Odor Perception Research Articles

Sex differences in olfactory behavior and neurophysiology in Long Evans Rats.

In many species, olfactory abilities in females are more acute than those in males. Studies in humans show that women have lower olfactory thresholds and are better able to discriminate and identify odors than men. In mice, odorants elicit faster activation from a larger number of olfactory bulb glomeruli in females than males. Our study explores sex differences in olfaction in Long Evans rats from a behavioral and electrophysiological perspective. Local field potentials (LFPs) in the olfactory bulb (OB) represent the coordinated activity of bulbar neurons. Olfactory gamma (65-120 Hz) and beta (15-30 Hz) oscillations have been functionally linked to odor perception. Spontaneous and odor-evoked OB LFPs were recorded from awake rats at the same time for 12 days. Odors used included urine of both sexes and monomolecular odorants characterized previously for correlation of volatility with behavior and OB oscillations. Sampling duration, baseline gamma and beta power, and odor-elicited beta and gamma power were analyzed. We find that females sample odorants for a shorter duration than males (just over 1s difference). While baseline gamma and beta power do not show significant differences between the two sexes, odor-elicited gamma and beta power in females is significantly lower than in males. Neither sampling duration nor beta and gamma power in females varied systematically with day of estrus. We further verify that variance of these behavioral and physiological measures is not different across sexes, adding to growing evidence that researchers need not be concerned about often-claimed additional variance in female subjects.

The experience of using a sociological survey to assess the perception of odour and noise by the population

Introduction. Sensory environmental factors, such as the odour of emissions from various enterprises and noise, are becoming increasingly relevant in connection with the development of industry and urban highways. This is due to their impact on the psychosomatic health of people living in areas where sources of odour and noise pollution of atmospheric air are located. The aim of the study – to evaluate the relationship between the perception of odours present in atmospheric air and noise with the subjective assessment of health status in the population of an industrial city. Materials and methods. The data were obtained as a result of a survey of seven hundred nineteen residents of the city with a population of about 90 thousand people, conducted over 2022. The questionnaire included questions to assess the frequency, intensity of perception of odours and noise, as well as the degree of annoyance by these factors. To study the health status of the respondents, it was suggested to note their health complaints. Results. The study identified symptoms associated with odour and noise perception such as headaches, dizziness, nausea, annoyance, and others. These symptoms are similar for odour and noise perception. Limitations of the study are related to a relatively small sample of interviewees, and a limited number of questions that allow assessing the relationship between the effects of the studied factors and the public health as well as the lack of data characterizing the full composition of emissions from all enterprises in the city. Conclusion. Factors of different nature – atmospheric odours and noise, affecting various analyzers and triggering biological processes in the body, lead to similar effects through the induction of annoyance. Stress caused by annoyance by odours and noise causes a number of symptoms and diseases and, in turn, affects the work of analyzers responsible for the perception of environmental factors.

Possible Mechanisms of the Influence of Oxytocin and Vazopressin on Perception and Memory of Odors and on Social Behavior

A possible mechanism is proposed for the influence of oxytocin and vasopressin on the functioning of the neural network in the CNS, in which olfactory information is processed and stored, and which plays an important role in social behavior. The effect of these neuropeptides on postsynaptic receptors associated with Gq/11 proteins contributes to the induction of LTP of the efficacy of excitatory synaptic inputs to the main projection cells and to inhibitory interneurons in the prefrontal cortex, hippocampus, piriform cortex, anterior olfactory nucleus, olfactory bulb and nucleus accumbens, including the olfactory tubercle. As a result of disynaptic inhibition in each of the structures, the signal-to-noise ratio is improved and the transmission of strong signals through projection neurons to their target cells is facilitated. Due to the fact, that oxytocin promotes the release of dopamine by the neurons of the ventral tegmental area, the conditions for processing and memorizing olfactory information in the interconnected olfactory and hippocampal neural networks, including cortical and subcortical structures, are improved, and attention is also included in this processing. Long-term modification of the effectiveness of interneuronal connections in these networks under the influence of oxytocin and dopamine contributes to the formation and stabilization of contrasting neuronal representation of odors formed in cortical areas. Orientation of attention increases the significance of socially important olfactory stimuli and improves the conditions for the functioning of the reinforcement system necessary for adequate social behavior. Taking into account the known data on the correlation between social behavior and the density of oxytocin and vasopressin receptors on neurons of different structures, understanding the mechanisms of the influence of these neuropeptides on the functioning of the olfactory system can be useful for finding ways to correct behavior if necessary.

Smellscape perceptions in hospital waiting areas: influential factors and semantic dimensions

ABSTRACT Smell can have significant physical and psychological impacts on space users, especially in hospital waiting areas where smells are complex, and users are vulnerable. Understanding how smellscapes affect patients and their companions may help improve space users’ interactions with such environments. This study aimed to identify odour types in hospital waiting areas, their influential factors, impacts on odour perception, and key aspects to characterise and evaluate the smellscape in typical waiting areas. An internet survey and field investigations were conducted in China, and subsequent data were analysed. Results showed that 1) nine primary odours were identified in hospital waiting areas, 2) people have negative but relatively tolerant attitudes towards the odours, 3) several demographic and environmental factors impact people’s odour perception and evaluation, 4) the evaluation of smellscapes is influenced by the overall environmental judgement, with better odour experience reported in smaller and relatively closed waiting areas, and 5) three dimensions – health, emotion, and quality – were identified to characterise the smellscape. This study highlights the importance of smellscape design and management in healthcare environments, considering odour types, individual differences, spatial features, and other senses to systematically improve the smellscape.

Transcriptional regulation of olfactory receptor OR51B5 by the TBX6.

Olfactory receptors (ORs) are G protein-coupled receptors primarily expressed in olfactory tissue, facilitating the perception of odors. Interestingly, they have also been detected in non-olfactory tissues such as the skin, where they regulate processes like collagen synthesis. This study aimed to analyze the promoter of the OR family 51 subfamily B member 5 (OR51B5) and identify the transcription factors that bind to it to understand the potential regulatory mechanisms for OR51B5 expression. We examined the promoter region spanning 2,000 base pairs upstream of the transcription start site and conducted a deletion analysis, revealing that the core promoter encompasses the region from -153 to -111 base pairs. A luciferase assay using various candidate transcription factors showed that the overexpression or knockdown of T-Box Transcription Factor 6 (TBX6) significantly regulated OR51B5 promoter activity, while other candidate transcription factors had no significant effect. Additionally, we validated TBX6 binding to the OR51B5 promoter using site-directed mutation and electrophoretic mobility shift assays. This study is the first to uncover the role of TBX transcription factors in regulating OR gene expression in mammals, which may have implications for treating related disorders.

An overview on olfaction in the biological, analytical, computational, and machine learning fields.

Recently, the comprehension of odor perception has advanced, unveiling the mysteries of the molecular receptors within the nasal passages and the intricate mechanisms governing signal transmission between these receptors, the olfactory bulb, and the brain. This review provides a comprehensive panorama of odors, encompassing various topics ranging from the structural and molecular underpinnings of odorous substances to the physiological intricacies of olfactory perception. It extends to elucidate the analytical methods used for their identification and explores the frontiers of computational methodologies.

Humans without a sense of smell breathe differently

Olfaction may play a restricted role in human behavior, yet paradoxically, its absence in anosmia is associated with diverse deleterious outcomes, culminating in reduced life expectancy. The mammalian nose serves two purposes: olfaction and breathing. Because respiratory patterns are impacted by odors, we hypothesized that nasal respiratory airflow may be altered in anosmia. We apply a wearable device that precisely logs nasal airflow for 24-hour-long sessions in participants with isolated congenital anosmia and controls. We observe significantly altered patterns of respiratory nasal airflow in anosmia in wake and in sleep. These differences allow classification of anosmia at 83% accuracy using the respiratory trace alone. Patterns of respiratory airflow have pronounced impact on health, emotion and cognition. We therefore suggest that a portion of the deleterious outcomes associated with anosmia may be attributed to altered patterns of respiratory nasal airflow rather than a direct result of lost odor perception per se.

El hedor en la Nueva España: sensibilidad olfativa ante el fenómeno de la otredad (siglo xvi)

Objective/Context: This article aims to analyze the olfactory descriptions of blood, the Indigenous, and their idols in sacrificial narratives in four early modern American sources (sixteenth century): Letters of Relation by Hernán Cortés, The Vision of the Defeated by Miguel León Portilla, General History of the Things of New Spain by Bernardino de Sahagún, and the inquisitorial process of the cacique of Texcoco. Methodology: Cultural history as a methodology allows examining the olfactory perception of stench as part of the narration of the body and Indigenous religious rituals during the Conquest. This approach helps to identify the discourses or representations about the Indigenous in the established period and to outline an interpretative matrix that combines the analysis of cultural elements with odorant perceptions. Originality: The study’s relevance lies in analyzing how odor affects the recognition and dominance of the Indigenous society. Odorant perception reveals the plurality of olfactory sensitivities as part of social relations. In this way, we study how the stench or the olfactory disdain toward the Indigenous sacrificial practices described in the chronicles contributed to the moral and sensory classification that justified the inequality between peninsular Spaniards and Indigenous people. Conclusions: Stench and fragrance can be read as control devices that legitimize the violence of the Conquest and the various debates surrounding American bodily aesthetics.

Behavioral separation of liking and wanting in response to olfactory and visual food cues

In real-world settings, food rewards are processed in parallel across several sensory modalities, but paradigms that compare contributions of different modalities are lacking. While odor perception in particular is frequently implicated in appetite regulation, the mechanisms by which food odors differentially evoke experiences of wanting and liking remain poorly understood. This study addressed this gap by dissociating liking from wanting responses for olfactory stimuli, and establishing commonalities and differences relative to the visual modality. In two separate experiments, participants (n1 = 37, n2 = 43) rated content-matched batteries of odors and pictures, respectively, for their ability to elicit pleasure (liking) and desire to eat (wanting). A third experiment (n3 = 39) utilized a combined olfactory-visual paradigm to test the separation of these dimensions in a multisensory context. Our results show that participants differentiated clearly and reliably between liking and wanting for both odors and pictures, as demonstrated by a high difference score between the two in non-food (high liking, low wanting), but not in food (both high) or disgusting stimuli (both low), and high within-session retest reliability. Higher variability for olfactory relative to visual assessments was observed and likely reflects well-established difficulties with odor object identification. Taken together, our study demonstrates that olfactory stimuli can be used in experimental settings to evoke separable experiences of liking and wanting for food and non-food stimuli. Manipulating these components independently across sensory modalities in experimental studies could generate novel insights into how olfactory and visual cues differentially contribute to anticipatory and consummatory food reward processing, in healthy and disordered eating.

Changes in weight secondary to improved odor perception in chronic rhinosinusitis with nasal polyps' patients treated with Dupilumab.

The advent of biologic therapies, notably Dupilumab, has transformed therapeutic approaches to nasal polyposis. This retrospective multicentric study aimed to investigate weight changes in CRSwNP patients undergoing Dupilumab treatment and explore potential correlations with olfactory improvement. Ninety-six patients with CRSwNP were followed for at least 12 months, with assessments including BMI (Body Mass Index), olfactory function, and disease severity. Significant increases in BMI and olfactory perception were observed after 1 year of Dupilumab treatment (p < .001). Subgroup analysis showed that patients with hyposmia and normosmia at T12 (1-year follow up) experienced significant weight gain (p < .001) alongside improved olfaction (both p < .001). Conversely, patients with anosmia after 1 year of therapy and also patients with stable or worsened olfaction did not show significant BMI changes (respectively p = .201 and p = .107). While these findings suggest a correlation between olfactory improvement and weight gain/BMI, factors like improved nasal airflow and corticosteroid cessation under Dupilumab treatment may also influence weight in CRPwNP patients. The study highlights the need for further research to elucidate the causal relationship and long-term implications of Dupilumab-induced olfactory improvement on weight regulation.

Multi-channel portable odor delivery device for self-administered and rapid smell testing

To improve our understanding of the perception of odors, researchers are often required to undertake experimental procedures with users exposed to multiple odors in a variety of settings, including to diagnose smell loss in clinics and care homes. Existing smell tests are typically administered using multiple sniffing pens, manually presented to patients by a highly specialized nurse using a time-consuming and complex testing paradigm. Automated odor delivery devices, such as olfactometer systems, exist but are expensive, bulky and typically lab based, making them difficult to use for on the ground odor delivery. Here we have developed a portable, affordable, odor delivery device that can deliver 24 odors through individual channels with high temporal precision and without cross-contamination. The device allows for the rapid, flexible sequencing of odors via digital control using a mobile application and has been experimentally validated in the lab, as well as tested on patients. The design provides several advantages for investigating olfactory perception and offers the possibility that users can one day self-administer smell tests in a range of settings, including at home, allowing smell healthcare services to evolve and become part of a routine practice and self-care culture.

Single-neuron representations of odours in the human brain

Olfaction is a fundamental sensory modality that guides animal and human behaviour1,2. However, the underlying neural processes of human olfaction are still poorly understood at the fundamental—that is, the single-neuron—level. Here we report recordings of single-neuron activity in the piriform cortex and medial temporal lobe in awake humans performing an odour rating and identification task. We identified odour-modulated neurons within the piriform cortex, amygdala, entorhinal cortex and hippocampus. In each of these regions, neuronal firing accurately encodes odour identity. Notably, repeated odour presentations reduce response firing rates, demonstrating central repetition suppression and habituation. Different medial temporal lobe regions have distinct roles in odour processing, with amygdala neurons encoding subjective odour valence, and hippocampal neurons predicting behavioural odour identification performance. Whereas piriform neurons preferably encode chemical odour identity, hippocampal activity reflects subjective odour perception. Critically, we identify that piriform cortex neurons reliably encode odour-related images, supporting a multimodal role of the human piriform cortex. We also observe marked cross-modal coding of both odours and images, especially in the amygdala and piriform cortex. Moreover, we identify neurons that respond to semantically coherent odour and image information, demonstrating conceptual coding schemes in olfaction. Our results bridge the long-standing gap between animal models and non-invasive human studies and advance our understanding of odour processing in the human brain by identifying neuronal odour-coding principles, regional functional differences and cross-modal integration.

Effect of Intranasal Insulin on Olfactory Recovery in Patients with Anosmia .

Olfactory dysfunction, defined as either a complete or partial impairment of smell, is a common condition that may substantially affect a person’s quality of life and is frequently difficult to treat. Physical activity, heredity, nutrition, smoking, head trauma, medical treatments, and virus exposure all influence one’s capacity to smell. Hyposmia or anosmia, or loss of smell, affects 3% to 20% of the population. Intranasal insulin can improve cognitive performance, reduce food intake, and boost olfactory thresholds in healthy individuals. As people age, they are more likely to experience olfactory dysfunction, which may be affected by a variety of reasons, such as acute and chronic sino-nasal illness, upper respiratory infections, toxic chemical exposure, and degenerative diseases. About ten percent of those over 65 develop olfactory impairment, which can range from mild loss to total anosmia. Insulin resistance in the central nervous system has been linked to conditions like type II diabetes, Alzheimer’s disease, obesity, and poor odor identification. Reduced odor perception may contribute to reduced olfactory function in anosmic patients.

Medidas de control de olores para un tanque homogeneizador de una planta de tratamiento de aguas residuales en Costa Rica

[Objective] This study aimed to evaluate the short-term response of four different odor control measures in a homogenization tank of a university Wastewater Treatment Plant (WWTP). [Methodology] The following were implemented: aeration, adding lime, adding iron sulfate, and adding the commercial product BiOWiSH® Odor over four hydraulic retention times. The effluent and the unit were monitored during each period, using a baseline to compare the measures. Hydrogen potential, oxidation-reduction potential, dissolved oxygen, and dissolved sulfide concentration were measured in triplicate every 30 minutes. An odor perception survey was administered to WWTP visitors to evaluate intensity, offensiveness, and character (15 surveys per monitoring period). Differences were determined between control measures and the baseline using Student’s t-tests (quantitative data) and Mood’s median tests (qualitative data). Minitab 2019 was used with a 95% confidence level. [Results] All control measures significantly reduced the dissolved sulfide concentration in the unit. Aeration prevented oxygen depletion, reductive regime, and acid fermentation, which favored the oxidation of odorants. Aeration was also the only studied control measure that reduced odor intensity and offensiveness. [Conclusions] Applying aeration changed unit behavior and odor perception, which confirms its effectiveness, while adding iron sulfate, lime, and BiOWiSH® did not significantly change odor perception.

Beyond Distracted Eating: Cognitive Distraction Downregulates Odor Pleasantness and Interacts with Weight Status.

Considering the widespread issue of distracted eating, our study investigates how cognitive distraction influences the sensory perception of food-related odors among individuals with varying weight statuses. We conducted an exploratory, randomized, and cross-sectional experimental study, using the Tetris game to simulate real-life cognitive distraction, incorporating two distraction levels (low and high) and presenting five distinct odors. A total of 59 participants, categorized into a lean (n = 30) and overweight/obese group (n = 29) based on their body mass index (BMI), received odor stimuli while playing Tetris at low and high difficulty, corresponding to low and high distraction levels, respectively. Participants subsequently rated odor intensity and pleasantness under the two cognitive distraction conditions. Respiratory movements were monitored to ensure accurate olfactory stimulation. Our findings revealed no significant difference in odor intensity ratings across distraction levels (p = 0.903). However, there was a significant reduction in odor pleasantness under high cognitive distraction (p = 0.007), more pronounced in lean participants compared to those with an overweight status (p = 0.035). Additionally, an interaction between gender and cognitive distraction effects was observed in odor pleasantness perception. The differential effects of distraction across weight-status groups and genders are discussed in the context of hedonic motivation and compensatory mechanisms. This study sheds light onto the sensory mechanisms underlying distracted eating and could inform more personalized strategies for promoting healthier eating habits in a world dominated by distractions.

The Context Matters: Women's Experiences of Their Partner's Odor in Intimate and Sexual Encounters.

Research shows that male body odor plays an important role in women's mate choice and that olfactory abilities are associated with women's sexual functioning. What remains unclear is what types of partner's odor actually shape women's experience during intimate activities. This study therefore explored women's experience associated with the partner's various odors and investigated how they affect women's intimate and sexual encounters. We performed semi-structured individual interviews with 20 single women and 20 women in a long-term relationship. Thematic analysis revealed four key natural odor types of the partner: body odor, sweat, genital odor, and semen odor. Further, we have identified three main types of fragrance odor (cologne, shower gel, and laundry agents) and investigated their perception in both intimate (hugging, kissing, cuddling, lying side by side) and sexual (intercourse, oral sex, ejaculation) contexts. Both partner's natural odor and fragrance affected women's emotional state (ranging from pleasant to unpleasant) and behavioral response (ranging from approach to avoidance of partner). Women's odor perception was frequently context-dependent, so that even mostly negatively perceived odors (e.g., semen, genital odor) were often accepted as part of sexual encounter. Finally, women's perception was negatively modified by partner's specific sweat (after workday, workout, or when the partner is ill) during intimate encounters. Our results highlight the complexity and interindividual variability of partner's odor perception.

Human perception of Parkinson's disease body odor in comparison to the volatile organic compounds of Parkinson's disease

IntroductionPatients with Parkinson's Disease (PD) have a distinctive body odor, which was first described by a patient's wife as musky and strong. Later analysis of sebum of patients with PD revealed four volatile organic compounds (VOC) (perillic aldehyde, hippuric acid, eicosane, octadecanal), that differed from healthy subjects, and the patient's wife confirmed that three of them smelled like patients with PD. However, it is unclear whether other people can also perceive this PD body odor and whether it can be artificially recreated. Hence, we aimed to systematically assess whether young women can perceive the PD body odor and whether they can discriminate between the PD body odor and the “artificial PD odor” composed of the four VOCs mentioned above. MethodsT-shirts were collected from 19 people with idiopathic PD and 15 age- and gender-matched healthy participants to represent the PD body odor and the healthy body odor, respectively. The four VOCs were diluted in 1,2-propanediol to prepare the artificial PD body odor. Body odors were rated by 26 young women. ResultsPD body odor was perceived as more musty, strong, smelly, and unpleasant compared to healthy and artificial PD body odor. Furthermore, around 80 % of women were able to discriminate PD body odor from artificial PD body odor. ConclusionOverall, this study confirmed a distinctive body odor quality of patients with PD, which can be perceived by young women. However, the four VOCs, composing the artificial PD body odor, were insufficient to reproduce the body odor from PD patients.

Revealing the dual impact of VOCs on recycled rubber workers: Health risk and odor perception

Volatile organic compounds (VOCs) pose potential hazards to human health and contribute significantly to odor pollution. This study examined VOC emissions from a representative recycled rubber industry, evaluating the occupational health risks for frontline workers in various workshops. Variables such as gender and workshop-specific concentration variations were considered using Monte Carlo simulation methods. Employees in the five production workshops and office areas face noncarcinogenic health risks with hazard indices (HIs) greater than 1, with the rubber compounding phase presenting the highest risk. Acetaldehyde is identified as the primary noncarcinogenic health risk substance, with hazard quotient (HQ) values exceeding 1 in all workshops. Carcinogenic health risks vary by area, with the highest risks found in compounding and refining workshops. Formaldehyde poses the greatest risk in rubber grinding workshops and offices, with cumulative weights exceeding unacceptable levels of M80.58 % and W77.56 % in grinding and M94.98 % and W92.24 % in the office. Male workers face 4–7 % greater noncarcinogenic VOC health risks than females and 5–14 % greater carcinogenic risks from individual VOCs, increasing their susceptibility to health risks caused by VOCs. Additionally, our analysis of odor identification and intensity classification revealed that 53 VOCs are capable of causing odor pollution, with several substances reaching odor levels of 2 or higher. The predominant perceived odors, as reflected in the odor wheel, include categories such as "solvent/aromatic" and "sweet/fruit," with aldehydes being the primary odor-causing substances. In summary, emissions of VOCs from rubber industrial processes not only pose substantial health risks to workers but also contribute significantly to odor pollution. Consequently, enterprises must prioritize optimizing workplace conditions to ensure the occupational health and well-being of their employees.

Boosting the odour perception of trace compounds exploiting three-dimensional GC-O with MS/FID simultaneous detection

ABSTRACT The study describes the effectiveness of a 3D GC system coupled with olfactometric detection and simultaneous MS and FID (3DGC-O-MS/FID) to improve the detection of odorants. Mega-bore columns were used to ensure a sample capacity able to enhance the odour perception. The heart-cut approach allowed to overcome the low efficiency of wide-bore columns, granting to purify enriched target fractions before olfactometry detection. After the third GC dimension, the isolated target peaks were eluted to the olfactometric port allowing the odour to last multiple seconds, making the panelist’s perception easier and more comfortable. The simultaneous FID/MS detection after the third GC dimension allowed to match specific odours to target molecules and their concentration in the sample. The 3DGC-O-MS/FID system boosts odour perception of trace components compared to conventional GC-O approaches. A reduced detection threshold of mg/kg levels was obtained compared to the mg/kg levels typical of monodimensional GC-O.

Smell perception in virtual spacecraft? A ground‐based approach to sensory data collection

SummaryThe study explored context‐driven food odour perception with links to chemical profiling of flavour compounds. Participants rated the intensity of three food odours (vanilla, almond, lemon) in a Neutral context and VR simulation of the International Space Station. The study involved 54 adults aged 18–39 years with no history of motion sickness and/or vertigo. The VR context demonstrated significantly higher intensity ratings for vanilla (P = 0.009) and almond (P &lt; 0.001) odours, compared to the Neutral context. Clustering based on perceived intensity identified that those less sensitive to the odours perceived significantly stronger almond odour in VR (P = 0.011). Gas chromatography–mass spectrometry analysis linked these findings to benzaldehyde, a common compound in both vanilla and almond odours. Therefore, a VR space context may impact odour perception, subject to their volatile composition and individual sensitivity. This underscores VR's potential as a ground‐based analogue for future sensory research, translating across similar settings beyond the space context.