For many years olfaction has been the most disregarded and least studied sense in the scientific and medical communities. Consequently, the amount of knowledge about how olfaction works is small compared to the vast knowledge we have about the other four human senses2. Olfaction is the chemical sense that is often taken for granted. In actuality olfaction's importance matches that of other senses in providing vital environmental information, senses of pleasure and protection7. Olfaction helps in object identification and it serves as an early warning device in dangerous situations. Since the olfactory system and the gustatory system are both chemical senses, that are closely connected and therefore problems with the olfactory tract can affect hunger and eating patterns. Anosmia (lack of the ability to smell) limits satiation by removing some of the pleasure derived from eating 5. The fact that olfaction has been thought of as a primitive sense and the idea that olfaction problems are not considered as tragic as problems of the other senses has also contributed to its lack of study. For many years, researchers in olfaction also lacked the quantitative tests needed to study olfaction properly.
[...] Research using the latest technology of fMRI imaging and mouse models, will help experimenters find the root cause of why Alzheimer's disease causes olfactory malfunction. Compared to other species, humans have a very poor sense of smell. It has been hypothesized that since humans are upright animals, the sense of smell is not as strong. The surface area of the nasal epithelium in humans is also quite small compared to the nasal epithelium of other species. The nasal epithelium, also called olfactory epithelium, is a sheet of receptors cells on the roof of the nasal cavity. [...]
[...] The fact that axons and signals from the olfactory bulb project to these specific parts of the brain shows how and why olfaction and the limbic system are closely connected. These connections serve as an explanation as why olfaction affects emotions and memory. These connections are also very important because they could be the cause of many olfaction disorders related to other degenerative neuronal disorders such as Alzheimers. Some preliminary research as been conducted looking at the olfaction disorders in connection with other neuronal disorders such as Alzheimer's disease. [...]
[...] Olfaction disorder is not a problem isolated only for people with Alzheimer's Disease. Currently million American adults have been diagnosed with an olfaction disorder 5. Olfaction has also been shown to be altered/affected in patients with Parkinson's Disease, multiple sclerosis and Korsakoff's psychosis 7. Olfaction problems are a major concern for the elderly, because by the time people reach age of of the elderly have an olfactory disorder 3. Olfaction problems are not trivial and must be focused on more in the scientific community. [...]
[...] Based on research conducted at University of Pennsylvania by Richard Doty PhD., many connections between olfaction and various neuronal disorders have been discovered. Doty, used the methods such as the UPSIT to test the olfactory sensitivity of patients with Alzheimer's disease versus patients without Alzheimer's disease. The results showed that people with Alzheimer's disease had drastically lower results in smell sensitivity than those people without Alzheimer's disease. Although age tends to cause decreased olfaction sensitivity, patients with Alzheimer's still performed poorly even when compared to those from their own age group. [...]
[...] In this theory, the signal transduction pathway from the nose to the olfactory bulb is still intact, it is simply the pathway that interprets the information that is malfunctioning therefore people can still sense the odorant but are just unable to interpret and distinguish what the odorant is. This hypothesis can be tested using new methods including specialized mouse models that produce excess beta amygloid plaque and imaging techniques such as the Computer Axial Tomography (CAT scan ) and Functional Magnetic Resonance Imaging (fMRI). [...]
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