Segregation of Unknown Odors From Mixtures Based on Stimulus Onset Asynchrony in Honey Bees

Active smelling in the American cockroach

Motion plays an essential role in sensory acquisition. From changing the position in which information can be acquired to fine-scale probing and active sensing, animals actively control the way they interact with the environment. In olfaction, movement impacts the time and location of odour sampling as well as the flow of odour molecules around the olfactory organs. Employing a detailed spatiotemporal analysis, we investigated how insect antennae interact with the olfactory environment in a species with a well-studied olfactory system - the American cockroach. Cockroaches were tested in a wind-tunnel setup during the presentation of odours with different attractivity levels: colony extract, butanol and linalool. Our analysis revealed significant changes in antennal kinematics when odours were presented, including a shift towards the stream position, an increase in vertical movement and high-frequency local oscillations. Nevertheless, the antennal shifting occurred predominantly in a single antenna while the overall range covered by both antennae was maintained throughout. These findings hold true for both static and moving stimuli and were more pronounced for attractive odours. Furthermore, we found that upon odour encounter, there was an increase in the occurrence of high-frequency antennal sweeps and vertical strokes, which were shown to impact the olfactory environment's statistics directly. Our study lays out a tractable system for exploring the tight coupling between sensing and movement, in which antennal sweeps, in parallel to mammalian sniffing, are actively involved in facilitating odour capture and transport, generating odour intermittency in environments with low air movement where cockroaches dwell.

Extracting spatial information from temporal odor patterns: insights from insects

Extracting spatial information from temporal stimulus patterns is essential for sensory perception (e.g. visual motion direction detection or concurrent sound segregation), but this process remains understudied in olfaction. Animals rely on olfaction to locate resources and dangers. In open environments, where odors are dispersed by turbulent wind, detection of wind direction seems crucial for odor source localization. However, recent studies showed that insects can extract spatial information from the odor stimulus itself, independently from sensing wind direction. This remarkable ability is achieved by detecting the fine-scale temporal pattern of odor encounters, which contains information about the location and size of an odor source, and the distance between different odor sources.

Robust odor identification in novel olfactory environments in mice

Relevant odors signaling food, mates, or predators can be masked by unpredictable mixtures of less relevant background odors. Here, we developed a mouse behavioral paradigm to test the role played by the novelty of the background odors. During the task, mice identified target odors in previously learned background odors and were challenged by catch trials with novel background odors, a task similar to visual CAPTCHA. Female wild-type (WT) mice could accurately identify known targets in novel background odors. WT mice performance was higher than linear classifiers and the nearest neighbor classifier trained using olfactory bulb glomerular activation patterns. Performance was more consistent with an odor deconvolution method. We also used our task to investigate the performance of female Cntnap2^-/- mice, which show some autism-like behaviors. Cntnap2^-/- mice had glomerular activation patterns similar to WT mice and matched WT mice target detection for known background odors. However, Cntnap2^-/- mice performance fell almost to chance levels in the presence of novel backgrounds. Our findings suggest that mice use a robust algorithm for detecting odors in novel environments and this computation is impaired in Cntnap2^-/- mice.

Sugar alcohols have the potential as bee-safe baits for the common wasp

BACKGROUND

Pest insects are often baited with poisoned feeding stimulants, the most common of which are sugars. However, sugars are attractive for most animal species, which makes it difficult to target only a specific pest insect species. Here, we assessed different sugar alcohols for their potential as more species-selective feeding stimulants for pest insects.

RESULTS

We tested the attractiveness of the sugar alcohols sorbitol, xylitol and erythritol with a capillary feeder assay in wasps (as potential pest insects, because introduced wasps are a pest in many regions) and bees (as non-target insects). For the common wasp (Vespula vulgaris), sorbitol and xylitol acted as nutritive feeding stimulants, and erythritol acted as a non-nutritive feeding stimulant. For the buff-tailed bumble bee (Bombus terrestris), sorbitol acted as a feeding stimulant, while for the honey bee (Apis mellifera), none of the sugar alcohols acted as feeding stimulant.

CONCLUSION

The species-specific preferences for sugar alcohols suggest their potential as species-selective insect baits. The wasp-specific preference for xylitol suggests its potential as a bee-safe alternative to sugar-containing bait for controlling the common wasp. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Beyond cognitive templates: re-examining template metaphors used for animal recognition and navigation

The term 'cognitive template' originated from work in human-based cognitive science to describe a literal, stored, neural representation used in recognition tasks. As the study of cognition has expanded to non-human animals, the term has diffused to describe a wider range of animal cognitive tools and strategies that guide action through the recognition of and discrimination between external states. One potential reason for this non-standardized meaning and variable employment is that researchers interested in the broad range of animal recognition tasks enjoy the simplicity of the cognitive template concept and have allowed it to become shorthand for many dissimilar or unknown neural processes without deep scrutiny of how this metaphor might comport with underlying neurophysiology. We review the functional evidence for cognitive templates in fields such as perception, navigation, communication, and learning, highlighting any neural correlates identified by these studies. We find that the concept of cognitive templates has facilitated valuable exploration at the interface between animal behavior and cognition, but the quest for a literal template has failed to attain mechanistic support at the level of neurophysiology. This may be the result of a misled search for a single physical locus for the 'template' itself. We argue that recognition and discrimination processes are best treated as emergent and, as such, may not be physically localized within single structures of the brain. Rather, current evidence suggests that such tasks are accomplished through synergies between multiple distributed processes in animal nervous systems. We thus advocate for researchers to move towards a more ecological, process-oriented conception, especially when discussing the neural underpinnings of recognition-based cognitive tasks.

Azadirachtin downregulates the expression of the CREB gene and protein in the brain and directly or indirectly affects the cognitive behavior of the Spodoptera litura fourth-instar larvae

BACKGROUND

Azadirachtin has the potential to be used for pest control. Nevertheless, few studies have investigated the effects of azadirachtin on the cognitive behavior of pests. In this study, expression of the cAMP response element-binding protein (CREB) and its gene were studied via a series of experiments in Spodoptera litura larvae treated with azadirachtin.

RESULTS

RNA-Seq analysis of S. litura larvae treated with azadirachtin was undertaken. According to Kyoto Encyclopedia of Genes and Genomes analysis, the top 20 enriched pathways included neuroactive ligand-receptor interaction pathways, with seven significantly differentially expressed genes including CREB. Quantitative real time polymerase chain reaction (qRT-PCR) results indicated that the CREB gene was expressed during all developmental stages of S. litura, but relative expression of the CREB gene was significantly downregulated after treatment with azadirachtin. Grayscale statistical analysis also showed that expression levels of protein kinase A (PKA), extracellular signal-regulated kinase (ERK) and CREB proteins were significantly downregulated after treatment with azadirachtin. Moreover, RNA interference results showed that the effect of azadirachtin on the cognitive behavior of S. litura was consistent with that seen after interfering with CREB. In addition, larval selectivity to addictive odor sources was reduced, and the initial reaction time was increased.

CONCLUSIONS

This study clarified that azadirachtin can affect the cognitive behavior of S. litura and treatment with azadirachtin resulted in a downregulation of gene and protein expression of CREB and its pathway proteins. © 2020 Society of Chemical Industry.

Insect olfactory communication in a complex and changing world

Insect intraspecific olfactory communication occurs in a complex sensory environment. Here we present recent results on how the olfactory system extracts specific information from a sensory background, and integrates it with complementary information to improve odor source localization. Recent advances on mechanisms of olfactory mixture processing, multi-modal integration, as well as plasticity of sensory processing are reviewed. Significant progress in the understanding of neural coding and molecular bases of olfaction reinforce our perception of the tremendous adaptability of insects to a changing environment. However several reports demonstrate that anthropogenic environmental perturbations interfere with insect olfactory communication and might as a consequence significantly alter the functioning of ecosystems and agroecosystems.

A spiking neural program for sensorimotor control during foraging in flying insects

Foraging is a vital behavioral task for living organisms. Behavioral strategies and abstract mathematical models thereof have been described in detail for various species. To explore the link between underlying neural circuits and computational principles, we present how a biologically detailed neural circuit model of the insect mushroom body implements sensory processing, learning, and motor control. We focus on cast and surge strategies employed by flying insects when foraging within turbulent odor plumes. Using a spike-based plasticity rule, the model rapidly learns to associate individual olfactory sensory cues paired with food in a classical conditioning paradigm. We show that, without retraining, the system dynamically recalls memories to detect relevant cues in complex sensory scenes. Accumulation of this sensory evidence on short time scales generates cast-and-surge motor commands. Our generic systems approach predicts that population sparseness facilitates learning, while temporal sparseness is required for dynamic memory recall and precise behavioral control. Our work successfully combines biological computational principles with spike-based machine learning. It shows how knowledge transfer from static to arbitrary complex dynamic conditions can be achieved by foraging insects and may serve as inspiration for agent-based machine learning.

Odor Stimuli: Not Just Chemical Identity

In most sensory modalities the underlying physical phenomena are well understood, and stimulus properties can be precisely controlled. In olfaction, the situation is different. The presence of specific chemical compounds in the air (or water) is the root cause for perceived odors, but it remains unknown what organizing principles, equivalent to wavelength for light, determine the dimensions of odor space. Equally important, but less in the spotlight, odor stimuli are also complex with respect to their physical properties, including concentration and time-varying spatio-temporal distribution. We still lack a complete understanding or control over these properties, in either experiments or theory. In this review, we will concentrate on two important aspects of the physical properties of odor stimuli beyond the chemical identity of the odorants: (1) The amplitude of odor stimuli and their temporal dynamics. (2) The spatio-temporal structure of odor plumes in a natural environment. Concerning these issues, we ask the following questions: (1) Given any particular experimental protocol for odor stimulation, do we have a realistic estimate of the odorant concentration in the air, and at the olfactory receptor neurons? Can we control, or at least know, the dynamics of odorant concentration at olfactory receptor neurons? (2) What do we know of the spatio-temporal structure of odor stimuli in a natural environment both from a theoretical and experimental perspective? And how does this change if we consider mixtures of odorants? For both topics, we will briefly summarize the underlying principles of physics and review the experimental and theoretical Neuroscience literature, focusing on the aspects that are relevant to animals’ physiology and behavior. We hope that by bringing the physical principles behind odor plume landscapes to the fore we can contribute to promoting a new generation of experiments and models.

Odor Stimuli: Not Just Chemical Identity

In most sensory modalities the underlying physical phenomena are well understood, and stimulus properties can be precisely controlled. In olfaction, the situation is different. The presence of specific chemical compounds in the air (or water) is the root cause for perceived odors, but it remains unknown what organizing principles, equivalent to wavelength for light, determine the dimensions of odor space. Equally important, but less in the spotlight, odor stimuli are also complex with respect to their physical properties, including concentration and time-varying spatio-temporal distribution. We still lack a complete understanding or control over these properties, in either experiments or theory. In this review, we will concentrate on two important aspects of the physical properties of odor stimuli beyond the chemical identity of the odorants: (1) The amplitude of odor stimuli and their temporal dynamics. (2) The spatio-temporal structure of odor plumes in a natural environment. Concerning these issues, we ask the following questions: (1) Given any particular experimental protocol for odor stimulation, do we have a realistic estimate of the odorant concentration in the air, and at the olfactory receptor neurons? Can we control, or at least know, the dynamics of odorant concentration at olfactory receptor neurons? (2) What do we know of the spatio-temporal structure of odor stimuli in a natural environment both from a theoretical and experimental perspective? And how does this change if we consider mixtures of odorants? For both topics, we will briefly summarize the underlying principles of physics and review the experimental and theoretical Neuroscience literature, focusing on the aspects that are relevant to animals' physiology and behavior. We hope that by bringing the physical principles behind odor plume landscapes to the fore we can contribute to promoting a new generation of experiments and models.