Familiar Odors Research Articles

Mind Over Age--Stereotype Activation and Olfactory Function

Given that context affects olfaction and the elderly exhibit olfactory deficits, the current study tested whether a subtle change in internal context, evoked by priming the elderly stereotype, would affect performance in a variety of olfactory tasks including odor sensitivity, discrimination, and identification (Experiment 1), as well as perceived odor intensity, pleasantness and familiarity, and an odor reaction time task (Experiment 2). Such internalization of the elderly stereotype has been demonstrated with slower walking speeds and fewer words recalled in a memory task. In the current study, 76 participants first listened to a presentation about age-related declines in olfaction and then participated in 3 language tasks which, unbeknownst to them, served as the elderly stereotype priming manipulation. This priming manipulation was effective at decreasing walking speed and word recall, confirming the findings of previous researchers; however, olfaction was not affected. Whether olfaction is resistant to stereotype priming is discussed.

Novel odors affect gene expression for cytokines and proteinases in the rat amygdala and hippocampus

Olfaction in rodents provides an excellent modality for the study of cellular mechanisms of information processing and storage, since a single occurrence of precisely timed stimuli has high survival value. We have followed up preliminary evidence of cytokine and proteinase involvement in normal (as opposed to pathologically-induced) brain plasticity by surveying for the presence of these factors in the olfactory circuitry of the rat. Genes for 25–30 common cytokines and their receptors, and over 30 cell matrix and adhesion molecules were found to be expressed across the olfactory bulb, insular cortex, amygdala, and dorsal hippocampus. We then measured by real-time PCR the transcriptional expression of seven of these genes following a one-time exposure to the novel odor of blueberry bars or cornnuts, in contrast to presentation of the familiar odor of lab chow. In the amygdala significant up-regulation of interleukin-1 receptor 1 (IL1r1), interleukin-4 receptor (IL4r), fibroblast growth factor 13 (FGF13), and cathepsin-H (CtsH) was observed in males in response to the odor of cornnuts only. Changes were less consistent and widespread in the hippocampus, but were again sex specific for three genes: cathepsin-L (CtsL), matrix metalloproteinase-14 (MMP-14) and MMP-16. Our results show that transcription for several specific cytokines, growth factors, and proteinases responds to a one-time exposure to a novel odor, in a manner that tends to be region- and sex-specific. This suggests considerable variation in the way that olfactory information is processed at the cellular level in different brain regions and by the two sexes.

QUESTIONNAIRE ON MEXICANS' FAMILIARITY WITH ODOR NAMES

ABSTRACTOur aim was to identify culture‐specific odors to design an olfactory assessment (identity and recognition, threshold, olfactory discrimination and memory tests) for Mexican population.A survey was made using 1,308 Mexicans. We asked them about their familiarity, preference and frequency with which they smelled 58 different kinds of odors. The most familiar odor names were guava, orange and lime, with orange, cinnamon and rose as the most preferred.Significant differences in familiarity were found between genders for some floral and spicy odors. Age and occupation were associated with people's ability to recognize floral, herbal, spicy, fruity and other odor names. Certain floral odor names are only familiar to people born in specific places. Overall, the variables age, gender and occupation had influence over the familiarity of odor names, with citrus as the most familiar scent for the Mexican population.PRACTICAL APPLICATIONSWe determined the most familiar and preferred scents to Mexicans, which will form the basis for designing a methodology suitable for olfactory assessment (identity and recognition, threshold, olfactory discrimination and memory tests) in this population, allowing the clinical use and study of correlation with chemoreception, chemosensory and chemical senses.

Odor Recognition Memory: Two Encoding Trials are Better Than One

The primary purpose of this study was to determine the effect of one versus two encoding trials in the classical yes/no recognition memory paradigm using olfactory stimuli. A group of 24 young adults rated 18 standard microencapsulated odorant targets for familiarity (first encoding block) or pleasantness (second encoding block). Once-encoded targets were in only one block and twice-encoded targets were in both, with items counterbalanced across participants. Participants performed a 20-min nonverbal distractor task followed by a yes/no recognition test incorporating 18 additional odors as foils. Memory performance for twice-encoded targets was superior to that for once-encoded targets. For once-encoded targets, performance did not differ between those rated for familiarity versus those rated for pleasantness. Less pleasant odors produced overall better recognition, with a tendency for less familiar odors to produce overall better recognition. There was a tendency for the second encoding trial to have a larger effect for less pleasant or familiar odors than for more pleasant or familiar odors. The main conclusion is that recognition memory for odors is better for items encoded two times than for items encoded only once. Implications of these findings and suggestions for future research are discussed.

Responses of common diving petrel chicks (Pelecanoides urinatrix) to burrow and colony specific odours in a simple wind tunnel

AbstractResearchers have previously assumed that common diving petrels (Pelecanoides urinatrix) have a limited sense of smell since they have relatively small olfactory bulbs. A recent study, however, showed that adult diving petrels prefer the scent of their own burrow compared to burrows of other diving petrels, implying that personal scents contribute to the burrow's odour signature. Because diving petrels appear to be adapted to use olfaction in social contexts, they could be a useful model for investigating how chemically mediated social recognition develops in birds. A first step is to determine whether diving petrel chicks can detect familiar and unfamiliar odours. We compared behavioural responses of chicks to three natural stimuli in a wind tunnel: soil collected from their burrow or colony, and a blank control. During portions of the experiment, chicks turned the least and walked the shortest distances in response to odours from the nest, which is consistent with their sedentary behaviour within the burrow. By contrast, behaviours linked to olfactory search increased when chicks were exposed to blank controls. These results suggest that common diving petrel chicks can detect natural olfactory stimuli before fledging, and lay the foundation for future studies on the role of olfaction in social contexts for this species.

Olfactory discrimination in the western lowland gorilla, Gorilla gorilla gorilla

The olfactory abilities of great apes have been subject to little empirical investigation, save for a few observational reports. This study, using an habituation/dishabituation task, provides experimental evidence for a core olfactory ability, namely, olfactory discrimination, in the gorilla. In Experiment 1, six zoo-housed western lowland gorillas were individually presented with the same odour on four trials, and with a novel odour on the fifth trial. Odours (almond and vanilla) were presented on plastic balls, and behavioural responses of sniffing and chewing/licking the balls were recorded. A second experiment presented the same odour on four trials and no odour on the fifth to examine whether any dishabituation was due to the presence of a new odour or the absence of the familiar odour. Gorillas habituated their behaviour with repeated presentation of the same odour, but dishabituated, i.e. increased sniffing and chewing/licking, when presented with the novel odour. No dishabituation was noted when using water as the stimulus across all trials or when used as the novel odour. Overall, results show that gorillas are able to discriminate between odours.

Electrophysiological responses of rat olfactory tubercle neurons to biologically relevant odours

Biologically relevant odours were used to stimulate olfactory tubercle neurons in anaesthetized male rats. Among 120 recorded neurons, 118 showed spontaneous activity (mean firing rate, 15.0 ± 1.4 spikes/s). Ninety-eight neurons were exposed to at least one of the four following odour sources: an empty vial, or a vial containing food pellets (familiar odour), a sample of oestrous rat faeces (conspecific sexual odour), or a sample of male fox faeces (predator odour). The proportion of neurons responding with a change in activity was significantly linked to the odour applied. Repetition of the stimulation with the same odour elicited the same activity change. Between 50 and 70% of neuronal activity changes were not accompanied by respiration changes. Fifty-six neurons were exposed successively to all four odours, and 38 of them showed an activity change in response to at least one. The response of a neuron to an odour was not affected by its response to the previous one, and no neuron responded in the same manner to all odours. Conversely, no odour elicited a unique response in this population of neurons. However, the proportions of excited, inhibited and insensitive neurons depended significantly on the odour applied, suggesting that the recruitment of olfactory tubercle neurons is directly dependent on the biological significance of the odour.

Prenatal stress produces sex differences in nest odor preference

Prenatal stress (PS) and early postnatal environment may alter maternal care. Infant rats learn to identify their mother through the association between maternal care and familiar odors. Female Wistar rats were exposed to restraint stress for 30min, 4 sessions per day, in the last 7days of pregnancy. At birth, pups were cross-fostered and assigned to the following groups: prenatal non-stressed mothers raising non-stressed pups (NS:NS), prenatal stressed mothers raising non-stressed pups (S:NS), prenatal non-stressed mothers raising stressed pups (NS:S), prenatal stressed mothers raising stressed pups (S:S). Maternal behaviors were assessed during 6 postpartum days. On postnatal day (PND) 7, the behavior of male and female pups was analyzed in the odor preference test; and noradrenaline (NA) activity in olfactory bulb (OB) was measured. The results showed that restraint stress increased plasma levels of corticosterone on gestational day 15. After parturition, PS reduced maternal care, decreasing licking the pups and increasing frequency outside the nest. Female pups from the NS:S, S:NS, S:S groups and male pups from the S:S group showed no nest odor preference. Thus, at day 7, female pups that were submitted to perinatal interventions showed more impairment in the nest odor preference test than male pups. No changes were detected in the NA activity in the OB. In conclusion, repeated restraint stress during the last week of gestation reduces maternal care and reduces preference for a familiar odor in rat pups in a sex-specific manner.

Odor-Based Recognition of Familiar and Related Conspecifics: A First Test Conducted on Captive Humboldt Penguins (Spheniscus humboldti)

Studies of kin recognition in birds have largely focused on parent-offspring recognition using auditory or visual discrimination. Recent studies indicate that birds use odors during social and familial interactions and possibly for mate choice, suggesting olfactory cues may mediate kin recognition as well. Here, we show that Humboldt penguins (Spheniscus humboldti), a natally philopatric species with lifetime monogamy, discriminate between familiar and unfamiliar non-kin odors (using prior association) and between unfamiliar kin and non-kin odors (using phenotype matching). Penguins preferred familiar non-kin odors, which may be associated with the recognition of nest mates and colony mates and with locating burrows at night after foraging. In tests of kin recognition, penguins preferred unfamiliar non-kin odors. Penguins may have perceived non-kin odors as novel because they did not match the birds' recognition templates. Phenotype matching is likely the primary mechanism for kin recognition within the colony to avoid inbreeding. To our knowledge this is the first study to provide evidence of odor-based kin discrimination in a bird.

Olfactory working memory: effects of verbalization on the 2-back task

Working memory for odors, which has received almost no attention in the literature, was investigated in two experiments. We show that performance in a 2-back task with odor stimuli is well above chance. This is true not only for highly familiar odors, as has been shown by Dade, Zatorre, Evans, and Jones-Gotman, NeuroImage, 14, 650-660, (2001), but also for unfamiliar ones that are notoriously difficult to name. We can conclude that information about an olfactory stimulus can be retained in the short term and can continuously be updated for comparison with new olfactory probes along the lines of a functional odor working memory. However, the performance in the working memory task is highly dependent on participants' verbalization of the odor. In addition, results indicated that odor working memory performance is dependent on the ability to discriminate among the odor stimuli (Experiment 2). The results are discussed in relation to recent ideas of a separate olfactory working memory slave system.

Absence of preference for social novelty and increased grooming in integrin β3 knockout mice: initial studies and future directions.

Elevated whole blood serotonin 5-HT, or hyperserotonemia, is a common biomarker in autism spectrum disorder (ASD). The integrin β3 receptor subunit gene (ITGB3) is a quantitative trait locus for whole blood 5-HT levels. Recent work shows that integrin β3 interacts with the serotonin transporter (SERT) in both platelets and in the midbrain. Furthermore, multiple studies have now reported gene-gene interaction between the integrin β3 and SERT genes in association with ASD. Given the lack of previous data on the impact of integrin β3 on brain or behavioral phenotypes, we sought to compare mice with decreased or absent expression of the integrin β3 receptor subunit (Itgb3 +/- and -/-) with wildtype littermate controls in behavioral tasks relevant to ASD. These mice did not show deficits in activity level in the open field or anxiety-like behavior on the elevated plus maze, two potential confounds in the evaluation of mouse social behavior. In the three-chamber social test, mice lacking integrin β3 were shown to have normal sociability but did not show a preference for social novelty. Importantly, the absence of integrin β3 did not impair olfaction or the ability to recall familiar social odors. Additionally, mice lacking integrin β3 showed increased grooming behavior in novel environments. These preliminary studies reveal altered social and repetitive behavior in these mice, which suggests that the integrin β3 subunit may be involved in brain systems relevant to ASD. Further work is needed to fully characterize these behavioral changes and the underlying brain mechanisms.

Newborn Interneurons in the Accessory Olfactory Bulb Promote Mate Recognition in Female Mice

In the olfactory bulb of adult rodents, local interneurons are constantly replaced by immature precursors derived from the subventricular zone. Whether any olfactory sensory process specifically relies on this cell renewal remains largely unclear. By using the well known model of mating-induced imprinting to avoid pregnancy block, which requires accessory olfactory bulb (AOB) function, we demonstrate that this olfactory memory formation critically depends on the presence of newborn granule neurons in this brain region. We show that, in adult female mice, exposure to the male urine compounds involved in mate recognition increases the number of new granule cells surviving in the AOB. This process is modulated by male signals sensed through the vomeronasal organ and, in turn, changes the activity of the downstream amygdaloid and hypothalamic nuclei involved in the pregnancy block response. Chemical depletion of newly generated bulbar interneurons causes strong impairment in mate recognition, thus resulting in a high pregnancy failure rate to familiar mating male odors. Taken together, our results indicate that adult neurogenesis is essential for specific brain functions such as persistent odor learning and mate recognition.

Odor Identification and Mortality in Old Age

The association of olfactory dysfunction with mortality was examined in 1162 older persons without dementia or Parkinson's disease. They completed a standard 12-item test of odor identification and then were followed for a mean of 4.2 years (standard deviation [SD] = 2.6, range: 0-9) during which 321 individuals died (27.6%). The relation of olfactory score to risk of death was assessed in a series of proportional hazards models adjusted for age, sex, education, and other covariates. Olfactory scores ranged from 0 to 12 correct (mean = 9.0, SD = 2.2). In an initial analysis, risk of death decreased by about 6% for each additional odor correctly identified (hazard ratio = 0.94; 95% confidence interval: 0.90, 0.98). Thus, mortality risk was about 36% higher with a low score (6, 10th percentile) compared with a high score (11, 90th percentile). The association persisted in subsequent analyses that controlled for naming ability, disability, cerebrovascular disease, characteristic patterns of leisure activity, depressive symptoms, and apolipoprotein E genotype. The results indicate that difficulty identifying familiar odors in old age is associated with increased risk of death.

Dear enemy relationships in the subterranean rodent Ctenomys talarum: the role of memory of familiar odours

Individual recognition is expected to enhance fitness by allowing animals to direct appropriate behaviours to specific individuals during interactions with conspecifics. Reduced aggression towards territorial neighbours (‘dear enemy phenomenon’) is based on the assumption that strangers lacking territories pose a greater threat than territory-holding neighbours. Based on the ability of the subterranean rodent Ctenomys talarum (tuco-tuco) to distinguish between familiar and unfamiliar conspecific odours, I assessed whether males, the more aggressive sex, show dear enemy relationships and whether social experience with odour donors affects the memory of conspecific odours. Male–male contests in the laboratory were used to compare the aggressive behaviour of pairs of males. Familiar male tuco-tucos responded less aggressively during contests than unfamiliar males, providing evidence of the dear enemy relationship in C. talarum . Memory for familiar odours was affected by social experience since discrimination of known from novel odours lasted longer when males encountered each other in dyadic contests following familiarization with odours. Familiarity by odour cues would represent an important mechanism mediating neighbour recognition and territorial behaviour for tuco-tucos in the wild; intruders may represent a threat of great consequence for territory-holding individuals since they represent the potential loss of their burrow system and their priority of access to neighbouring females.

Response competition associated with right–left antennal asymmetries of new and old olfactory memory traces in honeybees

Lateralized recall of olfactory memory in honeybees was tested, following conditioning of the proboscis extension reflex (PER), at 1 or 6 h after training. After training with lemon (+)/vanilla (−) or cineol (+)/eugenol (−) recall at 1 h was better when the odour was presented to the right side of the bee than when it was presented to the left side. In contrast, recall at 6 h was better when the odour was presented to the left than to the right side. This confirmed previous evidence of shorter-term recall via the right antenna and long-term memory recall via the left antenna. However, when trained with either a familiar appetitive odour (rose) as a negative stimulus, or with a naturally aversive odour (isoamyl acetate, IAA) as a positive stimulus, bees showed suppression of the response from both the right and the left side at 1 h after training (likely due to retroactive inhibition) and at 6 h responded to both odours on both sides. We argued that at 6 h, when access to memory has completed the shift from the right to the left side, memory of these familiar odours in the left side of the brain would be present as both positive (rose)/negative (IAA) (as a result of long-term memory either biologically encoded or acquired well before testing) and negative (rose)/positive (IAA) (as a result of the long-term memory of training) stimuli, thus producing response competition. As a direct test of this hypothesis, bees were first trained with unfamiliar lemon (+)/vanilla (−) and then (16 h later) re-trained with vanilla (+)/lemon (−); as predicted, 6 h after re-training bees responded to both odours on both the left and right side.

Maternal separation alters social odor preference development in infant mice (Mus musculus).

This study examined whether daily periods of maternal separation during the first two weeks of life would decrease attraction to familiar nest odors in CD-1 mice 10 and 14 days old. We also investigated whether placing a group of mice (Mus musculus) in nest shavings during the 180-min separation period would mitigate possible separation-induced deficits. The maternal separation procedure has been widely used as a rodent model for the effects of inconsistent or inadequate early caretaking on human development. From postnatal day (PND) 1 to 14, litters were separated from the dam, but not littermates for either 15 or 180 min, or were facility-reared controls. Control, facility-reared mice preferred home-cage nest to clean familiar shaving odors on PND 10, but not PND 14. In contrast, home-cage nest odors attracted maternally separated mice on both test days. Our results suggest that maternal separation maintains the olfactory tether to the nest in a period when the attraction normally begins to weaken.

Familiarity, Cued and Free Odor Identification and Their Association with Cognitive Functioning in Middle Aged and Older Adults

ABSTRACT The aim of the present study was to examine the association between familiarity of odors, cued and free odor identification performance and cognitive function in elderly adults. It was further investigated how age affects performance on the various odor tasks. A third aim was to investigate the role of familiarity in explaining performance on the free identification task. One hundred and thirty-six participants (aged 45–79 years) with normal olfactory sensitivity were assessed with the Scandinavian Odor Identification Test (SOIT) and standardized tests of cognitive function. Familiarity did not correlate with any measure of cognitive function, while verbal identification performance was associated with several cognitive measures, although correlations were modest. In this sample, free odor identification was affected by increasing age to a marginally larger extent than cued identification performance and familiarity ratings. The results suggest that the different olfactory tasks involve different levels of cognitive processing.

Age-related differences in the neural substrates of cross-modal olfactory recognition memory: An fMRI investigation

Impaired ability to remember what has gone before is one of the most distressing aspects of the aging process. Odor recognition memory is particularly vulnerable to the effects of aging, yet the underlying neural substrate is unknown. This study investigated the neural substrate of cross-modal olfactory recognition memory in young and older adults using fMRI. Participants were presented with 16 familiar odors immediately before entering the scanner, and were then tested for retrieval with words, either names of odors previously presented (targets) or names of new odors (foils), while being scanned at 3 T. Activation was reduced in the old subjects, both in regions involved in episodic memory retrieval and in regions involved in olfactory processing. Greater activation in the cerebellum of older adults was observed, suggesting increased response to attentional demands or compensatory mechanisms. Unlike in a number of studies in other sensory modalities, no increase in activation in frontal areas in older adults was observed during retrieval.

Nutritional status modulates behavioural and olfactory bulb Fos responses to isoamyl acetate or food odour in rats: roles of orexins and leptin

Food odours are major determinants for food choice, and their detection depends on nutritional status. The effects of different odour stimuli on both behavioural responses (locomotor activity and sniffing) and Fos induction in olfactory bulbs (OB) were studied in satiated or 48-h fasted rats. We focused on two odour stimuli: isoamyl acetate (ISO), as a neutral stimulus either unknown or familiar, and food pellet odour, that were presented to quiet rats during the light phase of the day. We found significant effects of nutritional status and odour stimulus on both behavioural and OB responses. The locomotor activity induced by odour stimuli was always more marked in fasted than in satiated rats, and food odour induced increased sniffing activity only in fasted rats. Fos expression was quantified in periglomerular, mitral and granular OB cell layers. As a new odour, ISO induced a significant increase in Fos expression in all OB layers, similar in fasted and satiated rats. Significant OB responses to familiar odours were only observed in fasted rats. Among the numerous peptides shown to vary after 48 h of fasting, we focused on orexins (for which immunoreactive fibres are present in the OB) and leptin, as a peripheral hormone linked to adiposity, and tested their effects of food odour. The administration of orexin A in satiated animals partially mimicked fasting, since food odour increased OB Fos responses, but did not induce sniffing. The treatment of fasted animals with either an orexin receptors antagonist (ACT-078573) or leptin significantly decreased both locomotor activity, time spent sniffing food odour and OB Fos induction in all cell layers, thus mimicking a satiated status. We conclude that orexins and leptin are some of the factors that can modify behavioural and OB Fos responses to a familiar food odour.

Differential involvement of cholinergic and beta-adrenergic systems during acquisition, consolidation, and retrieval of long-term memory of social and neutral odors

Acetylcholine and norepinephrine have been implicated during different kinds of social recognition that involves olfactory memory formation. For example, blockade of muscarinic and beta-adrenergic receptors has been shown to impair short-term memory of both socially relevant as well as of neutral odors. However, previous studies have not explicitly compared the role of cholinergic and adrenergic modulation in long-term memory for socially relevant odor vs. incidental odor stimuli. In this work, we studied the function of muscarinic and beta-adrenergic receptors during acquisition and/or consolidation of a novel odor and during the retrieval of a familiar odor. The effects of systemic injections of scopolamine and propranolol, before and after presentation of estrous urine odor or mint odor, were evaluated by a long-term odor habituation task. The results demonstrated that scopolamine disrupts memory acquisition and/or consolidation of mint odor, and did not have any effect during retrieval of mint odor memory. Conversely, scopolamine disrupts memory consolidation and retrieval of estrous odor, depending on the dose applied. Propranolol injections have no effect on acquisition or consolidation for mint or estrous odor, but disrupt memory retrieval of familiar odor regarding their social/sexual or neutral content. These results demonstrate that muscarinic receptors are required differentially during long-term odor memory formation and for familiar odor recognition depending on the socially relevant content of the stimulus. Furthermore, the beta-adrenergic system could play an important role in memory recognition for familiar odors, regardless of the sexual/social or neutral content of the stimuli.