Prosopagnosia

The most interesting topics to me from Perception are those concerning malfunctions of senses. For example, I was fascinated by prosopagnosia, the condition where a patient can see and describe another person’s face but cannot identify whose face it is, even if the person was very familiar to them. Even an intimate partner’s face is unrecognizable to the patient.

Prosopagnosia is usually accompanied by damage to the brain in the regions of the temporal lobe. Interestingly enough, this area houses the fusiform gyrus which many psychologists have pinpointed as the face recognition area. However, subsequent research has shown that this is not only a face recognition area, but a quasi-expertise area. That is, when bird experts are shown pictures of birds, this area becomes activated as well. With novice people are trained to become experts in object recognition of an novel object, this area becomes increasingly activated as the participants get more practice. People who are experts in certain object recognition but have this impairment have been reported to lose their ability.

I went online to find blogs of people with prosopagnosia so I could put a face to this condition. I found this blog written by a Swedish woman named Cecilia Burman. She is a 30 year old with this condition. However, like many others, she did not recognize this disorder until she read about it on the Internet. It was a pivotal moment in her life and has actually helped explain many of the troubling things in her life.

Before searching for these blogs, I had wondered whether these people could ever have any sort of romantic relationships.  It must be awfully hard to find a boyfriend if you can’t pick him out of a crowd. Also, imagine waking up next to someone you did not recognize. Must been pretty problematic. However, Cecilia is happily married to a man who understands this condition. Besides that, she can recognize his voice and, using contextual clues, she can identify the man that wakes up beside her in bed as her husband. But one can see how this condition can become dangerous. Imagine if someone took advantage of the situation and pretended to be Cecelia’s husband. She could go days without noticing if she were to base her decision on looks alone.  However, like most conditions, the patients learn to adapt and she learns to recognize people through other means besides looks.

Someone else on a different blog described having the condition as having to discriminate between an elbow and a stone for people. I couldn’t possibly imagine living my life without the ability to distinguish between my friends and strangers. Even as I walk the paths at Vanderbilt, I get super excited when I see a familiar face. It actually brightens up my day, especially if I haven’t seen this person in a long time. Such is a pleasure that prosopagnosia patients will not have anymore.

Cortical Magnification

     Gordon Holmes, a famous neurologist, observed that the cortical map of our visual world was greatly disproportionate. He noted that the amount of cortical tissue alloted to the central portion of the field was far greater than the amount given to the periphery. The term cortical magnification means was given to this phenomenon. It means that a large portion of the cortex is given to the fovea. The greatest amount of space in the visual cortex is given to the central region which is the reason for our acuity in vision.

Is cortical magnification a good thing? I would assume so because otherwise evolution would not have led us to this point! Jokes aside, cortical magnification is useful for humans because it allows us to save room in the brain for what is most important to us. Obviously the ability to see clear details of what is right in front of us is important to our survival. That is not to say that things on the periphery are unimportant. However, if we were to allot equal amounts of the cortex to our entire eye, we would be increasing our visual acuity, but we would need bigger brains to house these extra areas. It becomes a question of whether or not we want bigger heads to carry around or if we want the most important details magnified in our cortex.

We have seen in the study of touch that a disproportionate amount of cortex is allotted to different areas of our body that have more sensitivity and sensation in them. For example, our lips have a greater representation in the cortex. My opinion is that we were built a certain way for a certain reason. The allocation of brain space is this way because otherwise we would not function like we do. And obviously the way we function is pretty successful considering the fact that we have come a long way in history.

“The eye is at once the master and slave of vision.”

This week’s lecture about receptive fields and the cells of the eye made me understand the profoundness of the quote above. The eye is a master of vision because without the eye, there is no vision. The eye is a slave to vision because the eye does not choose how it sees; it is simply a slave to the anatomical make up of the eye. From class, we learned that the cells and photoreceptors of the eye have a lot to do with how we see things. Starting with the photoreceptors, we primarily have two types: cones and rods. Cones and rods are shaped differently so that their sensitivities to light vary. Rods are more sensitive to light so they are responsible for our ability to see in dimly lit situations. Also, where they are located on the eye is important to what we see as well. Cones are located more around the fovea which is in the center of the eye. The rods are more located in the periphery of the eye. The receptive fields of the ganglion cells are smaller in the center of the eye. The smaller the receptive field, the more acuity in vision. This is why things in the periphery are more blurry than what we stare at, which is what the center of the eye sees. For these reasons, how the eye is structured is how we see things.

When we first read the quote, I interpreted it differently than we did in class. I thought about the eye being a slave to vision because there is no way you can unsee something once you see it. For example, I am terrified of scary movies. Once, I watched a movie where you actually see someone killing another person. This image is forever burned in my memory. I can not “unsee” this image no matter how much I try. This is why I thought the eye is a slave to vision. We are at the mercy of what we see because we cannot unsee it. Then I thought maybe the eye was a slave to vision because of all the illusions that we fall for. We cannot control how we see certain things.

After the lecture, I began to wonder about the eye and vision in the same way that people wonder which came first, the chicken or the egg? Do we see things because of the way our eyes evolved, or did our eyes evolve this way so that we can see things this way? It is one of those things that we can never fully come to an agreement on.

Dilated Pupils

According to legend, Italian women used to put a drop of the juice from the berry of the belladonna plant directly into their eyes to make their pupils larger. When we first discussed this in class, I made a mental note to research on this fascinating plant. What I found was pretty shocking: apparently, the belladonna plant is poisonous! In fact, it is one of the most toxic plants found in the Western Hemisphere.  However, it seems that the belladonna plant has medicinal purposes as well! If one founds himself with opium poisoning, the belladonna plant is used as an antidote. Also, optometrists extract atropine from the plant and use it to dilate patients’ pupils to examine their retinas. Also, in one crazy website I found, someone reported using the belladonna plant as a hallucinogenic drug! He did not recommend it though because “the places belladonna takes you, you were not meant to go.”

This week’s lecture discussed the variations in pupil size that supposedly lead to attraction in the opposite sex.  Dilated pupils make someone appear more sexually aroused. Therefore if women had dilated pupils, they would be indirectly advertising their interest in the opposite sex. Thus, it would make them more appealing and desirable. BBW Magazine writes that if a woman wants to know if her partner is attracted to her, all she needs to look at is the size of his pupils. They also mention looking for watery eyes. Another physiological reaction to attraction, eyes will water to clean themselves so they can get a better picture of their heart’s desire. Clearly our eyes hold a lot of power when it comes to our romantic relationships.