5,211 research outputs found

    Odor sampling strategies in mice with genetically altered olfactory responses

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    Peripheral sensory cells and the central neuronal circuits that monitor environmental changes to drive behaviors should be adapted to match the behaviorally relevant kinetics of incoming stimuli, be it the detection of sound frequencies, the speed of moving objects or local temperature changes. Detection of odorants begins with the activation of olfactory receptor neurons in the nasal cavity following inhalation of air and airborne odorants carried therein. Thus, olfactory receptor neurons are stimulated in a rhythmic and repeated fashion that is determined by the breathing or sniffing frequency that can be controlled and altered by the animal. This raises the question of how the response kinetics of olfactory receptor neurons are matched to the imposed stimulation frequency and if, vice versa, the kinetics of olfactory receptor neuron responses determine the sniffing frequency. We addressed this question by using a mouse model that lacks the K+-dependent Na+/Ca2+ exchanger 4 (NCKX4), which results in markedly slowed response termination of olfactory receptor neuron responses and hence changes the temporal response kinetics of these neurons. We monitored sniffing behaviors of freely moving wildtype and NCKX4 knockout mice while they performed olfactory Go/NoGo discrimination tasks. Knockout mice performed with similar or, surprisingly, better accuracy compared to wildtype mice, but chose, depending on the task, different odorant sampling durations depending on the behavioral demands of the odorant identification task. Similarly, depending on the demands of the behavioral task, knockout mice displayed a lower basal breathing frequency prior to odorant sampling, a possible mechanism to increase the dynamic range for changes in sniffing frequency during odorant sampling. Overall, changes in sniffing behavior between wildtype and NCKX4 knockout mice were subtle, suggesting that, at least for the particular odorant-driven task we used, slowed response termination of the odorant-induced receptor neuron response either has a limited detrimental effect on odorant-driven behavior or mice are able to compensate via an as yet unknown mechanism

    Respiratory influences on pupil size dynamics and visual recognition memory

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    Breathing, a fundamental rhythm of life, has traditionally been associated with the exchange of oxygen and carbon dioxide. However, recent research in both animal models and humans has unveiled additional roles of respiration in modulating cortical neuronal activity, influencing sensory, motor, emotional, and cognitive processes. This dissertation aims to explore the impact of respiration on pupil size dynamics and visual recognition memory in humans. In Study I, we synthesized the research conducted on respiratory influences on pupil size dynamics in humans by conducting a systematic literature review. We discovered that the evidence for respiratory influences on pupil size dynamics in humans is less solid and extensive than previously believed. After more than 50 years of research, only 12 studies have directly investigated this topic. Not only was the underlying evidence for an effect of breathing phase, depth, and rate on pupil size dynamics weak, but the influence of breathing route (oral or nasal breathing) had not been investigated at all. In Study II, we conducted an experimental study to answer the outstanding questions identified in Study I. We collected pupil size data from participants during periods of rest while they breathed through their nose and mouth, on separate occasions. We demonstrated small but significant effects of breathing phase on pupil size and a spurious correlation and phase synchronization between the breathing and the pupil signal that is largely driven by breathing rate. After accounting for this spurious correlation and phase synchronization, we show that a small but significant interaction between the breathing and the pupil signal remains. Importantly, we show that, contrary to common belief, pupil size does not increase during inhalation, but rather during exhalation. Furthermore, we did not find any changes in pupil size in the time around inhalation and exhalation, and our results were not affected by the breathing route. In conclusion, we confirmed the influence of breathing on pupil size dynamics, while uncovering a more complex and intricate relationship than previously conceived. In Study III, we investigated the influence of breathing phase and breathing route on performance in a visual recognition memory task with a within-subject design and with stimuli presentation phase-locked to the inhalation or exhalation onset. We show that neither breathing phase nor breathing route affect memory performance. However, we did find an effect of breathing phase on response bias, with participants using a more conservative response bias during exhalation. Furthermore, we found that breathing route and breathing phase shape the Late Parietal Effect (LPE), but not the Frontal Negative Component (FN400), amplitude during encoding. Additionally, during recognition, both the LPE and FN400 component amplitudes were not, or only to a small extent, affected by breathing route and phase. While we demonstrated that breathing does not shape visual recognition memory performance, we also showed that breathing influences brain activity related to memory functions. Therefore, we highlight the importance of further research to elucidate the extent of respiratory influence on perception, cognition, and behavior. In Study IV, we further investigated the impact of breathing on visual memory performance by investigating the effects of nasal breathing phase on memory of repeated images presented in a rapid serial visual presentation (RSVP) task. In two separate, high-powered experiments, we did not find an effect of breathing phase on task performance. An exploratory analysis in the first experiment discovered a potential performance increase for stimuli presented approximately one second after inhalation. However, this was not replicated in the second, larger, and pre-registered study. Thus, we find no effect of breathing phase on performance in this RSVP task and urge for caution regarding the notion that visual memory is broadly affected by the breathing phase. Finally, in Study V, we investigated whether oral hormonal contraceptives (OC) affect chemosensory sensitivity and perception. Whereas previous research focused nearly exclusively on olfaction, we expanded this to also study the taste and trigeminal sense. Making use of Bayesian statistics, we evaluated the performance differences between a group of women taking OC, and a control group of normal cycling women. Our results indicated that the use of OC does not affect odor, trigeminal, or taste detection thresholds. Furthermore, neither odor nor taste perception were affected, with Bayes factors weighing the evidence in favor of the null hypothesis. We therefore conclude it to be unlikely that OC affect chemosensory perception to a degree that is of behavioral relevance. Collectively, this doctoral thesis challenges prevailing myths while paving the way for a more intricate understanding of the relationship between respiration and pupil size, and perceptual and cognitive processes. Importantly, it underscores the importance of implementing rigorous methodological paradigms in future research

    Indoor Air Pollutants and the Future Perspectives for Living Space Design

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    This study presents an overview on the indoor air pollutants and their implications in the living space design-related strategy implementation. Not only the buildings but also the cabins of diverse traveling vehicles (busses, trains, cars, spacecrafts, submarines, etc.) are envisaged in this regard. Overall, in the smart eco-efficient built environment, such indoor spaces should ensure an adequate indoor air quality (IAQ), along with accomplishing the performance for other key components such as durability, energy saving, aesthetical architecture, etc. General aspects on indoor air quality and indoor air pollution, IAQ monitoring, and remediation strategies, as well as the main types of indoor pollutants and their effects upon human health, are highlighted

    Olfactory Inputs Modulate Respiration-Related Activity In The Prefrontal Cortex And Fear Behavior

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    Voluntary control of respiration, especially via rhythmic nasal breathing, alleviates negative feelings such as fear and is used clinically to manage certain types of panic attacks. However, the neural substrates that link nasal breathing to fear circuits remains unknown. Here we show that during conditioned fear-induced freezing behavior, mice breathe at a steady rate (~4 Hz) which is strongly correlated with a predominant 4 Hz oscillation observed in the olfactory bulb and the prelimbic prefrontal cortex (plPFC), a structure critical for the expression of conditioned fear behaviors. We demonstrate anatomical and functional connectivity between the olfactory pathway and plPFC via circuit tracing and optogenetic approaches. Disrupting olfactory inputs significantly reduces the 4 Hz oscillation in the plPFC suggesting that respiration-related signals from the olfactory system play a role in entraining this fear-related signal. Surprisingly, we find that without olfactory inputs, freezing times are significantly prolonged. Collectively, our results indicate that olfactory inputs modulate rhythmic activity in fear circuits and suggest a neural pathway that may underlie the behavioral benefits of respiration-entrained olfactory signals

    Olfactory object recognition, segmentation, adaptation, target seeking, and discrimination by the network of the olfactory bulb and cortex: computational model and experimental data

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    Mammals are poor at individuating the separate components that comprise odor mixtures, but not when components enter environment serially and when there is top-down expectation. Li proposed in 1990 an odor segmentation mechanism using the centrifugal feedback from the olfactory cortex to the olfactory bulb. This feedback suppresses the bulbar responses to the ongoing and already recognized odors so that a subsequent addition of a foreground odor can be singled out for recognition. Additionally, the feedback can depend on context so as to, for example, enhance sensitivity to a target odor or improve discrimination between similar odors. I review experimental data that have since emerged in relation to the computational predictions and implications, and suggest experiments to test the model further

    Guide to industrial respiratory protection

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    "A guide was presented for providing users of respiratory protective equipment with a single source of pertinent information. Selection, use, and maintenance of respiratory protective devices available in 1987 were covered. Topics included types of respirators (respiratory inlet coverings, air purifying respirators, and atmosphere supplying respirators); respirator selection (based on regulatory requirements, general selection information, NIOSH respirator decision logic, and NIOSH Certified Equipment List); use of respirators according to Federal regulatory requirements; responsibility of employer and employee in a respiratory protection program; elements of a program (administration and components of the total program); respirator use under special conditions (facial hair, eye glasses, contact lenses, facial deformation, communication, dangerous atmospheres, low and high temperatures, and physiological response to respirator use); and new developments at NIOSH concerning respiratory physiology, filtration mechanics, sorption technology, quantitative respirator efficiency testing, certification of new types of respirators, and NIOSH respirator problem investigation. Appendices provided a sample respirator program, fit testing procedures, selected NIOSH respirator user notices, sample Mine Safety and Health Administration/NIOSH approval labels, respirator decision logic, and breathing air systems for use with pressure demand supplied air respirators in asbestos (1332214) removal." - NIOSHTIC-2Spine title: Guide to industrial respiratory protection.At head of title: A NIOSH technical guide...Author of previous edition: John A. Pritchard. Shipping list no.: 88-5-P."September 1, 1987"Also available via the World Wide Web.Bibliography: p. 131-133

    Body odors (even when masked) make you more emotional: behavioral and neural insights

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    Morality evolved within specific social contexts that are argued to shape moral choices. In turn, moral choices are hypothesized to be affected by body odors as they powerfully convey socially-relevant information. We thus investigated the neural underpinnings of the possible body odors effect on the participants\u2019 decisions. In an fMRI study we presented to healthy individuals 64 moral dilemmas divided in incongruent (real) and congruent (fake) moral dilemmas, using different types of harm (intentional: instrumental dilemmas, or inadvertent: accidental dilemmas). Participants were required to choose deontological or utilitarian actions under the exposure to a neutral fragrance (masker) or body odors concealed by the same masker (masked body odor). Smelling the masked body odor while processing incongruent (not congruent) dilemmas activates the supramarginal gyrus, consistent with an increase in prosocial attitude. When processing accidental (not instrumental) dilemmas, smelling the masked body odor activates the angular gyrus, an area associated with the processing of people\u2019s presence, supporting the hypothesis that body odors enhance the saliency of the social context in moral scenarios. These results suggest that masked body odors can influence moral choices by increasing the emotional experience during the decision process, and further explain how sensory unconscious biases affect human behavior

    The roles of the main and accessory olfactory systems in the detection of social odors in mice

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    Our understanding of olfaction has been built on the study of monomolecular (pure) odors, which are easily obtained and well characterized chemically. For most species social odors have far greater biological relevance than typical monomolecular odors, but much less is known about the neural circuits that process them. Three studies were conducted to further explore the neural pathways that process social odors in mice. In Study 1, a Go-No-Go olfactory discrimination task was used to ask whether social odors are more salient stimuli than non-social odors in males and females under different hormonal conditions. Performance (percent correct) was greater in males than females, and poorer in subjects without circulating gonadal hormones when mice were required to discriminate between two social odors (male versus female urine), but not when non-social odors (banana versus peppermint) were used. This suggests that social odors are more salient stimuli than non-social odors but only when gonadal hormones are present. The piriform cortex (PC) is the primary cortical target for volatile odors processed by the main olfactory system (MOS); whether the PC responds to social odor volatiles is not known. In Study 2 I recorded extracellularly from PC pyramidal neurons before and during exposure to urinary volatiles or amyl acetate (banana) in anesthetized males. Neuronal spiking was strongly dependent on testosterone levels. Notably, social odor exposure only weakly induced spiking, which contrasts with the strong behavioral effects these odors are known to induce, so it is likely that other, unknown pathways are more important for their detection. Non-volatile components of social odors are processed by the accessory olfactory system (AOS); however, the role of the AOS during ongoing social interactions is not clear. In Study 3 I used optogenetic activation of the AOB during mating to enhance signaling in the AOS of males; I found that this stimulation significantly increased copulatory behavior efficiency, suggesting that AOB activity during mating facilitates males’ sexual arousal and reproductive performance. Overall these results reveal new properties of social odor processing in mice: sex differences, dependence on gonadal hormones, and a role during ongoing behavioral interactions

    Gaseous emissions and toxic hazards associated with plastics in fire situations: A literature review

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    The hazards of plastics in fire situations, the gases emitted, the factors influencing the nature of these emissions, the characteristics of toxic gases, and the results of laboratory studies, are discussed. The literature pertaining to the pyrolysis and oxidation of plastics was reviewed. An effort was made to define the state of the art for determining the toxic gases emitted by plastics under fire conditions. Recommendations are made and research needs defined as a result of this review
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