Category Archives: Biology/Neuroscience

Tuning Timpani

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Starting in fourth grade and ending in tenth grade, I spent several days a week at our school’s concert band practice. I was a percussion player and that meant learning new and interesting instruments on a regular basis. I had grown up playing the piano which made me one of the few drummers who could quickly sight-read musical notes while playing mallet instruments like the marimba. The keys on a piano are very similar to most mallet percussion instruments.

When I moved on from middle school to high school I had the opportunity to play a new instrument, the timpani. These are very large drums that sit on the floor with the head of the drums at the height of most people’s waist. The drums are tuned using a pedal at their base. The pedal stretches the head of the drum and creates different sounds. The interesting part about tuning the timpani was matching the pitch of the drum to that of a specific note required for a song. While other instruments would be warming up for a song, I would be using a pitch pipe to dial in the notes required on each drum.

When I was matching the pitch of the drums to the pitch pipe, I was actually just comparing their perceived frequencies. Many people can relate to pitch: low frequency sounds have a low pitch and high frequency sounds high pitch. A low pitch would be the sound you hear from a large drum, while a higher pitch would be a note played on a flute. Playing around with the tension in the head of the drum changed the physical movement of the head when hit with a mallet, and that changed the pitch that I was hearing.

The actual movement  that takes place when a musician strikes a drum head is what creates a sound. The head moves up and down rapidly, creating changes in air pressure that follow a sinusoidal wave. This wave is commonly known as a sound wave. The frequency of the wave is perceived as pitch. The amplitude or intensity of the wave is perceived as loudness. A higher amplitude wave will produce a louder sound for the audience.

So it turns out that the entire time I was messing around with the tuning pedals on the timpani, I was really playing with the basic physics of creating sound.

3D Movies are a Blur

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When I was 4 years old, I had corrective surgery for strabismus in my left eye. Although it was minor, my pediatric ophthalmologist said that surgery would produce the best long-term results for my vision and appearance. This is a picture of me at the age of 2 years old with my left eye displaying esotropia, which is a form of strabismus causing one or both eyes to turn inward.

Logan 2

Since the surgery, I have worn glasses or contacts to correct my pre-existing hyperopic vision. Hyperopia, or farsightedness, occurs when the eyeball is too short and the image focuses behind the retina, which is the opposite mechanism of the more common condition, myopia. Eighteen years later and I am still living a life unhindered by strabismus complications, except for one thing; I am “stereoblind.”

It sounds worse than it actually is because this is the only vision I have ever known. In high school, I shadowed a pediatric optometrist who told me that I never developed stereopsis due to the interference of strabismus at a crucial age of development. Stereopsis is the perception of depth using binocular depth cues, such as binocular disparity. The lack of stereovision has not affected my ability to judge depth because I adapted to monocular cues at a very young age (as I was later a softball catcher and played basketball).

The only downfall that I have experienced is the inability to use the red/cyan 3D glasses. Three-dimensional books, television shows, and movies that are viewed at home with these glasses are blurry because I am unable to use binocular disparity and free fusion to view a single image. Surprisingly though, I can clearly see the 3D shows at amusement parks in their full 3D capacity. I was never told how this is possible, but I believe that distance is the major factor involved. Because I am farsighted, my eyes optimally function when fully diverged, or separated, which occurs in the large theaters at amusement parks. However, when I watch a 3D movie at my house or look at a 3D book, the images are less than 10 feet away, causing my eyes to converge to some extent. This is my only guess for the reasoning behind my odd ability to see large-scale 3D shows and not other forms of 3D entertainment. It is interesting that people can “see” the same things, yet perceive them in a completely different manner that cannot be adequately described for those with vision disorders.

Avoiding the Pressure

At first I was going to compare abrupt versus sustained sources of sound that have the ability to cause damage to one’s auditory system, such as a gunshot versus loud music, but then I thought of a much more interesting phenomenon. I do not know what most kids like to do when they go swimming, but, for a long time, I liked to just sink to the bottom of the deep end and pretend like I was dodging bullets – as if I were in one of the Matrix films. After a number of trips to the bottom of the pool, pressure would build in my head/ears, and I would have to take a break or call it a day. One afternoon, a companion of mine told me that if I held my nose shut and blew through my nostrils my ears would pop, just as if traveling at a high altitude. Without thinking clearly about what I was doing, I plugged my nose and blew as hard as I could. I’m quite sure I punctured an eardrum(s) – but did I do so without hearing any sound(s)?
If mammals hear because of pressure changes in a medium – furthermore due to vibrations – it makes good sense that a certain amount of pressure built up in one’s head will cause damage to their auditory system. The issue with my example is that the pressure that led to my punctured eardrum was not due to an external source of sound, nor did the pressure build from the outside in. In other words, the sound/pressure did not enter through my ears, but through my nasal cavity. My understanding is that, when plugging my nose and blowing through my nostrils, I was essentially attempting to balance the pressure between canals in the inner ear sections of my auditory system, and the outside environment (water).
The pressure of the water surrounding me at a depth of twelve feet was greater than the amount of pressure in my cochlear canals (parts of the inner ear where liquid is stored) – blowing lightly should have reduced this contrast in pressure, as it would have increased the pressure in my cochlear canals just the right amount. Unfortunately, I believe I did the complete opposite. By blowing really hard with my nostrils plugged, I increased the pressure in my ears so far beyond the pressure of the outside environment (water) that I did more harm than good. What exactly happened, I am not sure. I am most confused as to how pressure coming from within my body, not from vibrations in a medium in my surrounding environment, caused damage to my auditory system. It is not as if pressure/vibrations exited my body and re-entered through my ear, from the outside. Did I make a sound from within? Regardless, how did the pressure I induced reach my ear? If it came from inside, I feel like it would go through a different process/along a different path, before being interpreted as sound, than if it came from an external source. Can this pressure be considered a sound?

My Oh Myopia!

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When I was about 9 years old, my older sisters and I decided to attend a special screening of the original Toy Story movie. Unfortunately, this momentous event matched with spending an absolutely necessary amount of time mulling over the perfect choice of candy lead to a packed movie theater. This being the case, my sisters and I were forced to situate ourselves in the only available seats consecutive seats of three, which just so happened to be in the last row! This was a bit of an upset for me but I decided to let it go and enjoy the movie, which was about to begin. Unfortunately, upon taking our seats all the way in the back of the theater, I noticed that the preview that was wrapping up seemed fuzzy to me. Thinking it was just the quality of the movie trailer, I tried my best to brush it off – that was until the movie itself began. It was at this moment it dawned on me that there was going to be a major issue with my viewing of this special feature. I couldn’t discern Buzz Lightyear’s space cadet uniform from those worn by the Squeeze Toy Aliens, which you can assume, crushed me. Thinking that perhaps my eyes were just a little tired, I looked down at my sweets to see if the effect carried over but (to my surprise) I could read the tiniest words on the box perfectly clear.

As any logical 9 year old would do, I opted to sit in the aisle towards the front of the theater for the remainder of the flick. When it was over I told my mother about the difficulties I seemed to experience with my eyes and she, of course, made an appointment with my eye doctor within the next week. After a series of tests, which included having to read aloud the letter of the alphabet my eye doctor pointed to from this chart on the wall (referred to as the Snellen chart), I was diagnosed with the optic condition known as myopia. The condition (myopia) is better known as being nearsighted in everyday terminology. With vision at 20/40, according to my eye doctor, I had to begin wearing glasses in doing common activities because my eyes were not capable of observing things that were further off. Although I hadn’t the slightest idea what my eye doctor was talking about with all these numbers and medical terminology, unlike most other kids my age, I thought the idea of using glasses was the coolest thing since sliced bread.

What I didn’t discover until much later in my life was that those numbers and words my eye doctor used when describing my eyesight meant that my vision was notably worse than that of the average person’s. At 20/40 vision, I had to be 20 feet away from a given object to clearly observe it while the average person could be as far as 40 feet away while maintaining the same clarity! An example of this is evident in the image provided below:

20/40 Vision

More specifically, the biological reasoning behind my condition of myopia was accredited to the length of my eye, which happened to be much too long to be able to see as far as I would have liked. In fact, my lens system was unable to properly accommodate the images that appeared on my retina because of my eye’s length and so my nearsightedness became a prevalent issue that had to be dealt with. My glasses corrected this issue by diverging the rays of light before they entered my eye so the accommodation process could be conducted in a progressive manner. The end result was that I could perceive the world in a much more clear fashion while wearing some killer, hot-pink frames! (Not the best life decision I made as a 9 year old, in my opinion).

 

“What Color is This?”

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Throughout my life I have been corrected numerous times when stating the color of an object or material. Shades of purple and blue can get mixed up as well as shades of green and red. I am often corrected by my fiancé when picking out new clothing at a store, and there are even times when I have to ask her, “What color is this?” Although it can be frustrating at times admitting that I am wrong and my fiancé is right, this form of colorblindness has not affected me too much in my daily life. Maybe this colorblindness is a reason as to why I often chose neon colors as my favorite because they are the easiest for me to identify?

Unfortunately for my younger sister, this problem has become much more of an obstacle. During this class we have learned that red/green colorblindness can be hereditary and this has proved to be true for her as well. She is in her sophomore year at The United States Air Force Academy and recently found out she is red/green colorblind just like I am. However, she suffered immediate consequences regarding her future in the military. This colorblindness meant that she will never be allowed to pilot an airplane like she had once hoped. Many of the indicator lights in an airplane are small dots of red and green next to each other, so the slightest hesitation in determining them could prove deadly. Although I know this seemed like a huge setback for her at first, I believe she is handling it quite well. As a result of not being able to fly a plane, she has learned to fly her body, and has become an avid skydiver over the last year. She even is planning on helping me earn my skydiving license this summer.

This red/green colorblindness is a result of genetics. When light enters the eye is hits the rods and cones in the retina. The cones are responsible for color vision and contain photo pigments that respond to the amount of light that is hitting them. There are three types of cones in the eye that allow a person to see color when they send signals to the brain together. However, if any of the cones are deficient, then a person will not be able to see a full spectrum of color. My sister and I have most likely both inherited this from our parents due to a bad X chromosome. The difference is that I inherited this from only my mother because as a male I only have one X chromosome. My sister however, has received deficient X chromosomes from both my mother and father because she has two X chromosomes and still is red/green colorblind.

There are many tests to determine if a person is colorblind and the most popular is a dot test. These tests are often available for free online and can help a person gain some insight into their ability to see color. The following website has a free colorblind test for those readers who are interested.

http://enchroma.com/test/instructions/

Vision Impairment and Astigmatisms

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             Impaired vision can be defined as the functional limitation of an eye, eyes, or visual system. It has become more prevalent among individuals over the past few centuries. Research from the Arlene R. Gordon Research Institute shows that the number of individuals with impaired vision recorded in 2011 is predicted to double by the year 2020 (Gordon). Many forms of vision impairment affect my family on a daily basis. My mother has worn corrective lenses since third grade to assist with her myopia or nearsighted vision impairment. However, her vision is also distorted by a condition known as an astigmatism, which causes one or more refractive surfaces on the eye to curve. She recently visited an eye doctor to renew her corrective lens prescription and found the results to be somewhat unexpected.

            She arrived at the eye doctor and was prepped for an eye examination. When the doctor produced the results, my mother was extremely surprised. Relative to the general population, she had an exceptionally mild case of myopia; however, her astigmatism was so severe that it caused her vision to rank closely to that of a legally blind individual. The doctor prescribed her a corrective lens that would best fit her needs; however, her vision still remains slightly impaired. These results opened my eyes to the serious effects astigmatism can have on an individual’s vision.

            Astigmatism is an optical condition that blurs an individual’s vision due to the irregular curvature of the lens and/or cornea of the eye. This curvature restricts the lens or cornea from correctly focusing an object on the back of the retina to create a sharp image. With the addition of nearsighted vision impairment, this defect can cause extreme image distortion for an individual such as my mother. Nearsighted vision impairment is a condition that allows an individual to see close objects clearly, but objects in the distance are blurred or distorted. This is caused by an irregularly elongated eye shape that places the point of focus, which would normally lie on the retina, slightly in front of the retina. This newly positioned focal point creates impaired images for objects that are at a distance. Although this condition was not a large factor in my mother’s case, it can cause extreme issues for many people depending on the severity of the impairment.

            After hearing my mother’s experience and learning about the various conditions that contribute to vision impairment, I now understand how two individual vision cases can be extremely different from one another. My mother’s vision was distorted mostly because of an astigmatism; however, another individual may have a severe case of myopia that contributes to their vision impairment. The combinations are endless regarding the different defects in the eye and the type of corrective treatment needed to assist an individual with their vision impairment.

Works Cited:

Gordon, Arlene R. “Prevalence of Vision Impairment.” Lighthouse International.  n. page. Web. 18 Mar. 2014. http://www.lighthouse.org/research/statistics-on-vision-impairment/prevalence-of-vision-impairment/.

Trevor Kalinkos-Dark and Light Adaptation

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Dark and light adaptation involves the process of pupil dilation as well as the replacement and regeneration of photopigments.  This adaptation can be put into lay terms as being defined as “The process of adjusting the eyes to low levels of illumination,” this goes both ways like an alteration for high levels of illumination as well, aimed at adapting to dark and light environments (Biology-online).  There are still differences in the specifics of the dark adaptation versus the light one.  It takes our eyes longer to adjust and adapt to a dark environment than it does a light one, which is why walking out in the nighttime it is typically difficult to see anything for quite some time.  This is due to the fact that our cones in our eyes have faster photopigment regeneration than do our rods, which are responsible for helping to see in darkness.  The actual processes that are involved in this adaptation are pupil dilation along with this photopigment regeneration.  I recently experienced this light and dark adaptation when I attended a concert over break.  Outside of the venue there were many street lights that illuminated the external environment so that my eyes had some degree of light adaptation.  After getting inside I found it challenging to see at first as it was very dimly lit on the dance floor, especially as the musicians were setting up for the show.  This forced my eyes to go through a dark adaptation slowly as I was making my way through the crowd with my friends.  This is a slower process than light adaptation as mentioned which forced my pupils to dilate to a large size to allow any and all of the light available into my eyes to be able to see basic figures of people so I could avoid running into fellow concertgoers.  This is the first and most instantaneous reactionary mechanism our body has developed to be able to handle very large and sudden changes in the amount of illumination in our environments.  What is technically occurring during this transition phase is that our eyes use up less photopigments from the lack of illumination, which frees up many more photopigments to be able to process the small amount of light that there is. This means we “sensitize to light,” or become more sensitive to small portions of light making us more capable to perceive stimuli even under low light (Sparknotes).  Suddenly the artists came on stage as did the giant orchestrated lightshow that illuminated the stage, the crowd, and the entire venue making it very bright.  This once again forced my eyes to adapt to the change in lighting, this time using the light adaptation which luckily acts much quicker than dark adaptation.   When this occurred my pupils shrank greatly and rapidly to allow less light into the retina of the eye as there was a sudden increase in the total illumination as well as the light entering the eye.  This pupil constriction limits the amount of light able to enter my eyes, as there were far too many lasers and lights to be able to comprehend for my perception.  As a result of this occurring much quicker than the dark adaptation happens I was able to naturally and swiftly adjust to this sensory overload of lights.  Although at first I will admit I was blinded slightly by the sudden and rapid illumination of my visionary field.

 

Work cited

Dark Adaptation. (2005, October 3). Retrieved March 14, 2014, from
Biology-Online website: http://www.biology-online.org/dictionary/
Dark_adaptation

 

Sensation and Perception. (n.d.). Retrieved March 15, 2014, from Sparknotes
website: http://www.sparknotes.com/psychology/psych101/sensation/
section2.rhtml

Where at THON is Jesse?

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Every February Penn State’s Dance Marathon or “THON” packs thousands of people into the Bryce Jordan Center in order to dance for children with pediatric cancer, and this year I was on a committee called DAR or Donor Alumni Relations. Our committee gives mostly tours and often we have a lot of down time to simply go into the stands and watch THON casually together. Each of the tours crosses the floor twice once in the beginning of the tour and once near the end. People on tours can become astray in the crowd easily, and it can be very hard sometimes to locate lost donors, parents, and in our case committee members. Unfortunately, one girl was lost we will call her “Jesse” to protect the privacy of the individual, and one tour guide simply mentioned that she didn’t return to the concourse and no one has been able to find her on the floor.

During downtime, many of the committee members were in the upper bowl of the BJC watching THON, and we were trying to locate her if possible. One of my friend’s called our search “Where at THON is Jesse” in honor of the game “Where is Waldo”. It was very fitting, because in the sea of hundreds of dancers, moralers, and pass list holders we were looking for one specific person. Be it as it may, the moment that my friend mentioned trying to find her, I see her in the upper right corner of the floor standing with what seemed to be two other dancers. I told everyone the approximate location where I saw her with some context clues, and they immediately began to see her as well. How is it that humans can notice people so far away but also mixed with a large crowd?

This phenomenon is weird, because in reality the brain only sees detail from a very small portion of the retina called the fovea. The retina is located in the back of the eye and contains photo receptors that converts light images into electrical signals that are sent to the brain.  You see less and less detail the further the object’s images is from the fovea. If you extend your arm at full length and take a look at the width of your thumb, that is on average the size of your fovea. This is the only portion of your perceived surroundings that you can see in detail at a particular time. The human eye moves constantly, so that is why it appears we have full detail of everything all the time. Additionally, there are theories that humans recognize objects by a list of features and shapes that are stored in memory. Jesse was wearing a blue THON 2014 DAR committee shirt, she has brown skin, and she has very long black hair. Using these features and the fact that many objects on the floor were far enough away that their whole image was the size of our thumb, or lied entirely on our fovea, we were actually able to recognize people very far away in the large dancer crowd. Later, it was confirmed by one of our captains that it was indeed Jesse on the floor who we had spotted.

Light And Dark Adaptation

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Once when I was younger, I went to see a movie that was 4 hours long. When I was came out my eyes had to readjust just as they had to adjust when I first entered the dark theater. It took longer for my eyes to adjust to the darkness than to the light. This is a perfect example of the concept of dark and light adaptation. When I went into the movie theater my pupils dilated due to the decrease in light intensity. When I left the theater they constricted because of the increase in light intensity. In other words, the eye constricts and dilates to control the amount of light that enters the eye.

Another way the eyes adapt is that the amount of photopigments available in photoreceptors changes with the amount of light intensity.  When I left the theater, more light was entering my eye. In this situation, more photopigments are used up and fewer photopigments are available to process all of the light photons it is exposed to (Wede, 2014). When I was in the theater a smaller amount of photopigments were being used. There were more photopigments that were able to process the low intensity of light that was in the theater (Wede, 2014). When photopigments are used to process a photon, they have to regenerate before they can process more photons (Wolfe et al., 2012). As the level of light intensity increases, there are too many photons for the photopigments to handle because they are not regenerating at a pace where they can keep up with demand (Wolfe et al., 2012). However, the fact that it takes some time for the rods to regenerate actually increases how sensitive we are to situations with varying light conditions (Wolfe et al., 2012). To sum this mechanism up, when there is not much light we need all of our photoreceptors to sense the little light that is there (Wolfe et al., 2012). When there is sufficient light, we do not need all of the photoreceptors that we have so we can get rid of the ones that we do not need (Wolfe et al., 2012).

Another adaptation mechanism is the rods and cones. Rods are what allow us to see in situations where there is a low intensity of light such as in a movie theater (Wolfe et al., 2012). However, when there is a decent amount of light the level of cues the rods can pick up decreases. Cones do not perform well in situations where there is little light but they have a much broader range to process light than rods do (Wolfe et al., 2012). Cones also regenerate much quicker than rods do which is why my eyesight did not take nearly as long to recover when I left the theater than when I went in (Wolfe et al., 2012). In other words, rods and cones are in place to help us see in both dim and well lit situations.

Lastly, how the neural circuitry of the retina is wired plays a role as well. The receptive field of a ganglion cell will fire more than average as long as light on the ON center is more than the light on the OFF surround or vice versa (Wolfe et al., 2012). This helped my visual system to focus on the light and dark spots within and outside the theater that the retina sensed and not how much light was in the overall situation (Wolfe et al., 2012). This is relevant as long as the ganglion cells are completely covered with light or darkness (Wolfe et al., 2012).

During my time in high school, I enrolled in an art class to cover some of my required courses for college. In a very uneventful but stressful chain of events, my eye was severely damaged one day from a paper cut in class. While another student and I were both reaching for a sheet of paper to draw on, the corner of his accidentally came up and sliced me right in the left eye. Immediately after the corner hit my eye I knew there had been damage inflicted. The pain wasn’t too awful but it was more annoying than anything and I couldn’t get my eye to stop from watering. The scratch was so bad that I ended up having to leave school and have my parents drive me to an optometrist. Under further examination, the doctor explained to me that my cornea had been scratched. As we learned in Psych 253, the cornea is a clear surface at the front of the eye. This transparent tissue is responsible as being the primary refractive surface of the eye. The doctor went on to explain to me as I would again learn in Psych 253 that the cornea is responsible for eighty percent of the focusing power of the eye (Wolfe). The optometrist told me that although my left cornea was scratched, there were no traces of paper lodged in my eye and that it should heal within a few days. She sent me home with eye drops and a patch to wear for two days.

After the two day healing process I returned to the doctor and decided to get a full eye examination. After she looked at my eyes, the doctor determined that I actually was due to be wearing glasses. She found that I was actually near sighted, or formally known as having myopia. (Wolfe) This can be caused from the eyeball being too long, making the point of focus in front of the retina and creating challenges seeing far away objects (Wolfe). My condition was very mild and in fact I probably wouldn’t have known for a few more years had my cornea abrasion not happened. I decided to go forth and purchase glasses anyways and once I did I noticed a major difference while sitting in class and trying to read the board. The glasses corrected my vision and made it more or less 20/20.

The picture below shows what a normal eye versus a eye dealing with Myopia would look like. After my cornea scratch I learned that my eye looked like the picture on the left.

Cornea and Myopia

Wolfe, Jeremy M., Keith R. Kleunder, and Dennis M. Levi. “Sensation & Perception: Eye Structure.” Sensation & Perception: Eye Structure. N.p., n.d. Web. 17 Mar. 2014.