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Journal of Agricultural and Food... Nov 2023Olfaction is a multi-step process. At a peripheral level, nasal odorant metabolism contributes to olfaction via signal termination, variation, and regulation. We... (Review)
Review
Olfaction is a multi-step process. At a peripheral level, nasal odorant metabolism contributes to olfaction via signal termination, variation, and regulation. We summarize current techniques used to investigate nasal odorant metabolism and give an outlook on future approaches, such as nasal tissue models and their potential contributions in future research directions.
Topics: Odorants; Smell
PubMed: 37877768
DOI: 10.1021/acs.jafc.3c04662 -
Chemical Senses Jan 2024Different animals have distinctive anatomical and physiological properties to their chemical senses that enhance detection and discrimination of relevant chemical cues....
Different animals have distinctive anatomical and physiological properties to their chemical senses that enhance detection and discrimination of relevant chemical cues. Humans and other vertebrates are recognized as having 2 main chemical senses, olfaction and gustation, distinguished from each other by their evolutionarily conserved neuroanatomical organization. This distinction between olfaction and gustation in vertebrates is not based on the medium in which they live because the most ancestral and numerous vertebrates, the fishes, live in an aquatic habitat and thus both olfaction and gustation occur in water and both can be of high sensitivity. The terms olfaction and gustation have also often been applied to the invertebrates, though not based on homology. Consequently, any similarities between olfaction and gustation in the vertebrates and invertebrates have resulted from convergent adaptations or shared constraints during evolution. The untidiness of assigning olfaction and gustation to invertebrates has led some to recommend abandoning the use of these terms and instead unifying them and others into a single category-chemical sense. In our essay, we compare the nature of the chemical senses of diverse animal types and consider their designation as olfaction, oral gustation, extra-oral gustation, or simply chemoreception. Properties that we have found useful in categorizing chemical senses of vertebrates and invertebrates include the nature of peripheral sensory cells, organization of the neuropil in the processing centers, molecular receptor specificity, and function.
Topics: Animals; Humans; Smell; Taste; Taste Perception; Fishes; Cues
PubMed: 38422390
DOI: 10.1093/chemse/bjae009 -
Current Opinion in Insect Science Dec 2023Insects rely on their sense of smell to navigate complex environments and make decisions regarding food and reproduction. However, in natural settings, the odors that... (Review)
Review
Insects rely on their sense of smell to navigate complex environments and make decisions regarding food and reproduction. However, in natural settings, the odors that convey this information may come mixed with environmental odors that can obscure their perception. Therefore, recognizing the presence of informative odors involves generalization and discrimination processes, which can be facilitated when there is a high contrast between stimuli, or the internal representation of the odors of interest outcompetes that of concurrent ones. The first two layers of the olfactory system, which involve the detection of odorants by olfactory receptor neurons and their encoding by the first postsynaptic partners in the antennal lobe, are critical for achieving such optimal representation. In this review, we summarize evidence indicating that experience-dependent changes adjust these two levels of the olfactory system. These changes are discussed in the context of the advantages they provide for detection of informative odors.
Topics: Animals; Olfactory Pathways; Smell; Odorants; Olfactory Receptor Neurons
PubMed: 37741614
DOI: 10.1016/j.cois.2023.101117 -
The Laryngoscope Aug 2023This study aims to characterize the association between impairments in olfaction and balance, both of which are mediated in part by the cerebellum, and how this relates...
OBJECTIVE
This study aims to characterize the association between impairments in olfaction and balance, both of which are mediated in part by the cerebellum, and how this relates to prospective incidence of falls in a cohort of aging adults.
METHODS
The Health ABC study was queried to identify 296 participants with data on both olfaction (measured using the 12-item Brief Smell Identification Test) and balance-related function (measured using the Romberg test). The relationship between olfaction and balance was investigated using multivariable logistic regression. Predictors of performance on a standing balance assessment and predictors of falls were studied.
RESULTS
Of 296 participants, 52.7% had isolated olfactory dysfunction, 7.4% had isolated balance dysfunction, and 5.7% had dual dysfunction. Severe olfactory dysfunction was associated with increased odds of balance dysfunction when compared to those without olfactory dysfunction, even when adjusting for age, gender, race, education, BMI, smoking, diabetes, depression, and dementia (OR = 4.1, 95% CI [1.5, 13.7], p = 0.011). Dual sensory dysfunction was associated with worse performance on a standing balance assessment (β = -22.8, 95% CI [-35.6, -10.1], p = 0.0005) and increased falls (β = 1.5, 95% CI [1.0, 2.3], p = 0.037).
CONCLUSION
This study highlights a unique relationship between olfaction and balance, and how dual dysfunction is associated with increased falls. With substantial implications of falls on morbidity and mortality in older adults, this novel relationship between olfaction and balance emphasizes a potentially shared mechanism between olfactory dysfunction and increased fall risk in older adults; however, further study is required to explore the novel relationship of olfaction with balance and future falls.
LEVEL OF EVIDENCE
3 Laryngoscope, 133:1964-1969, 2023.
Topics: Humans; Aged; Smell; Olfaction Disorders; Prospective Studies; Accidental Falls; Aging
PubMed: 37159236
DOI: 10.1002/lary.30733 -
JAMA Otolaryngology-- Head & Neck... Mar 2024Decreased mobility is a hallmark of aging. Olfactory dysfunction is common in older adults and may be associated with declines in mobility.
IMPORTANCE
Decreased mobility is a hallmark of aging. Olfactory dysfunction is common in older adults and may be associated with declines in mobility.
OBJECTIVE
To determine whether poor olfaction was associated with faster declines in mobility in older adults.
DESIGN, SETTING, AND PARTICIPANTS
This cohort study included 2500 participants from the Health, Aging, and Body Composition Study. Participants completed the Brief Smell Identification Test during the year 3 clinical visit (1999-2000) and were followed for up to 7 years. A data analysis was conducted between January and July 2023.
EXPOSURES
Olfaction was defined as good (test score, 11-12), moderate (9-10), hyposmia (7-8), or anosmia (0-6).
MAIN OUTCOMES AND MEASURES
Mobility was measured using the 20-m usual and fast walking tests in clinical visit years 3 to 6, 8, and 10 and the 400-m fast walking test in years 4, 6, 8, and 10.
RESULTS
The primary analyses included 2500 participants (1292 women [51.7%]; 1208 men [48.3%]; 960 Black [38.4%] and 1540 White [61.6%] individuals; mean [SD] age, 75.6 [2.8] years). Multivariate-adjusted analyses showed that poor olfaction was associated with slower walking speed at baseline and a faster decline over time. Taking the 20-m usual walking test as an example, compared with participants with good olfaction, the speed at baseline was 0.027 (95% CI, 0-0.053) m/s slower for those with hyposmia and 0.034 (95% CI, 0.005-0.062) m/s slower for those with anosmia. Longitudinally, the annual decline was 0.004 (95% CI, 0.002-0.007) m/s/year faster for those with hyposmia and 0.01 (95% CI, 0.007-0.013) m/s/year faster for those with anosmia. Similar results were obtained for the 20-m and 400-m fast walking tests. Further, compared with participants with good olfaction, the odds of being unable to do the 400-m test were 2.02 (95% CI, 1.17-3.48) times higher for those with anosmia at the year 8 visit and 2.73 (95% CI, 1.40-5.35) times higher at year 10. Multiple sensitivity and subgroup analyses supported the robustness and generalizability of the findings.
CONCLUSION AND RELEVANCE
The results of this cohort study suggest that poor olfaction is associated with a faster decline in mobility in older adults. Future studies should investigate underlying mechanisms and potential health implications.
Topics: Male; Humans; Female; Aged; Smell; Cohort Studies; Anosmia; Aging; Walking Speed; Olfaction Disorders
PubMed: 38236595
DOI: 10.1001/jamaoto.2023.4375 -
Science Advances May 2024The world is undergoing massive atmospheric and ecological change, driving unprecedented challenges to human well-being. Olfaction is a key sensory system through which... (Review)
Review
The world is undergoing massive atmospheric and ecological change, driving unprecedented challenges to human well-being. Olfaction is a key sensory system through which these impacts occur. The sense of smell influences quality of and satisfaction with life, emotion, emotion regulation, cognitive function, social interactions, dietary choices, stress, and depressive symptoms. Exposures via the olfactory pathway can also lead to (anti-)inflammatory outcomes. Increased understanding is needed regarding the ways in which odorants generated by nature (i.e., natural olfactory environments) affect human well-being. With perspectives from a range of health, social, and natural sciences, we provide an overview of this unique sensory system, four consensus statements regarding olfaction and the environment, and a conceptual framework that integrates the olfactory pathway into an understanding of the effects of natural environments on human well-being. We then discuss how this framework can contribute to better accounting of the impacts of policy and land-use decision-making on natural olfactory environments and, in turn, on planetary health.
Topics: Humans; Smell; Olfactory Pathways; Odorants; Nature; Environment
PubMed: 38748806
DOI: 10.1126/sciadv.adn3028 -
The Journal of Neuroscience : the... Nov 2023Smell loss has caught public attention during the recent COVID-19 pandemic. Research on olfactory function in health and disease gains new momentum. Smell deficits have... (Review)
Review
Smell loss has caught public attention during the recent COVID-19 pandemic. Research on olfactory function in health and disease gains new momentum. Smell deficits have long been recognized as an early clinical sign associated with neuropsychiatric disorders. Here we review research on the associations between olfactory deficits and neuropathological conditions, focusing on recent progress in four areas: (1) human clinical studies of the correlations between smell deficits and neuropsychiatric disorders; (2) development of olfactory mucosa-derived tissue and cell models for studying the molecular pathologic mechanisms; (3) recent findings in brain imaging studies of structural and functional connectivity changes in olfactory pathways in neuropsychiatric disorders; and (4) application of preclinical animal models to validate and extend the findings from human subjects. Together, these studies have provided strong evidence of the link between the olfactory system and neuropsychiatric disorders, highlighting the relevance of deepening our understanding of the role of the olfactory system in pathophysiological processes. Following the lead of studies reviewed here, future research in this field may open the door to the early detection of neuropsychiatric disorders, personalized treatment approaches, and potential therapeutic interventions through nasal administration techniques, such as nasal brush or nasal spray.
Topics: Humans; Smell; Olfaction Disorders; Pandemics; COVID-19; Olfactory Mucosa
PubMed: 37940584
DOI: 10.1523/JNEUROSCI.1380-23.2023 -
Cells Apr 2024Alterations in olfactory functions are proposed as possible early biomarkers of neurodegenerative diseases. Parkinson's and Alzheimer's diseases manifest olfactory... (Review)
Review
Alterations in olfactory functions are proposed as possible early biomarkers of neurodegenerative diseases. Parkinson's and Alzheimer's diseases manifest olfactory dysfunction as a symptom, which is worth mentioning. The alterations do not occur in all patients, but they can serve to rule out neurodegenerative pathologies that are not associated with small deficits. Several prevalent neurodegenerative conditions, including impaired smell, arise in the early stages of Parkinson's and Alzheimer's diseases, presenting an attractive prospect as a snitch for early diagnosis. This review covers the current knowledge on the link between olfactory deficits and Parkinson's and Alzheimer's diseases. The review also covers the emergence of olfactory receptors as actors in the pathophysiology of these diseases. Olfactory receptors are not exclusively expressed in olfactory sensory neurons. Olfactory receptors are widespread in the human body; they are expressed, among others, in the testicles, lungs, intestines, kidneys, skin, heart, and blood cells. Although information on these ectopically expressed olfactory receptors is limited, they appear to be involved in cell recognition, migration, proliferation, wound healing, apoptosis, and exocytosis. Regarding expression in non-chemosensory regions of the central nervous system (CNS), future research should address the role, in both the glia and neurons, of olfactory receptors. Here, we review the limited but relevant information on the altered expression of olfactory receptor genes in Parkinson's and Alzheimer's diseases. By unraveling how olfactory receptor activation is involved in neurodegeneration and identifying links between olfactory structures and neuronal death, valuable information could be gained for early diagnosis and intervention strategies in neurodegenerative diseases.
Topics: Humans; Neurodegenerative Diseases; Smell; Alzheimer Disease; Parkinson Disease; Olfaction Disorders; Receptors, Odorant
PubMed: 38607054
DOI: 10.3390/cells13070615 -
Cold Spring Harbor Protocols Oct 2023When blood feeding from human hosts, female mosquitoes can transmit life-threatening pathogens to humans, including dengue virus, chikungunya virus, and Zika virus....
When blood feeding from human hosts, female mosquitoes can transmit life-threatening pathogens to humans, including dengue virus, chikungunya virus, and Zika virus. Olfaction is the primary sense mosquitoes use to locate and differentiate hosts and studying it can lead to new strategies to reduce the risk of disease. To effectively study host-seeking behavior in mosquitoes, a repeatable, quantitative assay that isolates olfaction from other cues is critical for interpreting mosquito behavior. Here, we contribute an overview of methods and best practices for the study of mosquito attraction (or lack thereof) by using olfactometry to quantify behavior. In the accompanying protocols, we present an olfactory-based behavioral assay using a uniport olfactometer that measures mosquito attraction rate to specific stimuli. We include construction details, setup of the uniport olfactometer, details of the behavioral assay, and data analysis guidelines, as well as how to prepare the mosquitoes before their introduction into the olfactometer. This uniport olfactometer behavioral assay is currently one of the most reliable methods to study mosquito attraction to a single olfactory stimulus.
Topics: Animals; Female; Humans; Olfactometry; Aedes; Smell; Feeding Behavior; Zika Virus; Zika Virus Infection
PubMed: 37024240
DOI: 10.1101/pdb.top107660 -
Neurosurgical Review Jul 2023Olfactory groove meningiomas (OGM) are a skull base neoplasm that represents between 8 and 13% of all intracranial meningiomas. Approach selection focuses on achieving... (Review)
Review
Olfactory groove meningiomas (OGM) are a skull base neoplasm that represents between 8 and 13% of all intracranial meningiomas. Approach selection focuses on achieving frontal lobe decompression, gross total resection and vision preservation. Recently, there has been a focus on olfaction and considering its preservation as a quality-of-life outcome measure. An electronic search of the databases Medline, Scopus, Embase, Web of Science and Cochrane library databases was performed and data extracted according 2020 Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement. Six articles were selected for inclusion mainly based due to reporting quantitative outcomes for olfaction assessed by a smell identification test (e.g. sniffin' sticks). Objective olfaction preservation can be achieved with a variety of surgical approaches. More research which includes objective assessment of olfactory function and ideally as well QoL outcome measures is needed to further optimize the treatment pathways in OGM patients.
Topics: Humans; Meningioma; Smell; Meningeal Neoplasms; Quality of Life; Olfaction Disorders
PubMed: 37500988
DOI: 10.1007/s10143-023-02096-z