FINAL BLOG ENTRY

I think that the most unexpected and interesting thing I learned this semester in Perception was in the “Motion” lecture. The clinical presentation of patient LM suffering from Akinetopsia was the most strange thing I have ever heard of. I have known that a motion areas exists in the brain since I took Introduction to Neuroscience freshman year, but I had never heard or even thought of a condition in which motion perception was afflicted. Motion seems to be just a quality inherent in nature, but this disorder erases this idea of motion. Just like color, motion is something that the brain creates.

Akinetopsia is caused by damage to area V5 or MT, which is the motion area of the brain as we also learned in class. Damage to this area can either be caused by stroke (as is the case for patient LM), lesions, or the affect of some antidepressant drugs. People afflicted with this disorder cannot perceive a fluid world. Instead, they see what would be similar to the effect unaffected people experience in the presence of a strobe light. They would see a series of still pictures that would trail each other like a comet trail. Besides the symptoms that patients with Akinetopsia describe, they appear completely normal. They can read, write, calculate things, etc. However, in the you tube video of patient LM:

she has trouble pouring liquid into a glass. The liquid would appear to be like a “glacier. She had a hard time following a conversation because she could not see face changes and lips moving. I think living like this would be similar to the images of a city in fast forward, like in movies when they show day change into night really fast. Cars pass by with comet trails, and people come and go quickly. The following video attempts to depict this:

Patient LM describes feeling uncomfortable in a room full of people because it appeared as if they just came and went suddenly. In the video above, because it is played in fast forward, cars and people and trains seem to appear out of no where and be gone the next second. Because of this patient LM could not cross the street alone because the speed of cars could not be determined.

Although the loss of motion due to damage to motion areas of the brain can be lived with, it would be extremely debilitating. When I am at a party with a strobe light, I start to get sick or get headaches. I cannot imaging living with this disorder. Motion perception is so instilled in every activity that I participate in that I find it hard to image what patient LM experienced even after knowing it is similar to a strobe light.

Some prodding into this disorder allowed me to come across hemi-akinetopsia, in which only one side of the brain is damaged. A stroke or lesion at area V5 of only one hemisphere will only affect motion perception in half of the visual field. One can experience hemi-akinetopsia by using transcranial magnetic stimulation in one of the MT areas of the brain. The magnetic field inhibits the perception of motion by interfering with the brain. The following clip will bring you to a website with an interactive simulation of akinetopsia. The link to the simulation is at the bottom of the page.

http://vectors.usc.edu/issues/04_issue/malperception/akinetopsia.html

Perceiving motion is just another type of perception that most people take for granted. Most people probably do not consider motion to be a form of perception; however, patient LM and others afflicted with Akinetopsia prove that motion is a characteristic of the visual world that the brain creates.

April 27, 2008 @ 11:45 pm

Works:

http://www.youtube.com/watch?v=B47Js1MtT4w

http://vectors.usc.edu/issues/04_issue/malperception/akinetopsia.html

http://www.youtube.com/watch?v=jZmPe_KUh5c

http://nawrot.psych.ndsu.nodak.edu/Publications/Nawrot.pdf/RizzoNawrotZihl.1995.pdf

A deeply moving experience

The Renaissance was a time of cultural change in the world, and during this revolution art was changed forever. One of the largest breakthroughs was the advent of depth perception in art. Previous art depicted scenes in two dimensions. Of course people who lived back then did not perceive the world in 2D, so this can probably be accredited to limitations of the materials available to artists. Much of the art was done on wood with limited color options, making complex art pieces almost impossible. However, they were able to demonstrate some grasp of depth in their paintings although very limited.

Medieval art around the 12th century serves as a good source to look at 2D art. This was before the Renaissance in Italy. The following drawing labeled as 12 Century Hunting Scenes is a great example of an art piece lacking complex depth perception.

As you can see everything appears to be on the same plane of sight. Some of the more interesting things to note are the dogs and hogs. The artist tries to depict the animals in depth, but can only accomplish this through the use of occlusion. Size variation is not made use of either. The objects in the back should look a little smaller since they are further back, but ,as seen with the hogs, all of the objects are the same size. The following picture is another good example of the depth limitations in the art from the Medieval period.

Again, the only way the artist depicted depth was through occlusion. The second face from the left almost seems to come from the same neck as the first figure showing the obvious faults with using occlusion as the only form of depth clue. What these art pieces lack are linear perspective, shading and size variation (kind of).

Renaissance art shows depth through the use of many different depth clues including occlusion, linear perspective, shading, and size variation. Linear perspective is one of the first big breakthroughs in art. As seen in the following paintings from Raphael and Mantegna, Renaissance art does a better job of depicting real life scenes.

Raphael

Mantegna

The Raphael painting, School of Athens, shows linear perspective in its early form.  The arc gets noticeable smaller into the distance, and figures can be seen at different distances from the front to the back.  The size of different figures also changes to provide depth perception.  Of course occlusion is used.  Shading is also used to an extent, but becomes way more obvious in the Mantegna painting Dead Christ.  In this painting size manipulations and shading allow Jesus to be depicted laying down with an observer, the painter, standing at the foot of the bed.  There also appears to be a light source, which is something lacking from pre-Renaissance paintings.

April 19, 2008 @ 3:22pm

Color me silly

Synesthesia is a very strange condition.  Its neurological basis is dependent on the idea that specific areas of the brain are devoted to specific functions.  Synesthesia results from and INCREASE in cross talk between different sensory modality areas of the brain.  This indicates that there already exists some talk between areas.  When you hear a certain noise or smell some scent alot of times you experience other intense feelings and memories.  This indicates that sensory modalities do not exist and function independently, but instead interact to give rise to conscious experience.  Synesthesia needs to be studied to give us a better understanding of how the “normal” brain functions in crossmodal perception or multisensory integration because what is happening in synesthesia is just a more intense form of what happens in a normal person.  The condition could also be caused by disinhibition of connections between different areas of the brain.  This is the reason why psychedelic drugs elicit similar experiences.

I imagine this condition to be similar to a combination of Rain Man and Fear and Loathing in Las Vegas.  For some reason I have this idea that you would be perceiving lots of odd things: colors, shapes, explosions, etc.  I also think that it would give you unrivaled skills in memorization, just as Rain Man has.  I can’t imagine how someone with this condition does not go crazy from seeing colors and shapes(etc.) associated with normal things like speech, numbers, and sounds.  However, if you have experienced this your entire life, then it would all appear normal.

Maybe synesthesia is the future of humanity in an evolutionary sense.  If you think about it they have a higher level of perception than the normal human.  They can use it to their advantage in a number of ways including intelligence (memorization) and possible survival.  If they could sense something approaching not only by hearing but also by seeing warning colors then they have an advantage.  This condition is very interesting and could provide great insights into not only normal perception today, but the future of human perception.

April 13, 2008 @ 11:50pm

Developmentally Speaking

I have always wanted to know what lazy eyes were all about. The technical name for lazy eye is Amblyopia and is indeed caused by abnormal development of the visual system. It is defined as any reduction in vision not accounted for by disease and non-correctable with glasses or contact lenses. It is estimated that about 3% of children under six have amblyopia. Amblyopia is caused by anything that interferes with normal vision for an extended amount of time during the critical period of eye development in children. This period lasts from birth to about age six. Cataracts which block the eye, trauma, lid droop, and anything else that impedes vision in one or both eyes are the most prominent causes of lazy eye.

The lazy eye or amblyopic eye may pick up light information, but the brain does not process this information. This is evidence that amblyopia is a neurologically active process and not one of just the eye. We know from this class that vision goes far beyond the eye, and this disorder is one instance in which a part of the visual system besides the eye is damaged. The loss of vision occurs in the brain. The brain can inhibit information coming from one of the eyes if that eye is significantly blurred. The brain also wants to prevent double vision, and thus has the ability to suppress information from an eye. Too much suppression of one eye can cause permanent loss of vision in the lazy eye. This is the reason that amblyopia cannot be treated with prescription lenses or contacts or even lasik.

Vision therapy seems to be the most used form of treatment. Until the age of 17 amblyopia can be reversed or successfully treated; however, after the age of 17 treatment becomes very difficult, requiring significantly more effort.

http://www.lazyeye.org/

April 6, 2008 @ 11:04

So much information, so little attention

I wanted to think more about change blindness and inattention blindness a little more.  These phenomenon are really interesting, and I get fooled completely every time I am presented with one of these movie clips.  Besides having fun exploiting this function of perception, I think that both of these “blindnesses” actually bring more positive things to the table than negative.  However, before getting into the good things that may come out of inattention blindness, Ill go through some problems it causes.

In the “old days” when movies were a new medium for telling a story, movie makers got away with some horrible special effects.  People were more concerned with the plot of the stories, the characters, the conflicts, the dialogs, etc.  The majority of movies were dramas and comedies, NOT action and adventure.  In order to create a successful action movie, you must have good special effects, which is something they did not have.  In old movies people were concentration on other things, and failed to notice things like the obviously fake vista in the background, or the wires holding the model plane.  Since movie goers now pay attention to special effects, old effects become very obvious.

Also, when editing papers or looking over a test that you are getting ready to turn in, many obvious mistakes go unnoticed.  The atmosphere of a test and the nervousness make you unable to concentrate completely on the small details of the paper in front of you.   Looking over these kinds of things after the fact is sometimes very frustrating.  Because of inattention blindness, many otherwise obvious mistakes went unnoticed.

Despite the fact that sometimes this effect brings negative consequences, the ability to channel most of your attention to a select few stimuli is for the most part a great ability.  Without this, humans would not have been able to accomplish what we have.  If every stimulus presented before you was recognized in full, then the brain would be clouded with too many things to be able to process any one thing to a heightened degree.  Heightened concentration of certain stimuli has protected us from many things including prey.  If you are swimming in the ocean and spot a shark, are you going to want to be distracted by every little fish that swims by, or do you want to have all focus on the thing that could potentially eat you?  I think I know the answer.  It would be nice to be able to process all stimuli equally, but it is just not realistic.  As in the video with the gorilla, I wonder how many people can notice the gorilla while also counting the number of tosses correctly at the same time.  I have a feeling that very few people do both.

March 30, 2008 @ 21:22

Edge Detection and then Some

I want to address the issue of cortical magnification and whether or not it is a good or bad thing.  Cortical magnification basically explains the phenomenon in which things in the center of the visual field have the best acuity, and things in the periphery have less acuity comparatively.  Areas of visual space corresponding to the fovea have the largest number of cortical neurons thereby giving it the best resolution.  When more neurons are available to process information from a smaller area, then a heightened sense is formed for that area.  If someone were to pass a pen in front of your face from left to right, the pen would go from a little fuzzy to perfectly clear to fuzzy again.  This can be explained by the number of neurons in the cortex available to process the pen information.  While in the periphery, the pen information is processed by fewer neurons than it is when in the center of the visual field.

Because nothing on the body evolved for no reason, cortical magnification is a good thing.  It provides a specific (and functionally logical) area in visual space with unrivaled resolution and focus.  It would be perfect if that kind of sharpness could be available for the entire extent of visual space, but this is not logistically possible with the amount of space for neurons in the cortex.  If the same acuity were available across visual space, then the resolution would be an average or combination of the current foveal resolution and peripheral resolution.  Overall this would be less affective because there would be no area of higher acuity.  Cortical magnification happened for the same reason that more areas of the somatosensory cortex and motor cortex are devoted to high use/need areas of the body.  Evolutionarily this makes a whole lot of sense.  Having higher functioning in certain areas of the body would help in survival.  Being able to resolve images to a great degree in the center of vision is an integral part of one of our most important senses.  Without this we would be vulnerable to a variety of things in nature and incapable of performing the necessary things that got humanity to where it is today.

March 23, 2008 @18:04

In the beginning, there is the eye

The line of importance in the Transformers theme song is “there is more than meets the eye.”  This line from the song should be the theme for visual perception.  Visual perception is the compilation of inputs from different areas of the brain that together create a visual experience.  What actually reaches the eye, light, is far from the final product.  As we have seen in class with the optical illusions, the mind manipulates what it sees through the eyes.  What actually is perceived may be vastly different from what actually IS.

Perception is also more than just the eye as well.  The eye is only one part of visual processing of information.  Different bipolar cells and ganglion cells set up receptive fields all that determine differences in light and dark.  Along with this, specific areas of the cortex are devoted to vision.  In these areas, the brain infers things about the environment based on the information received from the receptive fields and such.  The inferences are made to help us build a useful representation of the world; HOWEVER, this representation might not always be most accurate.

This line from the Transformers theme song can also be taken another way.  What the eye sees is not always the full picture of what is occurring in the environment.  The eye can only pick up photons of light.  By themselves these photons convey no information about the environment, they are what they are – just singular photons.  These photons of light are analyzed to create an image.  Much of what this image contains was inferred by the visual cortex.  Visual perception is not always completely accurate about what is actually out there, but it attempts to create an image that would be most useful in the survival sense.

March 13, 2008  @ 19:20

It’s all in the eyes

My eye sight tends to get worse with decreasing levels of light. I can see fine during the day when the lighting is fine, but when I am in low lit areas or at night my vision gets noticeably worse. Driving at night is the worst for me because I get really paranoid. All of the lights seems to glow brighter and combine into one another. It is actually pretty scary because I always feel overwhelmed and confused. I also have a hard time telling distance at night. I was curious to see what the cause for this was and came across astigmatism and night blindness.

After reading about the two, I definitely do not have night blindness. This is caused by a variety of things including cataracts, vitamin A deficiencies, birth defects, etc. I have none of these conditions and have a good diet which would give me proper amounts of vitamin A. My symptoms also do not line up because I don’t have an inability to see at night, I just have a diminished sense. My problem is not developed enough to be categorized by night blindness.

It turns out that my mother has the same problem. She informed me that it was most probably caused by an astigmatism, which is a distortion in the normal curvature of the cornea. Astigmatisms can be characterized by a variety of different symptoms, but a common symptom is blurred vision at a distance. This is something that everyone has to a certain degree. Astigmatisms can be treated by glasses, contacts and surgeries such as LASIK. Wearing my glasses at night, in class, and in other low light areas easily restores my vision back to normal. Also, astigmatisms tend to get worse with time, which explains how my vision has gotten progressively worse since high school.

http://www.healthvitaminsguide.com/deficiencies/night-blindness.htm

http://www.medicinenet.com/astigmatism/article.htm

March 9, 2008 @ 22:44

Mares, Oats and Ivy

Ill first off say that for some reason I always find myself involved with “mondegreens.”  I am always confusing lyrics, maybe because Im not the biggest music person.  In the song Air Force Ones by Nelly, I always thought that the song started with “Hey there Boo” but actually it says “Gator Boots.”  I thought this for a number of years before making a fool of myself at a party.  The funny thing is that now when I hear the song I can’t understand how I would make that confusion.  It is very similar to the example with the blurred dog picture we saw in class earlier on in the semester.  The lyrics so obviously say Gator Boots now.

The main thing I wanted to talk about are aphasias.  I think that these deficits in the various functions of communication, speech and language are very interesting and, to me, aweinspiring.  Because of the different types of aphasias including Broca’s and Wernicke’s and many others, doctors and scientists can begin to understand the role of the brain in language procession.  All of the different aphasias are caused by damage or something to specific areas of the brain, each having distinct symptoms and effects.  I was reading about them on Wikipedia, and found out that some aphasias can selectively disable the ability to speak while preserving the ability to sing.  This is very interesting because this means that there must be a different area of the brain that process singing.  The aphasias allow specialists to perform experiments on humans without actually having to manipulate brains.  That work was done naturally, unfortunately for those suffering. 

These aphasias indicate that language processing is an extremely more complex process than most people recognize.  It involves areas all over the cortex.  Processing auditory language signals occurs in one place, comprehension of what is heard and what is spoken are in other areas, etc.  Language problems cannot just be localized to one area, and not all language problems or disorders can be lumped into the same category.  The symptoms and treatments of the different aphasias and language problems also have to be different.

February 23, 2008 @ 23:11

Due 2-9 at midnight: taste

I think that there is a great application of the knowledge that the sense of taste is susceptible to adaptation. This application is in the area of weight loss. I have always had the mentality that the first bite of a dessert, or any food at that matter, is the most satisfying. This is proved by the experiment on page 545 in the text. When eating a large piece of chocolate lava cake, by the end most people are just eating in search of the sensation of that first great bite. This is almost, in a very slight degree, similar to someone doing addictive drugs like cocaine. They continue to use the drug in want of that euphoria they experienced the first time. When I mentioned my thoughts on desserts to my father over the summer, it was like a revelation to him. This idea is one that most people just don’t recognize on their own. At the time I was not really thinking about what was happening physiologically.

Getting back to the application to weight loss. If the finding that the sense of taste adapts to repetitive expose was published to the general public then I feel that most people would cut down on portion sizes. Of course, publishing this kind of information would not be in the best interest of the restaurant or marketing business, which is probably why most people are unaware of this occurrence. Everyone I have told of this effect has now started splitting desserts and treats. Now it seems so apparent, but before being enlightened it was almost like most were addicted to their food in search of some taste euphoria.

This blog has me thinking: Is food addictive? Because the sense of taste adapts to exposure, people will want to reestablish that initial sensation by eating more and more. Little do they know that this first feeling cannot be experienced again until the taste buds readjust.

February 08, 2008 @ 03:39