There is chemistry in social chemistry

Is androstadienone a human male pheromone? More research is needed

Androsta-4,16‑dien-3-one (androstadienone, AND), a steroid predominantly found in male secretions, has been associated with a variety of sex-specific effects on emotion, physiological states, cognition, and neural activity. An expanding body of literature has explored the influence of AND on human behavior and perception, leading to its frequent description as a "putative human sex pheromone." This article reviews the existing research on the physiological, cognitive, and neuroimaging effects of AND, critically assessing the evidence regarding its classification as a human sex pheromone. Additionally, it underscores the need for methodological standardization and rigor in future studies to establish clearer conclusions. Based on current evidence, the categorization of AND as a "human sex pheromone" remains inconclusive, highlighting the necessity for continued investigation. Future research directions are suggested to further elucidate AND's potential effects and applications.

Why dogs prefer zoomies to zoom and what it tells us about the importance of in-person meetings for learning and memory

As people commonly observe dog behaviors like the sudden bursts of physical movement colloquially known as "zoomies," and the canine penchant for sticking their nose out of car windows and for sniffing intently in dog parks, it is not surprising that people generally believe dogs learn and communicate by smell. While people generally discount their own olfactory sensitivity and the importance of smell overall, humans also learn and communicate by smell, in some cases even better than dogs. In this article, we discuss why this information exchange matters for learning and memory and why virtual meetings don't pass the sniff test.

Interoception, network physiology and the emergence of bodily self-awareness

The interplay between the brain and interoceptive signals is key in maintaining internal balance and orchestrating neural dynamics, encompassing influences on perceptual and self-awareness. Central to this interplay is the differentiation between the external world, others and the self, a cornerstone in the construction of bodily self-awareness. This review synthesizes physiological and behavioral evidence illustrating how interoceptive signals can mediate or influence bodily self-awareness, by encompassing interactions with various sensory modalities. To deepen our understanding of the basis of bodily self-awareness, we propose a network physiology perspective. This approach explores complex neural computations across multiple nodes, shifting the focus from localized areas to large-scale neural networks. It examines how these networks operate in parallel with and adapt to changes in visceral activities. Within this framework, we propose to investigate physiological factors that disrupt bodily self-awareness, emphasizing the impact of interoceptive pathway disruptions, offering insights across several clinical contexts. This integrative perspective not only can enhance the accuracy of mental health assessments but also paves the way for targeted interventions.

NEGR1 Modulates Mouse Affective Discrimination by Regulating Adult Olfactory Neurogenesis

Background

Affective recognition and sensory processing are impaired in people with autism. However, no mouse model of autism comanifesting these symptoms is available, thereby limiting the exploration of the relationship between affective recognition and sensory processing in autism and the molecular mechanisms involved.

Methods

With Negr1 -/- mice, we conducted the affective state discrimination test and an odor habituation/dishabituation test. Data were analyzed using the k-means clustering method. We also employed a whole-cell patch clamp and bromodeoxyuridine incorporation assay to investigate underlying mechanisms.

Results

When encountering mice exposed to restraint stress or chronic pain, wild-type mice discriminated between them by either approaching the stressed mouse or avoiding the painful mouse, whereas Negr1 -/- mice showed unbiased social interactions with them. Next, we demonstrated that both wild-type and Negr1 -/- mice used their olfaction for social interaction in the experimental context, but Negr1 -/- mice showed aberrant olfactory habituation and dishabituation against social odors. In electrophysiological studies, inhibitory inputs to the mitral cells in the olfactory bulb were increased in Negr1 -/- mice compared with wild-type mice, and subsequently their excitability was decreased. As a potential underlying mechanism, we found that adult neurogenesis in the subventricular zone was diminished in Negr1 -/- mice, which resulted in decreased integration of newly generated inhibitory neurons in the olfactory bulb.

Conclusions

NEGR1 contributes to mouse affective recognition, possibly by regulating olfactory neurogenesis and subsequent olfactory sensory processing. We propose a novel neurobiological mechanism of autism-related behaviors based on disrupted adult olfactory neurogenesis.

Nature and human well-being: The olfactory pathway

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.

Body odor samples from infants and post-pubertal children differ in their volatile profiles

Body odors change during development, and this change influences the interpersonal communication between parents and their children. The molecular basis for this chemical communication has not been elucidated yet. Here, we show by combining instrumental and sensory analyses that the qualitative odorant composition of body odor samples is similar in infants (0-3 years) and post-pubertal children (14-18 years). The post-pubertal samples are characterized by higher odor dilution factors for carboxylic acids and by the presence of 5α-androst-16-en-3-one and 5α-androst-16-en-3α-ol. In addition to the olfaction-guided approach, the compounds 6-methylhept-5-en-2-one (6MHO), geranyl acetone (GA) and squalene (SQ) were quantified. Both age groups have similar concentrations of 6MHO and GA, whereas post-pubertal children tend to have higher concentration of SQ. In conclusion, sexual maturation coincides with changes to body odor chemical composition. Whether those changes explain differences in parental olfactory perception needs to be determined in future studies with model odors.

Social odor choice buffers drug craving

Social interactions are rewarding and protective against substance use disorders, but it is unclear which specific aspect of the complex sensory social experience drives these effects. Here, we investigated the role of olfactory sensory experience on social interaction, social preference over cocaine, and cocaine craving in rats. First, we conducted bulbectomy on both male and female rats to evaluate the necessity of olfactory system experience on the acquisition and maintenance of volitional social interaction. Next, we assessed the effect of bulbectomy on rats given a choice between social interaction and cocaine. Finally, we evaluated the influence of olfactory sensory experience by training rats on volitional partner-associated odors, assessing their preference for partner odors over cocaine to achieve voluntary abstinence and assessing its effect on the incubation of cocaine craving. Bulbectomy impaired operant social interaction without affecting food and cocaine self-administration. Rats with intact olfactory systems preferred social interaction over cocaine, while rats with impaired olfactory sense showed a preference for cocaine. Providing access to a partner odor in a choice procedure led to cocaine abstinence, preventing incubation of cocaine craving, in contrast to forced abstinence or non-contingent exposure to cocaine and partner odors. Our data suggests the olfactory sensory experience is necessary and sufficient for volitional social reward. Furthermore, the active preference for partner odors over cocaine buffers drug craving. Based on these findings, translational research should explore the use of social sensory-based treatments utilizing odor-focused foundations for individuals with substance use disorders.

The absence of one's intimate partner promotes dyadic competition through enhanced interbrain synchronization between opponents

Competition is a common occurrence in life, but the influence of intimate relationships on people's competitiveness remains unknown. Grounded in Darwin's theory of sexual selection, this study utilized EEG hyperscanning technology to investigate the influence of the presence of romantic partners and the gender of competitors on the interbrain synchronization of female individuals during competitive contexts. The research results showed that in competitive interactions, there was a significant increase in Theta and Alpha frequency band activity between females and their competitors. Interbrain synchronization was strongest when their partners were not nearby and females competed with same gender competitors. The research results indicate that intimate companionship has an impact on the early alertness and late cognitive execution mechanisms of female individuals in competition, and due to intimate relationships, females pay more attention to same-gender competitors. This study demonstrates that the presence of intimate partners can affect a female's competitive state and brain synchronization with opponents of different genders, improving the theoretical explanation of intimate relationships and competitive interactions.

An electronic nose can identify humans by the smell of their ear

Terrestrial mammals identify conspecifics by body odor. Dogs can also identify humans by body odor, and in some instances, humans can identify other humans by body odor as well. Despite the potential for a powerful biometric tool, smell has not been systematically used for this purpose. A question arising in the application of smell to biometrics is which bodily odor source should we measure. Breath is an obvious candidate, but the associated humidity can challenge many sensing devices. The armpit is also a candidate source, but it is often doused in cosmetics. Here, we test the hypothesis that the ear may provide an effective source for odor-based biometrics. The inside of the ear has relatively constant humidity, cosmetics are not typically applied inside the ear, and critically, ears contain cerumen, a potent source of volatiles. We used an electronic nose to identify 12 individuals within and across days, using samples from the armpit, lower back, and ear. In an identification setting where chance was 8.33% (1 of 12), we found that we could identify a person by the smell of their ear within a day at up to ~87% accuracy (~10 of 12, binomial P < 10-5), and across days at up to ~22% accuracy (~3 of 12, binomial P < 0.012). We conclude that humans can indeed be identified from the smell of their ear, but the results did not imply a consistent advantage over other bodily odor sources.

Intrinsic and extrinsic factors affecting axillary odor variation. A comprehensive review

Humans produce odorous secretions from multiple body sites according to the microbiomic profile of each area and the types of secretory glands present. Because the axilla is an active, odor-producing region that mediates social communication via the sense of smell, this article focuses on the biological mechanisms underlying the creation of axillary odor, as well as the intrinsic and extrinsic factors likely to impact the odor and determine individual differences. The list of intrinsic factors discussed includes sex, age, ethnicity, emotions, and personality, and extrinsic factors include dietary choices, diseases, climate, and hygienic habits. In addition, we also draw attention to gaps in our understanding of each factor, including, for example, topical areas such as the effect of climate on body odor variation. Fundamental challenges and emerging research opportunities are further outlined in the discussion. Finally, we suggest guidelines and best practices based on the factors reviewed herein for preparatory protocols of sweat collection, data analysis, and interpretation.

Past, Present, and Future of Human Chemical Communication Research

Although chemical signaling is an essential mode of communication in most vertebrates, it has long been viewed as having negligible effects in humans. However, a growing body of evidence shows that the sense of smell affects human behavior in social contexts ranging from affiliation and parenting to disease avoidance and social threat. This article aims to (a) introduce research on human chemical communication in the historical context of the behavioral sciences; (b) provide a balanced overview of recent advances that describe individual differences in the emission of semiochemicals and the neural mechanisms underpinning their perception, that together demonstrate communicative function; and (c) propose directions for future research toward unraveling the molecular principles involved and understanding the variability in the generation, transmission, and reception of chemical signals in increasingly ecologically valid conditions. Achieving these goals will enable us to address some important societal challenges but are within reach only with the aid of genuinely interdisciplinary approaches.

Smells as Communication Pathways - why Emotions Pass through the Nose

For many species, the sense of smell is the most important sensory system for interacting with the environment and conspecifics. In contrast, the role of perception and communication of chemosensory information in humans has long been underestimated. The human sense of smell was considered less reliable, so that it was given less importance compared to visual and auditory sensory impressions. For some time now, a growing branch of research has been dealing with the role of the sense of sell in emotion and social communication, which is often only perceived subconsciously. This connection will be examine in more detail in this article. First, he basics regarding the structure and function of our olfactory system will be described for better understanding and classification. Then, with this background knowledge, the significance of olfaction for interpersonal communication and emotions will be discussed. Finally, we conclude that people suffering from olfactory disorders have specific impairments in their quality of life.