Final Blog Entry

One of the most interesting parts of this course for me was actually not something that we directly covered, nor something that we even discussed very often, yet it is one of the most crucial parts of all the sensory systems that we have been learnig about: efficiency. We’ve spent this term talking and reading about the intricacies of the central nervous system, and how vital its use is to our everyday lives. From a rabbit seeing a predator approaching, to a baseball player hitting a pitch, we perceive things at an astonishing speed, and with incredible accuracy. This is what I think made this course so interesting: learning about how complex our brain is and how it allows us to see, feel, smell, taste and touch, while keeping in perspective that all of the information is obtained, processed, and interpreted in a fraction of a second. Seeing is one of the best examples of this, and in my opinion is the most fascinating of all the senses (and the one that I have already said I would least like to loose: see blog entry “hearing vs. vision: the showdown”). Imagine you are the third baseman for the Boston Red Sox. The pitcher hangs a curveball, and a hitter hits a hard linedrive down the third base line. From the moment the pitcher releases the ball, to when the batter makes contact, to when you make Sportscenter’s top playes with a diving catch, is less than a second. Consider now what this third baseman needs to see in order to make the play. First, he needs to see the pitch. Assuming that the baseball is travelling 90 miles per hour, that means that from when the pitch is released to when it reaches the hitters bat, about 0.46 seconds have gone by. In this time, light must reach the retina, be absorbed by photoreceptors, get through the horizontal, amacrine, and bipolar cells, have an action potential from the retinal ganglion cells travel along the optic nerve to the LGN, where motion is picked up, then the LGN must transmit information to the V1 area for local motion detection using direction sensitive cells, then information must be passed to the MT area where the motion of the ball is further analyzed, and finally the information from all of these calls and areas must be processed in the MST area, where not only the ball is registered, but the pitcher’s bosy position, the runner on first breaking to steal second, and the batter taking swings in the on deck circle. And this all takes place in less than one half of a second. The situation becomes even more complicated once the batter hits the ball. According to Jonathan Drobnis (http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/Jon_Drobnis/bmb.html), if a player swings his bat 70 mph and connects with a ball going 90mph, the resulting speed, is close to 160mph. For the third baseman, this mean that he has less than 0.4 seconds until the ball reaches him, and there’s still a lot to be done to make the play. First, the ball must be seen. All of the connections just described would have to occur, as well as all of the necessary analysis of information, and the command impulses that would have to be sent to muscles in order for him to dive to his right, stretch his arm out, and close his glove around the ball, and remember, all of these commands, from pitch to catch, are occuring in less than 0.9 seconds.

Seeing is just the example I chose to use to show how efficient and accurate our sensory systems are. Touch hearing smell or taste are all extremely efficient, and would all provide excellent examples of the speed with which we process the events in our lives. If we were not able to perform these functions as fast as we do, or if our brain did not evolve in exactly the way it has, our lives would be drastically different from the way they are now. There are simply too many examples of how impressively fast our processing centers receive and interpret information, but I hope the one I used is a good one to give an idea of how fast everything that we have been learning about this semester happens. This blog entry was supposed to be about the most fascinating this we learned this semester, and I wrote about something we rarely, if ever, discussed. Why? Because evev if it was never explicitely stated, and no matter how long it took us to learn the pathways required for pain sensation, or color perception, the actual events that we were discussing happen every moment of the day, and happen faster than I can really appreciate or understand.

April 27, 2008

where to place the eyes?

I have been trying to imagine what life would be like if humans had eyes on the sides of their heads like prey animals pretty much since we began our study of the eye. Obviously from a simple “predator/prey” point of view, it makes evolutionary sense to have our eyes on the front of our heads rather than the sides, but given our extreme dominance on the food chain, if we now had the choice, which of the configurations would we choose? From an aesthetic point of view, it would be ridiculous looking for a person to have eyes on the sides of their head rather than on the front of their face, but looks aside (no pun intended), would humans benefit from having eyes on the sides of their heads?

For the most part, humans are untouchable on this planet in terms of evolutionary dominance. There is not even the slightest chance of our being challenged by anything else for control of the food chain, so thinking of us as either a predatory animal or a prey animal doesn’t really matter. My question, is what would life be like with eyes on the side of our head, and if we were able to choose, would our visual life be richer or more useful if our eyes were moved to the sides of our heads, rather than the front? The negatives of having eyes on the sides of our heads seem clear: a significant decrease in binocular vision; however, I think that the benefits of having eyes on the sides of our heads outweigh this negative. Animals with eyes on the sides of their heads simply see much more of the world. Think about how hard it is to sneak up on a rabbit. Because they can see much more of the world around them, it’s nearly impossible to get to them without you knowing that they’re coming. Now think about how many car accidents are caused every year by people who do not see cars that are in their “blind spot,” with eyes on the side of your head you would be well aware of the other car and would not get into one of those accidents. While the loss of binocular vision is a concern, we look at everything we pay attention to straight on. Think about reading this blog entry. You are staring straight at the screen, and while you are able to see the 3D form of the water bottle sitting to the right of your computer, if you are going to pick it up, you are going to look directly at it before you try to grab it (in most cases). My point is that the objects its most important to see with binocular vision are objects that we are staring straight at, and with eyes on the sides of our heads, we would still have binocular vision for these objects. I do not know what living with eyes on the side of my head would be like, and I probably never will. From an evolutionary standpoint it makes sense for us to have our eyes positioned where they are, but from a conceptual position, I wonder if we wouldn’t now, all other things remaining constant, be better off with eyes on the sides of our heads.

April 20, 2008

I’m color blind, and that makes you better than me…

I was first told that I was color blind when I was about 12 years old and got glasses for the first time. I was at the eye doctor’s and they gave me the Ishihara test for color blindness…I got 1 of 20 right, and it was more or less a guess. The funny thing about it is that I had been living for 12 years, and until that point I didn’t know that I was color blind. Since then, every time that I go to the eye doctor’s I get tested, and every time I fail in spectacular fashion, but if I had never been tested, I would probably never have known that I was severely color blind. I don’t see the world in black and white, and if someone were to ask me tomorrow what color their shirt is, I would be able to tell them without hesitation. I do not see the world in shades of gray, and I am able to appreciate a sunset or garden as much as anyone else, essentially, my color vision is not really that different from anyone else’s. As it was explained to me, since I was a child I have been learning what to call the colors I see, whatever they may be. When I was a kid, I was told that the sky is blue, grass is green, blood is red, and the ocean is blue (or a murky shade or garyish-brown in the case of my home town of Boston). I see all of those colors as shades, what shade I cannot really be sure, but a specific shade, unique and identifiable from other shades. I also began learning at a specific age the locations of certain colors. I know that when the bottom light of a stop light is illuminated, that that is a green light, yellow above that, and red above that. I also learned that my house is painted a light shade of blue, and that when I grab an orange, that the color I am seeing is orange. While all of this may seem confusing or hard to do on a day to day basis, I have been learning to distinguish different shades, or know the locations of certain colors since I was so young, I don’t even know that I am making the associations I am making when I perceive a color. The only time that I really know I am color blind is when I go to the eye doctor’s, or when Professor Boucher puts displays up in class that test for color blindness, normally, I don’t even know, or think about the fact that I am color blind.

There are occasional times that I am aware of my colorblindness. Colors that are similar to one another are very hard to tell apart, and I occasionally run into problems when I match clothing that I am subsequently told clash horribly (although this might just be a lack of fashion sense more than an effect of colorblindness). There are also times when I will mention the color of an unfamiliar object and am told that I was way way off on the actual color, but aside from these times, none of which really have drastic consequences, my colorblindness has not had a major impact on my life, its more of a conversation piece than anything else. So while everyone else might have “better” color vision than me, if I hadn’t told you that I was colorblind, you never would have known.

April 13, 2008

evolution and prosopagnosia

Of all the disorders we have covered and discussed in class, prosopagnosia has been the most difficult for me to imagine living with. While I understand that different areas of the brain are used in different stages of vision and recognition, but I cannot imagine what the evolutionary benefit is of having such important and necessary processing centers relegated to one are of the brain only. In an evolutionary sense, the ability to recognize faces seems to be paramount. It would be crucially important to be able to recognize a friend from an enemy at a distance if you were living in a hunter-gatherer world. This ability is so important that it seems foolish to have the location or locations necessary for it to all be located in one area of the brain.

While it is not concretely known which area of the brain cause prosopagnosia when damaged, it appears that damage to the right inferior temporal lobe is closely associated with the condition, as most patients who suffer from prosopagnosia also have damage to this area of the brain. While it might seem somewhat strange to consider the evolutionary benefits of planning for brain damage, it strikes me as strange to isolate such an important system to an area that can be damaged. However, back to my original point: what would living with prosopagnosia be like? What would it be like to see your mother, or roommate, walking towards you, be able to see and identify their ears and cheeks and facial features, to even be able to tell what color their eyes are, but to not be able to remember their name. Try as I might, it seems to be an impossible thing to do, there’s simply no way that I can imagine not being able to remember that anyone’s face looks like. One of the most interesting aspects about prosopagnosia, is that it does not alter your ability to remember a person’s voice. If you were suffering from prosopagnosia, and your mother and a complete stranger was standing behind you and called your name, you would turn around and expect to see your mother, but instead you would see two people who as far as you could tell were both complete strangers.

I find prosopagnosia to be a fascinating condition, in part because it is one that I cannot possibly imagine living with. While we have moved on to development, I wanted to use this blog entry to briefly talk about what I find to be one of the most interesting items that we have covered this term.

April 6th, 2008