Olfactory Experience Research Articles

Repeated unrewarded scent exposure influences the food choice of stingless bee foragers, Melipona scutellaris

The social organization of foraging processes is a principal key to the ecological success of eusocial insects. Floral odours brought back to the colony by successful foragers are important sources of information underlying an individual’s decision about which resource to collect. Food-source-naive individuals memorize and use this olfactory information when searching for food in the field. Odour familiarization as mechanism underlying the coordination of foraging processes has received little attention so far. Here, we asked whether and to what extent foraging decisions of stingless bees, Melipona scutellaris , are influenced by preceding unrewarded olfactory experiences. In a classical conditioning assay (proboscis extension reflex, PER, assay), foragers were exposed to a scented airflow, during which they either received (experimental group CS+) or did not receive (experimental group CS-) a sugar solution as reward. Subsequently, bees of both experimental groups were introduced into an arena where they could choose between two scented feeders, one of which carried the odour used during the PER assay. Independently of whether foragers had received a sucrose reward during scent exposure, between 70% and 75% of the individuals chose the food source that carried the conditioned odour in the choice arena. Bees from the control groups (harnessed or not; no scent exposure), by contrast, showed no preference for either of the two feeders. These findings point to the importance of preceding olfactory experiences for the food choice of M. scutellaris and suggest that both associative learning during trophallaxis as well as familiarization may influence to a similar extent the foraging decisions of these bees in natural settings.

Why humans do not make good vampires. Testing the ability of humans to detect true blood

Background: Research indicating the effects of real blood or of its iconic representation on human behaviour has thus far concentrated on phobia and aggressiveness. Little is known about other responses or, more fundamentally, about the biological basis of all such responses.Aim: In this study it is examined whether or not humans are able to detect real blood.Methods: Human subjects (n = 89) were asked to distinguish different kinds of blood from red control fluids under varying visual and choice conditions. Relevant differences between subjects were tested for through written questionnaires, including standardized scales for disgust sensitivity (DS-R) and blood phobia (MBPI) and performance on two clinical olfactory tests.Results: Analysis of variance shows that humans are excellent detectors of animal blood (in casu pig blood), whereas the ability of detecting human blood is much less developed. Surprisingly, differences in olfactory capacities and personal experience with blood have no effect on blood detection, while blood fear lowers and disgust sensitivity ameliorates this performance.Conclusion: This study allows further mapping of the exact role of disgust sensitivity in human behaviour, as well as a deliberate choice of materials in blood-related experiments. It is imperative for further research on the behavioural and psychological impact ‘blood’ resorts on humans.

Olfactory Experience Modifies Semiochemical Responses in a Bark Beetle Predator

A typical feature of forest insect pests is their tendency to undergo large fluctuations in abundance, which can jeopardize the persistence of their predaceous natural enemies. One strategy that these predators may adopt to cope with these fluctuations would be to respond to sensory cues for multiple prey species. Another possible adaptation to temporal variation in the prey community could involve the learning of prey cues and switching behavior. We conducted three experiments to investigate the ability of the generalist bark beetle predator Thanasimus dubius (F.) (Coleoptera: Cleridae) to respond to different prey signals and to investigate the effect of olfactory experience. We first conducted a field choice test and a wind tunnel experiment to examine the kairomonal response of individual predators toward prey pheromone components (frontalin, ipsenol, ipsdienol, sulcatol) along with the pine monoterpene α-pinene, which is a volatile compound from the host of the prey. We also presented semiochemically naive predators with two prey pheromone components, frontalin and ipsenol, alone or associated with a reward. Our results showed that T. dubius populations are composed of generalists that can respond to a broad range of kairomonal signals. Naive T. dubius also were more attracted to ipsenol following its association with a reward. This work constitutes the first evidence that the behavior of a predatory insect involved in bark beetle population dynamics is influenced by previous olfactory experience, and provides a potential explanation for the pattern of prey switching observed in field studies.

Life and Death Decision in Adult Neurogenesis: In Praise of Napping

Among the thousands of new neurons that integrate into the adult olfactory bulb each day, 50% are eliminated through apoptosis. In this issue of Neuron, Yokoyama etal. take steps toward deciphering the behavioral contexts that regulate newborn cell elimination.

Elimination of Adult-Born Neurons in the Olfactory Bulb Is Promoted during the Postprandial Period

Granule cells (GCs) in the mouse olfactory bulb (OB) continue to be generated in adulthood, with nearly half incorporated and the remainder eliminated. Here, we show that elimination of adult-born GCs is promoted during a short time window in the postprandial period. Under restricted feeding, the number of apoptotic GCs specifically increased within a few hours after the start of feeding. This enhanced GC apoptosis occurred in association with postprandial behaviors that included grooming, resting, and sleeping, and was particularly correlated with the length of postprandial sleep. Further, deprivation of olfactory sensory experience in the local OB area potentiated the extent of GC elimination in that area during the postprandial period. Sensory experience-dependent enhancement of GC elimination also occurred during postprandial period under natural feeding condition. These results suggest that extensive structural reorganization of bulbar circuitry occurs during the postprandial period, reflecting sensory experience during preceding waking period.

Sensory Input Regulates Spatial and Subtype-Specific Patterns of Neuronal Turnover in the Adult Olfactory Bulb

Throughout life, new neurons are added and old ones eliminated in the adult mouse olfactory bulb. Previous studies suggested that olfactory experience controls the process by which new neurons are integrated into mature circuits. Here we report novel olfactory-experience-dependent mechanisms of neuronal turnover. Using two-photon laser-scanning microscopy and sensory manipulations in adult live mice, we found that the neuronal turnover was dynamically controlled by olfactory input in a neuronal subtype-specific manner. Olfactory input enhanced this turnover, which was characterized by the reiterated use of the same positions in the glomeruli by new neurons. Our results suggest that olfactory-experience-dependent modification of neuronal turnover confers structural plasticity and stability on the olfactory bulb.

Sniffing and smelling

In this paper I argue that olfactory experience, like visual experience, is exteroceptive: it seems to one that odours, when one smells them, are external to the body, as it seems to one that objects are external to the body when one sees them. Where the sense of smell has been discussed by philosophers, it has often been supposed to be non-exteroceptive. The strangeness of this philosophical orthodoxy makes it natural to ask what would lead to its widespread acceptance. I argue that philosophers have been misled by a visuocentric model of what exteroceptivity involves. Since olfaction lacks the spatial features that make vision exteroceptive the conclusion that olfaction is nonexteroceptive can appear quite compelling, particularly in the absence of an alternative model of exteroceptivity appropriate to olfaction. I offer a model according to which odours seem to be external to the body because they seem to be brought into the nose from without by sniffing and breathing through the nostrils. I argue that some natural-seeming objections to this model rely on substantive assumptions about how the senses are distinguished from one another, and how perceptual experience is put together out of its modality-specific parts, that require defence.

How stable are the reef odor preferences of settling reef fish larvae?

Settlement-stage larvae of the coral reef fishes Ostorhinchus doederleini (Apogonidae) and Pomacentrus coelestis (Pomacentridae) prefer the odor of their settlement reef to that of other nearby reefs. It was unknown whether these olfactory preferences are temporally stable or the result of recent olfactory experience. Ostorhinchus doederleini and P. coelestis larvae were held in aquaria and exposed to water from either their settlement reef or a neighboring reef for 5–9 days and their olfactory preference was tested. We show that exposure to water from another reef did not influence olfactory preference. Ostorhinchus doederleini olfactory preference declined slightly over time whereas P. coelestis preference was gradually lost after 2–3 days in captivity. Neither species switched their preference to the new reef odor. While we cannot determine conclusively the time window of odor learning, imprinting at or shortly after birth is logical and has been demonstrated in other fish species.

Making Scents of Transition

In this article, the growing body of literature on transition within central and eastern Europe is developed by exploring how discussing the senses may illuminate the experience of change to post-socialism for urban dwellers. After situating the study within the rich ethnographic heritage on urban transition, the key tenets of ‘geographies of smell’ are outlined as a means of inquiry which emphasises the lived, sensually embodied experience of transition. The empirical study is focused upon the interrogation of the meanings created by, and attached to, olfactory experience in contemporary Poland, discussing three motifs that highlight the symbolic and transformative role of smell in relation to transition. In understanding smell as playing an active role in the creation of meaning, not only are current debates surrounding geographies of smell extended, but it is argued that addressing the relatively neglected sensual dimension of the social provides an avenue into more nuanced dimensions of urban transition.

Olfactory Experience I: The Content of Olfactory Experience

Much of the philosophical work on perception has focused on vision. Recently, however, philosophers have been turning their attention to the ‘other modalities’. In a pair of entries, I consider olfaction—a sense modality that, along with gustation, has been largely overlooked by philosophers. In this first entry, I consider the challenge that olfactory experience presents to upholding a representational view of the sense modalities. It is common for philosophers to think that visual experience is world-directed and, in particular, that it is representational. World-directed views contrast with subjectivist views—views according to which experiences are raw feels or mere sensations. Unlike visual experience, olfactory experience doesn't obviously support a representational view. Indeed, given its phenomenology, a subjectivist view of olfactory experience might seem unavoidable. But it is not. Once we begin to unravel ourselves from the dominant visual model of perception, we see that there is a representational view available that honors the phenomenology of olfactory experience. In turn, we learn that although there are some basic similarities between visual experience and olfactory experience, there are significant differences that prevent us from making easy generalizations from the visual case.

Olfactory Experience II: Objects and Properties

The philosophy of perception has been dominated by vision, with very little discussion of the chemical senses – olfaction and gustation. In this second entry of a pair on olfactory experience, I consider what olfaction has to tell us about two issues: (i) the nature of perceptual objects and (ii) the nature of perceptual properties and, in particular, the secondary qualities. Given the scant work on olfaction in the philosophical literature, my discussion not only surveys what philosophers have said about olfaction so far, but considers the most plausible views and/or most pressing questions in each area of inquiry.

A Representational Account of Olfactory Experience

Seattle rain smelled different from New Orleans rain…. New Orleans rain smelled of sulfur and hibiscus, trumpet metal, thunder, and sweat. Seattle rain, the widespread rain of the Great Northwest, smelled of green ice and sumi ink, of geology and silence and minnow breath.— Tom Robbins,Jitterbug PerfumeMuch of the philosophical literature on perception has focused on vision. This is not surprising, given that vision holds for us a certain prestige. Our visual experience is incredibly rich, offering up a mosaic of apparent three-dimensional objects. For this reason, it is commonplace to suppose that visual experience isworld-directed, with the view taking its most popular form in therepresentational, orcontent,view. World-directed views contrast with what we might callsubjectivist views— views according to which experiences are raw feels or mere sensations.

The Influence of Gustatory and Olfactory Experiences on Responsiveness to Reward in the Honeybee

BackgroundHoneybees (Apis mellifera) exhibit an extraordinarily tuned division of labor that depends on age polyethism. This adjustment is generally associated with the fact that individuals of different ages display different response thresholds to given stimuli, which determine specific behaviors. For instance, the sucrose-response threshold (SRT) which largely depends on genetic factors may also be affected by the nectar sugar content. However, it remains unknown whether SRTs in workers of different ages and tasks can differ depending on gustatory and olfactory experiences.MethodologyGroups of worker bees reared either in an artificial environment or else in a queen-right colony, were exposed to different reward conditions at different adult ages. Gustatory response scores (GRSs) and odor-memory retrieval were measured in bees that were previously exposed to changes in food characteristics.Principal FindingsResults show that the gustatory responses of pre-foraging-aged bees are affected by changes in sucrose solution concentration and also to the presence of an odor provided it is presented as scented sucrose solution. In contrast no differences in worker responses were observed when presented with odor only in the rearing environment. Fast modulation of GRSs was observed in older bees (12–16 days of age) which are commonly involved in food processing tasks within the hive, while slower modulation times were observed in younger bees (commonly nurse bees, 6–9 days of age). This suggests that older food-processing bees have a higher plasticity when responding to fluctuations in resource information than younger hive bees. Adjustments in the number of trophallaxis events were also found when scented food circulated inside the nest, and this was positively correlated with the differences in timing observed in gustatory responsiveness and memory retention for hive bees of different age classes.ConclusionsThis work demonstrates the accessibility of chemosensory information in the honeybee colonies with respect to incoming nectar. The modulation of the sensory-response systems within the hive can have important effects on the dynamics of food transfer and information propagation.

In Ovo Olfactory Experience Influences Post‐hatch Feeding Behaviour in Young Chickens

AbstractIn several mammalian species, prenatal exposure to odours can elicit later positive consummatory behaviour in response to substrates bearing that odorant. In birds, the sense of smell has been considerably underestimated, and very little is known about the effects of early sensory experience on the regulation of feeding behaviour. We tested the hypothesis that the feeding behaviour of the domestic chicken could be regulated by olfactory learning during the embryonic life. To that end, chicken embryos were exposed to an olfactory stimulus (blend of essential oil of orange and nature identical vanillin) from embryonic day (ED) 12 to ED20, and chicks were tested between 4 and 9 d of age. In short‐term choice tests, at day 4 and 5, chickens previously exposed to a low concentration (LC) of the olfactory stimulus spent a higher proportion of time eating a familiar or an unfamiliar food bearing the olfactory stimulus compared to non‐exposed control chickens. Conversely, chickens previously exposed to a high concentration (HC) of the olfactory stimulus were found to avoid all foods bearing the olfactory stimulus. On a 24‐ h time scale at day 7–8, LC and HC birds, but not controls, ingest significantly less familiar food containing the olfactory stimulus. This result indicated a long‐term effect of the early olfactory experience on feeding preferences. We demonstrated that chickens can utilize information from their pre‐hatch chemosensory environment to guide their later feeding behaviour. A pre‐hatch effect of the intensity of odour signals in the regulation of feeding behaviour is reported here for the first time.

Right Orbitofrontal Cortex Mediates Conscious Olfactory Perception

Understanding how the human brain translates sensory impressions into conscious percepts is a key challenge of neuroscience research. Work in this area has overwhelmingly centered on the conscious experience of vision at the exclusion of the other senses—in particular, smell. We hypothesized that the orbitofrontal cortex (OFC) is a central substrate for olfactory conscious experience because of its privileged physiological role in odor processing. Combining functional magnetic resonance imaging, peripheral autonomic recordings, and olfactory psychophysics, we studied a case of complete anosmia (smell loss) in a patient with circumscribed traumatic brain injury to the right OFC. Despite a complete absence of conscious olfaction, the patient exhibited robust “blind smell,” as indexed by reliable odor-evoked neural activity in the left OFC and normal autonomic responses to odor hedonics during presentation of stimuli to the left nostril. These data highlight the right OFC’s critical role in subserving human olfactory consciousness.

Olfactory Experience Affects the Response of Meadow Voles to the Opposite‐Sex Scent Donor of Mixed‐Sex Over‐Marks

Scent marking and over-marking are important forms of communication between the sexes for many terrestrial mammals. Over the course of three experiments, we determined whether the amount of time individuals investigate the scent marks of opposite-sex conspecifics is affected by four days of olfactory experience with those conspecifics. In experiment 1, female meadow voles, Microtus pennsylvanicus, spent more time investigating the scent mark of the novel male conspecific than that of the familiar male donor, whereas male voles spent similar amounts of time investigating the scent mark of the familiar female and a novel female conspecific. In experiment 2, voles were exposed to a mixed-sex over-mark in which subjects did not have four days of olfactory experience with either the top-scent donor or the bottom-scent donor. During the test phase, male and female voles spent more time investigating the scent mark of the opposite-sex conspecific that provided the top-scent mark than that of a novel, opposite-sex conspecific. Male and female voles spent similar amounts of time investigating the scent mark of the bottom-scent donor and that of a novel opposite-sex conspecific. In experiment 3, voles were exposed to a mixed-sex over-mark that contained the scent mark of an opposite-sex conspecific with which they had four days of olfactory experience. During the test phase, male voles spent more time investigating the mark of the familiar, top-scent female than the scent mark of a novel female donor but spent similar amounts of time investigating the mark of the familiar, bottom-scent female and that of a novel female donor. In contrast, female voles spent more time investigating the mark of a novel male donor than that of either the familiar, top-scent male or that of the familiar, bottom-scent male. The sex differences in the responses of voles to scent marks and mixed-sex over-marks are discussed in relation to the natural history and non-monogamous mating system of meadow voles.

Continuous Neural Plasticity in the Olfactory Intrabulbar Circuitry

In the mammalian brain each olfactory bulb contains two mirror-symmetric glomerular maps linked through a set of reciprocal intrabulbar projections. These projections connect isofunctional odor columns through synapses in the internal plexiform layer (IPL) to produce an intrabulbar map. Developmental studies show that initially intrabulbar projections broadly target the IPL on the opposite side of the bulb and refine postnatally to their adult precision by 7 weeks of age in an activity-dependent manner (Marks et al., 2006). In this study, we sought to determine the capacity of intrabulbar map to recover its precision after disruption. Using reversible naris closure in both juvenile and adult mice, we distorted the intrabulbar map and then removed the blocks for varying survival periods. Our results reveal that returning normal olfactory experience can indeed drive the re-refinement of intrabulbar projections but requires 9 weeks. Since activity also affects olfactory sensory neurons (OSNs) (Suh et al., 2006), we further examined the consequence of activity deprivation on P2-expressing OSNs and their associated glomeruli. Our findings indicate that while naris closure caused a marked decrease in P2-OSN number and P2-glomerular volume, axonal convergence was not lost and both were quickly restored within 3 weeks. By contrast, synaptic contacts within the IPL also decreased with sensory deprivation but required at least 6 weeks to recover. Thus, we conclude that recovery of the glomerular map precedes and likely drives the refinement of the intrabulbar map while IPL contacts recover gradually, possibly setting the pace for intrabulbar circuit restoration.

Post-eclosion odor experience modifies olfactory receptor neuron coding in Drosophila

Olfactory responses of Drosophila undergo pronounced changes after eclosion. The flies develop attraction to odors to which they are exposed and aversion to other odors. Behavioral adaptation is correlated with changes in the firing pattern of olfactory receptor neurons (ORNs). In this article, we present an information-theoretic analysis of the firing pattern of ORNs. Flies reared in a synthetic odorless medium were transferred after eclosion to three different media: (i) a synthetic medium relatively devoid of odor cues, (ii) synthetic medium infused with a single odorant, and (iii) complex cornmeal medium rich in odors. Recordings were made from an identified sensillum (type II), and the Jensen-Shannon divergence (D(JS)) was used to assess quantitatively the differences between ensemble spike responses to different odors. Analysis shows that prolonged exposure to ethyl acetate and several related esters increases sensitivity to these esters but does not improve the ability of the fly to distinguish between them. Flies exposed to cornmeal display varied sensitivity to these odorants and at the same time develop greater capacity to distinguish between odors. Deprivation of odor experience on an odorless synthetic medium leads to a loss of both sensitivity and acuity. Rich olfactory experience thus helps to shape the ORNs response and enhances its discriminative power. The experiments presented here demonstrate an experience-dependent adaptation at the level of the receptor neuron.

Shared Memory, Odours and Sociotransmitters or: "Save the Interaction!"

Collective memory, social memory, professional memory: although these notions are in current use when we name the shared (or assumed to be shared) representations of the past, they are very ambiguous. The point at issue is to show how memories can become common to some or to all members of a group. In this paper, I shall base my arguments on the simplest situation imaginable: The sharing of a memory of an olfactory experience by two individuals, namely one of my informants – a gravedigger – and myself.We can try to explain this shared olfactory memory, or the imagination of this sharing, by taking two facets into consideration. First of all, we must learn to take seriously those few seconds when a shared experience of the sensory world took shape between the anthropologist and his informant. Secondly, we must attempt to answer both of the following questions: what is the nature of this sharing? And what conditions make it possible? In the first part of this text, I examine the issue of the nature of sharing by weighing up its aspects as I consider protomemory, memory and metamemory. In the second part, I outline one of the essential conditions of sharing: the existence of what I call sociotransmitters. For the most part, my attention remains focused on that particular moment when the gravedigger said, “Smell this!”, and when what was at stake was to save the interaction.

Experience restores innate female preference for male ultrasonic vocalizations

Mouse models are increasingly contributing to our understanding of the neural genetics of sensory processing and memory. For example, strain differences have helped elucidate basic mechanisms of age-related hearing loss and auditory fear conditioning. Assessing sensory differences arising in acoustic communication contexts is also important for understanding natural audition. While this topic has not been well studied, it is currently being addressed through auditory neuroethological studies in the CBA/CaJ strain, where insights will help lay a foundation for future neural genetic studies. Here, we focus on the responses of adult females to ultrasonic vocalizations of males. We tested a group of female mice in a place-preference paradigm before and after auditory and olfactory experience with a male. A control group was housed with other female cagemates between trials. All females showed an initial preference for male calls that rapidly decayed over the course of a trial. However, only females that had been pair-housed with a male during the inter-trial interval displayed a reinstated interest in male vocalizations, suggesting possible group differences in the assessment of the calls' behavioral relevance. These findings provide a timeframe during which auditory processing of male ultrasounds might be expected to show a difference depending on behavioral relevance, and also suggest an importance of social interactions in maintaining call recognition.