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It has also been found through several studies that olfactory function and cognition correlates to the severity of AD. Therefore, UPSIT is a very good clinical test to be able to determine the severity of AD. [23] During AD, a patient's olfactory bulb, amygdala and temporal cortices are affected. There is also severe nerve cell loss.
The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity.The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate, a sieve-like structure of the ethmoid bone.
Unilateral loss indicates a possible nerve lesion or deviated septum. This test is usually skipped on a cranial nerve exam. [1] The short axons of the first cranial nerve regenerate on a regular basis. The neurons in the olfactory epithelium have a limited life span, and new cells grow to replace the ones that die off.
Olfactory sensory neurons project axons to the brain within the olfactory nerve, (cranial nerve I). These nerve fibers, lacking myelin sheaths, pass to the olfactory bulb of the brain through perforations in the cribriform plate, which in turn projects olfactory information to the olfactory cortex and other areas. [56]
A common psychophysical test of olfactory ability is the triangle test. In this test, the participant is given three odors to smell. Of these three odors, two are the same and one is different, and the participant must choose which odor is the unique one. To test the sensitivity of olfaction, the staircase method is often used.
The peripheral olfactory system consists mainly of the nostrils, ethmoid bone, nasal cavity, and the olfactory epithelium (layers of thin tissue covered in mucus that line the nasal cavity). The primary components of the layers of epithelial tissue are the mucous membranes, olfactory glands, olfactory neurons, and nerve fibers of the olfactory ...
In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the olfactory nerve or damage to brain areas that process smell (see olfactory system). The lack of the sense of smell at birth, usually due to genetic factors, is referred to as congenital anosmia.
Many tests have been developed to test olfactory memory in patients with mental disorders. The 40-item University of Pennsylvania Smell Identification Test (UPSIT) [44] and the 12-item Brief Smell Identification Test, [45] that was developed from the UPSIT, both test olfactory identification using a scratch and sniff booklet. The Sniffin ...