day blindness or hemeralopia. Hemeralopia (Day Blindness) -- Extreme Light and Glare Sensitivity In order to function across a wide range of lighting conditions, we must switch between two different visual systems, the photopic and scotopic systems. The photopic system uses cone cells that see color, function best in bright light and provide our best vision (20/20) due to the concentration of cones in the macula of our retinas. The scotopic system functions only in very low levels of light. It uses rod cells that are able to function only at very low levels of light. This provides our night vision. In patients with achromatopsia, the cone cells are not functioning. Thus the only cells left are the rod cells. Thus when the achromat goes into bright light, the scotopic visual system, meant to be used only at night is suddenly overwhelmed. Most of us see malls as bright colors, whereas people with this problem see black, white and gray. The bright lighting causes them to squint to see, the lighting overwhelms them and the squinting reduces visual field. They have invented glasses that are with red lenses to reduce glare and allow patients to see with their full visual field. Now they have developed a special type of contact lens for individual who do suffer from achromatopsia so they do not have to squint when in bright lighting. These come in red, blue or magenta depending on individual. Also come in amber brown and darker red-black filters. These help an achromat’s vision in dark and bright lighting.
Furthermore, Achromatopsia is an inherited condition that affects approximately 1 in every 33,000 Americans. It is also known as rod monochromatism. This condition is associated with color blindness, visual acuity loss, extreme light sensitivity and nystagmus. It is a condition found throughout the world with varying incidence. There are two primary forms, the complete achromatopsia and incomplete achromatopsia. Complete Achromatopsia Achromatopsia means “without color†and is defined as little or no function of the cone cells. Persons with achromatopsia are only able to perceive black, white and shades of gray. Patients with complete achromatopsia have no real understanding of the concept of color. A color like red may be perceived as dark gray while yellow may be perceived as a light gray. The vision is much like that of a black and white photograph with varying shades of gray. Incomplete Achromatopsia patients with incomplete achromatopsia have profound color impairment, but do have a small residual amount of color vision and slightly better visual acuity due to the presence of some functioning cone cells in the retina. In addition, Inheritance Achromatopsia is a recessive inherited condition. It requires both parents to contribute a gene in order for the condition to occur. All the offspring of an achromat may carry one gene for achromatopsia. In order to pass the condition onto their children, it would require having children with someone else carrying the same gene and passing a gene from each parent. Early Detection in Children Achromatopsia is present from birth. The first signs may be the presence of nystagmus, a pendular quivering of the eyes and light sensitivity with squinting in bright light. An electroretinogram may show an abnormal photopic or daylight signal while maintaining a normal scotopic or night vision signal. When the child is old enough, color vision testing like the Sloan Achromatopsia Test can further confirm the diagnosis.
http://www.youtube.com/watch?v=cGLloGqNpaY
http://www.achromatopsia.info/
http://www.lowvision.org/achromatopsia_and_color_blindnes.htm
I decided to do my topical blog on the topic of monochromacy, or complete color blindness. This means that you see everything in shades of gray. There are a few different forms of monochromacy: rod monochromacy, cone monochromacy, and cerebral achromatopsia. Rod monochromacy, also called achromatopsia, is when the cones are either absent or just not working and vision depends on the rods. Rods are the receptors in the eye that are responsible for night vision and brightness. They have little to do with color vision. Having this condition means that not only can you not see colors, but you’re extremely sensitive to light, which his called photophobia. Because night vision comes from rods, a person with this condition can see better at low-light levels. This condition is the most common type of complete color blindness.
Cone monochromacy is very rare. With this condition, rods and cones are present but only one type of cone exists, either S,M, or L-cone. Depending on which cone is present decides what type of monochromacy you have. Blue cone monochromacy is when S-cones are present. Green cone monochromacy is when M-cones are present. Red cone monochromacy is when L-cones are present. The reason you’re colorblind is because without the two of the cones working, there’s not enough information being received to make out the colors. Because the rods still work, vision at night is better because the rods are working with the cone that exists.
Cerebral achromatopsia is unlike the other forms of monochromacy because it’s not inherited. The condition is not well researched but it’s believed that the cause is from trauma or illness that inhibits the information from the visual system from reaching the brain through the cortex. People with this condition have normally functioning rods and cones but are still completely colorblind. Unlike regular monochromats, these people see gray because they once saw color so they know that the absence of color is gray. Regular monochromats view gray as their own “color”. Individuals with this condition do not experience sensitivity to light or impaired vision.
Terms: monochromacy, rods, cones, receptors, photophobia, S, M, L-cone, cortex
http://www.achromat.org/what_is_achromatopsia.html
http://www.associatedcontent.com/article/1925068/colour_blindness_the_difference_between_pg2.html?cat=5
http://www.colblindor.com/2007/07/20/monochromacy-complete-color-blindness/
A topic in chapter 5 that interested me was the topic of lights, filters, and finger paints, or in a shorter terms, color mixture. Television and computer monitors are largely possible by color mixing. If you take a magnifying glass to a yellow patch on the computer screen, you will see mixed red and green dots. This formula (red+green=yellow) is an example of additive color mixture, or a mixture of lights. Since red and green are both reflected from that surface to our eyes, the effects of those two lights add together and create the yellow color. According to the website I found, there are two types of color mixing. The first is mixing colors like paint, and the second is mixing light. Therefore, since red and green make yellow with light, it doesn't necessarily mean that red and green make yellow with paint or another substance. This is called subtractive color mixture, or a mixture of pigments. For example if red (A) is mixed with green (B), some of the light shining on the surface of those colors will be subtracted by each color. The remainder of the light is what will contribute to our perception of color. The first website listed is a really good website if you really want to know how television colors work. There are three electron beams and three different kinds of phosphors in a television. (A phosphor is any material that when exposed to radiation emits visible light). The beams are directed to certain phosphors which blend the colors and create color on the television. These blend of colors add together on the television they create different colors like stage lights. (Stage lights blend together and form different colors as seen in the book as well as the first website listed). These colors then work together on the television and create images. Most computer monitors work the same way. I really recommend checking out the first website listed. It is very interesting!
Another aspect included in this topic is the discussion of wavelengths. When red and blue light are mixed together, the different wavelengths are actually what causes the mix in color. I should have added these things in above, but here is an example. If blue and yellow lights are shined on the same platform, it will create a white or gray light. This is because yellow is made up of medium and long wavelengths, so blue and yellow results in short, medium, AND long wavelengths. This mixture is what creates the gray or white light.
This topic leads to other topics as well. For example, color space is the three-dimensional space that is created because our color perception is based on three cone types, and this describes the set of all colors. We look at color by different numbers and dimensions. For example, when we would like to create a color on something such as Word or Powerpoint, we are able to type in the percent or number of all the different colors we want. These different numbers and portions of certain colors will actually create a color in itself. The colors used in things like that are usually Red, Green, and Blue. These colors are able to create any color in the visible spectrum, which is why they are what's used in television as well as computer monitors. The different intensities are what creates the shades and different colors. We are able to look at the mixture of colors in different terms such as hue, saturation, and brightness. Hue is described as the chromatic (colorful) aspect of color. Each point on the spectrum of color (reverting back to the example on Word) represents a different hue. Saturation, however, is the chromatic strength of a hue. An example of this is what white has zero saturation, pink increases, and red is full saturation. When something is less saturated, it appears to be washed out or faded. A final term is brightness (or brilliance), which is the distance from black (0 brightness) in color space. For example, this also can be described as physical intensity. The sun is more physically intense than the moon, whose light is not as bright.
http://www.colorado.edu/physics/2000/tv/merging_color.html
http://electronics.howstuffworks.com/tv6.htm
http://whatis.techtarget.com/definition/0,,sid9_gci212262,00.html
http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci212900,00.html
I decided to talk about cultrual relativism and how people in different cultures create their own linguistic map of color space. It is interesting to me from cultural point of view.Living in a different country I can observe so many diffrences, but would not think we also perceive colors in different way; and we do.
I will start from explainign what exactly cultural relativism is. According to our textbook, the term cultural relativism is "In sensation and perception, the idea that basic perceptual experiences (color perception) may be determinated in part by the cultural environment.
The author of the textbook gives us couple answer on the question of everyone see colors the same way. I would like to foucs on the answer: "it depends on many factors, inter alia on place where you live. Thus, after surveying many langhuages researchers found that the 11 basuc color terms in English are about as many as any group possesses. Some languages have 2 basic colors, some three. Some languages do not even recognize the distinction between the two colors: green and blue. That means that culture does not necessary incluence on our color's percetpion. These two colors, blue and green are seen as categorically different even if one language does not emply color terms to express thuis difference.
One of my source abour cultural relativsim in perception is according to evolution. Culturlal differences in basic color cagorization have been explaines by biological evolution, linguistic relativism (according to out textbook), and semantci evolution. The study on color perception in differenct countries has been done and the researchers concluded that "hue discriminability
functions may vary systematically from one language community to the next to the extent
that color categories in different languages partition the hue continuum differently."
I found an interesting website that says what different colors mean in different countries. And, for instance, black signifies death and is worn during times of mourning in Western countries; black in Egypt, however, represents rebirth. It might seems obvious that we think of red color as love, heat, romance or even danger. That is in American culture. For example, in China people think of red color as sun, the phoenix, fire, summer, the south, joy, good fortune on the contrary to Nigeria red symbolizes wealth, plenty, virility.
In conclusion, reading about how people perceive colors in different placesin the world, I can say that definately it all depends on cultures, how we name the colors as well. There re many theories that some agree with each other and some do not. I believe that culture does affect how we perceive the color.
http://onlinelibrary.wiley.com/doi/10.1525/aa.1975.77.4.02a00030/pdf
http://cybertext.wordpress.com/2009/05/18/what-different-colors-mean-in-different-countries/
http://www.office.xerox.com/small-business/tips/color-guide/nigeria/enus.html
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2611923/pdf/jnma00509-0063.pdf
The topic that I decided to do more research on from chapter 5 is afterimages. The textbook defines afterimages as "a visual image seen after the stimulus has been removed". The text also mentions negative afterimages. Negative afterimages are defined as "an afterimage whose polarity is the opposite of the original stimulus. Light stimuli produce dark negative afterimages. colors are complementary: red produces green; yellow produces blue."
I started my search on Youtube and found some pretty cool videos. The first one I found worked really well. The music in the background is a little obnoxious but it is defiantly worth giving a try. Watching the videos and experiencing the afterimage for myself helped me get a better idea of what an afterimage is. The first clip I watched was an example of what a negative afterimage is. I found another cool clip that shows an afterimage. It is a castle and then it changes to a black and white picture of the same castle but it appears to have color. I found these examples of afterimages easier than the example that was in the textbook.
I found a few different websites that had some very interesting info about afterimages. One website states that "When our eyes are exposed to a hue for a prolonged period, the rods & cones become fatigued. You might notice this if you are reading something on colored paper, and then look away—you often see the inverse, or complement, of the image. This occurrence can be advantageous if you are seeking the opposite, or contrast, of a color. This may be dismaying to a viewer if presented with prolonged exposure to colored screens or reading materials" (http://www.worqx.com/color/after_image.htm) I thought this explanation was very helpful in understanding why afterimages occur. This website also offers another example of an afterimage. According to http://serendip.brynmawr.edu/bb/neuro/neuro06/web2/aschmid.html, the fatigue that our rods and cones experience and cause us to see the polar opposite in the afterimage is caused by "the temporary bleaching of the light sensitive pigments contained within the photoreceptors. This results in the information that is provided by the photoreceptors not being in balance, causing the afterimages to appear. As the photoreceptors become less "fatigued", which takes between ten and thirty seconds, the balance is recovered, resulting in the afterimage disappearing."
I normally don't like to use long quotes but with this topic it was hard to try to find a way to reword the quotes and still say the same main message. I am glad that I researched afterimages because it helped me understand what exactly there are and how they happen. I know understand what causes an afterimage to appear. I would recommend checking out some of the youtube clips, in my opinion they work better than the example in the book.
http://www.youtube.com/watch?v=zBSub8csvY0&feature=related
http://www.youtube.com/watch?v=w6ccBwnc5KU
http://serendip.brynmawr.edu/bb/neuro/neuro06/web2/aschmid.html
http://www.worqx.com/color/after_image2.htm
One topic that I was interested in was trichromacy. Trichormacy is when there is three independent channels for conveying color information. As we know from previous chapters rods are not very useful in color vision because they only contain one pigment called rhodospin. Color vision is primarily the job of the cones, and there are three different types of cones for color vision. The first type is called the S-Cone which is sensitive to short wavelengths, the second is the M-Cone which is sensitive to middle wavelengths and finally there is the L-Cone which is sensitive to long wavelengths. These three types of cones are responsible for all the colors that we see on a daily basis. People who are color blind often are color blind because of difficulties with these cones. If a person is missing a certain type of cone such as the S-cone, they would not be able to see blue very well or any colors that blue is apart of. The same goes from the M-Cone and L-cone, with out them you would not be able to see green and red respectively. In some cases people have absolutely no cone, which causes them to be very sensitive to light as well as unable to see color. Another fact about Trichormacy is that analog televisions were based off this same theory. Analog televisions used three primary colors of green, blue, and red to create most visible colors. Some other species that are also Trichormats are howler monkeys and honey bees ( which are sensitive to ultraviolet, blue and green). Other animals such as dogs, ferrets, and the spotted hyena are dichromats or with only two types of cone.
Sources
http://en.wikipedia.org/wiki/Trichromacy
http://en.wikipedia.org/wiki/Color_blindness
An Image to check out
http://nonemark.com/wp-content/uploads/2010/12/trichromacy-primaries-additive-and-primaries-substractive.jpg
I chose to emphasize Trichromacy, or the Trichromatic Theory of Color Vision. Our text defines this as 'The theory that color of any light is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the three cones. Thomas Young originally purposed the idea that our color system was based on three different color receptors, but the theory was expanded and largely credited to Hermann Von Helmholtz. The theory was finally proven physiologically by Gunnar Svaetichin in 1956. This leads me to wonder why we are still calling it a theory if Gunnar Svaetichin proved it through our own very objective physical anatomy. Would it need to be proven mathematically to become more than a theory? Anyway, we all understand the L, M, and S cones and how their receptive wavelengths overlap. This is even more interesting after further research has shown me that this trait is rare among animals and very rare among primates.
An interesting theory exists that accounts for our trichromatic status as being an evolutionary trait brought about by the variety of fruit we eat. Other primates have a very non diverse diet of nuts and berries that don't occur in very diverse colors, but our global span has introduced us to 1,000's of varieties. We had to adapt an ability to distinguish between many colors due to the need to identify them against their foliage background. Only humans and a few species of 'New World' primates have this ability. Jeremy Nathans of Johns Hopkins University has a very eloquent and insightful lesson on the evolution of trichromacy in primates, and he was kind enough to post it on YouTube:
http://www.youtube.com/watch?v=JPY-n8uqCVk
The Physiological Science Journal has a very exhaustive explanation of the Trichromatic System here: http://physiologyonline.physiology.org/content/17/3/93.full
And Wikipedia has a very brief overview of this topic, but it had good information on the researchers of this theory: http://en.wikipedia.org/wiki/Trichromacy
After reading Ch. 5 “Color Perception” I was interested in the topic of afterimages. An afterimage is a visual image seen after the stimulus has been removed. Afterimages are commonly used in optical illusions such as the first link I provided below. I don’t know about you but I saw that lightbulb for a good couple of minutes after trying it! What you just saw is actually a negative afterimage, where the dark stimuli create a light negative afterimages. This can also occur with color. A negative afterimage of color results in an afterimage of its complementary color (red to green, yellow to blue, black to white). The second link provides an example of a color negative afterimage (note: scroll down to the red image with green birds). You may have to stare at it longer than 20 seconds or come back to it after awhile. So why does this happen? After looking at the image for a prolonged amount of time rods and cones become fatigued. In other words they become desensitized and as a result you receive an afterimage. The opponent-process theory of color vision uses afterimages as an explanation of its theory that a person never sees some color combinations. This theory suggests that color vision is an activity of two opponent systems: one that is blue-yellow and one that is red-green. This is a different theory than the trichromatic theory of color vision (S, M & L cones).
http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/afterimage.html
http://www.worqx.com/color/after_image.htm
http://psychology.about.com/od/sensationandperception/f/opponproc.htm
Anomia is being able to recognize something but not being able to recognize it. Anomia relates to the chapter in that people who suffer from it cannot name colors. The example given in the book is that a person might see a banana but cannot say that it is yellow. After doing further research on this topic I now see how something like this is very realistic. First, I watched a youtube video of a patient who suffers from anomia. In the video a doctor showed her a picture of a saw. He response really caught my interest. She was able to say everything a saw is used for but not able to name it. She must have given about 5 different usages of the saw and even started saying “saw” but thought she was wrong. Mednet defines anomia as “a problem with word finding”. According to healthline, anomia is caused by damage in the part of the brain that controls language and communication. The parts of the brain that may be damage in a patient with anomia is that auditory cortex, Wernicke’s area (where words are stored), and Broca’s area (directly related to wernicke’s area). The main causes of anomia are head injuries, strokes, and tumors. The left side of the brain is what usually is affected when talking about patients with anomia. I found is very interesting that anomia is not related to loss of memory. Other than the loss of a word, patients can remember the object very well. This makes sense after watching the youtube video about the girl who could describe everything about the saw but could not recall its name. Patients who suffer from anomia are still able to perform every day task. Speech therapy is necessary in some cases, in others it is not.
Sources:
http://www.youtube.com/watch?v=LWAUmsgk8eg
http://www.medterms.com/script/main/art.asp?articlekey=21580
http://www.healthline.com/galecontent/anomia
My friends and I have recently discovered an application on facebook where we can challenge each other to endless games of Tetris
Contrary to misconceptions, this is not a complete waste of time. According to a website by BBC, tetris can be good for the brain. IT caused the grey matter in a group of teenage girls to thicken. It could also reduce the flashbacks of PTSD.
However, after playing for awhile I started to see the see after effect of color Tetris shapes falling every time I closed my eyes. I thought I was the only one who experienced this until I talked to another one of my friends, who said he was stopping because he didn’t like it. After looking online, I realized there were only web pages and blogs dedicated to this experience.
After Effect of colors is when you stare at a color for a long time; red, green or blue for a long time and then close your eyes or look at white you will see the complementary colors. There are three cones in the eye, one that picks up red, one for blue and one for green. When you stare at a color, like red, light is reflected as a combination of different lights. So that all cones are activated, but not as intense as the red-cone.
According to the article “Afterimages” by Anne-Marie Schmid, those cones become “fatigued” and you will see the complementary colors. Although Schmid states that his process is not completely understood, What I got from the website she is proposing these cells could be working like ON and OFF cells, that when a red-green cell is activated in the center it will stimulate as red. When it re-green cell stop firing, the brain will interpret this reduction in the stimulation as the presence of green. I wonder if this “tetris effect” and afterimage are connected, as similar reactions in the brain.
An article from Sciencedaily reported more about the posttramtic stress disorder and how it can reduce flashbacks. An Oxford team reasoned that “the recognizing of the shapes and moving the colored building blocks around in Tetris” will compete will the visions of the trauma retained in the sensory part of the brain. This will reduce the painful and distress flashbacks.
http://esciencenews.com/sources/science.daily/2009/01/08/computer.game.tetris.may.help.reduce.flashbacks.to.traumatic.events
http://serendip.brynmawr.edu/bb/neuro/neuro06/web2/aschmid.html
http://news.bbc.co.uk/2/hi/uk_news/magazine/8233850.stm
Thanks for the post. I used to play a lot of tetris on facebook and I experienced that too. A lot of the time it would make me feel sick so I drastically reduced my play time. I thought it was really interesting that you were able to find information on the effects of Tetris. It's good to know that I wasn't going crazy, I would never have thought to tie this experience in to the information we've been learning.
I am not sure if this went through? so I will try to post again...
Does a bull really get enraged by a red cape? How do bees know which flowers are plump with nectar? Why does your cat see and pounce upon an insect before you’re even aware of it? In short, what, exactly, do animals see - and do they see color? While no one knows exactly what animals see, there are several aspects of the question that beg exploration. We not only need to know how their eyes work from a physiological perspective, but also the spectral sensitivities of the photo-pigments present and how their brains perceive color.
Many animals can see things that we cannot. For example, cats rely on their night vision to give them an advantage as they hunt for prey, while our human ancestors - who couldn’t see well in the dark - sought safe refuge at night and hunted during the daylight hours. Although we know that sight differs among animals, we do not know what animals actually perceive. There is an important distinction between having light illuminate the retina, and understanding what is being seen. Color vision and perception across the animal kingdom is the subject of much ongoing research, as we have a very limited understanding of the many ways animals see.
The dance of the honeybee has been researched extensively, so we have a relatively good understanding of the color vision of bees and related insects. Mosquitoes and flies have been studied because of their role in spreading diseases, and it has been shown that they are attracted or repelled by specific surface colors, and by specific colored sources of light. Interestingly, the surface colors they prefer do not necessarily correlate with the light source colors that attract them.
There is an enormous diversity in the retinal structure and neuronal mechanisms across the animal kingdom, and a corresponding diversity in the role of color vision in animals’ perception, behavior, and interactions with the environment. Amongst invertebrates, eyes themselves take on a startling variety of shapes, forms, and numbers.
Light sensitivity has been observed in organisms such as amoeba; their activity levels change with varying light conditions. Earthworms have simple light receptors, enabling the earthworms to react and tunnel back into the earth immediately when they are exposed to the multiple hazards of sunlight, which include dehydration and predators.
At the other end of the spectrum, the mantis shrimp has complex eyes with more than double the number of ommatidia (simple, cone-shaped lenses) found in bees, and with at least a dozen distinct photoreceptors. A possible reason for the complexity of these eyes is that much of the color processing occurs in the eye itself, rather than in the brain. By contrast, our eyes send raw visual data to the brain, where it is processed so that we can make sense of it. There is no particular advantage to either system; the shrimp have just evolved in a completely different way.
The honeybee has complex eyes consisting of over 5000 ommatidia. Within each ommatidium, the visual cells that detect color are arranged like orange segments around a central core.
The range of vision for the bee and butterfly extends into the ultraviolet. The petals of the flowers they pollinate have special ultraviolet patterns to guide the insects deep into the flower.
Fish appear to have quite well developed visual systems, comparable in some species to those of birds. Some have photoreceptors with peak sensitivities in the ultraviolet range. This may be because, like birds, they move about in a blue environment and need to contrast food sources or predators against a blue background.
At the other end of the spectrum, the mantis shrimp has complex eyes with more than double the number of ommatidia (simple, cone-shaped lenses) found in bees, and with at least a dozen distinct photoreceptors. A possible reason for the complexity of these eyes is that much of the color processing occurs in the eye itself, rather than in the brain. By contrast, our eyes send raw visual data to the brain, where it is processed so that we can make sense of it. There is no particular advantage to either system; the shrimp have just evolved in a completely different way.
The honeybee has complex eyes consisting of over 5000 ommatidia. Within each ommatidium, the visual cells that detect color are arranged like orange segments around a central core.
The range of vision for the bee and butterfly extends into the ultraviolet. The petals of the flowers they pollinate have special ultraviolet patterns to guide the insects deep into the flower.
Fish appear to have quite well developed visual systems, comparable in some species to those of birds. Some have photoreceptors with peak sensitivities in the ultraviolet range. This may be because, like birds, they move about in a blue environment and need to contrast food sources or predators against a blue background.
While mammals have relatively weak color vision, humans and other primates have the most advanced color perception in this class. Dogs have two identified types of cones, suggesting they are dichromats with similar peak sensitivities to red-green colorblind humans. Cats are trichromatic, but have a much lower proportion of cones to rods than humans. In addition, dogs and cats have a much more highly developed sense of smell than humans. While we rely primarily on sight, their perception of the world is far more reliant on olfactory stimuli.
What we know about color perception in the animal kingdom pales in comparison to that which is yet to be discovered. Of species studied so far, the best color vision appears to be found in birds, aquatic creatures, and certain insects. Amongst insects, we know that butterflies and honeybees have advanced color discrimination.
In my last paragraph I stated that cats are trichromatic, but have a much lower proportion of cones to rods than humans. In addition, dogs and cats have a much more highly developed sense of smell than humans. While we rely primarily on sight, their perception of the world is far more reliant on olfactory stimuli.
What we know about color perception in the animal kingdom pales in comparison to that which is yet to be discovered. Of species studied so far, the best color vision appears to be found in birds, aquatic creatures, and certain insects. Amongst insects, we know that butterflies and honeybees have advanced color discrimination
trichromatic theory of color vision (or trichromacy)
The theory that the color of any light is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the three cones. Also known as the Young–Helmholtz theory
vs.
opponent color theory
The theory that perception of color is based on the output of three mechanisms, each of them based on an opponency between two colors: red–green, blue–yellow, and black–white.
After reading the chapter I became really interested in afterimages and how they effect your vision. I really like the figures in the book so I wanted to find more ways to test out afterimages. I found a test on youtube and its pretty cool because you get more specific afterimages like a mans face. I was really impressed because I could actually make out details in his face and not just the outline. The images that were present were also the opposing colors than the orignal image. I also found a study on after images that had strips and different shapes that were relating to the breathing light illusion that deals with the contrast of the image and distance. You see different sizes and colors depending how close you are to the object. The last website I found studied afterimages of facial expressions. They discovered that an afterimage of a smile is a frown and visa versa. Other expressions like disgust and surprise all have an afterimage of a smile.
These sources along with the book show more into the theories of color and how we have opposites that all work together in order for us to make out our visual world
http://www.youtube.com/watch?v=Z4oURqnIJGI
http://www.journalofvision.org/content/5/8/381.short
http://www.perceptionweb.com.proxy.lib.uni.edu/perception/editorials/p5785.pdf
I had a very difficult time choosing a topic to write this blog on. I started multiple times with various topics but was never happy with the website results that I was finding. After searching through the chapter for about the 5th time I came across a topic that I had somehow missed previously and ended up finding a topic that I was happy with. I chose to look into achromatopsia(ey-kroh-muh-top-see-uh). According to our text achromatopsia is "an inability to perceive colors that is caused by damage to the central nervous system".
My first Google search for achromatopsia confused me quite a bit and I almost decided to look for another topic. Everything that I originally found stated that it was a hereditary condition. According to the information about 5%-8% of men and .5% of women are affected by color blindness, or 1 in 33,000 people in the United States. People with this condition have abnormal cone vision. In chapter 2 we learned that cones " they have one of three different photo pigments that differ in wavelengths at which they absorb light most efficiently. Therefore, cones can signal information about wavelenth, and thus they provide the basis for our color vision". People with achromatopsia are either missing a type of cone or it has a different spectral sensitivity. There are different levels of achromatopsia depending on what cones are affected. The most serious is complete achromatopsia, where the person has to completely rely on their rod vision to see. All of this information was interesting, however it didn't fit into the definition that I got from the book stating it is caused by brain damage. What I found was there are different types of achromatopsia. The type that I described above is congenital achromatopsia, which is the one that most people would be familiar with.
The text should have used the term cerebral achromatopsia. People who have cerebral achromatopsia have no problems with the cones in their eyes. Instead, it is normally caused brain trauma or illness. Achromatopsia is due to damage to the occipitotemporal junction. Within this junction is the color remembering and imaging center which is located in the V4-lingual and fusiform gyri. The occipitotemporal junction is between the occipital and temporal lobes. One site stated that it can be caused by a "disruption to the neural pathways between the eye and the brain". Either way, since brain damage is generally not confined it is highly possible that other functions can also be affected causing disorders such as agnosia or color anomia. People with this disorder are unable to imagine or remember colors. Everything they see is in shades of gray.
There are a couple differences between what people who have congenital (ConA) or cerebral (CerA) achromatopsia experience. One is that people with CerA can still see shades of gray. This is because they previously experienced color which makes it possible for them to perceive the absence of color as being gray. People who have ConA who are complete achromats have no concept of gray. Another difference is that people with CerA have the ability to perceive chromatic borders.
Oliver Sacks and Robert Wasserman published a case study called The Case of the Colorblind Painter. I found this story extremely interesting. The case study was about Johnathan I's experience with CerA. The case study follows Johnathan I through his struggles with adapting and accepting a world without color. An excerpt from the study was on one of the websites that I looked at. It talked about Johnathan I's issues accepting the changed appearance of both people and food. When he saw himself and others instead of seeing a flesh color everything was "rat-colored". "He shunned social interactions and found sexual intercourse impossible." He also struggled with eating. Food now looked disgusting because it was all in shades of gray which is described as having a "dead appearance". He had to close his eyes to eat but it didn't really help because he didn't have the ability to see color in his mind either. Therefore, his mental image of food was still gray. The website states that he eventually because grateful for his condition. The study goes into detail about his practice as a painter and how it was affected by CerA.
I found information on 2 other types of achromatopsia but it was very brief. The first one (and I believe the most interesting of all of them) is hemiachromatopsia (HemA). This occurs when only one side of the brain is damaged. If the damage or lesion is in one hemisphere than the visual field on the other side would experience the damage. One of the websites showed great pictures of people with both CerA and HemA would see. A person with HemA has the ability to see color but only in half of their visual field. The picture shows an image of a garden. One side of the garden has bright red, purple, yellow and green and on the other side it's mostly gray. The other type of the disorder is transient achromatopsia (tranA). TranA is temporary color blindness. It is caused by constriction of a blood vessel in the brain. It occurs when oxygen in the blood can't get to the area of the brain that recognizes color. Having a stroke is the most common cause of TranA.
I tried to find incidence rates of CerA, HemA and TranA but was unsuccessful. From what I did read they are all very rare conditions. I can't imagine seeing color one day and then having the ability taken away even for a short amount of time such as with TranA. I believe that HemA would be the most unusual to experience because half of what you see would be in color. People who experience these disorders have a lot of obstacles that most people can't imagine and it would be interesting to learn more about how they overcome them.
http://www.achromat.org/what_is_achromatopsia.html
http://www.macalester.edu/psychology/whathap/ubnrp/visionwebsite04/achromatopsia.html
http://www.wikidoc.org/index.php/Cerebral_achromatopsia
http://www.webexhibits.org/causesofcolor/2C.html