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Biology 202, Spring 2005
Third Web Papers
In order to understand the symptoms that can develop over the course of the illness, it is necessary to recognize some of the etiologies that are associated with Alzheimer's disease. The oldest theory, which is still used today, is the cholinergic hypothesis, which states that a deficiency in acetylcholine is responsible for the development of Alzheimer's disease. Some of the first generation anti-Alzheimer's medications are used to increase the production of acetylcholine by inhibiting acetylcholinesterases. The treatments include lecithin, choline, physostigmine, deprenyl, hydrochloride, and tacrine. Studies have shown that these medications are efficient in treating Alzheimer's symptoms, but they can not stop or reverse the development of the disease (2). Some side affects of the drugs include the elevation of liver functioning.
People with Alzheimer's disease are also suspected to be genetically predisposed for it. Scientists have divided the disease into two types: the Familial Alzheimer's Disease (FAD) and the Sporadic Alzheimer's Disease (SAD). FAD shows clear inheritance pattern, while SAD show vague family history of the disease. Most of the cases that are identified are SAD, where the disease occurs around or after the age of 65. FAD , however, occurs between the ages of 30 to 60. In addition, Alzheimer's disease is less common in men than women for any age-group. Some evidences have pointed to a defect in to the Amyloid Precursor Protein (APP) gene on chromosome 21, the Pr-Senilin1(PS1) and Pre-Senilin 2 (PS2) gene at chromosome 14 and 1, and the apolipoprotein -e (APOE) gene at chromosome 19, which increase people's chances of developing the illness (3). Most of the FAD cases are resulted from PS1 alteration, while a large percentage of SAD cases are caused by APOE gene complication. The changes of certain genes at specific chromosomes can have deadly consequences.
A recent hypothesis that was generated in 2004 suggests that Alzheimer's disease is caused by the interaction between three proteins or the triple-protein pathology theory. Some studies have shown that Tau protein abnormalities occur first in the brain, which is later followed by the development of Amyloid beta protein. Amyloid beta will cluster into amyloid plaques, and these plaques can settle themselves on the blood vessels and outside of the neuronal surface of the brain. Inflammation and Neuro Fibrillary Tangles (NFTs) are two processes that follow after the formation of amyloid plaques to kill neurons and cause dementia. During inflamation, numerous astrocytes and microglial cells activate to produce prostaglandin acid medicated inflammation and harmful free radical to damage neurons. When Tau protein has been phosphorylated, it loses its ability to bind to microtubules and keeps the microtubules' structures and functions intact. The tau proteins, instead, will bind with each other into a knot and this process is called NFTs (4). Neurons that no longer have any functional microtubules will eventually die. A third protein called alpha synuclein will also form and interact with the other proteins, to cause Alzheimer's disease. The function of Alpha synyclein, however, has not been identified yet, but studies have shown that it can be related other illness like Parkinson's disease (5).
Other less known etiologies of Alzheimer's disease are the autoimmune theory, the slow virus theory, and the toxic chemical theory. For instance, excess level of toxic chemicals like aluminum and mercury are found to be extremely high in people with Alzheimer's disease. The body's immune system can also attack its own tissues, thus making antibodies for it own cells. Aging neurons might undergo late changes that can trigger an autoimmune response that direct the production of Alzheimer's symptoms. Since a very similar brain disorder (Creutzfeldt-Jakob disease) is caused by the Mad Cow virus, many have speculated that Alzheimer's disease might also be developed by a virus entering the system (5). However, there have not been recent studies able to determine the one true virus that may cause the disease.
Due to the numerous etiologies of Alzheimer's disease, there are also many different types of symptoms that are can develop with the different stages of the disease. In the beginning of the illness, the individuals will feel tired, anxious, and upset easily. They have problems coping with changes, and so they get confused when they travel to a new place. They will also try to blame others for their forgetfulness. Making decisions will become very difficult for them, and balancing the checkbook seems like an impossible task. They can also anger easily, and driving becomes dangerous for them and others. They will seek isolation, and thus are very susceptible to depression (2).
In the later process of the Alzheimer's disease, the symptoms can become so devastating that affected individuals can no longer take care of themselves. Many will lose their ability to identify dates or read words, and some will have severe emotional problems. They will also lose touch with reality as they become suspicious of people around them and develop paranoid notions about being murdered. Dressing, bathing, and feeding themselves are daily routines that they can no longer accomplish (2). Some will encounter problems with walking and are forced to live with a caregiver. Death will eventually follow afterward from pneumonia or other health problems.
The most severe and vicious symptom produced by Alzheimer's disease is the loss of memory. Recent or short-term memory will be the first type of memories to disappear from the individuals' minds. The memory problem will continue to worsen with the progress of the disease, and so some people with the disease find themselves asking or repeating the same questions over again. They will forget people's names and lifelong friends. When people with the disease lose recent memory, they can also lose entire sections of time. For instance, a person can forget who is the current president or the current year and month. Many will no longer be able to recognize and identify family and friends.
People suffering from Alzheimer's disease are not only losing their memory, but they are also losing their personality. In order to understand the relationship between personality and memory, it is important to define personality and memory. Personality, as defined by some neurobiologists and psychologists, is a collection of behaviors, emotions, and thoughts that are not controlled by the I-function. Memory, on the other hand, is controlled and regulated by the I-function of the neocortex. It is a collection of short stories that the I-function makes-up in order to account for the events and people. Memory is also defined as the ability to retain information, and it is influenced by three important stages. The first stage is encoding and processing the information, the second stage is the storing of the memory, and the third stage is memory retrieval. There are also the different types of memories like sensory, short-term, and long-term memory. The sensory memory relates to the initial moment when an event or an object is first detected. Short-term memories are characterized by slow, transient alterations in communication between neurons and long-term memories (1). Long-term memories are marked by permanent changes to the neural structure.
It is very possible that when Alzheimer's patients lose their memories, they will also lose their personalities. If memories and personalities are controlled and influenced by certain structures in the brain, like the neocortex, then plaques and tangled formations around these structures can cause the individuals to lose their memories and also their personalities (3). For example, an Alzheimer's patient (Margo) has left an advance directive requesting euthanasia if she developed dementia. A couple of years later, the Alzheimer's disease left her severely demented. The problem is that Margo's personality had changed dramatically. She enjoys life and does not want to die anytime soon. After Margo suffered from the full affect of Alzheimer's disease, she is no longer the same person who wrote the request asking for euthanasia (4). The changes in Margo's brain structures are assumed to have altered her personality and wiped her memory clean.
Another example that supports the theory that one's personality will changes as the brain structure alters is by looking at the development of a child to an adult. Over the years, as a child brain begins to mature by changing the size or the shape of several brain structures, their behaviors in turn will also alter. When my brother was little, he used to play violent video games. He was the big bully in school and was very competitive in sport. As he grew older, however, my brother became very patient and friendly to other kids in school. He no longer plays violent video games, but instead took up swimming and chess. Since my brother's brain is not the same brain 5 years ago, it is only natural to expect a change in my brother's behaviors as well. Since there are so many alterations to the brain structure as one develops, it is expected that personalities will also change to fit the brain structure.
Alzheimer's disease can alter the brain structures, and the consequences of this alteration are memory loss and changes in personality. When one learns new things or experiences new events, it is assumed that changes in the brain will take place. Thus, a person's personality will alter as the brain structures change over time. Changes in behaviors that are caused by alterations of certain structures of the brain create and define changes in personality.
1) Wikipedia, Alzheimer's Disease Wikipedia
2) Mental Health, History and Orgin of Alzheimer's Disease
3) Alzheimer's Disease and Symptoms , Overview of Alzheimer's Disease
4) Psych.org, Etiologies of Alzheimer's Disease
4) Senior Health, Questions about Alzheimer's Disease
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