Odor Stimuli Research Articles

Zebrafish (Danio rerio) behavioural response to an odorant mixture containing attracting and repelling odorants

Abstract Odorants guide essential activities such as foraging and fleeing predators. Studies usually examine behavioural and physiological effects of individual odorants, while animals in the environment are exposed to multiple stimuli simultaneously. In this study, we exposed zebrafish to a mixture of attraction-evoking and aversion-evoking amino acids, and behavioural responses were observed. Attraction to l-alanine and avoidance to l-cysteine were observed, and so these amino acids were used to make the mixture (zebrafish also avoided l-serine, but this was weaker than with l-cysteine exposures). When exposed to the mixture, fish responded with avoidance, which suggests that aversion-evoking stimuli outweigh attraction-evoking stimuli. Attraction towards the mixture was seen only when the concentration of l-cysteine was decreased from 0.1 to 0.001 mM. Olfactory ablation surgery confirmed that the behaviours were olfactory-mediated. Overall, this study demonstrated that odorant stimuli that repel outweigh stimuli that attract until their concentration decreases by as much as 100-fold.

Brain response to odors presented inside the nose, directly in front of the nose or with ambient air.

Functional magnetic resonance imaging (fMRI) allows the measurement of changes in blood flow in association with changes in brain activity. This technique has been used frequently to study brain activation in response to odorous stimuli. The aim of this study was to evaluate the effects of odor delivery conditions on brain responses obtained with fMRI. Prospective cohort study SETTING: Academic institution. Twenty healthy volunteers (mean age = 29.5years; 9 women, 11 men) participated. Three odor delivery methods were used: "tube" (odor presented intranasally with separate tubing for each nostril), "mask" (odor presented in a face mask covering the subject's nose) and "vacuum" (odor presented into the ambient air). Presentation of the pleasant "peach" odor was performed using a computer-controlled olfactometer. Subjects were asked to evaluate the intensity of the odors after each fMRI run. "Tube" showed higher self-rated odor intensity compared to "mask" and "vacuum" (F = 18.4, p < 0.001). Odor intensity had a positive correlation (r = 0.6, p < 0.05) with percent signal change extracted from the secondary olfactory cortex region in the mask condition. In the tube condition, several selected regions of interest (Amygdala, Insula, Thalamus) showed lower activations compared to the other two conditions (puncorrected < 0.001, mask > tube, vacuum > tube). Activations of region of interests (ROIs) in response to the odorous stimuli showed differences under the three conditions (mask, tube, vacuum). In this passive fMRI paradigm, this may partly reflect the differences in odor intensity, but also in attention and contextual variables related to odor perception.

Parsing Sage and Rosemary in Time: The Machine Learning Race to Crack Olfactory Perception.

Color and pitch perception are largely understandable from characteristics of physical stimuli: the wavelengths of light and sound waves, respectively. By contrast, understanding olfactory percepts from odorous stimuli (volatile molecules) is much more challenging. No intuitive set of molecular features is up to the task. Here in Chemical Senses, the Ray lab reports using a predictive modeling framework-first breaking molecular structure into thousands of features and then using this to train a predictive statistical model on a wide range of perceptual descriptors-to create a tool for predicting the odor character of hundreds of thousands of available but previously uncharacterized molecules (Kowalewski et al. 2021). This will allow future investigators to representatively sample the space of odorous molecules as well as identify previously unknown odorants with a target odor character. Here, I put this work into the context of other modeling efforts and highlight the urgent need for large new datasets and transparent benchmarks for the field to make and evaluate modeling breakthroughs, respectively.

Central Nervous System Processing of Floral Odor and Mother's Milk Odor in Infants.

Newborns have a functioning sense of smell at birth, which appears to be highly significant for feeding and bonding. Still, little is known about the cerebral odor processing in this age group. Studies of olfactory function relied mostly on behavioral, autonomic, and facial responses of infants. The aim of the present study was to investigate central odor processing in infants focusing on electroencephalography (EEG)-derived responses to biologically significant odors, namely a food and a non-food odor. A total of 21 term-born, healthy infants participated (11 boys and 10 girls; age range 2-9 months, mean 5.3 ± 2.2 months). Odor stimuli were presented using a computer-controlled olfactometer. Breast milk was used as food odor. Farnesol was presented as a non-food odor. In addition, odorless air was used as a control stimulus. Each stimulus was presented 30 times for 1 s with an interstimulus interval of 20 s. EEG was recorded from 9 electrodes and analyzed in the frequency domain. EEG amplitudes in the delta frequency band differed significantly after presentation of food (breast milk) odor in comparison to the control condition and the non-food odor (farnesol). These changes were observed at the frontal recording positions. The present study indicates that central odor processing differs between a food and a non-food odor in infants. Results are interpreted in terms of focused attention towards a physiologically relevant odor (breast milk), suggesting that olfactory stimuli are of specific significance in this age group.

Suppression of Interference of Fixative With Odorant Samples in Mass Spectrum Using ICA

Odor sensing enables us to sense odorant stimuli. This sensation causes a deep subconscious response in humans in various ways and represents an indispensable sensation in daily life. However, unwanted compounds called fixatives, which can cause interference and contradiction in odorant analysis especially using mass spectrometry and human subject, are included in odorant samples. Moreover, we do not know the pure odorant mass spectrum. Therefore, it is essential to eliminate the interference of fixatives from the odor sample mass spectrum data and to extract the pure odor mass spectrum. In the present study, we performed independent component analysis (ICA) on the mass spectra of odor samples to remove the influence of fixatives. The advantage of the ICA in separating independent components without a priori knowledge of the original data is useful. The abundance of essential-oil mass spectra that we gathered were utilized as odorant samples. The results were compared with sensory test data from a human subject for a better study of fixative influence. It was revealed that ICA could extract the pure odor sample mass spectrum data without the influence of fixatives, even if the fixatives were added to the odor samples. This study’s outcomes allow us to analyze more odor samples for odorant analysis, not hindered by the influence of unwanted compounds.

Functional Magnetic Resonance Imaging in the Olfactory Perception of the Same Stimuli

Background. Data in the literature report that a number of studies have attempted to identify the exact location of the cortical olfaction representation, searching for evidence suggesting that sniffing odors can initiate a primary activation of the piriform cortex and the insula. Nowadays, due to the SARS-CoV-2 (COVID-19) outbreak, the functional study of the olfactory system could offer a better understanding of the physiopathology of olfactory perception, elucidating better the possible site(s) of damage induced by the COVID-19 infection. The aim of this paper was to evaluate brain maps generated from functional Magnetic Resonance Imaging (fMRI) data, collected from healthy individuals in response to the same olfactory stimulus. Methods. A total of 45 healthy volunteers, without history and/or no clinical signs of sinonasal disease and without history and/or presence of olfactory dysfunction underwent fMRI assessment. Subjects were presented with the same odorous stimuli at specific intervals. fMRI generated brain maps were used in the identification of different cortical areas, involved in the stimuli perception. Results. The fMRI brain maps showed that odorous stimuli activate primarily the left anterior insula (in 35/45 cases or 77.8%). Other activated areas include: the low temporal gyri, the middle and superior temporal gyri, the frontal and piriform cortex, the anterior cingulate gyrus, the parahippocampal gyrus, the temporopolar area, the para-insular area, the subcentral area, the supramarginal gyrus, the occipital cortex and the cerebellum. Conclusions. fMRI resulted as a safe and reliable means to study the perception of olfaction in the cortex. The data of this study suggest that the anterior insula is the main stimulated area when olfactory stimuli are present. This area is always activated, despite the hand and nostril dominance.

Inactivation of the ventral hippocampus facilitates the attenuation of odor neophobia in rats

Food neophobia is a behavior observed in rodents involving reduced consumption of a novel food or drink. In the absence of negative post-ingestive consequences, consumption increases with exposure (attenuation of neophobia), which is seen as an associative safe memory. Olfaction and gustation are sensory modalities essential for the development of a food preference. However, little is known about the neural mechanisms underlying neophobia to a food-related odor stimulus. In the present study, we examined the effect of pharmacological inactivation of the ventral hippocampus (vHPC) on neophobia to orally consumed solutions in rats using muscimol, a gamma aminobutyric acid type A receptor agonist. Two different types of solutions, almond odor (benzaldehyde) and sweet taste (saccharin), were prepared. In the results, microinjections of muscimol into the bilateral vHPC before the first odor and taste exposures did not alter the neophobic reactions of the rats to each stimulus. However, in the second odor, but not taste, exposure, the muscimol-injected rats showed higher consumption in comparison to that observed in the control rats, suggesting that the vHPC inactivation facilitates the attenuation of odor neophobia. On the other hand, intra-vHPC muscimol microinjections after the first odor and taste exposures did not facilitate consumption at the second exposures. These results indicate that neural activations within vHPC during orally consuming a novel odor, but not taste, solution play an inhibitory role in the subsequent attenuation of neophobia.

Structural and Functional Plasticity in the Regenerating Olfactory System of the Migratory Locust.

Regeneration after injury is accompanied by transient and lasting changes in the neuroarchitecture of the nervous system and, thus, a form of structural plasticity. In this review, we introduce the olfactory pathway of a particular insect as a convenient model to visualize neural regeneration at an anatomical level and study functional recovery at an electrophysiological level. The olfactory pathway of the locust (Locusta migratoria) is characterized by a multiglomerular innervation of the antennal lobe by olfactory receptor neurons. These olfactory afferents were axotomized by crushing the base of the antenna. The resulting degeneration and regeneration in the antennal lobe could be quantified by size measurements, dye labeling, and immunofluorescence staining of cell surface proteins implicated in axonal guidance during development. Within 3 days post lesion, the antennal lobe volume was reduced by 30% and from then onward regained size back to normal by 2 weeks post injury. The majority of regenerating olfactory receptor axons reinnervated the glomeruli of the antennal lobe. A few regenerating axons project erroneously into the mushroom body on a pathway that is normally chosen by second-order projection neurons. Based on intracellular responses of antennal lobe output neurons to odor stimulation, regenerated fibers establish functional synapses again. Following complete absence after nerve crush, responses to odor stimuli return to control level within 10–14 days. On average, regeneration of afferents, and re-established synaptic connections appear faster in younger fifth instar nymphs than in adults. The initial degeneration of olfactory receptor axons has a trans-synaptic effect on a second order brain center, leading to a transient size reduction of the mushroom body calyx. Odor-evoked oscillating field potentials, absent after nerve crush, were restored in the calyx, indicative of regenerative processes in the network architecture. We conclude that axonal regeneration in the locust olfactory system appears to be possible, precise, and fast, opening an avenue for future mechanistic studies. As a perspective of biomedical importance, the current evidence for nitric oxide/cGMP signaling as positive regulator of axon regeneration in connectives of the ventral nerve cord is considered in light of particular regeneration studies in vertebrate central nervous systems.

Perilaku Mencit (Mus musculus) terhadap Feses Ular Kobra Jawa (Naja sputatrix)

This research aimed to confirm the predator avoidance behavior of mice from snake droppings as a stimulant. Snake droppings are obtained from snakes fed with mice that come from the same strain as the mice being tested for response. Snake droppings were diluted into three different concentrations (25%, 50%, and 75%). The results showed that male individuals tend to avoid the odor stimuli than the female, it’s shown by the higher avoidance duration in males than the females. The results also indicate that innate behavior takes role in the avoidance response since the mice have never been exposed to any presence of predator.&#x0D;

Visualization of antennal lobe glomeruli activated by nonappetitive D-limonene and appetitive 1-octen-3-ol odors via two types of olfactory organs in the blowfly Phormia regina

Appetite or feeding motivation relies significantly on food odors. In the blowfly Phormia regina, feeding motivation for sucrose is decreased by the odor of d-limonene but increased by the odor of 1-octen-3-ol odor. These flies have antennal lobes (ALs) consisting of several tens of glomerular pairs as a primary olfactory center in the brain. Odor information from different olfactory organs—specifically, the antennae and maxillary palps—goes to the corresponding glomeruli. To investigate how odors differently affect feeding motivation, we identified the olfactory organs and glomeruli that are activated by nonappetitive and appetitive odors. We first constructed a glomerular map of the antennal lobe in P. regina. Anterograde fluorescence labeling of antennal and maxillary afferent nerves, both of which project into the contralateral and ipsilateral ALs, revealed differential staining in glomerular regions. Some of the axonal fiber bundles from the antennae and maxillary palps projected to the subesophageal ganglion (SOG). We visualized the activation of the glomeruli in response to odor stimuli by immunostaining phosphorylated extracellular signal-regulated kinase (pERK). We observed different glomerulus activation under different odor stimulations. Referring to our glomerular map, we determined that antennal exposure to d-limonene odor activated the DA13 glomeruli, while exposure of the maxillary palps to 1-octen-3-ol activated the MxB1 glomeruli. Our results indicated that a nonappetitive odor input from the antennae and an appetitive odor input from the maxillary palps activate different glomeruli in the different regions of ALs in the blowfly P. regina. Collectively, our findings suggest that compartmentalization of glomeruli in AL is essential for proper transmission of odor information.

Mixture Coding and Segmentation in the Anterior Piriform Cortex.

Coding of odorous stimuli has been mostly studied using single isolated stimuli. However, a single sniff of air in a natural environment is likely to introduce airborne chemicals emitted by multiple objects into the nose. The olfactory system is therefore faced with the task of segmenting odor mixtures to identify objects in the presence of rich and often unpredictable backgrounds. The piriform cortex is thought to be the site of object recognition and scene segmentation, yet the nature of its responses to odorant mixtures is largely unknown. In this study, we asked two related questions. (1) How are mixtures represented in the piriform cortex? And (2) Can the identity of individual mixture components be read out from mixture representations in the piriform cortex? To answer these questions, we recorded single unit activity in the piriform cortex of naïve mice while sequentially presenting single odorants and their mixtures. We find that a normalization model explains mixture responses well, both at the single neuron, and at the population level. Additionally, we show that mixture components can be identified from piriform cortical activity by pooling responses of a small population of neurons—in many cases a single neuron is sufficient. These results indicate that piriform cortical representations are well suited to perform figure-background segmentation without the need for learning.

Biomimetic integrated olfactory sensory and olfactory bulb systems in vitro based on a chip

A variety of mammalian or insect behaviors rely on the recognition of relevant odor stimuli. The olfactory system detects and translates complex olfactory stimuli (odors) through the unique and reproducible dynamic ensembles of neuronal activities. This process is involved in various types of neurons of olfactory parts, thereby encoding olfactory information or predicting progression in some neuropsychiatric diseases. In this paper, we constructed a biomimetic model including olfactory sensing system and olfactory bulb processing system to map olfactory-associated ensembles of neuronal activity. The olfactory receptor neurons (ORNs) and olfactory bulb (OB) neurons were primarily cultured and the immunofluorescence images were performed to identify the types of neurons. Diacetyl solution was used as an odor stimulus, and the spike bursts and random spike firing patterns of concentration-dependent excitatory responses were obtained from the ORNs network. The spike waveform and feature parameters were extracted including the spike number and interval in per burst to program the stimulation unit and sequences. The sequences containing odor information were applied to the OB neuronal network for the simulation of the primary olfactory processing. The response pattern and change rule of the OB neuronal network were consistent with the OB neurons affected by the neurotransmitter, which is the carrier of olfactory information transmission in vivo. This biomimetic integrated olfactory sensory and processing system can serve as a novel model for studying the physiological and pathological mechanisms of olfaction, and the pharmacological application in vitro.

A systematic review of physiological responses to odours with a focus on current methods used in event-related study designs

ObjectivesIn odour research, there is still a lack of knowledge regarding the detailed understanding of the determinants and the magnitude of an odour's impact on human psychophysiology. Therefore, the present review aims to summarize current evidence on psychophysiological responses to olfactory events, to highlight diversity in research methods, and to provide recommendations for further research. Material and methodsPredefined search items were used for literature research in two databases, focussing on recent investigations of cardiac and electrodermal responses to short (<10 s) olfactory stimulations, combined with self-reports on odour experience, in a healthy population. The selected 27 publications were evaluated with regard to their methods and their findings on psychophysiological correlates of odour stimulation, following a conceptual scheme proposing mediating and moderating factors of physiological responses to odour stimuli. ResultsThe cardiac and electrodermal activity generally followed a discriminative pattern depending on the perceived pleasantness of an odour. Moreover, the trigeminal aspect of an odour stimulus became evident in electrodermal activity in several studies. Finally, for many of the here addressed potentially mediating and moderating variables, initial findings were obtained in some studies but these await corroboration by future research. With regard to the applied methodology, the reviewed studies were highly diverse, in terms of odour application, study design, and analysis of the time series data. ConclusionsFuture research is needed to advance our understanding of, and theoretical concepts beyond, psychophysiological responses to olfactory events, and to achieve experimentally validated methodological guidelines for psychophysiological measurements in olfaction research.

Decoding Odor Mixtures in the Dog Brain: An Awake fMRI Study.

In working and practical contexts, dogs rely upon their ability to discriminate a target odor from distracting odors and other sensory stimuli. Using awake functional magnetic resonance imaging (fMRI) in 18 dogs, we examined the neural mechanisms underlying odor discrimination between 2 odors and a mixture of the odors. Neural activation was measured during the presentation of a target odor (A) associated with a food reward, a distractor odor (B) associated with nothing, and a mixture of the two odors (A+B). Changes in neural activation during the presentations of the odor stimuli in individual dogs were measured over time within three regions known to be involved with odor processing: the caudate nucleus, the amygdala, and the olfactory bulbs. Average activation within the amygdala showed that dogs maximally differentiated between odor stimuli based on the stimulus-reward associations by the first run, while activation to the mixture (A+B) was most similar to the no-reward (B) stimulus. To clarify the neural representation of odor mixtures in the dog brain, we used a random forest classifier to compare multilabel (elemental) versus multiclass (configural) models. The multiclass model performed much better than the multilabel (weighted-F1 0.44 vs. 0.14), suggesting the odor mixture was processed configurally. Analysis of the subset of high-performing dogs' brain classification metrics revealed a network of olfactory information-carrying brain regions that included the amygdala, piriform cortex, and posterior cingulate. These results add further evidence for the configural processing of odor mixtures in dogs and suggest a novel way to identify high-performers based on brain classification metrics.

Ultrasonic courtship vocalizations of male house mice contain distinct individual signatures

Acoustic communication mediates many types of social interactions; however, few studies have investigated whether courtship vocalizations contain distinctive individual signatures necessary for individual recognition. Male house mice, Mus musculus, produce spectrally complex ultrasonic vocalizations (USVs) during courtship and mating, which appear to attract females and increase male reproductive success. Our goals were to (1) describe quantitative and qualitative changes in the vocalizations of wild-derived male house mice, M. m. musculus, induced by a female odour stimulus; (2) measure individual variation and consistency in male USV emission over time; (3) test whether the variation in USVs is greater between than within individuals; and (4) identify individual signatures in spectrotemporal features using univariate statistics, multivariate models and machine learning methods. We recorded males once per week for 3 weeks, used an automated method (A-MUD) to detect USVs, and manually classified them into distinct syllables. We found that most males did not vocalize until they encountered female scent, and then most males dramatically increased the number and the types of different vocalizations (repertoire size and composition). Male USVs showed high interindividual variation and most showed intraindividual consistency, and we found greater inter- than intraindividual variation for both USV count and repertoire size. Male USVs contained individual signatures in most spectrotemporal features, regardless of the method of analysis. Males sometimes produced few, if any, vocalizations when presented with female scent, but consistent nonvocalizers were rare. Our study provides the first evidence that individual signatures in USVs of male house mice are stable over time and across recording trials, although studies are still needed to investigate repeatability across social contexts and to test whether USVs mediate individual recognition.

Coyote urine, but not 2-phenylethylamine, induces a complete profile of unconditioned anti-predator defensive behaviors.

Predator odors from various sources (e.g. fur/skin, urine, feces) provide prey animals valuable information that allows them to gage potential environmental threat via the detection of semiochemicals called kairomones. However, studies in rodents have revealed inconsistent and often conflicting results, which may occur from any combination of factors, including source and freshness of the odorant, sex, and genetic strain of the prey animal and/or predator. Regardless of cause, few odorants tested, if any, have lived up to the potent unconditioned predator odor stimuli – cat fur/skin odor – that induces a complete profile of innate unconditioned defensive behaviors (e.g., avoidance, risk assessment and freezing) and produces rapid aversive conditioned responses, both of which are sensitive to standard anxiolytic/anxiogenic drugs. Therefore, the present study investigated the effectiveness of coyote urine and 2-phenylethylamine (PEA), two commercially available predator odor cues, in satisfying the first of these criteria in predator odor naïve, adult male Long-Evans hooded rats. The data revealed that coyote urine, but not PEA, was effective in inducing a complete profile of anti-predator defensive behaviors characterized by avoidance, risk assessment, freezing and a reduction in exploratory behavior. We conclude that commercially available coyote urine satisfies the first criterion of a defense inducing unconditioned predator odor stimulus. In order to fully validate the use of coyote urine as an anxiety- and/or fear-like threat stimulus, future research needs to examine whether it produces aversive conditioning and whether the defensive profile induced by the odorant responds to standard anxiolytic drugs.

Data based predictive models for odor perception

Machine learning and data analytics are being increasingly used for quantitative structure property relation (QSPR) applications in the chemical domain where the traditional Edisonian approach towards knowledge-discovery have not been fruitful. The perception of odorant stimuli is one such application as olfaction is the least understood among all the other senses. In this study, we employ machine learning based algorithms and data analytics to address the efficacy of using a data-driven approach to predict the perceptual attributes of an odorant namely the odorant characters (OC) of “sweet” and “musky”. We first analyze a psychophysical dataset containing perceptual ratings of 55 subjects to reveal patterns in the ratings given by subjects. We then use the data to train several machine learning algorithms such as random forest, gradient boosting and support vector machine for prediction of the odor characters and report the structural features correlating well with the odor characters based on the optimal model. Furthermore, we analyze the impact of the data quality on the performance of the models by comparing the semantic descriptors generally associated with a given odorant to its perception by majority of the subjects. The study presents a methodology for developing models for odor perception and provides insights on the perception of odorants by untrained human subjects and the effect of the inherent bias in the perception data on the model performance. The models and methodology developed here could be used for predicting odor characters of new odorants.

Prefrontal Responses to Odors in Individuals With Autism Spectrum Disorders: Functional NIRS Measurement Combined With a Fragrance Pulse Ejection System.

Individuals with autism spectrum disorders (ASD) are impaired not only in social competencies but also in sensory perception, particularly olfaction. The olfactory ability of individuals with ASD has been examined in several psychophysical studies, but the results have been highly variable, which might be primarily due to methodological difficulties in the control of odor stimuli (e.g., the problem of lingering scents). In addition, the neural correlates of olfactory specificities in individuals with ASD remain largely unknown. To date, only one study has investigated this issue using functional magnetic resonance imaging (fMRI). The present study utilized a sophisticated method−a pulse ejection system−to present well-controlled odor stimuli to participants with ASD using an ASD-friendly application. With this advantageous system, we examined their odor detection, identification, and evaluation abilities and measured their brain activity evoked by odors using functional near-infrared spectroscopy (fNIRS). As the odor detection threshold (DT) of participants with ASD was highly variable, these participants were divided into two groups according to their DT: an ASD-Low DT group and an ASD-High DT group. Behavioral results showed that the ASD-High DT group had a significantly higher DT than the typically developing (control) group and the ASD-Low DT group, indicating their insensitivity to the tested odors. In addition, while there was no significant difference in the odor identification ability between groups, there was some discrepancy between the groups’ evaluations of odor pleasantness. The brain data identified, for the first time, that neural activity in the right dorsolateral prefrontal cortex (DLPFC) was significantly weaker in the ASD-High DT group than in the control group. Moreover, the strength of activity in the right DLPFC was negatively correlated with the DT. These findings suggest that participants with ASD have impairments in the higher-order function of olfactory processing, such as olfactory working memory and/or attention.

A systematic review of olfactory related questionnaires and scales.

Although neglected by science for a long time, the sense of olfaction has received increasing attention from research areas including psychology, neuroscience, clinical medicine and nutrition. With the rise of psychophysical and neuroimaging re- search into olfaction, psychometric tools (e.g. questionnaires and scales) are the basis for the quantitative exploration of inter-in- dividual variability regarding olfactory related responses. The current systematic review is to summarize existing olfaction related questionnaires and/or scales. Peer-reviewed literature on scales and questionnaires related to perception of odors were searched from online databa- ses (PubMed, Web of Science and PsycINFO). Twenty-one articles that meet the following criteria were included in the review: "human species", "physical odor stimuli" and "describing the original development of the tool" and "specific focus on olfaction or odor related responses or behaviors". The psychometric properties, advantages and possible disadvantages were discussed. Existing psychometric measures focus on various aspects of olfactory related responses and behaviors, including af- fective experiences of odor perception, awareness and attitude towards olfaction, olfactory function and the quality of life change due to olfactory dysfunction, and the ability to create vivid mental odor images. While most of them have been tested to have good reliability and validity, some were relatively time-consuming due to the number of questionnaire items. Besides, although many measures have been used in clinical populations, few have provided information on the predictive validity regarding effecti- veness of clinical intervention on changes of certain responses or behaviors. The current review provides an overview of olfactory related questionnaires and scales, highlighting the emotional and affective impact of olfaction and the impact on quality of life due to olfactory dysfunction. With growing interest in olfaction as an important sense, the development and use of psychometrically sound measurements in conjunction with objective assess- ments will advance our understanding of human olfaction and olfactory dysfunction. The review provides a guide for researchers and clinicians alike to select olfactory scales suitable for olfactory research with different experimental purposes and specific samples.

Impact of visual features on capture of Aedes aegypti with host decoy traps (HDT).

The host decoy trap (HDT) is a surveillance trap that presents a combination of heat, visual and odour stimuli to attract bloodmeal-seeking mosquitoes. Here we employed a semi-field study to demonstrate the role of the visual attributes present on the HDT on the effectiveness of Aedes aegypti capture. Our results show that the HDT is an effective means of capturing Ae. aegypti mosquitoes in semi-field conditions, with a per trial capture rate of up to 69% across four visually distinct HDTs. The solid black coloured HDT captured more mosquitoes than HDTs with black-white stripes, black-white checkerboard patches or solid white colour by a factor of 1.9, 1.7 and 1.5, respectively. In all cases, mosquito capture was not evenly distributed on the HDT surface, with captures on the HDT's outer downwind half, away from the odour delivery, exceeding captures on the inner upwind half. We conclude that the solid black surface of the original HDT design is more effective than the other surfaces (white or black/white patterns) for the capture of Ae. aegypti. Our results demonstrate that mosquito attraction to the thermal and odorant cues of the HDT is modulated by visual information.