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Neuroscience and Biobehavioral Reviews Oct 2022The sense of smell is interrelated with psychosocial functioning. Olfactory disorders often decrease quality of life but treatment options for people with olfactory loss... (Review)
Review
The sense of smell is interrelated with psychosocial functioning. Olfactory disorders often decrease quality of life but treatment options for people with olfactory loss are limited. Additionally, olfactory loss accompanies and precedes psychiatric and neurodegenerative diseases. Regular, systematic exposure to a set of odors, i.e., olfactory training (OT) has been offered for rehabilitation of the sense of smell in clinical practice. As signals from the olfactory bulb are directly projected to the limbic system it has been also debated whether OT might benefit psychological functioning, i.e., mitigate cognitive deterioration or improve emotional processing. In this review we synthesize key findings on OT utility in the clinical practice and highlight the molecular, cellular, and neuroanatomical changes accompanying olfactory recovery in people with smell loss as well as in experimental animal models. We discuss how OT and its modifications have been used in interventions aiming to support cognitive functions and improve well-being. We delineate main methodological challenges in research on OT and suggest areas requiring further scientific attention.
Topics: Animals; Humans; Odorants; Olfaction Disorders; Olfactory Bulb; Quality of Life; Smell
PubMed: 36064146
DOI: 10.1016/j.neubiorev.2022.104853 -
Bio Systems Feb 2018Sensory coding represents a basic principle of all phyla in nature: species attempt to perceive their natural surroundings and to make sense of them. Ultimately, sensory... (Review)
Review
Sensory coding represents a basic principle of all phyla in nature: species attempt to perceive their natural surroundings and to make sense of them. Ultimately, sensory coding is the only way to allow a species to make the kinds of crucial decisions that lead to a behavioral response. In this manner, animals are able to detect numerous parameters, ranging from temperature and humidity to light and sound to volatile or non-volatile chemicals. Most of these environmental cues represent a clearly defined stimulus array that can be described along a single physical parameter, such as wavelength or frequency; odorants, in contrast, cannot. The odor space encompasses an enormous and nearly infinite number of diverse stimuli that cannot be classified according to their positions along a single dimension. Hence, the olfactory system has to encode and translate the vast odor array into an accurate neural map in the brain. In this review, we will outline the relevant steps of the olfactory code and describe its progress along the olfactory pathway, i.e., from the peripheral olfactory organs to the first olfactory center in the brain and then to the higher processing areas where the odor perception takes place, enabling an organism to make odor-guided decisions. We will focus mainly on studies from the vinegar fly Drosophila melanogaster, but we will also indicate similarities to and differences from the olfactory system of other invertebrate species as well as of the vertebrate world.
Topics: Animals; Genetic Code; Humans; Odorants; Olfactory Pathways; Smell
PubMed: 29054468
DOI: 10.1016/j.biosystems.2017.10.010 -
Cell Reports Nov 2022The evolution of feeding habits leads to speciation in insects. Bactrocera true fruit flies display diverse feeding habits across species. We combine behavioral and...
The evolution of feeding habits leads to speciation in insects. Bactrocera true fruit flies display diverse feeding habits across species. We combine behavioral and functional genomic studies to probe the divergence between the specialist B. minax and the generalist B. dorsalis. We find that both vision and olfaction contribute to their respective host preferences, with a dominant effect of vision over the olfaction in short range. Correspondingly, host location-related genes are significantly enriched in the phototransduction pathway, of which the long-wavelength rhodopsin confers the color preference in both species and has been subject to selection in the specialist. We also find a massive expansion of olfactory receptors in the generalist, along with signatures of conditional expression and positive selection. The phylogenetic context suggests an ancestrally important role of vision in the host location of Bactrocera, as well as the increased performance and plasticity of olfaction alongside the arising of generalism.
Topics: Animals; Phylogeny; Genomics; Tephritidae; Receptors, Odorant; Smell
PubMed: 36384127
DOI: 10.1016/j.celrep.2022.111654 -
ELife Sep 2020Unexplained repeated pregnancy loss is associated with an altered perception of male odors and differences in brain regions that process smells.
Unexplained repeated pregnancy loss is associated with an altered perception of male odors and differences in brain regions that process smells.
Topics: Abortion, Spontaneous; Brain; Female; Humans; Male; Odorants; Pregnancy; Smell
PubMed: 32988454
DOI: 10.7554/eLife.62534 -
Current Biology : CB Jan 2019Animals can smell odors from the external environment or from their mouth via two routes: orthonasal and retronasal, respectively. Little is known about how the brain...
Animals can smell odors from the external environment or from their mouth via two routes: orthonasal and retronasal, respectively. Little is known about how the brain processes orthonasal and retronasal odors associated with taste, but a new study has revealed an important role for the gustatory cortex in such odor processing.
Topics: Animals; Mouth; Odorants; Smell; Taste; Time Perception
PubMed: 30620909
DOI: 10.1016/j.cub.2018.11.038 -
Philosophical Transactions of the Royal... Jun 2020The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology.... (Review)
Review
The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.
Topics: Adaptation, Biological; Adolescent; Adult; Aged; Aged, 80 and over; Child; Child, Preschool; Female; Humans; Infant; Infant, Newborn; Male; Middle Aged; Nonverbal Communication; Odorants; Olfactory Perception; Parent-Child Relations; Smell; Young Adult
PubMed: 32306879
DOI: 10.1098/rstb.2019.0261 -
Annual Review of Entomology 2016In insects, olfaction plays a crucial role in many behavioral contexts, such as locating food, sexual partners, and oviposition sites. To successfully perform such... (Review)
Review
In insects, olfaction plays a crucial role in many behavioral contexts, such as locating food, sexual partners, and oviposition sites. To successfully perform such behaviors, insects must respond to chemical stimuli at the right moment. Insects modulate their olfactory system according to their physiological state upon interaction with their environment. Here, we review the plasticity of behavioral responses to different odor types according to age, feeding state, circadian rhythm, and mating status. We also summarize what is known about the underlying neural and endocrinological mechanisms, from peripheral detection to central nervous integration, and cover neuromodulation from the molecular to the behavioral level. We describe forms of olfactory plasticity that have contributed to the evolutionary success of insects and have provided them with remarkable tools to adapt to their ever-changing environment.
Topics: Animals; Cell Plasticity; Insecta; Neuronal Plasticity; Olfactory Perception; Smell
PubMed: 26982441
DOI: 10.1146/annurev-ento-010715-023523 -
British Journal of Industrial Medicine Jul 1961A simple olfaction test, based on graded solutions of phenol in liquid paraffin, was examined for repeatability. Of 98 persons tested, 79 repeated their initial result...
A simple olfaction test, based on graded solutions of phenol in liquid paraffin, was examined for repeatability. Of 98 persons tested, 79 repeated their initial result to within ± one grade on a second occasion. The time interval between tests (varying from a few hours to three weeks), observers, age, smoking habits, or initial grade did not appear to affect the degree of repeatability. There was a tendency to improve the grading on the second occasion. Tests on 147 persons provided no evidence of an association between cigarette smoking and acuity of smell. There was an indication that pipe smoking had an adverse effect. An association between age and acuity was shown.
Topics: Humans; Occupational Diseases; Smell
PubMed: 13700743
DOI: 10.1136/oem.18.3.213 -
Current Opinion in Neurobiology Dec 2016Over one billion people worldwide are infected with parasitic nematodes. Many parasitic nematodes actively search for hosts to infect using volatile chemical cues, so... (Review)
Review
Over one billion people worldwide are infected with parasitic nematodes. Many parasitic nematodes actively search for hosts to infect using volatile chemical cues, so understanding the olfactory signals that drive host seeking may elucidate new pathways for preventing infections. The free-living nematode Caenorhabditis elegans is a powerful model for parasitic nematodes: because sensory neuroanatomy is conserved across nematode species, an understanding of the microcircuits that mediate olfaction in C. elegans may inform studies of olfaction in parasitic nematodes. Here we review circuit mechanisms that allow C. elegans to respond to odorants, gases, and pheromones. We also highlight work on the olfactory behaviors of parasitic nematodes that lays the groundwork for future studies of their olfactory microcircuits.
Topics: Animals; Behavior, Animal; Caenorhabditis elegans; Chemotaxis; Nematoda; Olfactory Nerve; Smell
PubMed: 27668755
DOI: 10.1016/j.conb.2016.09.002 -
Current Opinion in Neurobiology Aug 2000The fruit fly, Drosophila melanogaster, is equipped with a sophisticated olfactory sensory system that permits it to recognize and discriminate hundreds of discrete... (Review)
Review
The fruit fly, Drosophila melanogaster, is equipped with a sophisticated olfactory sensory system that permits it to recognize and discriminate hundreds of discrete odorants. The perception of these odorants is essential for the animal to identify relevant food sources and suitable sites for egg-laying. Advances in the last year have begun to define the molecular basis of this insect's discriminatory power. The identification of a large multi-gene family of candidate Drosophila odorant receptors suggests that, as in other animals, a multitude of distinct odorants is recognized by a diversity of ligand-binding receptors. How olfactory signals are transduced and interpreted by the brain remains an important question for future analysis. The availability of genetic tools and a complete genome sequence makes Drosophila a particularly attractive organism for studying the molecular basis of olfaction.
Topics: Animals; Drosophila; Gene Expression; Genome; Olfactory Receptor Neurons; Receptors, Odorant; Smell
PubMed: 10981620
DOI: 10.1016/s0959-4388(00)00111-2