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Current Biology : CB Jan 2022Many odorants are attractive at low concentrations but repulsive at higher concentrations. A new study demonstrates that, in Caenorhabditis elegans, a single odorant...
Many odorants are attractive at low concentrations but repulsive at higher concentrations. A new study demonstrates that, in Caenorhabditis elegans, a single odorant receptor acts in two different neuron pairs to mediate both attractive and repulsive responses to an odorant.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Odorants; Receptors, Odorant; Smell
PubMed: 35077699
DOI: 10.1016/j.cub.2021.12.008 -
Trends in Endocrinology and Metabolism:... May 2009Olfaction and gustation are important sensory modalities for locating food and for determining which foodstuffs to ingest. It is becoming apparent that there is a strong... (Review)
Review
Olfaction and gustation are important sensory modalities for locating food and for determining which foodstuffs to ingest. It is becoming apparent that there is a strong link between olfaction, gustation and metabolic control. Because endocrine signaling in the naso-oropharynx is likely to influence food intake, satiety and general metabolic control, it is important to examine some of the major hormones that play an integral part in energy homeostasis. Here, we provide an overview of the main endocrine factors known to be present in the naso-oropharynx and discuss their functional roles in maintaining metabolic function. Gaining a greater appreciation of how flavor perception is linked to peripheral metabolism could lead to novel therapeutic strategies for obesity and lifestyle-related diseases.
Topics: Animals; Hormones; Humans; Models, Biological; Nasopharynx; Oropharynx; Smell; Taste
PubMed: 19359194
DOI: 10.1016/j.tem.2009.01.006 -
Current Biology : CB Feb 2023A recent study has shown that, in the fly Drosophila, olfactory neurons stop signaling when smells get too strong. This changes the way we think about odor encoding...
A recent study has shown that, in the fly Drosophila, olfactory neurons stop signaling when smells get too strong. This changes the way we think about odor encoding across concentrations.
Topics: Animals; Smell; Drosophila; Neurons; Signal Transduction
PubMed: 36854272
DOI: 10.1016/j.cub.2023.01.018 -
Current Biology : CB Oct 2004
Review
Topics: Humans; Odorants; Olfaction Disorders; Olfactory Receptor Neurons; Perception; Psychophysics; Receptors, Odorant; Smell
PubMed: 15498475
DOI: 10.1016/j.cub.2004.09.066 -
Chemical Senses Jan 2022Our goal in this article is to provide a perspective on how to understand the nature of responses to chemical mixtures. In studying responses to mixtures, researchers...
Our goal in this article is to provide a perspective on how to understand the nature of responses to chemical mixtures. In studying responses to mixtures, researchers often identify "mixture interactions"-responses to mixtures that are not accurately predicted from the responses to the mixture's individual components. Critical in these studies is how to predict responses to mixtures and thus to identify a mixture interaction. We explore this issue with a focus on olfaction and on the first level of neural processing-olfactory sensory neurons-although we use examples from taste systems as well and we consider responses beyond sensory neurons, including behavior and psychophysics. We provide a broadly comparative perspective that includes examples from vertebrates and invertebrates, from genetic and nongenetic animal models, and from literature old and new. In the end, we attempt to recommend how to approach these problems, including possible future research directions.
Topics: Animals; Olfactory Receptor Neurons; Sensory Receptor Cells; Smell
PubMed: 35226060
DOI: 10.1093/chemse/bjac002 -
Journal of Neurology, Neurosurgery, and... Mar 2017The connection between Alzheimer's disease (AD) and olfactory deficits is well documented and further, alterations in olfactory functioning may signal declines in... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The connection between Alzheimer's disease (AD) and olfactory deficits is well documented and further, alterations in olfactory functioning may signal declines in functions associated with dementia. The aim of the present comprehensive meta-analysis was to investigate the nature of olfactory deficits in mild cognitive impairment (MCI).
METHODS
Articles were identified through computerised literature search from inception to 30 June 2016 using PubMed, MEDLINE and PsychInfo databases. In order to control for differences in sample size during effect size computation, studies were weighted according to their inverse variance estimates.
RESULTS
31 articles (62 effects) were identified, which included 1993 MCI patients and 2861 healthy older adults (HOA). Included studies contrasted odour identification, discrimination, detection threshold and/or memory between cases and controls. Moderate to large and heterogeneous effects were seen for olfactory deficits in MCI relative to HOA (d=-0.76, 95% CI -0.87<δ<-0.64). Moderator analysis revealed that tests of odour identification yielded larger effect sizes than those of odour detection threshold or memory. In addition, a potential interaction between age and sex was observed, with male patients carrying a larger burden of olfactory deficit and older female patients performing better on olfactory tests.
CONCLUSIONS AND RELEVANCE
Olfactory deficits are present and robust in MCI. Odour identification is most impaired in MCI, which parallels the most prominent sensory deficit seen in AD. As such, a simple-to-administer test of odour identification warrants inclusion in the screening of individuals at risk for developing AD.
Topics: Cognitive Dysfunction; Disease Progression; Humans; Olfaction Disorders; Sex Factors; Smell
PubMed: 28039318
DOI: 10.1136/jnnp-2016-314638 -
Cellular and Molecular Life Sciences :... Feb 2018The sense of smell enables insects to recognize and discriminate a broad range of volatile chemicals in their environment originating from prey, host plants and... (Review)
Review
The sense of smell enables insects to recognize and discriminate a broad range of volatile chemicals in their environment originating from prey, host plants and conspecifics. These olfactory cues are received by olfactory sensory neurons (OSNs) that relay information about food sources, oviposition sites and mates to the brain and thus elicit distinct odor-evoked behaviors. Research over the last decades has greatly advanced our knowledge concerning the molecular basis underlying the reception of odorous compounds and the mechanisms of signal transduction in OSNs. The emerging picture clearly indicates that OSNs of insects recognize odorants and pheromones by means of ligand-binding membrane proteins encoded by large and diverse families of receptor genes. In contrast, the mechanisms of the chemo-electrical transduction process are not fully understood; the present status suggests a contribution of ionotropic as well as metabotropic mechanisms. In this review, we will summarize current knowledge on the peripheral mechanisms of odor sensing in insects focusing on olfactory receptors and their specific role in the recognition and transduction of odorant and pheromone signals by OSNs.
Topics: Animals; Insecta; Odorants; Olfactory Receptor Neurons; Pheromones; Receptors, Odorant; Signal Transduction; Smell
PubMed: 28828501
DOI: 10.1007/s00018-017-2627-5 -
Experimental Brain Research Aug 2010Paradoxically, although humans have a superb sense of smell, they don't trust their nose. Furthermore, although human odorant detection thresholds are very low, only... (Review)
Review
Paradoxically, although humans have a superb sense of smell, they don't trust their nose. Furthermore, although human odorant detection thresholds are very low, only unusually high odorant concentrations spontaneously shift our attention to olfaction. Here we suggest that this lack of olfactory awareness reflects the nature of olfactory attention that is shaped by the spatial and temporal envelopes of olfaction. Regarding the spatial envelope, selective attention is allocated in space. Humans direct an attentional spotlight within spatial coordinates in both vision and audition. Human olfactory spatial abilities are minimal. Thus, with no olfactory space, there is no arena for olfactory selective attention. Regarding the temporal envelope, whereas vision and audition consist of nearly continuous input, olfactory input is discreet, made of sniffs widely separated in time. If similar temporal breaks are artificially introduced to vision and audition, they induce "change blindness", a loss of attentional capture that results in a lack of awareness to change. Whereas "change blindness" is an aberration of vision and audition, the long inter-sniff-interval renders "change anosmia" the norm in human olfaction. Therefore, attentional capture in olfaction is minimal, as is human olfactory awareness. All this, however, does not diminish the role of olfaction through sub-attentive mechanisms allowing subliminal smells a profound influence on human behavior and perception.
Topics: Animals; Attention; Awareness; Blindness; Humans; Odorants; Olfactory Pathways; Perception; Sensory Thresholds; Smell
PubMed: 20603708
DOI: 10.1007/s00221-010-2348-6 -
The Journal of Physiological Sciences :... Nov 2021The odorant arrives at nasal olfactory epithelium ortho- and retronasally. This experiment aimed to study the potential different olfactory habituation in orthonasal and...
The odorant arrives at nasal olfactory epithelium ortho- and retronasally. This experiment aimed to study the potential different olfactory habituation in orthonasal and retronasal pathways. 68 subjects were stimulated by constant airflow with an odor (50% phenethyl alcohol, PEA or 5% n-butyl acetate, BA) presented ortho- or retronasally. Participants rated the perceived odor intensity (0-10 points) per minute until the odor sensation disappeared. We also investigated the cross-habituation: when the subjects achieved full habituation, continue to rate odor intensity in a different pathway after instantly switching the odor stimulation pathway. The olfactory habituation curve was drawn. The differences of ratings between the orthonasal and retronasal olfaction at different time points and between male and female subjects were analyzed. The two odor intensity ratings decreased as the time extended, share the same "fast followed by slow" type. The ratings of orthonasal olfaction decreased faster than that of retronasal. The intensity rating of PEA of male retronasal approach was lower than that of female at the 5th min (p = 0.018). When orthonasal full habituation achieved, there was significant difference between the intensity ratings and the initial ratings of the retronasal stimulation pathway (p < 0.0001), and vice versa. We found obvious habituation as well as cross-habituation in both orthonasal and retronasal olfaction. The habituation of orthonasal olfaction was faster than that of retronasal olfaction. These different habituations were related to the gender.
Topics: Female; Humans; Male; Odorants; Smell
PubMed: 34837939
DOI: 10.1186/s12576-021-00822-0 -
The Yale Journal of Biology and Medicine Mar 2018Modern lifestyles are disrupting the human senses-primarily sight, sound, and smell. Noise-induced hearing loss has been noted for centuries and increasing over time... (Review)
Review
Modern lifestyles are disrupting the human senses-primarily sight, sound, and smell. Noise-induced hearing loss has been noted for centuries and increasing over time following the industrial era. From the mid-20 century, the numbers of individuals with myopia (the leading visual impairment) have been increasing globally. Historical evidence for olfactory dysfunction is not known but its etiological links to pollution suggest it increased following industrialization. Clinical interventions for sight and sound loss include preventative and corrective measures but none exist for olfactory dysfunction. Further, olfactory loss is linked to multiple negative health outcomes across physical, mental, and social domains. Due to the global rates of exposure to pollution, olfaction is a global health concern. The environmental injustice inherent in human society (locally and globally) results in inequitable risk for sensory loss by the most vulnerable populations and creates an even deeper gradient in health disparity. Situated within the environmental justice and health disparity literature, this paper introduces the term to describe variation in sensory environments based on socio-economic status (which is often entwined with race and education). A key challenge to risk management is awareness of sensory inequity experienced by vulnerable populations and incorporating that awareness into basic research and policy.
Topics: Environment; Healthcare Disparities; Humans; Life Style; Models, Biological; Sensation; Smell
PubMed: 29599658
DOI: No ID Found