Olfactory perception

The aim of this study was to investigate the role of the human hippocampus in episodic retrieval of odors, in comparison with episodic retrieval of visual objects. Subjects encoded a set of unique odors and objects, and retrieval was tested the next day during functional magnetic resonance imaging (fMRI). Subjects were shown the names of old (studied) and new (unstudied) odors and objects, and asked to indicate which of these stimuli had been presented the previous day. The results showed that brain activation was weaker and more restricted during retrieval of odors than during retrieval of objects, which possibly reflects a general visual dominance effect. Yet, retrieval of odors and objects yielded overlapping clusters of activation the bilateral hippocampi, and the left-sided activation was specifically increased during successful retrieval (hits > correct rejections) in both modalities. Moreover, retrieval of odors uniquely activated olfactory cortical regions, likely to reflect cortical reinstatement of sensory details. Our fMRI study is the first to make a direct comparison between olfactory and visual episodic memory, and the results provide clear evidence for modality-independent functions of the hippocampus. V V C 2012 Wiley Periodicals, Inc.

The investigation of the semantic space associated with subjective affective experiences or feelings linked to odour perception has recently emerged. Because of the specificity of the emotional effects of odours, the terms derived from traditional models of emotion are unlikely to optimally account for odour-associated feelings. In this study, sets of terms derived from two traditional models, basic emotions and valence by arousal by dominance dimensional emotions, were compared with a recently elaborated olfaction-specific set of terms (Geneva Emotion and Odour Scale; GEOS). Three main criteria were considered: (1) the feeling's intensity reported in response to odours; (2) the inter-rater agreement concerning the reported feelings; and (3) the power to discriminate feelings evoked by various odorous substances. The evidence strongly suggested that the set of terms proposed by GEOS outperformed the terms derived from the two classical models in measuring the subjective affective experience elicited by odours. These results are interpreted with respect to a good correspondence between the functions of olfaction and the meaning conveyed by GEOS terms.

Behavioral evidence indicates that odor evoked autobiographical memories (OEAMs) are older, more emotional, less thought of, and induce stronger time traveling characteristics than autobiographical memories (AMs) evoked by other modalities. The main aim of this study was to explore the neural correlates of AMs evoked by odors as a function of retrieval cue. Participants were screened for specific OEAMs and later presented with the odor cue and its verbal referent in an fMRI paradigm. Because the same OEAM was retrieved across both cue formats (odor and word), potential cue dependent brain activations were investigated. The overall results showed that odor and word cued OEAMs activated regions typically associated with recollection of autobiographical information. Although no odors were presented, a verbal cuing of the OEAMs activated areas associated with olfactory perception (e.g., piriform cortex). However, relative to word cuing, an odor cuing of OEAMs resulted in more activity in MTL regions such as the parahippocampus, and areas involved in visual vividness (e.g., occipital gyrus and precuneus). Furthermore, odor cues activated areas related to emotional processing, such as limbic and tempopolar regions, significantly more. In contrast, word cues relative to odor cues recruited a more widespread and bilateral prefrontal activity. Hippocampus activity did not vary as function of the remoteness of the memory, but recollection of OEAMs from the 1 st vs the 2 nd decade of life showed specific activation in the right OFC, whereas the 2 nd reflected a higher activation in the left inferior frontal gyrus.

Changes in smell function can modify feeding behaviour but there is little evidence of how acute negative energy balance may impact olfaction and palatability. In a within-subjects repeated measures design, 15 subjects (nine male; six female) aged 28.6 ± 4.5 years with initial body weight (BW) 74.7 ± 4.9 kg and body mass index (BMI) 25.3 ± 1.4 kg/m 2 were randomized and tested at baseline (FED) and Post Deprivation (FASTED) for nasal chemosensory performance (Sniffin' Sticks) and food palatability (visual analogue scale). Significant main effects for time indicated improvements in the FASTED session for odor threshold, odor discrimination, and total odor scores (TDI), and for increased palatability. There were significant positive correlations between initial BW and the change in odor threshold (r = .52) and TDI scores (r = .53). Positive correlations were also noted between delta identification score and delta palatability (r = .68). When the sample was split by sex, only for females were there significant correlations between delta palatability and: delta BW (r = .88); delta odor identification (r = .94); and delta TDI score (r = .85). Fasting for 24 h improved smell function and this was related to increased palatability ratings and initial BW. Further studies should confirm the role of BW and sex in the context of olfaction, energy deprivation and palatability.

The article is devoted to the problem of the visitors’ olfactory perception of museums. The smells are an important part of the intangible heritage, and the use of smells can stimulate personal and collective olfactory memories, which shapes an entirely different perception of a museum exhibition. Olfactory perception contributes to the enrichment of the meanings of the exposition, encourages new interpretations of traditional museum materials and familiar exhibits. In this regard, the main goal of this study was to analyze the attitude of visitors and museum staff to using smells in a museum space. The primary source of the study was an online survey of 230 museum visitors and staff conducted in 2020–2021. The research data showed that most visitors support the use of olfactory elements in museum exhibits. However, many respondents mentioned the possible risks, especially allergies and distraction from exhibits. In addition, it was partially confirmed that smells are an important element that increases museums’ recognition. The study results also confirmed the hypothesis that olfactory memory contributes to the successful branding of a museum.

Background: Several carbohydrate-based models of feeding have been described. The influence of the substrate oxidation rate on liking, wanting, and macronutrient selection, however, is not known in humans. Objective: The aim of this study was to investigate the influence of the substrate oxidation rate on the above variables. Design: A randomized 4-condition study was conducted in 16 normalweight men (mean 6 SD age: 23 6 3 y). The sessions differed in the composition of breakfast, which was either high in carbohydrates (HC) or low in carbohydrates (LC) or high in fat (HF) or low in fat (LF). Two hours and 20 minutes after breakfast, energy expenditure (EE) and respiratory exchange ratios (RERs) were measured. Next, olfactory liking for 4 foods (sweet and fatty) and ad libitum energy intake (carbohydrate-and fat-rich bread) were evaluated. Results: EE was higher (P , 0.001) and subsequent intake was lower (P , 0.01) after the HC and HF breakfasts than after the LC and LF breakfasts. The HC and LC breakfasts induced a higher RER (P , 0.001), lower olfactory liking for sweet foods (P , 0.05), and the consumption of a lower proportion of carbohydrate-rich bread (P, 0.05) than did the HF and LF breakfasts. The HF breakfast induced the lowest RER (P , 0.001), the lowest olfactory liking for fatty foods (P , 0.05), and the lowest proportion of fat-rich bread consumed (P , 0.01). Above all, a negative correlation was found between the RER and olfactory liking for sweet foods (P , 0.001). Conclusion: A high fat oxidation rate induces a strong liking for carbohydrates and a low liking for fats, which lends new support to the carbohydrate-based model of feeding. This trial is registered at clinicaltrials.gov as NCT01122082.

To sense myriad environmental odors, animals have evolved multiple, large families of divergent olfactory receptors. How and why distinct receptor repertoires and their associated circuits are functionally and anatomically integrated is essentially unknown. We have addressed these questions through comprehensive comparative analysis of the Drosophila olfactory subsystems that express the ionotropic receptors (IRs) and odorant receptors (ORs). We identify ligands for most IR neuron classes, revealing their specificity for select amines and acids, which complements the broader tuning of ORs for esters and alcohols. IR and OR sensory neurons exhibit glomerular convergence in segregated, although interconnected, zones of the primary olfactory center, but these circuits are extensively interdigitated in higher brain regions. Consistently, behavioral responses to odors arise from an interplay between IR-and OR-dependent pathways. We integrate knowledge on the different phylogenetic and developmental properties of these receptors and circuits to propose models for the functional contributions and evolution of these distinct olfactory subsystems.

Like odor perception, odor imagery is characterized by wide variability between individuals. The present two-part study sought to assess whether this inter-individual variability is underlain by behavioral differences in actual odor perception. In study 1, subjects judged the intensity, pleasantness, familiarity and edibility of 3 odorants. Participants were split into two olfactory imagery groups ("good" versus "poor" olfactory imagers) according to their scores on an imagery questionnaire. Results showed that good olfactory imagers judged all odors as more familiar and more edible than did poor olfactory imagers. Study 2 sought to determine whether these effects derived from a particular strategy of reenacting olfactomotor responses to smells on the part of good olfactory imagers, by recording their sniffs during odor perception. Results revealed that good olfactory imagers sniffed all odors longer and, again, judged these same odors as more edible and familiar. This supports the hypothesis of more complete odor processing and better access to odor semantics in good olfactory imagers.

In nature, animals form memories associating reward or punishment with stimuli from different sensory modalities, such as smells and colors. It is unclear, however, how distinct sensory memories are processed in the brain. We established appetitive and aversive visual learning assays for Drosophila that are comparable to the widely used olfactory learning assays. These assays share critical features, such as reinforcing stimuli (sugar reward and electric shock punishment), and allow direct comparison of the cellular requirements for visual and olfactory memories. We found that the same subsets of dopamine neurons drive formation of both sensory memories. Furthermore, distinct yet partially overlapping subsets of mushroom body intrinsic neurons are required for visual and olfactory memories. Thus, our results suggest that distinct sensory memories are processed in a common brain center. Such centralization of related brain functions is an economical design that avoids the repetition ...

While we humans exist in space through our bodies, we experience it via all our senses and build up an integrated knowledge of the world in our memories. However, children’s conception of the world differs from adults due to their developmental stages. This study aims to examine human-space interaction with a new approach to reveal the effects of sensory stimuli on children's perception and memory of space. The case study was conducted in a theme park that offers various sensory stimuli with particularly designed spaces and activities. For the behavioral data, the spatial preferences of the participants (33 children, age 10) were recorded during the tour, and for the memory data participants were asked to draw pictures (cognitive maps) afterwards. The data sets were redefined by the main sensory stimuli offered by the spatial units (spatial data), and the number of stimulus experiences and the number of stimulus recalls were analyzed comparatively. Contrary to popular belief, the results show that (1) all of the senses take part in perception depending on the existing stimuli in the space, vision does not have any precedence; (2) the functioning of the senses during an experience changes depending on how much stimulus they are exposed to and how much the body participates in the perception process; (3) kinesthetic stimuli come to the fore as the best stored stimuli in memory, whereas the taste stimuli remain in the background as the least remembered ones. The case study group was limited, the subjective aspects of perception, and the age and gender differences that may exist are ignored. With the inclusion of age and gender factors precisely, this methodology could reveal promising alternatives for design methods and guide the production of all types of architectural spaces, including the children's spaces. This study proposes an original perspective that regards both the physical and social components of the space as the source of perception; and it attempts to make up for a deficiency by regarding the children who are mostly neglected in other studies, yet are active users of the space.