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Science (New York, N.Y.) Sep 2023Mapping molecular structure to odor perception is a key challenge in olfaction. We used graph neural networks to generate a principal odor map (POM) that preserves...
Mapping molecular structure to odor perception is a key challenge in olfaction. We used graph neural networks to generate a principal odor map (POM) that preserves perceptual relationships and enables odor quality prediction for previously uncharacterized odorants. The model was as reliable as a human in describing odor quality: On a prospective validation set of 400 out-of-sample odorants, the model-generated odor profile more closely matched the trained panel mean than did the median panelist. By applying simple, interpretable, theoretically rooted transformations, the POM outperformed chemoinformatic models on several other odor prediction tasks, indicating that the POM successfully encoded a generalized map of structure-odor relationships. This approach broadly enables odor prediction and paves the way toward digitizing odors.
Topics: Humans; Neural Networks, Computer; Odorants; Olfactory Perception; Smell; Cheminformatics
PubMed: 37651511
DOI: 10.1126/science.ade4401 -
Journal of Comparative Physiology. A,... Jul 2023Using odors to find food and mates is one of the most ancient and highly conserved behaviors. Arthropods from flies to moths to crabs use broadly similar strategies to... (Review)
Review
Using odors to find food and mates is one of the most ancient and highly conserved behaviors. Arthropods from flies to moths to crabs use broadly similar strategies to navigate toward odor sources-such as integrating flow information with odor information, comparing odor concentration across sensors, and integrating odor information over time. Because arthropods share many homologous brain structures-antennal lobes for processing olfactory information, mechanosensors for processing flow, mushroom bodies (or hemi-ellipsoid bodies) for associative learning, and central complexes for navigation, it is likely that these closely related behaviors are mediated by conserved neural circuits. However, differences in the types of odors they seek, the physics of odor dispersal, and the physics of locomotion in water, air, and on substrates mean that these circuits must have adapted to generate a wide diversity of odor-seeking behaviors. In this review, we discuss common strategies and specializations observed in olfactory navigation behavior across arthropods, and review our current knowledge about the neural circuits subserving this behavior. We propose that a comparative study of arthropod nervous systems may provide insight into how a set of basic circuit structures has diversified to generate behavior adapted to different environments.
Topics: Animals; Arthropods; Olfactory Pathways; Smell; Odorants; Brain
PubMed: 36658447
DOI: 10.1007/s00359-022-01611-9 -
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 -
Biosensors Nov 2023Animals can easily detect hundreds of thousands of odors in the environment with high sensitivity and selectivity. With the progress of biological olfactory research,... (Review)
Review
Animals can easily detect hundreds of thousands of odors in the environment with high sensitivity and selectivity. With the progress of biological olfactory research, scientists have extracted multiple biomaterials and integrated them with different transducers thus generating numerous biosensors. Those biosensors inherit the sensing ability of living organisms and present excellent detection performance. In this paper, we mainly introduce odor biosensors based on substances from animal olfactory systems. Several instances of organ/tissue-based, cell-based, and protein-based biosensors are described and compared. Furthermore, we list some other biological materials such as peptide, nanovesicle, enzyme, and aptamer that are also utilized in odor biosensors. In addition, we illustrate the further developments of odor biosensors.
Topics: Animals; Odorants; Receptors, Odorant; Smell; Peptides; Biosensing Techniques
PubMed: 38131760
DOI: 10.3390/bios13121000 -
Sensors (Basel, Switzerland) Jul 2023Among the five human senses, light, sound, and force perceived by the eye, ear, and skin, respectively are physical phenomena, and therefore can be easily measured and... (Review)
Review
Among the five human senses, light, sound, and force perceived by the eye, ear, and skin, respectively are physical phenomena, and therefore can be easily measured and expressed as objective, univocal, and simple digital data with physical quantity. However, as taste and odor molecules perceived by the tongue and nose are chemical phenomena, it has been difficult to express them as objective and univocal digital data, since no reference chemicals can be defined. Therefore, while the recording, saving, transmitting to remote locations, and replaying of human visual, auditory, and tactile information as digital data in digital devices have been realized (this series of data flow is defined as DX (digital transformation) in this review), the DX of human taste and odor information is not yet in the realization stage. Particularly, since there are at least 400,000 types of odor molecules and an infinite number of complex odors that are mixtures of these molecules, it has been considered extremely difficult to realize "human olfactory DX" by converting all odors perceived by human olfaction into digital data. In this review, we discuss the current status and future prospects of the development of "human olfactory DX", which we believe can be realized by utilizing odor sensors that employ the olfactory receptors (ORs) that support human olfaction as sensing molecules (i.e., human OR sensor).
Topics: Humans; Odorants; Receptors, Odorant; Smell; Nose; Tongue
PubMed: 37448013
DOI: 10.3390/s23136164 -
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 -
Appetite Nov 2023It is often suggested in the popular press that food chains deliberately introduce enticing product aromas into (and in the immediate vicinity of) their premises in... (Review)
Review
It is often suggested in the popular press that food chains deliberately introduce enticing product aromas into (and in the immediate vicinity of) their premises in order to attract customers. However, despite the widespread use of odours in the field of sensory marketing, laboratory research suggests that their effectiveness in modulating people's food behaviours depends on a range of contextual factors. Given the evidence that has been published to date, only under a subset of conditions is there likely to be a measurable effect of the presence of ambient odours on people's food attitudes and choices. This narrative historical review summarizes the various ways in which food odours appear to bias people's food preferences (appetite) and food choices (food consumption and purchase). Emphasis is placed on those experimental studies that have been designed to investigate how the characteristics of the olfactory stimuli (e.g., the congruency between the olfactory cues and the foods, intensity and duration of exposure to odours, and taste properties of odours) modulate the effects of olfactory cues on food behaviour. The review also explores the moderating roles of individual differences, such as dietary restraint, Body Mass Index (BMI), genetic and cultural differences in odour sensitivity and perception. Ultimately, following a review of empirical studies on food-related olfaction, current approaches in scent marketing are discussed and a research agenda is proposed to help encourage further studies on the effective application of scents in promoting healthy foods.
Topics: Humans; Smell; Taste; Food; Taste Perception; Odorants
PubMed: 37673129
DOI: 10.1016/j.appet.2023.107023 -
BMC Biology Dec 2023Olfactory sensory neurons detect odourants via multiple long cilia that protrude from their dendritic endings. The G protein-coupled receptor GPRC5C was identified as...
BACKGROUND
Olfactory sensory neurons detect odourants via multiple long cilia that protrude from their dendritic endings. The G protein-coupled receptor GPRC5C was identified as part of the olfactory ciliary membrane proteome, but its function and localization is unknown.
RESULTS
High-resolution confocal and electron microscopy revealed that GPRC5C is located at the base of sensory cilia in olfactory neurons, but not in primary cilia of immature neurons or stem cells. Additionally, GPRC5C localization in sensory cilia parallels cilia formation and follows the formation of the basal body. In closer examination, GPRC5C was found in the ciliary transition zone. GPRC5C deficiency altered the structure of sensory cilia and increased ciliary layer thickness. However, primary cilia were unaffected. Olfactory sensory neurons from Gprc5c-deficient mice exhibited altered localization of olfactory signalling cascade proteins, and of ciliary phosphatidylinositol-4,5-bisphosphat. Sensory neurons also exhibited increased neuronal activity as well as altered mitochondrial morphology, and knockout mice had an improved ability to detect food pellets based on smell.
CONCLUSIONS
Our study shows that GPRC5C regulates olfactory cilia composition and length, thereby controlling odour perception.
Topics: Animals; Mice; Cilia; Mice, Knockout; Odorants; Olfactory Receptor Neurons; Receptors, G-Protein-Coupled; Smell
PubMed: 38110903
DOI: 10.1186/s12915-023-01790-0 -
Comprehensive Reviews in Food Science... Nov 2023The impact of sugary foods on public health has contributed to the development of low-sugar and sugar-substituted products, and sugar reduction has become a major... (Review)
Review
The impact of sugary foods on public health has contributed to the development of low-sugar and sugar-substituted products, and sugar reduction has become a major challenge for the food industry. There is growing empirical evidence that odor can enhance the perception of sweetness without increasing the caloric load. This current review summarizes the researches on odor-induced sweetness enhancement published in recent years and discusses the mechanisms and influencing factors of odor-sweetness interactions. In addition, by combing existing studies, this paper also summarizes the research methods and strategies to investigate odor-induced sweetness enhancement. Finally, the feasibility of synergistic enhancement of sweetness through the superposition of odor with other senses (texture, visual, etc.) is also discussed and analyzed. In conclusion, odor-induced sweetness enhancement may present an alternative or complementary approach for developing foods with less sugar.
Topics: Odorants; Taste; Sweetening Agents; Sugars
PubMed: 37755237
DOI: 10.1111/1541-4337.13245 -
Proceedings of the National Academy of... Aug 2023Long-range olfactory search is an extremely difficult task in view of the sparsity of odor signals that are available to the searcher and the complex encoding of the...
Long-range olfactory search is an extremely difficult task in view of the sparsity of odor signals that are available to the searcher and the complex encoding of the information about the source location. Current algorithmic approaches typically require a continuous memory space, sometimes of large dimensionality, which may hamper their optimization and often obscure their interpretation. Here, we show how finite-state controllers with a small set of discrete memory states are expressive enough to display rich, time-extended behavioral modules that resemble the ones observed in living organisms. Finite-state controllers optimized for olfactory search have an immediate interpretation in terms of approximate clocks and coarse-grained spatial maps, suggesting connections with neural models of search behavior.
Topics: Smell; Odorants
PubMed: 37579168
DOI: 10.1073/pnas.2304230120