FINAL BLOG ENTRY

In class, we’ve gone into depth on each of the five senses. Each have similarities to some of the other senses, but they all share something in common. They can all be tricked. Illusions were the most interesting aspect of the course to me. Comprehending all the facets of something as complicated as vision can be daunting, but being able to see visible or tangible perceptual illusions help solidify some of the ideas. Most of the illusions we talked about were visual since it is the most studied sense. An example of how an interesting illusion helped was in the case of receptive fields. In the Hermann grid, we perceive faint gray squares in the white crosses when not focused on them. This illusion shows how receptive fields in the fovea are smaller since when we look directly at the cross we see no gray square due to the fact that our receptive field contains only white space and no black corners. This was a visual way to understand size of RFs and how illumination of ON and OFF center/surround caused different perceptions.

I have a book of illusions that was given to me a while ago just for fun (Al Seckel’s Great Book of Optical Illusions). It’s entertaining to just look through them and be baffled at how objects appear to be moving or growing, etc. But now I was able to go back to this book and come up with explanations for many of these illusions. After covering motion, color, and receptive fields in class among other topics in vision, most optical illusions I’ve come across can be explained. For example, one of the illusions was a block where the top half seemed white and the bottom dark gray with a sharp black line dividing the two. Then in the description it says the top and bottom are the same. These color illusions always seem unreal, but for this one if you cover the black line, they look exactly the same. This is because the sharp contrast and how they faded it made it look like the bottom was heavier shaded. This is an example of light contrast that we discussed where the same wavelength of light is perceived in different ways, in this case due to neighboring colors.

Some of the coolest tricks to me include some that aren’t visual. In class we talked about the ‘mosquito’ ringtone that takes advantage of adult high frequency hearing loss. In another class, they had a tactile illusion where if you draw your hands across three spaced metal wires it feels like they’re moving over silk. It was really convincing. These tricks tell me that although we do not know everything about the senses, we know enough to use them to our advantage or pleasure. They also are a fun and informative way to learn new things about senses. Many of the illusions came about by accident and tell us information about the sensory and/or cortical systems. One that I came across multiple times is a spinning dancer that supposedly can determine if you use your left or right sides of your brain more. I’ve never really believed in the whole right side equals creative thing although I am interested in the changes in the brains of left-handed people. But for this illusion, if you perceive the dancer spinning clockwise, it may mean you use your right-side of your brain more. A link to this illusion is: http://www.maniacworld.com/Spinning-Silhouette-Optical-Illusion.html

It took awhile for the switch to happen to me, but when it did it was pretty amazing.

Besides being informative and creative, illusions can also be used to test for deficits in individuals. If you can’t perceive the ‘moving’ concentric ring illusion, perhaps there’s a problem in the magnocellular system or MT. It may not be an accurate way to go about things, but it’s fast and also tells where the problem is in a general way instead of specifics found in other tests.

I’ll always be interested in illusions, and now I can at least explain them to friends and also understand them myself. They really show for me how complicated the sensory systems are. And to be able to see something that seems to defy physical laws is just exciting. They give me knowledge I can apply in my daily life.

Motion areas

To me, having multiple areas for motion processing isn’t redundant when looked at compared to the rest of the visual system and brain. If there was no overlap, we could get away with just having V1. But to enhance our visual experience, we have specialized areas that have evolved over time. We have already talked about some of these specific visual areas such as the ‘face recognition area’ which is really for recognizing well-known objects. Also, there’s the ventral and dorsal streams that help us tell where something is and what it is. It only makes sense to have areas specific to motion. MT is responsible for the more basic components of motion. Also, it is involved in eye movements in response to motion. Beyond this is MST where we can distinguish complex movements like optic flow and STS where we can notice biological motion. As the neural signal continues, more information is discovered about the targeted object.

An interesting disorder that may come out of a deficit in MT is dyslexia. I’ve read a few papers about this developmental disorder lately and thought it tied in with motion discussion. One of the theories behind dyslexia is the ‘Visual Deficit Hypothesis’ that posits that problems in MT cause blurring and altered scanning during reading. In some individuals, it was found that MT had lower activation and also had smaller neuron size and larger disorganization (Eden, 1996). We already talked about some of the abnormal eye movements that may be causing blurring. One is the vergence eye movements where eyes move in opposite directions like when focusing on an incoming object. Another is the concept of spatial constancy where we know that an object is moving relative to our retina. In the papers, some of the quick fixes they thought of was larger print and closing one eye to reduce blurring.

Some of the disorders we talked about in class regarding motion were also pretty ‘moving.’ The one condition where the woman experienced snapshots of the world was one of the more amazing, and bad, disorders we’ve talked about in the whole class. We can never really know what it is to see the world with a disorder like this, but it must be so confusing and disorienting. I’d almost rather be blind than be in such a scary world where everything is moving about you but it is impossible to tell how. It seems like we take much of vision for granted, but really a deficit in any aspect could be pretty debilitating whether it is in color, motion processing, or object recognition. The least harmful condition would be a problem with depth perception. It was a different world when we wore the eye patches for our third paper, but after a few minutes I was able to get used to it. I wonder how plastic the brain is when it comes to losing something like motion processing. It seems to me that higher cortical areas have higher plasticity than sensory processing areas. Maybe because these are so hard-wired from an early age. Either way, a problem in any area of the visual system could cause a large array of problems.

Coloring

I thought that bringing up subtracting colors versus adding them was really interesting in class. Especially when we discussed what are really the primary colors. Seeing the difference between the primary colors of light and the primary colors otherwise was cool and showed how much perception factors into something such as color. White light is the combination of all colors. By subtracting light we mean taking away a certain wavelength or wavelengths of light from the overall white (or colored) light. If we subtracted every light except for one from white light we would have a single pure color. What I also found intriguing was how it is possible to have either pure yellow or yellow from the combination of two colors. I know we talked about metamers before, but each new one I learn about is interesting. I wonder how the properties besides their composition differ. Do we always perceive them to be the same?

Synesthesia is one of the most interesting conditions, from my perspective. Combining different modalities and experiencing light with sound or words with touch seems exciting although I could see how it is like a hallucination out of control. I can never guess what it would really be like. Since it is so hard to explain the senses that most people have, how can people with synesthesia explain it and how can we understand it? But their condition helps us understand normal processing. If we can tell where a difference in their brain is, we can tell that something different in this area will cause a problem in sensory processing. I think the kind I would want the most is experiencing images when listening to music. It seems like this could really be put to use to make some great compositions. But any type would cause some unique connections between different senses.

To me it does not seem like having color blindness between two colors would cause too many problems. Like when watching a show in black-and-white we can still tell a great deal of detail. Sure there’s the problem of telling between green and red at stop lights, but the number of problems isn’t insurmountable. I used to like to think that everyone sees different colors but we have the same names for them. How would anyone know since we always call them by the same name? But I guess there are ways to test this by seeing what wavelengths activate what photoreceptors since certain wavelengths always have the same properties. Perhaps this doesn’t result in the same color perception. But they must be close in perception if people can agree on colors matching. They are both probably seeing the same two colors like blue and green instead of one seeing neon yellow and purple. Also, we associate feelings with colors like sad with blue. This seems natural due to the color. So if someone sees my green but we both call it blue, I think we’d be able to notice. But maybe not…

Visual Development

Considering the visual system, I see its development as much more driven by nurture than nature. Sure, the eyes and brain would not develop correctly without nature, but for our perceptual world to grow, we need experiences to base further knowledge on. I think our eyes are more sensitive to stimuli like horizontal and vertical bars because we see this stimuli more often. In this case, experiences drive development. This probably happens very early on in a child’s life. When cats are reared in the dark as kittens, they are functionally blind and cannot recover at a certain point. This shows that even a typically-developing animal can have sensory deficits depending on its surroundings. The lack of stimulation causes lack of connections in a “use it or lose it” fashion. In a normal visual system, I think that most of the specialized functions we have originate from our experiences with a lesser result from genetics.

An abnormally developed visual system could have a wide range of deficits ranging from a problem in detecting motion to color blindness to myopia. It seems like the least problematic one is being far or near-sighted now since we are able to correct it with glasses, contacts, or laser surgery. Also, there’s new surgeries for even larger problems. A relative of mine had to have his lens removed due to many cataracts within his eye. Now he can see with better vision than he had most of his life. I think a deficit in detecting motion or color would be the worst. I seem to remember a study on depression and color blindness how people view the world as dull if they become colorblind almost like a loss of appetite after losing taste or smell sensations. And a problem in MT could lead to blurriness or even worse problems.

I believe that there are so many areas within the visual cortex because the visual world is more complex than we sometimes think. We can recognize objects, colors, functions of objects, groups, people, interpret expressions, quick reflexes, read, and accommodate to name a few. Each of these functions are pretty specialized and therefore would probably have their own area in the cortex. There is probably some overlap in some of these areas, but for the amount of things we can do with vision, it doesn’t surprise me that a whole lobe and then some is devoted to visual processing. It is not a waste of space either since it is the sense that we rely most upon. The other senses are very helpful but usually complementary to our vision.

Recognition and Attention

When I stop to think about how much information is involved in vision and the speed in which it is transmitted, it is a little overwhelming. I also feel a little insecure when I notice just how small our visual field is and how little of it is in high resolution. But after a few moments, these things go unnoticed. But really, having such a small area of clarity isn’t so bad, and actually necessary. Like the duplex theory says, we need both rods and cones. If we had our whole retina with a 1:1 convergence, we would not be able to perceive low light levels that we can due to our spatial summation in the periphery. Also, our eyes move quick enough that we never really notice how blurry everything outside of the fovea is.

The spatial frequency examples were pretty interesting, especially for the gratings. I never would have thought of images being comprised of different sets of resolutions to create a clear picture. It is also cool how at one point we can notice high spatial frequency and low contrast, and once we go over our threshold it just looks gray. Gratings seem like such a popular stimuli because they are so simple yet effective when it comes to adaptation tests. Also, if we use the hypercolumn model, we can test orientations easily with different gratings. Since we prefer vertical and horizontal orientations, the stimuli can really cater to our visual system.

I really enjoy the change blindness and inattentional blindness studies. I’ve gotten many of my friends to watch the gorilla basketball movie and every single time they do not notice the gorilla. The last time I did this a few months ago, my friend even refused that it existed once I replayed the clip. One of the obvious situations where change blindness would occur is with a magician. So much of their act is either diverting attention or making sly movements that we do not notice. All of this is done so that when the trick is completed we do not remember the action that caused it. It’s also done many times in the movies. Everytime they cut away there was probably a scene change and time change that we do not notice. Sometimes they do this on purpose for comedic effect. My favorite examples of this is that Starburst commercial where everytime they cut back and forth, the ‘cleptomaniac’ has stolen something else. Also, in “Wet, Hot, American Summer” they show one of the characters yelling to the cabin and in a second or two they cut back to him. Almost none of my friends noticed that in the first clip he has a massive mullet and in the second clip he has short hair. I’ve also noticed it in accidental situations. In the movie “You, Me, and Dupree” when Matt Dilon is talking to his guy friends and the camera switches back and forth, in one cut he’s holding a glass of whiskey and in the next it is a bottle of beer although to us it would have been all of 2 seconds. I’m sure this happens hundreds of times in movies and television but we rarely pick up on it since we focus in on faces and other inviting stimuli.

Vision III

Retinal processing and cortical processing of visual information differ on many levels. The main difference is that while retina processes physical information, the cortex processes perceptual information. In other words, the retina takes in the physical stimulus of light and converts it into a neuronal stimulus through sensory transduction. We know how this occurs, by light hitting the photoreceptors to the bipolar and then the retinal ganglion cells. We even know about the receptive fields which give a good explanation of how humans can define edges and changes in light levels. But once the stimulus enters the cortex, everything is not so clear. There are many known areas in visual cortex, from V1 to areas responsible for motion detection. However, how our brain changes the physical stimulus into a perceptual one isn’t known. There are some relationships between the retina and cortex which makes studying the cortex easier. In the visual areas, there is a retinotopic map. This section lays out what each retinal ganglion cells ‘see’ into a coherent map. Beyond this point, the cortical organization of visual cortex becomes a little confusing for me. I’ve learned about the hypercolumn theories where each orientation of a shape has its own column defined also by color and some third dimension. But it is hard for me to imagine that there is a cell only designated to one orientation of one edge in a certain level of light. I would think there would somehow be a way for neurons to be used more efficiently through multiple wirings.

 

On the topic of cortical magnification, I see it as a good thing, or more of a necessary thing. In our brain the physical area designated for the fovea is much greater than that reserved for the periphery. This makes where we look very clear compared to the blurry peripheral vision. If we had the same cortical magnification for all retinal cells, the best case would be extreme clarity for our whole field of vision. With this system, however, I don’t see how we would shift our attention in a specific manner. When we see something move, we naturally move our eyes so that the highest point of clarity is on the object. But our attention cannot be everywhere at once. With a whole field of vision clear, objects within this field would not be distinct and our eyes would not be drawn to stimulating objects since the field would be uniform. Also, the system would be inefficient. We really don’t notice how blurry our periphery is since we are constantly moving our eyes and heads. The periphery works well for warning of us of moving objects or changes in lights which is all we really need it for. Therefore, a uniform cortical magnification wouldn’t really help us out much. But having eyes in the back of our heads, on the other hand…

Vision II

The most interesting aspect of vision to me is the difference between the physical world and what we as humans actually perceive. In school, we learn about both sides from Physics and Psychology but it is still impossible to imagine what a different perceptual world would actually look like. If we could see Infrared wavelengths, would it just be another color? or some other sense we cannot comprehend? I’m interested to learn about the circuit that takes the sensory information and interprets it in the brain. I also wonder about how the brain evolves into different perceptions and how long this actually takes. Is it because we have the certain photoreceptors? Or could we perceive more with the same hardware. What will be the next evolved version of our eyes? For humans, the eyes seem so much more important, perhaps they will take on an even larger role as we continue to evolve.

I also like to think about the differences in perception within people. One thing pertaining to vision is the perception of color. We could never know if people actually see the same colors as everyone else. Maybe to me my actual green is your blue. But since they would stay constant, we would have the same names for possibly different colors.

As far as the eye as the master and slave, I can see both sides. The eye is responsible for vision, but not its perception. Also, the eye depends on the brain. When something is moving in front of us, we automatically move our eyes to look at it. Our brain is responsible for this. In this way, the eye is the slave to the brain. But without the eye, we would see nothing. It is more like the eye is the instrument where its input is controlled and its output to the brain is altered into perception.

I’m glad we talked about the light and dark currents as that’s what I was interested in my last blog post. My interest for the upcoming week would be talking about the brain areas responsible for the perception of vision; such as color, motion, etc. It seems like in each Neuroscience class I take, there is a different theory for how most of these areas operate, so it is always interesting to see a new perspective.

Vision

Illusions are probably my favorite part of Perception, whether they are auditory, tactile, or visual. However, there exist many more optical illusions that are easy to test. I do not like the “Magic Eye” drawings or other illusions where the image flips between two perceptions (like the old man or two people). The constant change in focus starts to hurt my eyes after awhile. I prefer the illusions where objects seem to be moving or shade illusions. To me, for the illusion where the horizontal bars seem tilted, the boxes on them also seem to slide down the ramps to me. If I do not focus on a certain area, they seem to slide forever even though they do not physically move. My second favorite illusion is one of a shape with the top and bottom separated by a sharp contrast. The top and bottom seem different colors, but when the contrast is covered, they are the same. I cannot get over this illusion. Even though I know there is no difference, I cannot force myself to see them as the same. The illusion is just too strong. Maybe some of these perception pathways are earlier on in the circuitry than I thought so that conscious intervention is not possible. I would never be able to tell if it was sensory or perception without interacting with it.

 

I often see the brain like a computer. Hard drive for memory, RAM for short-term, graphics/sound cards for vision/hearing, etc. It works for the most part except the eyes are more like a webcam or camera than a monitor. The comparison of the eyes to a camera seems well-founded. Both take in physical light and convert them into an electrical signal. But the camera reproduces the image faithfully, where the brain has higher visual areas that interpret and change the perception of the image. I am sure there are many ways in which the transduction to a signal differs, but I am not really sure how videocameras do it. I know that the eyes are much more sensitive to light than cameras are. Humans can see a single photon of light in a dark room which is extremely sensitive. Also, we are drawn to moving and colorful objects by making constant saccades. The camera is a passive viewer.

 

An interesting thing to me about the eyes is that the photoreceptors hyperpolarize in response to light whereas most every other neuron depolarizes in response to a stimulus. The light and dark currents that occur within the eye just seem so advanced. I wonder why the eyes are the only ones that have evolved into this formation. Is it more energy efficient? Or was it just an artifact of evolution? Hopefully we’ll touch on that if we go into the more biological aspects of the eye.

Listening in

    Interaural cues can usually specify the sound we listen to, where it’s coming from, and how loud it is. Our brain is programmed so that when the sound reaches the left ear faster than the right ear, the sound is localized to the left. Also, if the sound is louder in the right ear, we localize to the right side. Without any help though, these cones of confusion cannot be overcome. To do so, we must move our head to gain more information from the changes in the frequency spectrum off of our pinnas. Without conscious knowledge, we do this and are able to tell by comparing different points where the sound is coming from. It seems very similar to triangulation for GPS. If you note the interaural intensity and time differences from three different points, you can compare them to find the exact location. What I am not so sure of, is how we can tell whether it is a soft, close sound; or a loud, faraway sound. I would think we can tell since there are more echoes when sounds travel longer distances which makes them sound softer. The aphasias are a good way to shed some light on many of the acoustic processes.

 

    I think the aphasias can tell a great deal about auditory processing. It is the same situation as a brain lesion. By looking at the deficits, you can make a good guess on what the structure does or at least tell that the structure is important in some circuit. From Broca’s and Wernicke’s aphasias, we now know where the language production and processing areas are. By studying some of the specific aphasias, we may be able to find ways to help future generations of people with language disabilities. I have no idea how this could be done since the aphasias usually occur in the loss of neural tissue, but maybe there is a way to prevent the tissue from dying off in the first place.

 

    On the topic of “mondegreens,” I personally go through misheard lyrics a ton. Especially in faster songs or some rock ballades, I just have no idea what they are saying. But for most of the music I listen to, it is more about the sound of the words than their actual meaning. For one my favorite bands, The Mars Volta, I just had to look up what they were actually saying to find out the lyrics weren’t even sentences or close to grammatically correct… However, there are some great videos of these “mondegreens.” Two of my favorite mash-ups of misheard songs are of a Sean Paul and a Fallout Boy song. The links are below. The creators put what lyrics they think they are hearing. When you read them while listening it really does sound like them, which is a cool effect.

 

http://www.collegehumor.com/video:1677672

 

 

(warning: This one has some graphic drawings, so click at ur own risk!)

http://www.collegehumor.com/video:1650561

Hearing

People do rely on vision the most, however auditory information can also be really helpful. Some of the better uses of hearing are localization and recognition. When we hear a loud noise, we instinctively turn our head to the spot. This way we can aid our ears by having visual information as well. But it is the sound that alerts us. This way we can have an auditory space of 360 degrees whereas our eyes are only in front of us. Localization also tells an object’s movement. Like the ambulance siren when it drives past, the frequency changes so that we can tell whether the object is moving towards us or away. Recognition is also a key use for hearing since we can identify a large number of stimuli. The amplitude and frequency let us know if what we are hearing is background noise or something dangerous.

I think that both vision and hearing are good connectors to people. When Hellen Keller said that quote, it may be because she had neither that she thought that auditory was the best connector. While each person has their own unique voice, they also have a unique face and expressions. I don’t believe that auditory is necessarily linked to people and vision connected to objects. By having one or the other, a lot can be told about a person. With audition, the person has to make a noise, whereas with vision, there is always information available.

I think the acoustic reflex dampens our voice so that we speak louder. We are used to a certain level of our own voice in our head. When it is dampened, we speak louder so that it matches the same level. This way, when we are in a loud setting, we automatically speak up so that we can be heard. This is important because it ensures that the information we are trying to give is received.