What I would like you to do is to find a topic from chapter 6 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.
Thanks,
I chose to find out more information on binocular rivalry and suppression which is the competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes. For example, if you free-fuse two images one with vertical lines that are black and blue and the other horizontal lines are black and orange, you will be able to watch the blue verticals and orange horizontals engage in the perceptual battle. Our visual system will not actually combine the perpendicular stripes. Instead, you will see a battle between the vertically and horizontally striped patches, with regions of dominance growing and shrinking over time. Binocular rivalry describes alternating suppression of the two eyes resulting in alternating perception of the two images. This usually occurs when lines are presented to the two eyes differ in orientation, length or thickness. An example of binocular rivalry occurs when one eye is presented with a horizontal line and the other eye is presented with a vertical line. Binocular rivalry occurs at the intersection of the lines and some suppression also exists. During binocular rivalry the average duration of a suppression phase depends on the stimulus strength (i.e., contrast) of the input to the suppressed eye. Objects in the world often project images on our two retinas that don’t overlap (that is, the images fall on non-correponding retinal points,) and that the visual system is physiologically prepared to deal with these discrepancies via disparity tuned neurons in striate cortex and beyond. The visual system chooses instead to suppress one image and perceive the other. In addition, binocular rivalry occurs when incongruent patterns are presented to corresponding regions of the retinas, leading to fluctuations of awareness between patterns. One attribute of a stimulus may rival whereas another may combine between the eyes, but it is typically assumed that the dominant features are perceived vertically. Here, we can see that it is not necessarily the case and that a suppressed visual feature can alter dominant perception. Furthermore, both high-level areas and early visual areas closely reflect the observer's moment to moment perception during binocular rivalry. Rivalry seems to involve early visual competition, and precedes the stage at which perceptual filling-in occurs in the visual system.
http://www.psy.vanderbilt.edu/tonglab/web/Binocular_Rivalry_and_Visual_Awareness.html
http://webvision.med.utah.edu/KallDepth.html
http://www.deepdyve.com/lp/psycarticles-reg/on-the-inhibitory-nature-of-binocular-rivalry-suppression-ZILyD7jsSS
http://www.cell.com/current-biology/abstract/S0960-9822%2805%2901366-7
http://www.google.com/imgres?imgurl=http://www.perceptionweb.com/perception/perc1200/fig2.gif&imgrefurl=http://www.perceptionweb.com/perception/perc1200/alais.html&usg=__5wNts7F9PwLRsX7zdpy3ASoDVLc=&h=315&w=600&sz=41&hl=en&start=0&zoom=1&tbnid=FCd9Q5Gl3O8lLM:&tbnh=92&tbnw=175&ei=sNBaTYyIHI-Wtwf93-38Cg&prev=/images%3Fq%3Dbinocular%2Brivalry%26um%3D1%26hl%3Den%26biw%3D1440%26bih%3D742%26tbs%3Disch:1,ic:color&um=1&itbs=1&iact=hc&vpx=783&vpy=125&dur=743&hovh=163&hovw=310&tx=98&ty=77&oei=sNBaTYyIHI-Wtwf93-38Cg&page=1&ndsp=30&ved=1t:429,r:4,s:0
This really has nothing to do directly with the eye but it does have some role in binocular rivalry.
It is interesting so check it out and compare the two situations.
Abigail Hensel and Brittany Hensel (born March 7, 1990 in Carver County, Minnesota, US) are dicephalic parapagus twins, meaning that they are conjoined twins of whom each has a separate head, but whose bodies are joined. They are highly symmetric, giving the appearance of having just a single body with little variation from normal proportion. In fact, several vital organs are doubled up, each woman having a separate heart, stomach, spine and spinal cord.
Each twin controls half their body, operating one of the arms and one of the legs. This means that as infants, the initial learning of physical processes that required bodily coordination, such as clapping, crawling, and walking required the cooperation of both children. While each is able to eat and write separately and simultaneously, activities such as running and swimming must be coordinated and alternate symmetrically. Other activities as diverse as brushing hair and driving a car require that each twin perform a sequence of quite separate actions that coordinate with the other.
http://www.hollywoodcelebgossips.com/wp-content/uploads/2009/01/minnesota-siamese-twins-abigail-and-brittany-hensel-phicture.jpg
Binocular rivalry is a pretty cool phenomena. When exposed to two different stimulus patterns in the retinas the brain essentially chooses one image from one retina and that is what we perceive. Which retina should the brain trust, which image should be delivered to our consciousness? There is no right answer, but our brain seems to try to make the decision based on some criteria. If you have ever shot a gun before you know that to aim and even to hold the gun you need to know which of you're eyes is dominant. Literally you need to know which of your eyes will win the binocular rivalry in this particular situation. I found a description of how to determine which eye is dominant from a shooting skills website. It says that you must focus on something far away and hold your thumb up in front of your face. We may experience some diplopia but for the most part we see our thumb in a relative position to what we are focusing on. You then close one eye, then the other. Which ever eye is dominant will be the one open when your thumb is in the same position in the visual field. Dominant eye simply means that this is the eye your brain seems to default to in moments of binocular rivalry. We still experience switching, however, between the perspectives of both retinas. Just because one eye is dominant does not mean the brain accepts its contribution alone, it incorporates the other eye and may decide that the non-dominant eye's information is more relevant. When we shoot a gun we don't experience this shift between each perspective because we close one eye so no binocular effects are present at all. An article in Sciencedaily.com discusses a study in which scientists were able to prolong the amount of time of processing per eye. That is to say when exposed to stimuli that elicits binocular rivalry our brain switches perspectives between the two retina at a regular interval of time. The scientists exposed each retina to a different image, one a house and one a face, and measured the amount of time the brain spent processing each image. They found that when they exposed the posterior parietal lobe to an alternating magnetic field they were able to prolong the amount of time the brain processed each image. The authors of the study concluded that the parietal lobe plays some role in deciding which information from which retina is relevant at what time. The parietal lobe is conceptually thought of as a sort of dispatch. It activates neurological paths either corresponding to the ventral or the dorsal streams. So it seems like the parietal lobe is active in making decisions on where to route data, perhaps it is the switch with a programmed interval of time dedicated to each retina. The application of the magnetic field may interfere with nuerometabolism and cause the brain to dedicate more time to processing in this particular area.
http://www.sciencedaily.com/releases/2010/11/101119083226.htm
http://homestudy.ihea.com/shootingskills/03dominanteye.htm
http://en.wikipedia.org/wiki/Parietal_lobe
I decided to do more research on the concept of double vision, otherwise known as diplopia. There are several causes to this problem. One includes the cornea. If the cornea is damaged, incoming light is distorted, causing double vision. This usually only occurs in one eye (called monocular diplopia) so covering the problem eye makes double vision go away. Ways that the cornea can be damaged are infections, like shingles or herpes, or complications of LASIK eye surgery. Another way to have double vision is problems of the lens. The most common lens problem is cataracts, which is a clouding developed in the lens that obstructs the passage of light. Cataracts can also occur in one eye, resulting in monocular diplopia. Luckily, cataracts can be corrected with minor surgery.
Problems with the muscles of the eyes can also lead to double vision. If a muscle is weak, the eye can’t function at a normal, healthy level. If one eye has normal muscles and one has weak muscles, they won’t move smoothly together and the results will be double vision. Muscles problems can be caused by an autoimmune illness called myasthenia gravis “that blocks the stimulation of muscles by nerves inside the head.” Another disease that causes muscles problems is Graves’ disease which is a thyroid condition that weakens the eye muscles. Nerve problems are another way to cause double vision. Some of these problems include multiple sclerosis – damage to nerves in the brain or spinal cord, Guillain-Barre syndrome - causes progressive weakness, and diabetes – not controlling diabetes can lead to nerve damage in an eye. The last problem that can lead to double vision involves the brain. Because the nerves that control the eye are directly connected to the brain, damage to these nerves can cause diplopia. Examples of this include strokes, aneurysms, increased pressure inside the brain, brain tumors, or migraine headaches.
There are a few different types of treatment for double vision. As mentioned before, surgery is in option for problems involving the eye or lens. Another treatment form is orthoptics, which is the medical term for eye muscle training procedures. Orthoptics helps fix problems with visual clarity. There’s another form of eye training called Vision Therapy that looks at the whole visual system and helps to correct eye movements and visual-motor deficiencies. It’s important to treat double vision because loss of vision can occur without it. Because double vision is useless in our survival, the brain will try to avoid it by ignoring one eye. This is called suppression. Suppression leads to loss of vision because it appears that the double vision has gone away.
http://www.strabismus.org/double_vision.html
http://www.webmd.com/eye-health/double-vision-diplopia-causes-symptoms-diagnosis-treatment
What really interests me is the fact that most of the information we are learning in S & P we have all learned as children but never had a name for it.
Remember the cards that from the front just looked like a bunch of lines but when you lied them flat they said a word or sentence. That was just a little blurb I wanted to add.
I am going to do my topic on anamorphosis or anamorphic projection just because it is AWESOME.
Anamorphosis or anamorphic projection use the rules of linear perspective to create a two-dimensional image so distorted that it looks correct only when viewed from a special angle or with a mirror that counters the distortion.
There are two main types of anamorphosis: Perspective oblique and Mirror catoptric. Examples of perspectival anamorphosis date to the early Renaissance 15th Century, whereas examples of mirror anamorphosis or catoptric anamorphosis occurred at the time of the baroque 17th century.
With mirror anamorphosis, a conical or cylindrical mirror is placed on the drawing or painting to transform a flat distorted image into a three dimensional picture that can be viewed from many angles. The deformed image is painted on a plane surface surrounding the mirror. By looking uniquely into the mirror, the image appears undeformed. Current in the 17th and 18th centuries, this process of anamorphosis made it possible to diffuse caricatures, erotic and scatologic scenes and scenes of sorcery for a confidential public.
Leonardo's Eye (Leonardo da Vinci, c. 1485) is the earliest known example of perspective anamorphosis. Hans Holbein the Younger is well known for incorporating this type of anamorphic trick. His painting The Ambassadors is the most famous example for anamorphosis, in which a distorted shape lies diagonally across the bottom of the frame. Viewing this from an acute angle transforms it into the plastic image of a skull. During the 17th century, Baroque trompe l'oeil murals often used this technique to combine actual architectural elements with an illusion. When standing in front of the art work in a specific spot, the architecture blends with the decorative painting. The dome and vault of the Church of St. Ignazio in Rome, painted by Andrea Pozzo, represented the pinnacle of illusion. Due to complaints of blocked light by neighbouring monks, Pozzo was commissioned to paint the ceiling to look like the inside of a dome, instead of actually constructing one. However, the ceiling is flat, and there is only one spot where the illusion is perfect and a dome looks real.
In 18th and in 19th century, anamorphic images had come to be used more as children's games than fine art. In the 20th century some artists wanted to renew the technique of anamorphosis. Important to mention is Marcel Duchamp's interest in anamorphosis, some of his installations are paraphrases of anamorphoses (See The Bride Stripped Bare by Her Bachelors, Even/The Large Glass). Salvador Dalí also utilized the effect in a number of his paintings. Jan Dibbets conceptual works, the so-called "perspective corrections" are examples of "linear" anamorphoses.
The Swedish artist Hans Hamngren produced and exhibited a great deal of examples of the mirror anamorphosis in the 60s and 70s. Shigeo Fukuda, a Japanese artist, designed both types of anamorphosis in the 70s and 80s. Also Patrick Hughes (artist), Fujio Watanabe, William Kentridge, István Orosz, Felice Varini, Matthew Ngui, Kelly Houle, Nigel Williams, and Judy Grace are fine artists creating anamorphic images.
Another example is the sidewalk chalk paintings of Kurt Wenner and Julian Beever where the chalk painting, the pavement and the architectural surroundings all become part of an illusion. Art of this style can be produced by taking a photograph of an object or setting at a sharp angle, then putting a grid over the photo, another, elongated grid on the footpath based on a specific perspective, and reproducing exactly the contents of one into the other, one square at a time.
Cinemascope, Panavision, Technirama and other widescreen formats use anamorphosis to project a wider image from a narrower film frame.
The system of anamorphic projection can be seen quite commonly on text written at a very flat angle on roadways — such as "Bus Lane" or "Children Crossing" — which is easily read by drivers who otherwise would have difficulty reading as the vehicle approaches the text; when the vehicle is nearly above the text, its true abnormally elongated shape can be seen. Similarly, in many sporting stadiums, especially in Rugby football in Australia, it is used to promote company brands which are painted onto the playing surface; from the television camera angle, the writing appear as signs standing vertically within the field of play.
On some 0.5 liter Sprite bottles in Europe, an extra "bar code" was present. When the bottle is tilted towards the mouth while drinking, the bar code resolves into writing due to the anamorphic effect.
In the the twentieth century artists began to play with perspective by drawing impossible objects. These objects included stairs that always go up or cubes where the back meets the front. Such works were popularized by artist M. C. Escher and mathematician Roger Penrose. Although referred to as impossible objects such objects as the Necker Cube and the Penrose triangle can be built using anamorphosis.
http://www.deziland.com/asae/pages/gallery.htm
http://www.worldlingo.com/ma/enwiki/en/Anamorphosis
http://www.reference.com/browse/anamorphosis
http://www.generativeart.com/salgado/anamorphic.htm
The topic I was most interested in after reading Ch. 6 was the pictorial depth cues. According to our book, artists use pictorial depth cues to depict a 3D depth on a 2D picture. By viewing the picture in a particular way the retinal image formed by the 2D picture will be the same as if it were formed by the 3D world. Our book states that “our visual system compensates for the perceptual distortion”. Our visual system wants to make sense of the world and assumes it is seeing something with actual depth. I find this really fascinating how artists can “trick” our visual system into seeing a 3D image when it is actually 2D. Pictorial depth cues are actually a collection of monocular cues (depth available with one eye). These include: occlusion (position in depth), relative size, texture gradient, relative height, familiar size, aerial perspective, and linear perspective. Artists manipulate these cues to produce a 3D effect.
Anamorphic projection (anamorphosis) is the use of linear perspective depth cues to create a 2D image that when viewed correctly will appear 3D. There are two types of anamorphosis: perspective (oblique) and mirror (catoptric). In a mirror anamorphosis you must place a mirror on the drawing to create the 3D illusion. A perspective anamorphic image needs to be viewed at a specific angle or perspective point. Anamorphosis is actually used to create road markings such as turn arrows and words directing traffic. When driving you are viewing a shallow angle that results in an effect called foreshortening, which shrinks objects as they move further away. In order to be viewed at a distance road markings are stretched so that drivers can view them properly.
Anamorphosis is most often seen in art. Leonardo da Vinci’s “Leonardo’s Eye” is considered the earliest example of perspective anamorphosis (c. 1485). The most famous example however is Andrea Pozzo’s painting of the ceiling in the Church of Saint Ignazio in Rome (check out my 2nd link for pictures). Trompe l’oeil is common term for this style of painting, which in French means “deceiving the eye”. Julian Beever is a well know trompe l’oeil chalk artist in Europe. The last link is his website and there are some amazing pictures of his work under “Pavement Drawings”. I also included a YouTube video that shows Julian at work and it is amazing what he does! It is a little long but definitely worth seeing a great perspective artist at work.
http://en.wikipedia.org/wiki/Anamorphosis
http://www.anamorphosis.com/what-is.html
http://www.youtube.com/watch?v=hfn8Dz_13Ms
http://users.skynet.be/J.Beever/
I choose to talk about abnormal vision, specifically I would like to talk about strabismus- it is most common as cross-eyed, wall-eyed.Strabismus is a misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye, and on a nonfoveal area of the other (turned) eye.One or both of the eyes may turn in, out, up or down.An eye turn may be constant (when the eye turns all of the time) or intermittent (turning only some of the time, such as, under stressful conditions or when ill). Whether constant or intermittent, strabismus always requires appropriate evaluation and treatment.
How does it happen? When one eye is misaligned, as in strabismus, two different pictures are sent to the brain. When misalignment occurs in childhood the consequences can be severe. If the eyes are misaligned, two different views of the world are sent to the brain. The brain often responds by ignoring one of the images.
The primary sign of strabismus is an eye that is not directed straight.
And what kind of treatment can we use? The goal of the treatment is to preserve vision, to straighten the eyes, and to restore binocular vision.Treatment may involve repositioning the unbalanced eye muscles, removing a cataract, or correcting some other conditions that cause that the eyes turn.
I am attaching the link for the video that the show how do they fix strabismus during surgery.
http://www.youtube.com/verify_age?next_url=http%3A//www.youtube.com/watch%3Fv%3DVcwJi8hj6Ao
http://www.strabismus.org/
http://www.strabismus.org/all_about_strabismus.html
http://www.nlm.nih.gov/medlineplus/ency/article/001004.htm
When reading chapter 6, I became interested in stereopis which basically is our perception of three-dimensional objects. I thought this was interesting because I have been to quite a few three dimensional movies but never really understood how the process worked. Ways you can use your 3D perception would be to use a stereoscope or free fusion. A stereoscope is a device that will presents one image to one eye and another image to the other eye. With free fusion you converge(cross) and diverge(uncross) your eye in order to see the stereogram oject.
When we were younger we were often shown random dot stereograms and were told to stare at the image for an extended period of time while converging and diverging our eyes. After a while a picture would pop out of the image of a animal or flower. 3D glasses are also a way for us to use our 3D perception. It will take the 2 images that our visual system is processing and overlap them which creates the illusion.
3 to 5% of the population have stereoblindness which means that they are not able to make use of their binocular disparity as a depth cue. Many people do not even realize that they have this disorder. This can be caused by the two eyes being misaligned(strabismus) or a genetic disorder. When you have stereoblindness you can go to a 3D movie but the glasses will have no effect on the images that you are seeing. With the help of optometrists, you can learn or train your eyes to see these images. The majority of people with stereo blindness can be helped. A person who is able to see in 3D with no problems is stereoacute.
http://www.mediacollege.com/3d/depth-perception/stereoblind.html
http://www.mediacollege.com/3d/depth-perception/stereoblind.html
http://www.psy.unipd.it/~kramer/files/CecchettoKramerPerception2010.pdf
here's another article from a reporter with stereoblindness
http://www.cnn.com/2010/TECH/01/15/3d.tv.opinion/index.html
After reading this chapter and the comment article on the problems with 3D, I wanted to read more about how the magic of 3D movies are possible. The website “How 3D Glasses Work” explains how 3D works. Binocular disparity is the main key to 3D. The brain uses the slights differences between the two retina images to gage distance of objects. According to the article "Gadget lab" older 3D movies there are two projectors that layer two synchronized images, one in red and in blue. The filters on the glasses allow only one image to enter each eye and in combining the images, the brain created the depth in 3D. However the limitations of this 3D process is there was little color in the images. Today 3D is a little different. The articlestates that instead of the differences in color, a filter in front of the projector creates two separate images with different light waves. So instead of blue and red lens, each lens picks up different waves.
The article “Stereo-Blind: People who can’t see 3D” states that color-blinded people can see 3D today, however if you suffer from loss of vision in one eye or medical disorders, that cause stereo-blindness, it could prevent the eye focusing or aligning correctly together.
The last article I read was “View Masters” was to understand Stereo-blind, or the inability to see stereopsis, better. According to the article, only about 10% of the population is stereo-blind, and use other cues to perceptive depth. What I thought was interesting about this article was what it stated about paintings and art. Normal stereopsis tells our brain that images on flat surfaces are 2D. Only cues like occlusion, shading, height and size can create depth. The author suggests to stop our stereopsis and to look at paint and the cues with only one eye. In this way, it is almost helpful for an artist to be stereo-blind because of their understanding of different depth cues.
http://harvardmedicine.hms.harvard.edu/fascinoma/mysteries/viewmasters.php
http://www.mediacollege.com/3d/depth-perception/stereoblind.html
http://www.wired.com/gadgetlab/2009/12/3d-movies/
One topic that I found interesting was the topic on stereograms. Stereograms are an optical illusion of depth that is created from flat images. This optical illusion was originally discovered by Charles Wheatstone in 1838, when he found an explanation of binocular vision. He constructed a stereoscope out of prisms and mirrors which allowed a person to see 3D images from two 2D pictures. This illusion was the bases for the 3D movies that we enjoy today. 3D movies use anaglyph images, or the combination of two stereo images from slightly different viewpoints into a single image. However, these images must be viewed with special anaglyph glasses, which make use of color filters to moderate the light that reaches each eye to create an illusion of a 3D image. This concept has been used for more than just entertainment. Recently NASA used stereoscopic equipped cameras on the Mars Exploration Rovers. The two cameras were placed on the rover allow the images from it to be made into a stereoscopic image which leads to scientists being able to see a 3D image from the Rover. The cameras are placed at roughly human height, so it gives researchers some insight into the landscapes being viewed; it also helps researcher’s judge distances on the surface of Mars.
Cool Images
http://upload.wikimedia.org/wikipedia/commons/8/8a/SpiritsShadow-Sol153-6-8-2004.jpg
http://upload.wikimedia.org/wikipedia/en/c/c0/Peninsula_correct.png
http://en.wikipedia.org/wiki/File:Asiatic_hybrid_lilium_stereogram_flipped.jpg
Sources
http://en.wikipedia.org/wiki/Stereogram
I chose to look more into the topics of Binocular Vision and Stereopsis. Binocular vision is described as the ability to maintain focus on a certain image with both eyes, creating a single image. Many infants do not have binocular vision. If adults do not have this, they will experience lack of depth perception and distance. Stereopsis, however, is when two eyes perceive an object at slightly different angles because of the different positions of the eyes. This is perfectly normal in eyesight. The angles are what helps animals and humans perceive depth and distance. It can also be described as 3D vision. There are also some photos that describe this aspect in the website below.
As you can see, these two concepts are very similar. Binocular disparity is the differences between the images falling on both of our retinas whereas stereopsis is the impression of three-dimensionality of objects, or how things seem to "pop out" when humans perceive the real world. Therefore, stereopsis is actually an aspect of binocular vision. Animals with binocular vision will have a wider range of vision than animals who do not.
I thought a description of birds image was very interesting in this topic. Different types of birds have different types of eyes and vision. Some birds may have monocular vision which means that birds can see with one eye and don't have that binocular vision. Some have binocular vision and can move their eyes in the heard and can see all around without moving their head. Some birds' eye sockets do not move in their heads, so they have to turn their necks all the way around to look around them. I thought this was an interesting aspect of animals' vision. There was also a picture on that page that showed which area is binocular vision and which areas are monocular vision.
I was interested in this topic because obviously it is a very important part of our vision and our would would basically be two dimensional without it. The world and living would not be the same without this thing that our eyes can do for us.
http://www.wisegeek.com/what-is-binocular-vision.htm
http://www.wisegeek.com/topics/binocular-vision.htm
http://idahoptv.org/dialogue4kids/season10/birdsofprey/facts.cfm
http://mysite.du.edu/~jcalvert/optics/stereops.htm
I decided to further research motion parallax. In lay persons terms motion parallax is when you are passing by and looking out a window (ex. car) the things closest to you seem to be moving much faster than the things further away from you. Motion parallax is a depth cue. The way the depth cue works is that our mind associates it with movement. One website that I found had a very basic, yet very good illustration of what motion parallax is. http://psych.hanover.edu/krantz/motionparallax/motionparallax.html
Another website I found talked about the importance of the position in which an object is viewed. Parallax comes from a Greek word meaning “alteration”. Parallax can be used to determine distance. Objects that are closer to you have a larger parallax, whereas objects that are further from you have a smaller parallax. Humans use parallax to gain depth perception. This process is called stereopsis. This is how parallax plays into the bigger picture of the visual system. One way that humans’ vision differs from animal vision is parallax because human eyes are positioned differently than animal eyes.
http://www.universetoday.com/78860/motion-parallax/
http://psychology.wikia.com/wiki/Motion_parallax
http://medical-dictionary.thefreedictionary.com/Motion+parallax
I was interested in what can go wrong with binocular vision. The book talks about strabismus which is a misalignment of the two eyes that causes the same image to be located on the fovea of one eye and the non-fovea of the other eye. The book explains two different types of strabismus, esotropia and exotropia where the eye deviates inward and outward respectively. What is really interesting is a phenomena that occurs in individuals with strabismus called suppression. Suppression is the inhibition of an unwanted image. Suppression primarily occurs in the form of a suppression scotoma. These scotomas are within the center of the visual field. As the book explains, binocular rivalry is a type of suppression. Binocular rivalry is when two eyes compete for control of the perception of a visual image. Studies show that if information that is conflicting is sent to the eyes input to one eye is sent at a time while the other information is suppressed. This changing between the two images is due to binocular rivalry. Researchers at the Werner Reichardt Center for Integrative Neurosciences and the Max Planck Institute for Biological Cybernetics have found what they believe to be a mechanism to explain these phenomena. The research they conducted suggests that the parietal cortex is involved in this process and deciphering information that is consciously perceived. Interestingly, recent studies have found that individuals with bipolar disorder have significantly slower rates of binocular rivalry than control groups, schizophrenic groups, and other depression groups. Although the authors did not attempt to explain the connection they emphasized the results provide promise for new ways of studying psychiatric illnesses using the perceptual phenomena that we have talked about in this course. Similar twin studies have been conducted by neuroscientists at the Queensland Institute of Medical Research measuring binocular rivalry switching rates. Results of these studies suggest a genetic link in these rates. These researchers said that individuals with bipolar disorder made switches between images significantly slower (up to 10 seconds) where non-bipolar individuals made the switch between images much faster (every one to two seconds) The authors suggest that this genetic link combined with the link between binocular rivalry and bipolar disorder suggest that binocular rivalry might be a test clinicians can use in the future for mental illnesses. What to you guys think? Does anything explain this link I can’t seem to think of very many plausible explanations.
http://www.sciencedaily.com/releases/2010/11/101119083226.htm
http://eprints.usq.edu.au/3226/1/Miller_Gynther_Heslop_Liu__Mitchell_Ngo_Pettigrew_Geffen.pdf
http://www.monash.edu.au/news/newsline/story/1568
I decided to learn more about Stereograms and Stereoscopes and how they work for this weeks topical blog. According to the textbook, A stereoscope is a device for presenting one image to one eye and another image to the other eye, thereby creating a single, three-dimensional image. The first patented stereoscope was invented by Sir Charles Wheatstone in 1838. This however, is not the most common version of a stereoscope that we are familiar with today. The more common version was developed by Oliver Wendell Holmes. With a stereoscope, scientists are able to manipulate the disparitites between the two eyes. Even though the stereoscope was intended for science, it became very popular in home entertainment. If anyone is familiar with the movie Tuck Everlasting, there is an example of a family using a stereoscope for home entertainment.
Stereoscopes somewhat resemble a pair of old-school binoculars with a card with two similar pictures located about a foot away from the end of the binoculars...(there is a picture at this site http://courses.ncssm.edu/gallery/collections/toys/html/exhibit01.htm) On the card, there will be two pictures that are from the viewpoint of each eye. The viewer (thing that looks like the old binoculars) helps the eyes merge the two images, giving the appearance of a 3-d image. One site that I visited also mentioned how the pictures for the stereoscopes were taken. A camera was mounted on a tripod and the first picture was taken, the camera was then rotated and the second picture was taken. The stereoscope has not disappeared from todays culture...and I am sure that at least some people in the class owned one when they were children. Today, it is more commonly referred to as the Viewmaster. (I included the website just in case you wanted to reminiscence about this great toy from your childhood!)
The main purpose of a stereoscope is to get the eye to see a 3-D image from a 2-D image. However, this can be achieved without using a stereoscope. Free Fusion, is the technique of converging (crossing) or diverging the eyes in order to view a stereogram without a stereoscope. Free fusion is used when trying to view a stereogram. A stereogram is a 3-D image burried in a 2-D image. Normally you will be presented with a photo with a two-tone color picture in some strange design. In order to see the 3-D image, you need to stare at the picture and either converge or diverge your eyes. The last website in my references has a bunch of good examples of stereograms if you want to give it a try.
http://courses.ncssm.edu/gallery/collections/toys/html/exhibit01.htm
http://www.fisher-price.com/fp.aspx?t=page&a=go&s=viewmaster&p=landing_flash&site=us
http://www.funsci.com/fun3_en/stscp/stscp.htm
http://www.eyetricks.com/3dstereo.htm
This week I chose to look at the issue of strabismus. I chose this because one of my clients is having her 2nd surgery next week to try and correct this condition. Her family mentioned it to me by name weeks ago but at the time I had no idea what it was. Therefore when I came across the term in the reading I thought it was a great opportunity to find out more.
Strabismus is a condition where a person's eyes do not look at the same place at the same time. This is commonly referred to by other names such as cross-eyed or wall-eyed. There are a couple different causes for strabismus; one cause is poor muscle control of the eyes where the muscles do not work together, it can be caused by a high amount of farsightedness, it could be problems with the nerves that send information to the muscles in the eye, an issue in the part of the brain that controls eye movement, or other general health issues or eye injuries. The eyes are attached to 6 muscles that control how they move. Normally the muscles work together and point the eyes at the same location. When this does not occur the eye can turn in, out, up, or down. Strabismus can be a constant condition or it can be intermittent where it happens when the eyes have been under stress. It is said that between 2%-5% of children in the U.S. have some type of strabismus. Generally, the first thing that is noticed is double vision which causes confusion in the brain. After awhile the brain ignores the image from the eye that is not properly aligned. If this becomes constant and occurs for too long it may permanently reduce vision in the in the eye which is a condition called amblyopia (lazy eye).
There are a different names of strabismus depending on which way the eyes turn. When one or both eyes turn outward it is called exotropia. When one or both eyes turn inward it is called esotropia. When the eyes turn upward it is hypertopia and when they turn downward it is hypotropia. A child can be born with strabismus but it can also develop in young children, generally before age 3. Strabismus can develop later in life due to eye injuries or other health conditions. It is very important for strabismus to be caught early because the sooner a child receives treatment the better chance they have of the condition being corrected. Without treatment the condition could become amblyopia which is permanent. Strabismus will not go away on it's own therefore treatment is vital.
There are different treatment options that are used for strabismus. The easiest treatment option is eye glasses that will correct extreme farsightedness. Sometime s this is the only treatment necessary but often other treatments will need to be used. Another treatment option is lenses that have prism power in them. These lenses will alter the light that enters the eye. This assists in reducing the amount of turning the affected eye has to do to focus on an object. Vision therapy is another treatment option. Vision therapy is a set of visual activities that is meant to improve eye coordination and focusing abilities. The goal of this therapy is to train the eye and brain to work together more effectively. Medication may also be used with or without other treatment options. A more invasive approach is eye muscle surgery. This surgery can "change the length or position of the muscles around the eye in an attempt to better align the eyes". This is often used in conjunction with other forms of treatment such as vision therapy.
http://www.strabismus.org/
http://www.aoa.org/x4700.xml
http://www.preventblindness.org/children/strabismusFAQ.html