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.
Let me know if you have any questions.
I found the concept of time to collision (TTC) from chapter 7 interesting, because I have been hit in the nose with a soccer ball and softball as a child, due to not being able to stop the imminent collision. I have often joked at my lack of hand-eye-coordination, and thought learning about what visual information we use to avoid or achieve collisions with approaching objects and our bodies was interesting. Being able to avoid getting hit in the face or body with a lethal object can be life-saving, and in a less dramatic realm, being able to estimate the time to collision of any object approaching your body can simply result in avoiding injury or unwanted pain. Estimating time to collision can also help an organism achieve a desired collision, like hitting an object with a body part or another object. This can be beneficial in a variety of settings, like kicking a goal in soccer, or deflecting a knife from making contact with your skin in an attack.
Surprisingly, despite humans’ distance judgment abilities, we are far better at judging time to collision than would be expected-well most of us, anyway. There is an alternative source of information in the optic flow that could signal TTC without the necessity of estimating either absolute distances or rates, known as tau. An example of how tau works is a ball coming toward one’s face, and the image on one’s retina growing larger as it approaches. The ratio of the retinal image size at any moment to the rate at which the image is expanding is tau, and TTC is proportional to tau. An advantage of using tau to estimate TTC is that it relies solely on information available directly from the retinal image.
The survival of many animals hinges upon their ability to avoid collisions with other animals or objects, or to precisely control the timing of collisions. Optical expansion provides a compelling impression of an object’s approach. In principle, this can provide the basis for judgments of time to collision. Some animals even have neural systems that can initiate rapid coordinated actions on the basis of optical expansion. But in humans, the link between judgments of TTC and coordinated action has not been established at a cortical level.
This time to collision ability used by humans and animals has even carried over into our motor vehicle world. Back-up cameras and warning systems installed in new vehicles allow drivers to see how close they are getting to another object, how much time they have before needing to change directions, or being warned if their car has gotten unsafely close to another object. According to the European Commission for Safety, the time to collision period between 10 seconds and the human reaction time of about one second, constitutes the warning and assistance phase which features optic, acoustic and/or haptic warnings. The warning even transforms into active assistance under one second. In a haptic warning system, the active accelerator starts to develop an increasingly stronger force during the warning phase, indicating the need for corrective measures. This is followed by breaking assistance, and finally by autonomous braking in order to prevent the vehicle from running over a pedestrian or hitting another car. I would love to have this feature in my next vehicle, because I enjoy having the visual and audio warnings with the back-up camera, but the haptic warning system would be very beneficial in winter weather. It would also make me feel safer as a driver and a pedestrian if more vehicles had this feature installed. This new feature can prevent, or lessen the damage of a collision. These new features serve as the time to collision abilities our human visual system has, but now our cars can utilize these abilities to protect us while driving. I think it’s interesting that humans have continued to adapt the tools we use to make our lives easier and more efficient, by integrating the biological abilities we possess into the tools we use. With these time to collision warning systems, our cars will help us to do what our visual system has always done to protect our bodies.
Sources:
http://pdn.sciencedirect.com/science?_ob=MiamiImageURL&_cid=272099&_user=10&_pii=S0960982205001661&_check=y&_coverDate=2005-03-08&view=c&_gw=y&wchp=dGLbVBA-zSkzV&md5=772ee3f8ab17c2202cd3eabb950c2832/1-s2.0-S0960982205001661-main.pdf
http://www.prevent-ip.org/en/about_preventive_safety/introduction/time_to_collision_02.htm
http://pdn.sciencedirect.com/science?_ob=MiamiImageURL&_cid=272099&_user=10&_pii=S0960982200004930&_check=y&_coverDate=2000-05-15&view=c&_gw=y&wchp=dGLzVlt-zSkzk&md5=d32cc26d2d1cc73f3c8ca040221c2467/1-s2.0-S0960982200004930-main.pdf
Terms: time to collision, TTC, distance judgment abilities, optic flow, absolute distances, absolute rates, retinal image, tau, optical expansion, neural systems, cortical levels, optic/acoustic/haptic warnings, visual system
Good post. Started with a relevant personal experience as an example and then filtered it down to the technical stuff. I like that you cited sources from science direct. This likely means they were empirical articles and thus the most credible sources related to this stuff.
For today's topical blog I decided to research more about visual search, and more specifically, visual search in children. I found the most interesting articles on "where's waldo" searches. I loved doing these as a kid and to my understanding, it is a good way to develop the child's vision. Something interesting I found was a thing called microsaccades, which are the jerky movements your eyes make when you are looking for a specific something (like waldo). Recent research has been made on the connection between microsaccades and visual searches. Barrow Neurological Institute at St. Joseph's Hospital and Medical Center have recently done an experiment in 2009, asking participants to find waldo in a cluttered picture, full of distractors, waldo being the target. At the same time, the experimenters were keeping track of their eye movements. They found that when the subject found the target (waldo) the rate of microsaccades dramatically increased. Researchers believe these findings will help with making it possible for visually disabled people to see just as normal-visioned people can. I also learned that foveal vision and peripheral vision are two main "visions" that help us find the waldo in "where's waldo" pictures. Foveal vision and peripheral vision works together with the prefrontal cortex, which has picked out certain neurons to fire to look for a little man dressed in red and white. It is very interesting to me that we have specific neurons being fired, just to see these colors. It's like when you look at a picture of a bunch of different dots. It is easy to relax your eyes and make certain colors pop out! Fun study to do. Another fun little experiment I found on visual search, I have included in my sources. I took the visual search test, and what I observed is this. I found myself really nervous at first. I wasn't doing well. I was giving myself a goal to try and get below 4ooms's. When i relaxed a bit, it was easier to concentrate and I did better! It took about 15 minutes but of course, perceptually, it felt like it took longer. Worth doing if you are interested in visual searching though!
Terms: visual search, target, distractor, foveal vision, peripheral vision, microsaccades
http://www.sciencedaily.com/releases/2009/03/090303161313.htm
http://eyetrackingupdate.com/2010/02/01/where%E2%80%99s-waldo-eye-tracking-only-registers-half-of-the-visual-search-process/
http://bigbird.psych.purdue.edu/psy200lab/VisualSearch/VS.html
Cool. I didn't know they were still doing stuff with Where's Waldo, specifically. Again, you did the next chapter I think, so next week, just do the motion chapter. Thanks!
After reading chapter 7, I had a strong interest to learn more about saccades and their relation to reading. According to the book a saccade is rapid movement of the eyes that changes fixation from one object to another. What I wanted to take away from looking up more information on this topic was if some people have better saccade vision than others while reading. Mainly, I wanted to know if saccades have an effect on reading.
When we are reading out of a textbook, our eyes are not viewing the words continuously as we move on. Instead ours eyes are using reflexive eye movements for looking for the parts of interest and taking pieces of it combining them to form letters, words, sentences, and so on. We fixate in the middle of a word and only about 4 to 5 characters are seen with 100 percent acuity. These images are then resolved and formed in the center of the retina or fovea. As we go over the page our eyes are taking parts of each word as we go and we decipher them and that’s how we read the words on a page. We have no control over the speed over which saccades happen but the eyes work as fast as they can. I posted a cool video of what it looks like when we read. Our eyes look like they are going crazy!
Reading can be very difficult for people. If a person’s saccades don’t pick the whole picture, we’re missing valuable information while reading (Ex. like skipping a word) and we have to back track and reread or scan that section in order for it to make sense. These errors could be caused by too long or too short reaction times. If saccades are too short, insufficient information may be taken and letters, words or phrases may be misread or skipped. If one or more eyes drift point of focus, binocular instability can occur. This can make reading frustrating because a person is constantly back tracking to pick up missed parts. Fluent readers have a reliable cycle of saccades and fixation. They are able to pause over difficult parts of text to decipher it more carefully. Both eyes are fixated on the point of interest and there is little to no binocular instability.
There are some signs to having poor saccadic fixations. When reading do people with poor fixations will frequently lose their place, leave out words, put in words that are not there, and move their head when they try to read. If these things happen then your body also has signs of stress on eyes. If your eyes water when you read, if you rub your eyes frequently, gets frontal headaches when trying to read, or have trouble copying from the board than you could possibly have poor saccadic fixations.
Many reading abilities such as dyslexia are now being looked about from an eye fixation stand point. Many children with reading disabilities are have slower eye movements and had a hard time fixating on the sentence they were trying to read. It raises the question whether these reading disabilities are only language problems or poor saccadic fixations.
This topic really interested me because I’ve always had a hard time on fixating when reading. I started to read some of this and it sounded exactly like what I go through when I read. It’s some really interesting stuff but I couldn’t find a lot research to go along with it.
Terms: saccadic, dyslexia, fixation, retina, fovea, reflexive eye movements, binocular instability, saccadic suppression.
http://www.youtube.com/watch?v=YsU1Yb6wkJ0
http://en.wikipedia.org/wiki/Eye_movement_in_language_reading
http://en.wikipedia.org/wiki/Saccade
http://vantagereading.com/vision-problems/symptoms-of-poor-saccadic-fixations.html
http://www.lookingforlearning.com/assess/sac.htm
http://www.ncbi.nlm.nih.gov/pubmed/8023443
Saccades are definitely important and allow the brain to do what it does with respect to vision. I like that you got an idea of what it looks like for our eyes to saccade by finding that video. This makes you more aware of your own saccade process. I always think about my eyes saccading when I am looking for a disc after I throw it (disc golf). This is interesting, but usually pulls my attention away from the task at hand (tracking the moving disc in the air). Anyway, cool post.
I found the topic of akinetopsia really interesting. I know that I do a lot of the visual disorders for my topical blogs but I find them to be really fascinating. The reason why I find these interesting is because I cannot imagine not being able to have the abilities to perceive motion or perception and people with these disorders do not have the privilege to see or experience things like motion, color, or faces.
Akinetopsia is the inability for someone to see motion. In other words, people affected by akinetopisa are unable to perceive the physical thing of motion. This disorder is known as a neuropsychological disorder because of the change in the structure of the brain, which in turn, disturbs the typical psychological processes of understanding sensory and visual information. With this disease the disturbance of the perception of color can also occur as well. As discussed in an earlier chapter (and topical blog) the inability to perceive color is called achromatopsia. Although the patient may not be able to detect or perceive motion, they are able to assimilate between visual space perception and visual identification of shapes, objects, and faces. Although they (the patient) may be able to identify shapes and other physical objects, other visuomotor tasks and skills such as reaching for objects, pouring things, and catching objects proves to be a very difficult process. Furthermore, day to day processes are some of the most difficult things to do for people affected by akinetopsia. Because visual motor tasks are affected, pouring coffee or juice for example, are difficult because judgment of when the cup or glass is full is wiped away. When carrying on a conversation with someone, it is difficult for those affected to follow along with the movements of the speaker’s lips. Driving cars and crossing streets are also things of difficulty that are everyday processes of life for those affected by akinetopsia.
There are three causes of akinetopsia. It can be caused by brain lesions, trans cranial magnetic stimulation, and possibly Alzheimer’s disease. Brain lesions have been known to cause this disorder, especially when they occur on the back side of the visual cortex. The motion-processing area of the brain, called the middle temporal cortex, is the main area of the brain that processes physical motion. Although the cause of akinetopsia to be brain lesions is very rare, it does occur, but for the most part if a lesion was going to affect that process of the occipital lobe, then it would also affect other parts and in turn affect other visual processes. It has been found that akinetopsia can be selectively or temporarily induced by using something called trans cranial magnetic stimulation or TMS. There have been reports of akinetopsia in Alzheimer’s patients as well, although there has not been very much research done in this area.
There have been a few case studies conducted on the study of this disorder. Researchers Potzl and Redlich did a case study on a 58 year old woman with bilateral damage to the posterior part of her brain. This study was conducted in 1911. She noted that when she was looking at a moving object, it remained stationary but then ended up in a different succession of places. Goldstein and Gelb in 1918 reported that there was a 24 year old man who suffered from a gunshot wound to the brain. The patient had reported having no impressions of seeing movement. He could state the new position of objects when they moved but he could not describe the successive movements that had led up to the final resting spot of the object. The most famous case study was conducted on a 43 year old female by the name of LM. She was admitted to a hospital in October of 1978 complaining of headaches and vertigo. She was first diagnosed with thrombosis, which is a blood clot inside a blood vessel obstructing the flow of blood to the circulatory system, of the sagittal sinus which obstructed her vision. She developed effective coping tools by using sound detection in order to cross the street and judge distances.
TERMS: akinetopsia, visual information, achromatopsia, visuomotor, transcranial magnetic stimulation
http://en.wikipedia.org/wiki/Akinetopsia
http://www.medscape.com/viewarticle/410860_6
http://www.youtube.com/watch?v=B47Js1MtT4w
http://www.youtube.com/watch?v=QW53fRQv3Zo
Cool post on a really dehabilitating neuropsychological disorder. TMS is cool because you can transiently "lesion" areas of the brain by inducing a current into the neurons and making populations of neurons in a certain brain area under the scalp less likely to fire. OR, what can happen is you can actually improve performance because you silence the inhibitory inputs being sent to a population of neurons and thus the next population will "fire". Pretty interesting newer technique of cognitive neuroscience.
Topical Blog week 8:
I was interested in learning more about Akinetopsia or motion blindness because I had never heard of it and it seems that it would make life very difficult. This is a neuropsychological disease which makes people unable to see the moving world around them. What is interesting though is that these people can see still objects with no difficulty which would be better, I suppose, than not being about to see at all. This disease happens when there are damaging lesions, such as with a traumatic brain injury, to the middle temporal cortex, which we learned about from our textbook as being one of the known areas where motion is perceived in the brain. As of now there is no cure for this disease.
While no human being could truly display with a video what it would be like to have motion blindness I thought one youtube video in particular did a nice job. The music was very dramatic with captions of information. This video discussed how light is reflected onto the retina that sends the information to the occipital lobe. The two systems then work together, constantly scanning the world to create a “smooth motion.” I just cannot get over what this must look like, the video tried to show how it might look but it just seems like it would be so much more confusing than that. So much of today’s world, which is increasingly digital, would be off limits for a person with this disease. Someone on the YouTube comments made a comment, “solution- blink really fast.” While this seems a little bit silly and is probably a joke, I wonder if that would help at all when in a desperate situation. While it was easy to find that this is a rare disease I was eager to figure out what the actual incidence rate is. I had a difficult time finding a straight statistic for this but I did find out that akinetopsia can be a rare side effect of medications such as nefazodone which is a drug used to treat depression.
http://en.wikipedia.org/wiki/Akinetopsia
http://www.youtube.com/watch?v=tYFhDzQ1rYU&feature=related
http://books.google.com/books?id=Xx7iNGdV25IC&pg=PA410&lpg=PA410&dq=incidence+rate+of+Akinetopsia&source=bl&ots=Ut7YBp3cJx&sig=ynFpwSyo28-uRknGA7321ZT_sIs&hl=en&sa=X&ei=9_1PT8z3MOz4sQLKxsSaDg&ved=0CDcQ6AEwBDgK#v=onepage&q=incidence%20rate%20of%20Akinetopsia&f=false
Terms: akinetopsia, motion blindness, neuropsychological, middle temporal cortex, lesions, occipital lobe, retina, and smooth motion.
That is scary that you found a drug that has been linked to akinetopsia. That would be terrible and I don't think I would ever use that drug even if it had a remote possibility of affecting my MT area. Crazy.
I chose to do my topical blog on akinetopsia because I think it is an interesting neuropsychological disorder. Akinetopsia is a disorder where the individual’s MT is effected in a way that eliminates the individuals perception of motion. The interesting part about this disorder is that when an individual is in a place where nothing is moving at all their vision is unaffected. But the second something moves the image appears distorted much like if a film projector only showed you every 6 or 7 slides of a movie. There would be skips in movement and it would be hard to tell what was going on. Think about how that would be while walking around the world. Patients report many issues with every day tasks such as driving, going for walks, crossing the street and even pouring a cup of liquid. Usually when doing something like pouring yourself a glass of juice, you can perceive when to stop by seeing that the fluid is rising to the top of the glass, for someone that does not perceive motion this is difficult. Many of them compare it to looking like the juice is frozen.
Other names for this disorder include, cerebral akinetopsia and motion blindness. Akinetopsia is a disorder, which disturbs vasomotor tasks, such as reaching for objects and catching objects. There are many causes for akinetopsia, including brain lesions, trasnscranial magnetic stimulation, Alzheimer’s disease, and prescription antidepressant drugs.
When the right size brain lesion occurs in the right place in the middle temperal cortex akinetopsia can occur. For this to happen the lesion has to be on the posterior side of the visual cortex in the part of the MT that is responsible for motion. This is rare because damage (lesions) in the occipital lobe usually effects more than just motion perception.
Transcranial magnetic stimulation is a shock treatment for individuals with migraines, strokes, Parkinson’s disease, dystonia, tinnitus, depression and auditory hallucinations. They induce very weak electric currents into the brain. This can also cause akinetopsia, if damage is done to the MT by the treatment.
Patients with Alzheimer’s disease may or may not have varying degrees of akinetopsia. Not enough research has been done on this topic to draw significant conclusions. Akinetopsia can also be linked to a prescription antidepressant drug. Although, their symptoms went away after being taken off the medication.
There is really only one well known case study on akinetopsia and it was done on a woman whom they call LM. LM reported having slightly better perception of moving objects when allowed to track the stimulus instead of fixating at a central point. She could see slow movement. What I found interesting is when they studied her peripheral vision, she was unable to detect the speed or the direction of the motion. I found that interesting because the rods in the retina are what control your peripheral vision and they are much better at detecting motion than the cones in the retina. I found it unusual that she was worse at detecting motion in her peripheral vision than if she was directly looking at an object. I also thought it was really interesting that she was not able to detect any motion when something was moved farther or closer away from her. So her depth perception was really off when it came to motion. There have been a few other case studies and some research on monkeys done with this, but it is really rare so it makes it hard to do research on it.
Terms: Akinetopsia, MT, occipital lobe, visual cortex, rods, peripheral vision, cones, retina, depth perception,
http://kevinleung.com/archives/akinetopsia/
http://en.wikipedia.org/wiki/Akinetopsia
http://www.youtube.com/watch?v=tYFhDzQ1rYU&feature=related
So I just figured why there is problems with the peripheral vision is worse even though peripheral vision is usually better than non peripheral vision because of the way that rods and cones fire.
The reason LM's peripheral vision for motion is worse is because the problem isn't in the retina it is in the MT area.
Cool stuff. I keep seeing this drug that has been linked to akinetopsia in posts from people in the class. If this is a valid interpretation of what ever results emerged from such a study (probably correlational), I would not use such a drug, even if it has the potential to help with 5HT-type modulation.
To really understand how something works sometimes, one has to understand how it may break and become dysfunctional. When reading Ch. 7 and mentioned previously in class is the topic of Akinetopsia or motions blindness. Akinetopsia is a rare neuro-psychological disorder in which the affected individual has no perception of motion. Our eyes take in our world around us by use of our retina and how a wave of light is reflected off of object around us through use of saccades. Saccades being the rapid movements of the eyes that changes as we fixate on one object from another. So when a person’s brain is damaged, rather than perceiving motions, what they perceive is much like still pictures of moving objects as optic flow is disrupted. Apparent motion is the impression of rapid smooth motion resulting from the rapid alteration of objects that appear in different locations in rapid succession which is an example of this disorder only slow down. Like having to look at a page of a flip book for a few seconds before moving on, this stopping motion to just see surroundings can become an issue. Hence, resulting in life being rather difficult due to motion is something that we are genetically per-disposition to as it’s our brains that allow us to see motion and so much of our life is in motion.
In an average brain signals from the eyes go along the optic nerve, to the posterior area of the brain where our vision is perceived. This place being the primary visual cortex, the area of the cerebral cortex of the brain that receives direct input from the lateral geniculate nucleolus, as well as feeding back from other brain areas, and is responsible for processing visual information. But that isn’t all, the middle temporal lobe, an area of the brain that is now believe to be important in not just vision but more so perception of motion.
This can be caused by injuries to those areas of the brains as well as lesions from strokes or head injuries. It is however a rare disorder that isn’t common and plenty of case studies that have been done on those that do have it. An interesting thing I found was that in some cases of patients with Alzheimer’s that Akinetopsia occurred. With the deterioration of other parts of their brains, their perception of motion also was deterioration and watching action movies and sports became issue for some. There is no treatment and far from a cure for this rare disorder.
Terms: ankietopisa, saccade, apparent motion, retina, optic nerve, primary visual cortex, wave, optic flow, middle temporal (MT)
http://simple.wikipedia.org/wiki/Motion_blindness
http://www.psychologicalscience.com/perception/2011/03/akinetopsia.html
http://www.enotes.com/topic/Akinetopsia
Good lead in with the reverse engineering metaphor of the brain. We learn so much from these unfortunate people who have suffered brain injuries and as a result have some particular deficit. Interesting post.
After reading Chapter 7 I chose to research the disorder akinetopsia. I wanted to know more information about this topic and why it happens. I was first introduced to this disorder from the video we watched in class, I never realized this was a real disorder until taking this class and that is why I became very interested in it.
Akinetopsia was discussed at the end of the chapter and it was only discussed briefly. It related to the chapter because it is a disorder that affects of visual perception of motion. The disorder mainly affects the MT of the brain. We need the MT to be working correctly to perceive motion.
Akinetopsia is a neuropsychological disorder that affects a person’s ability to perceive motion. In some cases a person will still be able to see some motion, but not how a normal person would, and in other cases a person may not be able to see motion at all. Akinetopsia would be like looking at something that is in motion and seeing it pause all the time, once you see it ten feet away then you see it two feet away.
Akinetopsia is not a disorder that is in the retina or the visual cortex, it is a disorder that happens in the brain. Akinetopsia only effects the motion perception; people with this disorder still have the same visual perceptions as others do, like color vision and depth perception. The main area in the brain that causes akinetopsia is the MT (middle temporal). The MT is the area in the brain that makes us able to perceive motion. In most cases akinetopsia is caused by damage to the MT, like a stroke, lesions, or antidepressant drugs. Although we know where the disorder takes place there has been no treatment found to correct it.
After researching akinetopsia I found it is a very rare disorder and there is little data on individuals who have the disorder. When I originally read about this disorder I thought back to the video we watched in class. In this case the women suffered from a stroke and after the stroke she could not perceive motion. She mainly said it was disturbing and made her feel in a way unsafe. She never really knew how close something was to her. Also after I researched akinetopsia I found that many of the people who are affected by this disorder feel the same as the women in the video. This disorder makes them feel very unsafe. It is hard for someone with akinetopsia to even cross the street or pour a glass of water. Akinetopsia affects everyday tasks.
Also after researching I found in some cases people with Alzheimer’s can develop akinetopsia. They do not develop the disorder fully, but they do have characteristics of the disorder. This could be because they are already disoriented. Also everything is slowing down and the message from the retina to the brain can be affected by Alzheimer’s, which is why they can develop akinetopsia.
Terms: akinetopsia, MT (middle temporal), retina, visual cortex, color vision, depth perception , Alzheimer’s, motion perception
http://www.medscape.com/viewarticle/410860_6
http://en.wikipedia.org/wiki/Akinetopsia
http://psychology.wikia.com/wiki/Akinetopsia
http://www.youtube.com/watch?v=B47Js1MtT4w
Did they say that the link between akinetopsia and alzheimer's was based on the drugs alz patients take? Or was it more of a gradual degradation of the myelinated axons which would lead to slower, less efficient, transmission of the neural signals? Interesting, I hadn't heard that link between Alz Dis. and akinetopsia.
Good post. See other posts that talked about akinetopsia for more feedback.
What really stuck out to me in chapter 7 was the section about the saccades. I was particularly shocked to read that we experience over 172,800 saccades in one day, and this is not even counting rapid eye movement when we sleep. A saccade is a voluntary eye movement that moves quickly from object to object. More specifically, a saccade is when there is a change in the fixation point from one spot to another. This is something can happen deliberately, as in when we are specifically focusing on an object. A saccade can also occur involuntary, as in if there is something that “catches our eye” or something that stands out in our visual field. An interesting thing about the human eye is that it is always moving, hence why we have 4 saccades every second. If I understand this correctly, then that means that we change our fixation point four times within every second. The saccade also fixates on “interesting” objects. This means that our fixation point does not fire randomly. The eye movements humans make are unique upon the objects that one is looking for. An example of this would be when a person is reading. Their saccade will focus on a word and then change to the next word, it happens so quickly that it typically goes unnoticed. The saccade connects to the retina in the back of the eye. It is able to move so quickly because of the high sensitivity of the retina.
An interesting phenomenon related to saccadic eye movements is called saccadic masking. This is when the brain blurs some motion so that humans cannot detect every detail in every visual instance. More specifically, when small movements are made within the saccadic rhythm, then the small movements are blurred. This is because the brain only attends to important visual stimuli. An interesting way to test this is to look into the mirror. When a person looks into the mirror they will see that it is not possible to see their own eyes move, the brain blurs the movement because it is not very significant. There are two types of saccadic masking: flash suppression and saccadic suppression of an image displacement. Flash suppression is the inability to see a flash of light during a saccade. So if the saccade is changing fixation points, and a flash of light happens between that change, then the light will go unseen. The saccadic suppression of an image displacement is the inability to see if an object has changed positions or not.
Saccadic eye movements are relevant to sensation and perception because it is something that humans experience 172,800 times a day! Now that I understand what happens below the surface, I can finally see what it is that the retina is connecting to to receive the images. Saccadic eye movements can be a sensation that we interpret on our own when we realize that we are changing focus points, but it also deals with perception. There has been research to show that people can perceive that an image has changed when in fact it hasn’t, and this has to do with the saccadic eye movements changing position.
Terms: Saccadic eye movements, rapid eye movement, fixation point, visual field, retina, optic nerve, saccadic masking, flash suppression, saccadic suppression of an image displacement.
http://en.wikipedia.org/wiki/Saccade
http://www.merriam-webster.com/dictionary/saccade
http://www.journalofvision.org/content/11/11/1195.short
Cool post. Saccades to me are one of the most important ways in which we gain access to our external world (which is typically changing).
I picked smooth pursuit as my topic. It fits into the chapter by being the controlled movement of the eye as it smoothly follows an object. I’m interested in it because it is something police look for when giving a field sobriety test. And since becoming a police officer is my future police goal I wanted to find out more about why police look at it.
When I was doing my research I came across a condition called nystagmus (since smooth pursuit is apparently not the titles in the field sobriety test), which is a condition that involves involuntary movements of the eye. The portion of the field sobriety test I looked at is called Horizontal Gaze Nystagmus or HGN. This is the test where the officer tells someone to follow the tip of their pen with just their eyes without moving their head. While the person is doing this the officer looks for three things: (1) smooth pursuit, (2) jerking of the eye when it is at its maximum deviation (the farthest point that the eye can see in its peripheral vision), and (3) eye jerking continues at 45 degrees or less from the center of vision. Each step has to be led for four seconds and the entire test should take about 83 seconds. I found out some very interesting things pertaining to this test. First, if an officer is going to incorrectly test someone during the HGN test they are likely going to do it during the third step of the test. Probably because it can be difficult to measure 45 degrees when you are standing on the side of the road. Second, the test can be taken two quickly. And third, the flashing lights on top of the police vehicle can also contribute to nystagmus. But event when faced with all of these issues, police are 88% accurate in identifying someone who is over the legal limit. Nystagmus can also appear two other ways; other influences and genetics. The HGN test can also show when someone has taken depressants, barbiturates, phencyclidine, seizure medications, or a variety of inhalants. These come with warnings about driving since nystagmus can affect a person’s ability to focus and their depth perception. Nystagmus can also be passed down genetically and appears in three forms; congenital (2-3 months old), spasmus nutans (6 months – 3 years old), and acquired (childhood-adulthood). When police test someone they are looking for acquired since it is the form that can be brought on through impairments due to drugs or alcohol.
http://www.youtube.com/watch?v=Xj4mWkNvq3c
http://www.nhtsa.gov/people/injury/alcohol/sfst/appendix_a.htm
http://www.aoa.org/x9763.xml
Terms: smooth pursuit, nystagmus, Horizontal Gaze Nystagmus (HGN), smooth pursuit, maximum deviation, peripheral vision, depth perception, congenital nystagmus, spasmus nutans nystagmus, and acquired nystagmus.
I think if I got pulled over I would simply ask for a blood test (regardless of my condition), unless they have a mobile eyetracker on hand (probably not). It would be really hard to determine with absolute accuracy whether a person was actually messed up. Just my opinion, but I feel like at least with blood or some other marker, you get an accurate prediction about how much of substance A, B, C is in the person's system. This would make things much more objective. I've heard the nystagmus argument before, but I just don't think it is the best marker in these situations (usually dark, so a flashlight pointed at your eyes will bleach the hell out of your rods, then you have to track some object?). Doesn't seem fair to me.
This week I decided to investigate the interactions between motion and color. One way that these two phenomena interact is by motion causing a perception of color that would not otherwise exist. This is somewhat similar to our previous discussion of afterimages and negative afterimages from Chapter 5. One of the most prominent examples of this effect was first documented by Bidwell near the turn of the 20th century and has subsequently been termed “Bidwell’s ghost”. An example of this effect can be demonstrated by spinning a half-black, half-white disk through which a red light is shone. As the disk spins it appears to be cyan, the complementary color to the red light, but once it stops, it becomes clear that the disk is black and white.
Another fun example of motion-induced color comes from about the same time. This phenomenon is called “Benham’s top”, and it involves a disk marked with a pattern of black and white rings. As the top is spun, a color spectrum appears from the outside in, and this spectrum can be switched to originating from the inside out by spinning the top in the opposite direction. This demonstrates the effect of pattern-induced flicker colors (PIFCs). This experience is thought to come from the lateral interactions in the retina followed by further spatial interactions in the visual cortex. In general, this sort of phenomenon is interpreted as being complementary to the neural mechanism that maintains color constancy under typical conditions.
But that’s not all – just as motion can induce the perception of color, so too can the reverse effect occur. This mechanism is much like the apparent motion phenomenon we discussed in class, except that instead of objects appearing and disappearing in sequence to produce illusory motion, with color-induced motion they simply alternate between a pair of colors in sequence. From this effect can arise another phenomenon that marks the additional interaction of spatial stimulus configuration. This effect is known as “dynamic texture spreading,” and it works under a set of rules similar to those of the illusory contours and Gestalt principles previously discussed in our textbook, except that in this case, edges and illusory objects are formed by chromatic differences. The strength of this effect varies depending on the placement and density of dots within the illusion. Arranging dots in geometric shapes instead of merely at random can also increase the prominence of the spreading effect and its contours.
http://www.perceptionweb.com/abstract.cgi?id=p240695
http://aris.ss.uci.edu/HIPLab/staff/sperling/PDFs/Sperling_NegAI_woPosImage_Sci_1960.pdf
http://www.springerlink.com/content/wr32xl2t35610uk7/
http://www.cogsci.uci.edu/~ddhoff/1995-37-CFM.pdf
Terms: afterimage, negative afterimage, Bidwell’s ghost, Benham’s top, pattern-induced flicker colors, visual cortex, color constancy, apparent motion, dynamic texture spreading, illusory contour
Good post. I like how you related stuff you already learned and integrated the two types of signals as would happen in the brain. Interesting stuff.
For this weeks topical I chose to do further research on motion aftereffect. I mainly chose to do it because I was mesmerized by the stuff that we did with it in class. It also made me think about afterimages which we talked about in our chapters on color. As I thought about after images and the things that I have learned about color I began to see a lot of similarities in what the visual system does for color and for motion. I think that this was very good topic to do further research on.
Just as afterimages are images that we perceive when there is no longer and image, a motion aftereffect is the perception of motion when there is none. This occurs because neurons in our eyes have opponents to whatever they do. For example if we have neurons that are coded to detect movement from right to left we also have neurons that are coded for movement from left to right. When certain neurons experience stimulation for an extended period of time they become fatigued. Since those neurons that are coded to do the opposite of whatever was being stimulated when out and when we focus on a new thing they will then fire off faster causing us to perceive something that is not actually there. It has also been determine that these affects do not come due to retinal processing.
In one research experiment the perception of motion was paired with a sound frequency to determine if this stimulus could induce a motion aftereffect. The result of this study showed that after prolonged exposure to the stimuli the sound frequency could indeed induce an aftereffect. Unlike the other aftereffects however this one could not be transferred interocularly. Although there are arguments to say that the tones served as a bias to causes those being studied to see aftereffect, the experiments did a number of different things to make sure that this was not the case.
Key terms: motion aftereffect, afterimage, retina, interocular transfer.
http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/motion_aftereffect.html
http://en.wikipedia.org/wiki/Motion_aftereffect
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118223/
The illusion stuff is interesting and shows you what we can miss from our environment. Upward motion of water defies gravity and I think that is why the MAE and illusions like the waterfall illusion are so appealing.
After completing Chapter 7, the number one thing that stuck out to me was the unfortunate condition called akinetopsia. Akinetopsia is a rare neuropsychological disorder in which the affected individual has no perception of motion. It is also known as motion blindness or cerebral akinetopsia. There are a couple different causes which include, Alzheimer’s, traumatic brain injuries and brain lesions. Unfortunately there has not been very much research on exactly why Alzheimers patients get akinetopsia besides the usual memory problems that also occur that the disease. However, according to Medscape.com, motion processing can decline with Alzheimers patients. Akinetopsia is an acquired deficit from lesions in the posterior side of the visual cortex. This terrible disease also affects the patient’s visuomotor tasks such as reaching and catching objects. According to wikipedia, one patients describes having this disease being very difficult to master everyday tasks such as pouring a cup of coffee. The patients describes the coffee as looking frozen and experiencing no movement when watching themselves pour the liquid into a cup.
When doing further reason on this disease, I came across something called V1 and V5. V5 is also known as the visual area MT (middle temporal). Neurons found in V5 are motion and directionally selective. If V5 happens to have lesions, this may cause akinetopsia. V1 is known as the primary visual cortex and is also known as the pre-processing capabilities for our visual information. Individuals who have damage to their V1, have something called blindsight and also limits motion but doesn’t completely extinct motion. After completing my research, I found a brilliant youtube video that demonstrates this disease. It’s quite disturbing to believe that there are some individuals who have to suffer through this. It reminded me of a movie that was trying to portray someone who has become sick and dilusional and is trying to walk. Though there is no known cure at this point, we can only hope that in time there will be.
Terms: Akinetopsia, perception of motion, cerebral akinetopsia, alzheimer’s, visual cortex, visuomotor, middle temporal, motion selective, directionally selective, primary visual cortex, blindsight,
http://en.wikipedia.org/wiki/Akinetopsia.
http://www.medscape.com/viewarticle/4108606
http://www.youtube.com/watch?v=QW53fRQv3Zo&feature=related
Cool post. See replies I made to other posts which were on the same topic.
The topic I decided to further research was akinetopsia. Akinetopsia, according to Wiki, is an extremely rare neuropsychological disorder in which a patient cannot perceive motion in their visual field, despite being able to see stationary objects without issue. This fits into the chapter, because it was a term in chapter 7 and since it was such a strange disorder to me to me, I decided I wanted to know a little bit more about it.
The world for a person with akinetopsia is motionless, and as of right now there is no cure and no treatment for akinetopsia. The science behind what akinetopsia is and how it occurs is due to a change in brain structure disturbs the psychological process of understanding sensory information. Typical causes of akinetopsia are brain lesions, transcranial magnetic stimulation, and Alzheimer’s disease. Characteristics of akinetopsia are not being able to detect motion despite having normal spatial acuity, stereo vision, color vision, and flicker detection. Many patients grow weary of having more than two people in a room at the same time because they are not able to keep track of everybody and what they are saying, and grow anxious. Simple tasks are very difficult to complete, such as drinking, because patients cannot tell when to stop pouring and described the fluid as looking like a glacier moving. While watching the youtube video, which is posted below, I could not imagine how it would be to live with that type of vision. I think it would be very unsettling not being able to see things right away as they happen, and I now know how much I take my vision for granted.
http://www.medscape.com/viewarticle/410860_6
http://en.wikipedia.org/wiki/Akinetopsia
http://www.youtube.com/watch?v=B47Js1MtT4w
Terms- Akinetopsia, Alzheimer’s disease, spatial acuity, stereo vision, and color vision.
Cool, see other posts I made in reply to other people's blogs about the same topic.
For this week’s topical assignment I decided to investigate more information regarding saccades. Saccades are fast movements of the eye from a particular object or part of the environment to some other object or visual. Humans have around 173000 saccades daily (not including REM sleep, which includes multiple more). This concept fits nicely into the chapter regarding motion because of how we visualize movement and are continuously and often unconsciously producing rapid saccade movements. One particular type of saccade can be seen in vergence. Vergence is a term defined as a movement from both eyes that move in complete opposite directions. Similarly, convergence is where both eyes look toward the center toward the nose. Divergence, on the other hand, shifts the eyes away in the opposite direction outward and away from the nose. A lot of times saccades are expressed because of our bodily movements, where our eyes turn to accompany this gradual shift of motion. This is known as the reflexive eye movement. During this shift of body, our eyes attempt to continue a fixation on a particular set object. One of the biggest interests from saccades that I have learned through studying is the saccadic suppression we undergo during this eye movement. I learned that the visual system shuts down, but more accurately suppresses information, and our visual sensitivity is reduced. One way to help envision this idea is to think of it as similar to when we blink. There is a postponed visual activity. Eye movement has a component from the fovea that demands the eye to be highly mobile and curve through a large angle of vision. There are two types of motion in regards to saccades through the use of foveola movement. There are major saccade movements that are easily noticeable by clinicians and other professionals. The other type of motion is a minor saccade that is virtually unnoticeable without the use of some sort of professionally used equipment. Major saccades are associated with low frequency from the oculomotor muscles. Minor saccades are associated with a much greater frequency from the oculomotor muscles. They can be further subdivided into micro and minisaccades. Large saccades are more infrequent and associated with the bodily movements, similarly related to the reflexive eye movement saccades. Minor saccades are more common and related to the mechanics of scene perception and the interpretation of environment. These minisaccades are very important for humans in how we perceptually visualize and interpret images. Both humans and animals alike do not use a fixed steadiness. The eyes are constantly moving to locate different objects and incorporate different information. Just by simply looking at each and every word written on this blog we produce a mass amount of saccade movement important for the function of motion activity. We are unable to control speed between stops of saccade in saccadic suppression. Therefore, these are unconscious movements. Once again, it is important to reemphasize the importance of the fovea, a central part of the retina. Without this important piece of our saccades we would not be able to clearly resolve objects with a greater resolution of clarity. This visual clarity is also clear during the saccadic suppression, sometimes called saccadic masking. If our brains were not continually passing information from the optic nerve, we would have a motion blur. The Youtube link on the bottom shows a video of both horizontal and vertical eye movement. It’s a short video, but I learned that with certain disorders such as someone with MS may not have the same precise eye movement speed between both eyes. Overall, I believe the book did a nice job of identifying and incorporating the saccadic movement into the concept of our motion through sensation and perception. The links are great ways to further research this activity and expand the knowledge given on the topic.
http://neuronresearch.net/vision/reading/saccades.htm
http://en.wikipedia.org/wiki/Saccade
http://www.youtube.com/watch?v=P6uTlnyNaTs
Terms: Saccades, vergence, saccadic suppression, oculomotor muscles, fovea.
Good post. See other replies above that I made to other people's posts on the same topic if you want more feedback.
I found the reflexive eye movement particularly interesting. The reflexive eye movement is a movement of the eye that is automatic and involuntary.
Although we call them “voluntary,” you generally do not consciously think about making saccades, pursuit, and vergence eye movements. Certain portions of your brain are continuously firing away in the background to plan these eye movements, but all you are concerned with is the visual information received once the eyes get to their final destinations. The portion of the brain that is continuously firing away is particularly the superior colliculus.
However, even if you try to keep your eyes perfectly still, your gaze continues to jitter a little. These miniscule tremors of the eye muscles are called involuntary eye movements, and you normally do not even notice them.
What possible function could these eye tremors serve? Some fascinating experiments have revealed that when an image is kept perfectly stationary on the retina. This is actually counteracting the effect of the normal involuntary eye movements. The image actually disappears after a few seconds! It is not known exactly why this happens, but the result implies that constant retinal motion is necessary for the visual system to function properly.
http://www.mitpressjournals.org/doi/abs/10.1162/089892904322984599
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5333504&abstractAccess=no&userType=inst
www.medlectures.com/Neuro%20Lectures/eye_movements.ppt
http://fmri.nl/index.php?option=com_content&task=view&id=30&Itemid=279
Cool post. Definitely interesting that you can maintain a stable image on the retina given the constant movement and saccades of the eyes.
The topic that I chose to investigate further is biological motion. Biological motion is that people can perceive movement of people by just a few different points in a persons body. This was first demonstrated by Gunnar Johansson in 1973. He demonstrated this having ten small light bulbs attached to a person wearing all black in a black room. He then video taped this the person doing a task. These takes were then shown to participants. After viewing the tapes for a very short time participants were able to interpret the light bulbs as a human doing a certain task. Later experiements with the same type of research have shown that humans are also able to tell different animals apart, gender, and mental state. Humans as young as 3 months have the ability to do this. This is related to sensation and perception because just by a few points humans are able to tell if the animal is a potential food source, a potential enemy, a potential friend, or a potential mate. Brain studies have shown that the superior temporal sulcus, premotor cortex, cerebellum, and the temporal lobe have high levels of activities when doing these studies. This has shown consistence because people with autism have a trouble with these studies and also have problems in their superior temporal sulcus.
The video clip clearly demonstrates biological motion. You are able to clearly make out what is happening in the video even though you are only able to see a few dots on the screen.
http://www.biomotionlab.ca/Text/biomotionTroje08.pdf
http://www.psy.vanderbilt.edu/faculty/blake/BM/BioMot.html
http://www.youtube.com/watch?v=ObBRkifC2sM
Terms: Biological motion, temporal lobe,cerebellum,
After reading this chapter I wanted to focus on the mirroring others actions. I found this to be interesting, because many people tend to mirror others once they have watched or observed another person perform an action. Also, I found this to be useful when I am working with training my dog, she likes to imitate my actions.
1. An article on the BBC news website is about how dogs mimic their owners. This article is very useful in my everyday life when I am with my dog, and I learned more about this process. When dogs sight another’s body movement it causes the observer to move the same way. This is a type of learning ability in humans and in dogs. The mirror neurons are used to imitate the ability to learn and develop a desired action. This is a new concept that it is not “inborn” but rather mirror neurons that learn from trial and error and ultimately imitation. When a dog learns how to go through a box or clap their paws, the owner has to take a lot of time to train them and show them the action. Dogs will not just perform these desired actions on response, they need to learn how to do them. The owner can go through the box or clap their hands over and over again until the dog learns the stimuli. Dogs them can remember and use their mirror neurons to go through the box or clap their hands when they have learned the action.
http://www.bbc.co.uk/news/science-environment-10777586
2. The second article I found supports the evidence of mirror neurons are used to understand one another. The mirror neurons can be found in the brains movement and memory section that helps us understand actions of others. Human and infants can use this process to respond to what they have just observed. Active mirror neurons responds to learned tasks in front of them and the neurons work together to make it a mirroring response. There is a study that shows the link between Autism and mirror neurons that can help scientists analyze these particular parts of the brain to develop treatments and plans for these disorders. The mirroring neurons are active when processing the task and doing the repeated task. Memory is a great importance to this learning process, and further research can help the public understand more about autism and other learning disorders.
http://www.livescience.com/11002-mirror-neurons-understand.html
3. The third article I found that relates to this chapter is about relating mirroring neurons in an everyday situation. I watched a video of a sports game and how we use our mirror neurons in our brain to understand the actions and imitate them. A person can connect with a sports game that uses the mirror neurons to look and copy. When a person is moving and you learn and copy the set of moves, you can move with them. This could be used in dancing and many other activities. When a person use the learning of tense action they know the game and get attached. The motor system and emotional system are connect together and that is what science is trying to further understand. The mirror neurons are used to interact and relate to other people and is an important process in the brain and in everyday life.
http://www.pbs.org/wgbh/nova/body/mirror-neurons.html vocab- motor system, mirror neurons, imitate
This week, I chose to do my topical blog over Akinetopsia. This topic was interesting to me first of all because I didn't even know this disorder existed. I really want to look into how this is caused and learn more about the disorder.
First I decided to look into an article all about Celebral Akinetopsia. One thing I learned through this article that I didn't fully understand before is that akinetopsia is a disorder in which you loose your perception of motion. I thought that you just didn't see the motion, but that isn't the case. Your mind can't make out what is happening but you are still seeing it take place. I also learned that this disorder doesn't always come in the same way. It can be manifested by itself or it can come along with several other disorders. I found that interesting because some of the other disorders I have looked into usually are caused by other trauma, but akinetopsia comes at random times.
http://www.allpsych.uni-giessen.de/karl/teach/SemVisNeuro/Zeki1991.pdf
I usually don't watch videos for my topical blog, but this video actually caught my attention. It shows the basis as to what this disorder is and gives great insight in a way that anyone can understand. Through this video, I learned how rare it is to have akinetsopia. I learned about saccades and actually understood the meaning! Saccades are when your eyes are constantly scanning images to perceive depth and motion. Basically, in skinetsopia, your brain doesn't connect to these saccades and does not perceive the motion like its supposed to. The video used a great way to describe what the mind is doing in someone with akinetopsia. A normal person is constantly seeing a video in their head but someone with the disorder is only seeing specific pictures.
http://vimeo.com/13717641
This week, I chose to do my topical blog over Akinetopsia. This topic was interesting to me first of all because I didn't even know this disorder existed. I really want to look into how this is caused and learn more about the disorder.
First I decided to look into an article all about Celebral Akinetopsia. One thing I learned through this article that I didn't fully understand before is that akinetopsia is a disorder in which you loose your perception of motion. I thought that you just didn't see the motion, but that isn't the case. Your mind can't make out what is happening but you are still seeing it take place. I also learned that this disorder doesn't always come in the same way. It can be manifested by itself or it can come along with several other disorders. I found that interesting because some of the other disorders I have looked into usually are caused by other trauma, but akinetopsia comes at random times.
http://www.allpsych.uni-giessen.de/karl/teach/SemVisNeuro/Zeki1991.pdf
I usually don't watch videos for my topical blog, but this video actually caught my attention. It shows the basis as to what this disorder is and gives great insight in a way that anyone can understand. Through this video, I learned how rare it is to have akinetsopia. I learned about saccades and actually understood the meaning! Saccades are when your eyes are constantly scanning images to perceive depth and motion. Basically, in skinetsopia, your brain doesn't connect to these saccades and does not perceive the motion like its supposed to. The video used a great way to describe what the mind is doing in someone with akinetopsia. A normal person is constantly seeing a video in their head but someone with the disorder is only seeing specific pictures.
http://vimeo.com/13717641