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Progress in Neurobiology Sep 2023Olfaction is an important sensory modality for many species and greatly influences animal and human behavior. Still, much about olfactory perception remains unknown. The... (Review)
Review
Olfaction is an important sensory modality for many species and greatly influences animal and human behavior. Still, much about olfactory perception remains unknown. The anterior olfactory nucleus is one of the brain's central early olfactory processing areas. Located directly posterior to the olfactory bulb in the olfactory peduncle with extensive in- and output connections and unique cellular composition, it connects olfactory processing centers of the left and right hemispheres. Almost 20 years have passed since the last comprehensive review on the anterior olfactory nucleus has been published and significant advances regarding its anatomy, function, and pathophysiology have been made in the meantime. Here we briefly summarize previous knowledge on the anterior olfactory nucleus, give detailed insights into the progress that has been made in recent years, and map out its emerging importance in translational research of neurological diseases.
Topics: Animals; Humans; Olfactory Pathways; Olfactory Bulb; Smell; Olfactory Cortex
PubMed: 37343762
DOI: 10.1016/j.pneurobio.2023.102486 -
Balkan Medical Journal Jan 2019This report produces a bibliographic study of psychophysical tests proposed clinical assessments of retronasal olfaction.
BACKGROUND
This report produces a bibliographic study of psychophysical tests proposed clinical assessments of retronasal olfaction.
AIMS
We review how these tests can be utilized and discuss their methodological properties.
STUDY DESIGN
Systematic review.
METHODS
We undertook a systematic literature review investigating the retronasal olfaction test methods. PubMed, the free online MEDLINE database on biomedical sciences, was searched for the period from 1984 to 2015 using the following relevant key phrases: “retronasal olfaction”, “orthonasal olfaction”, “olfaction disorders”, and “olfaction test”. For each of the selected titles cited in this study, the full manuscript was read and analyzed by each of the three authors of this paper independently before collaborative discussion for summation and analytical reporting. Two reviewers independently read the abstracts and full texts and categorised them into one of three subgroups as follow, suitable, not-suitable, and unsure. Then they cross-checked the results, and a third reviewer decided assigned the group “unsure” to either the suitable group or the not-suitable group. Fifty eight studies revealed as suitable for review by two authors whereas 13 found not suitable for review. The total amount of 60 uncertain (unsure) or differently categorized articles were further examined by the third author which resulted in 41 approvals and 19 rejections. Hence 99 approved articles passed the next step. Exclusion criteria were reviews, case reports, animal studies, and the articles of which methodology was a lack of olfaction tests. By this way excluded 69 papers, and finally, 30 original human research articles were taken as the data.
RESULTS
The study found that the three most widely used and accepted retronasal olfaction test methods are the retronasal olfaction test, the candy smell test and odorant presentation containers. All of the three psychophysical retronasal olfaction tests were combined with orthonasal tests in clinical use to examine and understand the smell function of the patient completely. There were two limitations concerning testing: “the lack concentrations and doses of test materials” and “performing measurements within the supra-threshold zone”.
CONCLUSION
The appropriate test agents and optimal concentrations for the retronasal olfaction tests remain unclear and emerge as limitations of the retronasal olfaction test technique. The first step to overcoming these limitations will probably require identification of retronasal olfaction thresholds. Once these are determined, the concept of retronasal olfaction and its testing methods may be thoroughly reviewed.
Topics: Diagnostic Techniques, Neurological; Humans; Nasal Cavity; Olfaction Disorders; Olfactory Bulb; Smell
PubMed: 30264731
DOI: 10.4274/balkanmedj.2018.0052 -
Journal of Neuroinflammation Dec 2022Sinonasal diseases, such as rhinosinusitis, affect up to 12% of individuals each year which constitutes these diseases as some of the most common medical conditions in... (Review)
Review
Sinonasal diseases, such as rhinosinusitis, affect up to 12% of individuals each year which constitutes these diseases as some of the most common medical conditions in the world. Exposure to environmental pathogens and toxicants via the nasal cavity can result in a severe inflammatory state commonly observed in these conditions. It is well understood that the epithelial and neuronal cells lining the olfactory mucosa, including olfactory sensory neurons (OSNs), are significantly damaged in these diseases. Prolonged inflammation of the nasal cavity may also lead to hyposmia or anosmia. Although various environmental agents induce inflammation in different ways via distinct cellular and molecular interactions, nasal inflammation has similar consequences on the structure and homeostatic function of the olfactory bulb (OB) which is the first relay center for olfactory information in the brain. Atrophy of the OB occurs via thinning of the superficial OB layers including the olfactory nerve layer, glomerular layer, and superficial external plexiform layer. Intrabulbar circuits of the OB which include connectivity between OB projection neurons, OSNs, and interneurons become significantly dysregulated in which synaptic pruning and dendritic retraction take place. Furthermore, glial cells and other immune cells become hyperactivated and induce a state of inflammation in the OB which results in upregulated cytokine production. Moreover, many of these features of nasal inflammation are present in the case of SARS-CoV-2 infection. This review summarizes the impact of nasal inflammation on the morphological and physiological features of the rodent OB.
Topics: Humans; Olfactory Bulb; COVID-19; SARS-CoV-2; Smell; Interneurons
PubMed: 36494744
DOI: 10.1186/s12974-022-02657-x -
Biosensors Apr 2022Humans, as well as other organisms, tend to recognize their surroundings by smells/odors [...].
Humans, as well as other organisms, tend to recognize their surroundings by smells/odors [...].
Topics: Humans; Odorants; Smell
PubMed: 35448316
DOI: 10.3390/bios12040256 -
International Journal of Molecular... Mar 2024There is very little knowledge regarding the terminal nerve, from its implications in the involvement and pathogenesis of certain conditions, to its embryological... (Review)
Review
There is very little knowledge regarding the terminal nerve, from its implications in the involvement and pathogenesis of certain conditions, to its embryological origin. With this review, we try to summarize the most important evidence on the terminal nerve, aiming to clarify its anatomy and the various functions attributed to it, to better interpret its potential involvement in pathological processes. Recent studies have also suggested its potential role in the control of human reproductive functions and behaviors. It has been hypothesized that it plays a role in the unconscious perception of specific odors that influence autonomic and reproductive hormonal systems through the hypothalamic-pituitary-gonadal axis. We used the PubMed database and found different articles which were then selected independently by three authors. We found 166 articles, of which, after careful selection, only 21 were analyzed. The terminal nerve was always thought to be unimportant in our body. It was well studied in different types of animals, but few studies have been completed in humans. For this reason, its function remains unknown. Studies suggest a possible implication in olfaction due to the anatomical proximity with the olfactive nerve. Others suggest a more important role in reproduction and sexual behaviors. New emerging information suggests a possible role in Kallmann syndrome and COVID-19.
Topics: Animals; Humans; Smell; Kallmann Syndrome; Nerve Endings; Autonomic Nervous System; COVID-19
PubMed: 38612730
DOI: 10.3390/ijms25073920 -
Current Opinion in Insect Science Apr 2017Mosquitoes transmit many debilitating diseases including malaria, dengue and Zika. Odors mediate behaviors that directly impact disease transmission (blood-feeding) as... (Review)
Review
Mosquitoes transmit many debilitating diseases including malaria, dengue and Zika. Odors mediate behaviors that directly impact disease transmission (blood-feeding) as well as life history events that contribute to mosquito survival and fitness (mating and oviposition, nectar foraging, larval foraging and predator avoidance). In addition to innate olfaction-mediated behaviors, mosquitoes rely on olfactory experience throughout their life to inform advantageous choices in many of these important behaviors. Previous reviews have addressed either the chemical ecology of mosquitoes, or olfactory-driven behaviors including host-feeding or oviposition. Adding to this literature, we use a holistic life history perspective to integrate and compare innate and learned olfactory behavior at various stages of mosquito development.
Topics: Animals; Culicidae; Feeding Behavior; Learning; Life Cycle Stages; Mosquito Vectors; Smell
PubMed: 28602240
DOI: 10.1016/j.cois.2017.03.002 -
Neurological Sciences : Official... Apr 2022The phenomenon that longstanding impaired olfactory function is associated with the decreased gustatory function was described in present studies, which was seems...
The phenomenon that longstanding impaired olfactory function is associated with the decreased gustatory function was described in present studies, which was seems attributed to mutual chemosensory interactions. And the interaction between olfaction and gustation still needs more research to figure out. The objective of the study was to investigate how the taste was influenced by olfactory impairment in the central pathway. We tested 33 subjects with normal (n = 19) or impaired (n = 14) olfactory function for their gustatory event-related potentials (gERPs). Validated tests were used for olfactory and gustatory testing (Sniffin' Sticks, gERPs, and three-drop test). This study reported an objective gustatory function decline in olfactory dysfunction participants. However, it also reported the increased gustatory event-related potentials of olfactory dysfunction participants, especially at the frontal electrode (F) and electrode 16 (E16), and the reduced latency of P2 peak of them at electrode 21 (E21), while no obvious difference was observed at the centro-parietal electrode (P). Inferior insula might be the main response area for the increase in gERPs, and this increase averaged amplitude of the P2 component may attribute to compensation of the secondary gustatory response that occurred in the gustatory processing of olfactory-impaired patients.
Topics: Evoked Potentials; Humans; Olfaction Disorders; Smell; Taste; Taste Perception
PubMed: 35106693
DOI: 10.1007/s10072-022-05876-5 -
Anatomical Record (Hoboken, N.J. : 2007) Nov 2014The cetacean nose presents a unique suite of anatomical modifications. Key among these is posterior movement of the external nares from the tip of the rostrum to the top... (Review)
Review
The cetacean nose presents a unique suite of anatomical modifications. Key among these is posterior movement of the external nares from the tip of the rostrum to the top of the head. Concomitant with these anatomical changes are functional changes including the evolution of echolocation in odontocetes, and reduction of olfaction in Neoceti (crown odontocetes and mysticetes). Anatomical and embryological development of the nose in crown cetaceans is reviewed as well as their functional implications. A sequence of evolutionary transformations of the nose is proposed in the transition from a terrestrial to an aquatic lifestyle made by whales. Basilosaurids and all later whales reduce the nasal turbinates. The next stage characterizes Neoceti which exhibit reduction of the major olfactory structures, i.e. the ethmoturbinates, cribriform plate and maxilloturbinates with further reduction and subsequent loss in odontocetes. These anatomical modifications reflect underlying genetic changes such as the reduction of olfactory receptor genes, although mysticetes retain some olfactory abilities. Modifications of the facial and nasal region of odontocetes reflect specialization for biosonar sound production.
Topics: Animals; Biological Evolution; Cetacea; Humans; Nasal Cavity; Nose; Smell
PubMed: 25312374
DOI: 10.1002/ar.23034 -
Environmental Health Perspectives Nov 2016Olfactory dysfunction affects millions of people worldwide. This sensory impairment is associated with neurodegenerative disease and significantly decreased quality of... (Review)
Review
BACKGROUND
Olfactory dysfunction affects millions of people worldwide. This sensory impairment is associated with neurodegenerative disease and significantly decreased quality of life. Exposure to airborne pollutants has been implicated in olfactory decline, likely due to the anatomic susceptibility of the olfactory nerve to the environment. Historically, studies have focused on occupational exposures, but more recent studies have considered effects from exposure to ambient air pollutants.
OBJECTIVES
To examine all relevant human data evaluating a link between ambient pollution exposure and olfaction and to review supporting animal data in order to examine potential mechanisms for pollution-associated olfactory loss.
METHODS
We identified and reviewed relevant articles from 1950 to 2015 using PubMed and Web of Science and focusing on human epidemiologic and pathophysiologic studies. Animal studies were included only to support pertinent data on humans. We reviewed findings from these studies evaluating a relationship between environmental pollutant exposure and olfactory function.
RESULTS
We identified and reviewed 17 articles, with 1 additional article added from a bibliography search, for a total of 18 human studies. There is evidence in human epidemiologic and pathologic studies that increased exposure to ambient air pollutants is associated with olfactory dysfunction. However, most studies have used proxies for pollution exposure in small samples of convenience. Human pathologic studies, with supporting animal work, have also shown that air pollution can contact the olfactory epithelium, translocate to the olfactory bulb, and migrate to the olfactory cortex. Pollutants can deposit at each location, causing direct damage and disruption of tissue morphology or inducing local inflammation and cellular stress responses.
CONCLUSIONS
Ambient air pollution may impact human olfactory function. Additional studies are needed to examine air pollution-related olfactory impacts on the general population using measured pollution exposures and to link pollution exposure with olfactory dysfunction and related pathology. Citation: Ajmani GS, Suh HH, Pinto JM. 2016. Effects of ambient air pollution exposure on olfaction: a review. Environ Health Perspect 124:1683-1693; http://dx.doi.org/10.1289/EHP136.
Topics: Air Pollutants; Animals; Dogs; Environmental Exposure; Humans; Macaca mulatta; Olfaction Disorders; Smell
PubMed: 27285588
DOI: 10.1289/EHP136 -
Current Biology : CB Sep 2021A new study finds that mammalian olfaction may be far faster than previously thought. Mice can discriminate between olfactory stimuli that differ in fine temporal...
A new study finds that mammalian olfaction may be far faster than previously thought. Mice can discriminate between olfactory stimuli that differ in fine temporal structure, at frequencies of up to 40 Hz. But how might mammals achieve high-bandwidth olfaction, and why?
Topics: Animals; Mammals; Mice; Odorants; Smell
PubMed: 34520717
DOI: 10.1016/j.cub.2021.07.010