FINAL BLOG ENTRY
Prior to taking this class, I was aware as to the fact that perception of senses was a complex process in every regard, but I had no idea the extent of how complex it truly is. Through this class, we have been able to study the numerous mechanisms that constitute the processes of perceiving sounds, touch, smell, taste, and vision. There are a variety of aspects that may be delved further into, in regards of how fascinating they truly are, such as the Phantom Limb Syndrome. It is unbelievable to process the idea that all of these items are taking place at once, and it is equally unbelievable to conceive of how much work is occurring inside our minds and bodies to successfully perceive anything from the smallest sound to the mind creating the feeling of an entirely missing limb, as observed in the aforementioned Phantom Limb Syndrome. It is difficult to grasp the fact that the cortexes of our brains can literally reshape itself as life continues in respect to all the events that we must deal with. However, one component of perception that is especially astounding in terms of how much work takes place without our realization is the perception of sight in regards to the biological processes that take place to achieve this sense, the manners in which it can subconsciously effect the everyday decisions of an individual, and its effects upon individuals with mental disabilities.
One must primarily focus upon the biological processes that take place so as to ensure a functioning sense of vision. These processes are so numerous and complex and are constantly in action, despite one’s realization of this, in order to provide individuals with the foremost mechanism of importance in terms of perceiving the world. Light travels through the lens of an eye, and the eye generally uses a process of accommodation to essentially alter the eye a bit to perceive what is being seen better. Light travels through the lens and the remainder of the eye until it reaches the retina, on the back of the eyeball. It then hits the photoreceptors on the back of the eye, and travels forward until it reaches the ganglion cells. When it hits these photoreceptors, the orientation and direction of the light can matter in regards to whether or not it is even perceived. There are simple, complex, and hypercomplex cells that take these aspects, as well as where the light is hitting the cell in terms of its “On” center or “Off” surround area, into consideration. These ganglion cells are the cells that actually send a signal to the brain through the optic nerve, despite the fact that they do not actually absorb these photons.
Light is absorbed as signals through cell-membrane receptors termed G Protein coupled receptors. An optical G Protein coupled receptor is known as rhodopsin, and is composed of two subunits: opsin and retinal. Opsin is the actual receptor portion of this G Protein coupled receptor, while retinal functions as a chromophore. Simply put, retinal serves as somewhat of a rope that wraps around opsin and keeps it in place, to ensure its ability to absorb these said photons. Absorption of a photon by opsin causes retinal to isomerizes, which thereby activates the receptor. Activation of this receptor complex changes its name from rhodopsin to metarhodopsin and causes it to diffuse down the cell membrane until it reaches its corresponding G Protein complex known as transducin, which consists of an alpha, beta, and gamma subunit. Upon its reaching this G Protein complex, the G protein complex is then activated, which in turn causes the GDP that is latched onto the alpha subunit of the protein complex to be converted to GTP. This conversion gives the complex the energy it needs to allow the breakage of the alpha+GTP subunit from the beta and gamma subunits, in order for this alpha subunit to diffuse down the cell membrane until it reaches its effector, which, in this case is cGMP phosphodiesterase. The activation of this effector, once the alpha+GTP subunit reaches it, causes the conversion of cGMP to GMP, which leads to closure of the cGMP gated channels that allow sodium ions to enter the cell. This brings about a hyperpolarization of the cell as no sodium ions can enter through these channels, which causes a halt in the sending of the glutamate neurotransmitter (2000). Essentially, when there is light, there is no neurotransmitter sent to the brain, and this is how an individual can perceive light. After this takes place, one must consider how vision is perceived in the actual brain, after the signal leaves the eyes. The occipital lobe, in the back of the brain, is the primary area for vision perception. Damage to this area can lead to blindness, or damaged sight.
One must also consider the variety of ways in which vision unconsciously effects the everyday actions and choices of individuals. Vision must be considered in regards to color, and color has the ability to strongly affect one’s appetite, perception of the taste of various foods, and the effect and perception of the environment. As research has illustrated, foods that are the color blue are likely to cause a loss in appetite. Weight loss experts typically in fact ask that those attempting to lose weight place a blue light in their refrigerators, eat from blue plates, or in an extreme case perhaps even color their food blue. Interestingly enough, this can be due to the ancestral avoidance of foods that were colored blue and purple as those were typically the poisonous ones. Also, as each sense has a pathway to the brain, sometimes these wires are crossed, so to speak. Due to this, a yellow-green color can produce a sour taste, a pink color can produce a sweet taste, and a grey color can produce a smoky taste. Also, due to the visual perception of color, the sensations of fatigue, danger, stress, and a loss of orientation may come about. Colors can stand out in the environment and alert individuals to important environmental cues (Morton). Colors are processed through the use of three cones, which gives respect to the term “trichromatic.” Short wavelength, middle wavelength and long wavelength cones are used perceive color, and if one is missing or damaged, this individual will not have normal color vision. Instead, they may have red-green colorblindness, due to a lack of M or L cones, or blue-yellow colorblindness due to a lack of S cones which is much less common.
Finally, the amazing qualities of the perception of vision branch to its potential effects upon those with mental disabilities. Those with mental disabilities generally have a lessened perception of vision in terms of acuity. This can be corrected by a treatment known as “Vision Therapy.” Vision therapy is a treatment that is in fact used by a plethora of optometrists in modern society. This therapy allows patients to get a better grasp upon everyday activities, which is crucial and generally taken for granted by those that have accurate, functioning vision perception. Vision therapy involves utilities such as eye patches, optical filters, computer programs, light prisms, balancing vestibular equipment, and general prescription lenses (1996). This therapy builds upon itself, so as to help vision on a multiplicity of levels as those with mental disabilities usually have vision problems in more than one area, as vision is indeed so complex. This therapy focuses primarily on individuals afflicted with autism, rather than just any mental disability. The idea has a foundation upon the thought that vision utilizes muscles to function, and just as regular physical exercise, one can train these muscles to the point of a dramatically improved level of vision. Generally, those with autism cannot follow a moving object which can be quite dangerous in terms of getting around from day to day, nor do autistic patients have a grasp on vertical and horizontal tacking, in regards to follow the horizontal words on the page of a book, for instance. Vision therapy can help correct this problems, and even a slight amount of help can aid the life of an autistic patient tremendously.
Vision is an extraordinary aspect of perception, and the aforementioned items are only a bit of the numerous things I have learned about this semester. Individuals must take the time to understand how much work goes into visual perception, how it can subconsciously effect the simple and not entirely simple choices of individuals from day to day, and how it can effect autistic patients as well as methods being implemented to solve these problems in autistic patients. It is truly difficult to fathom that so much is taking place at once, parallel to so many other complex processes that we learned about in terms of the other senses we are capable of.
Works Cited
(2000). Sensory Transduction. Retrieved April 27, 2008, from http://www.ncbi.nlm.nih.gov/books/bv.fcgi? rid=mcb.section.6255/
(1996). Vision Therapy. Retrieved April 27, 2008, from www.visiontherapy.org/
Morton, J. (1995). Color Matters. Retrieved April 27, 2008, from http://www.colormatters.com/optics.html/
*Note: I tried to format my references multiple times (ie appropriate spacing with a tab on the second line) but the actual weblog format/program would not let me do so!
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