Olfactory Ability Research Articles

Development of Children’s Olfactory Abilities and Odor Awareness Is Not Predicted by Temperament: a Longitudinal Study

Temperament affects olfaction in cross-sectional studies. However, it is not clear whether it is linked to olfactory development. Here we examined the links between temperament and olfaction over a nearly 2-year period, expecting that children showing higher levels of negative affectivity would exhibit greater odor awareness across repeated testing. As a subsidiary aim, we investigated whether olfactory scores differ as a function of olfactory performance at a younger age. The participants were 73 Czech children (mean age = 5.8 years). Their olfactory abilities were assessed using the Sniffin’ Sticks, and odor awareness was evaluated with the Children’s Olfactory Behaviors in Everyday Life Questionnaire. These were reassessed 21 months later. Mothers provided information on the children’s temperament by completing the Short Form of the Children’s Behavior Questionnaire at the same interval. Children’s temperament was not found to relate to olfactory development over a 21-month period. Odor identification and awareness, but not odor discrimination and threshold, differed as a function of scores achieved at an earlier age. Odor identification and awareness predict themselves over a 21-month period. Links between temperament and olfaction may be only beginning to form at preschool age. While this study suggests that temperament does not play a role in olfactory development, longitudinal studies over a broader timespan are needed to determine the robustness of this finding.

No Sensory Compensation for Olfactory Memory: Differences between Blind and Sighted People.

Blindness can be a driving force behind a variety of changes in sensory systems. When vision is missing, other modalities and higher cognitive functions can become hyper-developed through a mechanism called sensory compensation. Overall, previous studies suggest that olfactory memory in blind people can be better than that of the sighted individuals. Better performance of blind individuals in other-sensory modalities was hypothesized to be a result of, among others, intense perceptual training. At the same time, if the superiority of blind people in olfactory abilities indeed results from training, their scores should not decrease with age to such an extent as among the sighted people. Here, this hypothesis was tested in a large sample of 94 blind individuals. Olfactory memory was assessed using the Test for Olfactory Memory, comprising episodic odor recognition (discriminating previously presented odors from new odors) and two forms of semantic memory (cued and free identification of odors). Regarding episodic olfactory memory, we observed an age-related decline in correct hits in blind participants, but an age-related increase in false alarms in sighted participants. Further, age moderated the between-group differences for correct hits, but the direction of the observed effect was contrary to our expectations. The difference between blind and sighted individuals younger than 40 years old was non-significant, but older sighted individuals outperformed their blind counterparts. In conclusion, we found no positive effect of visual impairment on olfactory memory. We suggest that daily perceptual training is not enough to increase olfactory memory function in blind people.

Physiological Impact of Statins Experimentally Revealed on Ants

Statins are nowadays largely used for caring of persons suffering from hypercholesterolemia. Their use was recently debated. We studied the effects of simvastatin on ants as models. We observed that this product enlarged the insects' sugar food consumption, reduced their general activity, linear speed, orientation ability, trail following, audacity, tactile and pain perception, cognition, ability in escaping from an enclosure, visual and olfactory conditioning ability (thus their shortterm memory), and their middle term visual and olfactory memory. Simvastatin did not affect the ants' relationship with their nestmates. The ants developed adaptation to some adverse effects of simvastatine, and presented no habituation to beneficial effects. Also, simvastatine did not lead to dependence. Consequently, even if simvastatin is efficient in reducing the amount of cholesterol, and leads to some adaptation, no habituation and no addiction, it has several harmful effects. This drug should thus be used only in case of high necessity, never for children, and natural alternative with very few adverse effects should be advantageously researched.

Effects of olfactory training: a meta-analysis

The neural plasticity of the olfactory system offers possibilities of treatment in terms of stimulation of the sense of smell, and different studies have suggested effectiveness of smell training, i.e., daily exposition to certain odors. To obtain reliable and precise estimates of overall treatment benefit on the olfactory function, we meta-analyzed the effects of smell training reported in 13 previous studies. We analyzed the smell training effectiveness across three different olfactory abilities, smell identification, discrimination and threshold for odor detection. We found a significant, positive effect of olfactory training for all olfactory abilities, with large effects of training on identification, discrimination and TDI-score and small-to-moderate effect in the case of threshold for odor detection. Interestingly, the pattern of results differed across Sniffin Sticks subtests depending on the origin of participants smell disorder, and the smell training duration influenced its effectiveness in the case of identification and the TDI score. Although the exact mechanism of olfactory recovery following the smell training still requires further investigation, our meta-analysis showed that such training should be considered an addition or alternative to existing smell treatment methods.

Olfactory discrimination of anal sac secretions in the domestic cat and the chemical profiles of the volatile compounds

Scent emitted from anal sac secretions provides important signals for most Carnivora. Their secretions emit a variety of volatile compounds, some of which function as chemical signals with information about the scent owners. The domestic cat has a pair of anal sac glands to secrete a pungent liquid. Their anal sac secretions may give information about sex, reproductive state, and recognition of individuals. However, little is known about the volatile compounds emitted from anal sac secretions and their biological functions in cats. In this study, we examined the volatile chemical profiles of anal sac secretions in cats and their olfactory ability to discriminate intraspecific anal sac secretions. Analysis with gas chromatography–mass spectrometry showed that the major volatile compounds were short-chain free fatty acids, whose contents varied among individuals, as well as other carnivores. There was no sex difference in the volatile profiles. In temporal analyses of individual anal sac secretions performed 2 months apart, the profiles were highly conserved within individuals. Habituation–dishabituation tests showed that cats can distinguish individual differences in the odor of anal sac secretions. These results suggest that cats utilize short-chain free fatty acids emitted from anal sac secretions to obtain scent information for individual recognition rather than species or sex recognition.

Reduction of olfactory sensitivity during normobaric hypoxia

ObjectiveAcute mountain sickness (AMS) is caused by a low partial pressure of oxygen and may occur above 2500m. The aim of this research was to evaluate olfactory and gustatory abilities of healthy subjects during baseline conditions and after seven hours of normobaric hypoxia. MethodsSixteen healthy subjects were assessed using the Sniffin’ Sticks, as well as intensity and pleasantness ratings. Gustatory function was evaluated utilizing the Taste Strips. Experiments were carried out under baseline conditions (518m altitude) followed by a second testing session after seven hours of normobaric hypoxia exposure (comparable to 4000m altitude). ResultsDuring normobaric hypoxia olfactory sensitivity and intensity estimates were significantly reduced. ConclusionsWe conclude that normobaric hypoxia leads to a significant decrease of olfactory sensitivity and intensity ratings.

Assessing olfactory functions in patients with Barth syndrome.

Barth syndrome is a rare X-linked disease affecting less than 200 individuals worldwide. Several comorbidities have been associated with the pathology and, among those, cardiac myopathy and neutropenia are the most life threatening. The appropriate nutritive support is important to sustain the everyday life of Barth syndrome patients given the chronic fatigue they experience. Since they often prefer salty and fried food, and avoid vegetables and fruits, their eating habit and food preferences do not always provide the proper amount of vitamins and amino acids. It has been indeed reported that Barth syndrome patients have altered taste sensitivity. As olfaction also contributes to food consumption and flavor perception, we decided to investigate their olfactory abilities using the “Sniffin’ sticks’ extended test”. We found no significant difference in any of the tested olfactory abilities between the group of Barth syndrome patients and the healthy controls. In summary, altered food preference of Barth boys could not be easily explained with an altered olfactory perception.

Olfactory biosensor based on odorant-binding proteins of Bactrocera dorsalis with electrochemical impedance sensing for pest management

PurposeUsing the remarkable olfaction ability, insects can sense trace amounts of host plant volatiles that are notorious for causing severe damage to fruits and vegetables and in consequence the industry. The purpose of the paper is to investigate the interactions between olfactory proteins, odorant-binding proteins (OBPs) and host plant volatiles through the developed olfactory biosensors. It might be helpful to develop novel pest control strategies.Design/methodology/approachUsing the successfully expressed and purified OBPs of the oriental fruit fly Bactrocera dorsalis, a biosensor was developed by immobilizing the proteins on interdigitated electrodes through nitrocellulose membrane. Based on electrochemical impedance sensing, benzaldehyde emitted by the host plants, such as Beta vulgaris, was detected, which could be used to investigate and analyze the mechanisms of pests’ sense of chemical signals. The relative decreases of charge transfer resistances of the sensor were proportional to the odorant concentrations from 10−7 M to 10−3 M. Meanwhile, the interactions between OBPs and benzaldehyde were studied through the process of molecular docking.FindingsThe paper provides a pest OBPs-based biosensor that could sensitively detect the host odorants benzaldehyde. Meanwhile, the most related amino acids of OBPs that bind to host plant volatiles can be distinguished with molecular docking.Originality/valueAn olfactory biosensor was developed to explore interactions and mechanism between the pest OBPs and benzaldehyde, which showed promising potentials for small organic molecule sensing. Simultaneously, it might be helpful for novel pest control strategies.

Low plasma tryptophan is associated with olfactory function in healthy elderly community dwellers in Japan

BackgroundDecreased circulating tryptophan (Trp) levels are frequently observed in elderly patients with neurodegenerative disease including Alzheimer’s disease. Trp may serve as a potential biomarker for monitoring disease risk in elderly people. We aimed to investigate the association between low plasma Trp levels and olfactory function, which is known to predict age-related diseases including dementia in elderly people.MethodsA total of 144 healthy elderly Japanese community (≥ 65 years old) dwellers from the Health, Aging and Nutritional Improvement study (HANI study) were the subjects of our analysis. Low Trp levels were classified using the lower limit values of the reference interval according to a previous report. Olfactory function was assessed using a card-type test called Open Essence, which includes 12 odour items that are familiar to Japanese people. The elderly subjects with low circulating Trp levels were compared to a control group with normal plasma Trp levels.ResultsWe conducted the analyses using 144 people aged 65 years or older (mean age 73.7 ± 5.5 years; 36.1% men). The subjects showed normal serum albumin levels (4.4 ± 0.2 g/dL) and no daily living disabilities. Low plasma Trp levels (low Trp group) were found in 11.1% of the study population. The low Trp group showed a significantly lower correct-answer rate for the items india ink, perfume, curry and sweaty smelling socks than control group (P < 0.05). There was also a significant association between low Trp levels and low olfactory ability, after adjusting for age and sex.ConclusionsLower plasma Trp levels were associated with a decrease in olfactory function in functionally competent older individuals. Because olfactory dysfunction predicts age-related diseases, low plasma Trp levels may represent a clinical sign of disease risk in elderly people.

Olfactory dysfunction in Parkinson's disease

Background: Evaluation of olfactory ability can help ensure the correct diagnosis and treatment strategy for neurodegenerative disease. In Parkinson’s diseases (PD), olfactory dysfunction is a frequent non-motor symptom.

A semitransparent snake-like tactile and olfactory bionic sensor with reversibly stretchable properties

Many organisms and animals have sensing abilities that are different from those of human beings; for example, snakes have strong smell-, vibration-, touch- and heat-sensing abilities. A nature-mimicking sensing platform capable of sensing multiple stimuli, such as strain, pressure, temperature and other uncorrelated conditions, is highly desirable to broaden the applications of sensors. Here, we construct a semitransparent intelligent skin-like sensing platform based on polyaniline (PANI) nanowire arrays that can act as a bionic component by simultaneously sensing tactile stimuli and detecting colorless, odorless gas. Our multifunctional bionic sensing strategy is remarkably adaptive for versatile applications. The strain-sensing performance is superior to that of most conducting polymer-based sensors reported so far and is comparable to or even better than traditional metal and carbon nanowire/nanotube-based strain sensors. The highest gauge factor demonstrated is 149, making our system a remarkable candidate for strain-sensing applications. The sensor can accurately detect a wide range of human motions. We also demonstrate the simultaneous controlled olfaction ability for the detection of methane with high sensitivity and a fast response time. These results enable the realization of multifunctional and uncorrelated sensing capabilities, which will afford a wide range of applications to augment robotics, treatment, simulated skin, health monitoring and bionic systems.

Preliminary evidence for differential olfactory and trigeminal processing in combat veterans with and without PTSD.

Structural and functional changes in the olfactory system are increasingly implicated in the expression of PTSD. Still, very little is known about the neurobiological networks of trauma-related odor sensitivity or how they relate to other objective and subjective measures of olfaction and PTSD. The purpose of this study was to replicate prior findings and further characterize olfactory function in trauma-exposed combat veterans with and without PTSD. We also sought to extend this area of research by exploring the effects of time since the combat-related index trauma (TST) on post-trauma olfactory function, as well as by correlating odor-elicited brain activity to general olfactory ability and odor-elicited PTSD symptoms. Participants included combat veterans with PTSD (CV+PTSD; n = 21) or without any psychiatric disorder (CV-PTSD; n = 27). TST was coded as greater (n = 24) or less (n = 24) than 5 years. There were main effects and/or interaction for PTSD-status and TST across several parameters of olfactory function: odor detection, odor identification, ratings for trauma-related odor intensity and triggered PTSD symptoms, and trauma odor-elicited brain activation. Overall, results suggest olfactory impairment in chronic PTSD, but not necessarily in the earlier stages of the disorder, although some early-stage olfactory findings may be predictive of later olfactory impairment. Results also suggest that trauma-exposed individuals who never develop PTSD may demonstrate olfactory resiliency. Finally, results highlight a potentially unique role of trigeminal odor properties in the olfactory-PTSD relationship.

Effects of Sublethal Concentrations of Chlorpyrifos on Olfactory Learning and Memory Performances in Two Bee Species, Apis mellifera and Apis cerana

Chlorpyrifos is a widely used organophosphorus insecticide. The acute oral 24 h median lethal dose (LD50) value of chlorpyrifos in Apis mellifera and in Apis cerana was estimated to assess differential acute chlorpyrifos toxicity in the two bee species. The LD50 values of chlorpyrifos in A. mellifera and in A. cerana are 103.4 ng/bee and 81.8 ng/bee, respectively, which suggests A. cerana bees are slightly more sensitive than A. mellifera bees to the toxicity of chlorpyrifos. Doses half the acute LD50 of chlorpyrifos were selected to study behavioral changes in the two bee species using proboscis extension response assay. A. mellifera foragers treated with chlorpyrifos showed significantly lower response to the 10% sucrose solution compared to control bees after 2, 24 and 48 h. Chlorpyrifos significantly impaired the olfactory learning abilities and 2 h memory retention of forager bees regardless of honey bee species, which may affect the foraging success of bees exposed to chlorpyrifos.

Metal concentrations and distributions in the human olfactory bulb in Parkinson\u2019s disease

In Parkinson’s disease (PD), the olfactory bulb is typically the first region in the body to accumulate alpha-synuclein aggregates. This pathology is linked to decreased olfactory ability, which becomes apparent before any motor symptoms occur, and may be due to a local metal imbalance. Metal concentrations were investigated in post-mortem olfactory bulbs and tracts from 17 human subjects. Iron (p < 0.05) and sodium (p < 0.01) concentrations were elevated in the PD olfactory bulb. Combining laser ablation inductively coupled plasma mass spectrometry and immunohistochemistry, iron and copper were evident at very low levels in regions of alpha-synuclein aggregation. Zinc was high in these regions, and free zinc was detected in Lewy bodies, mitochondria, and lipofuscin of cells in the anterior olfactory nucleus. Increased iron and sodium in the human PD olfactory bulb may relate to the loss of olfactory function. In contrast, colocalization of free zinc and alpha-synuclein in the anterior olfactory nucleus implicate zinc in PD pathogenesis.

Assessing individual performance and maintaining breath sample integrity in biomedical detection dogs

In empirical tests of biomedical detection dogs, exhaled breath samples are often used because breath contains volatile organic compounds that can signal metabolic states, infection, or disease. However, in studies that present dogs with breath samples, results show a notable degree of variability both between and within studies. Differing protocols for the collection and storage of exhaled breath samples may contribute to this observed variability. The goal of the current study was therefore to test whether there was a difference in the detectability of breath samples collected using silicone-coated versus uncoated cotton balls. This was tested in two experiments. In the first experiment, breath samples were prepared using both silicone-coated and uncoated cotton balls, which were then left exposed to the surrounding air. Four dogs’ detection of the samples was tested using a cued, three alternative forced choice (3AFC) procedure at regular intervals up to two hours after the samples were prepared. The results of Experiment 1 showed that the dogs’ performance was above chance and there was no significant difference in the dogs’ detection of the breath samples across conditions. In the second experiment, a series of breath samples were prepared and stored for one, two, three, and four week periods. The same four dogs’ ability to detect the breath samples was tested each week using the same cued 3AFC procedure. The results of Experiment 2 showed that when silicone-coated cotton balls were used, all four dogs could detect the breath samples at above chance levels after the samples were stored for three weeks, and two dogs could detect the samples that were stored for four weeks. When the dogs were tested on their ability to detect the breath samples prepared using uncoated cotton, two dogs’ performance fell to below chance levels at one week of storage time, while the other two dogs could detect the breath samples at above chance levels after the samples were stored for four weeks. Taken together, the results of the two experiments illustrate that silicone-coated cotton balls do not improve detectability of breath samples within two hours, but can greatly improve the detectability of breath samples stored over longer periods of time. Since the use of silicone-coated cotton balls only improved the detectability of the breath samples for two of the four dogs, these results highlight the importance of examining individual differences in dogs’ performance. Furthermore, we argue that, given the inherent differences in olfactory ability across dogs, widespread use of silicone-coated cotton balls for the collection of breath samples would increase the pool of testable dogs for biomedical detection studies and would decrease the degree of variability both within and between studies.

Females of the annual killifish Austrolebias reicherti (Cyprinodontiformes: Rivulidae) recognize conspecific mates based upon chemical cues

Olfactory abilities to discriminate conspecifics can be determinant to prevent hybridization between closely-related species in many taxa. Annual killifish Austrolebias reicherti and A. charrua are sister species inhabiting temporary ponds within Eastern Wetlands of Uruguay with an overlapping area in their distributions. Herein, we assess species recognition sensory abilities in females of A. reicherti in classic dual-choice tests. We exposed two different groups of females, one to olfactory but not visual cues, and the other to visual but not olfactory cues, from conspecific and heterospecific A. charrua males. Austrolebias reicherti females preferred conspecific males when based solely on olfactory cues, and showed no discrimination when exposed to visual traits only. Austrolebias inhabit shallow, muddy and highly turbid ponds that may promote the use of non-visual cues. Although preliminary, the results of this study suggest the importance of chemical communication in species mate recognition in A. reicherti and points annual fishes as a promising model to study the role of mate choice in reproductive isolation and speciation.

Development of test for determining olfactory investigation of complex odours in cattle

The sense of smell is likely to influence the behaviour of domestic and captive animals in a wide range of management and housing situations. In domestic cattle, there may be unexploited potential for using odours and olfaction in the management; however, published studies on bovine olfactory capacity are scarce. By applying an olfactory Habituation/Dishabituation test developed for rodents, this study aimed to assess olfactory ability in cattle. Twenty-three cows (n=10) and heifers (n=13) were tested with three different odours (orange juice, liquid coffee and tap water as an odourless control) presented in a test bucket. The test was conducted on individual animals in their home pen and consisted of each odour being presented twice in a row for 2min each with an inter-trial pause of 2min. Following another 2-min pause without odour the animal was presented with a new odour, with order of odour presentation balanced among animals. Duration of sniffing (muzzle in proximity or contact with) the test bucket as well as the occurrence of licking or biting the test bucket were recorded by direct observation. All animals sniffed an odour (i.e. the test bucket) less when presented for the second time (habituation; all 1st vs. 2nd presentations: P<0.001). Sniffing duration increased at the subsequent presentation of a new odour (dishabituation; all 2nd vs. 1st presentations: P<0.001). All animals sniffed coffee and orange longer than water (water vs. coffee: P<0.001 and water vs. orange: P<0.001), but they also sniffed coffee longer than orange (P=0.021). Licking or biting behaviour occurred only when presented with coffee or orange (13 out of 23 animals for both samples). The test showed that cows and heifers were able to distinguish between different complex odours (coffee and orange juice), and that the animals showed increased interest for one of the odours (coffee). This is the first example of a Habituation/Dishabituation test being adapted for and applied to cattle. The test may require further development, but represents the first steps towards exploring the possibility of using odours when adapting or enriching the environment in which we keep cattle.

The Subjective-Objective Disjunction in Psychometrically-Defined Schizotypy: What it is and Why it is Important?

An interesting set of findings has emerged from the literature regarding schizotypy. Individuals with psychometric schizotypy self-report pathology in certain neuropsychological, affective experiential, expressive and olfactory abilities and subjective quality of life at levels between one and two standard deviations more severe than their non-schizotypal peers; a level often similar to that seen in chronic schizophrenia. Objectively however, individuals with psychometric schizotypy do not show concomitant impairments in these domains. This “subjective-objective” disjunction is remarkable in that samples are largely drawn from college settings; thus likely reflecting the healthiest individuals within the schizophrenia-spectrum. We propose that this disjunction can be conceptualized as a “cognitive bias”, and that it reflects a dysfunction in the systems underlying reasoning and self-evaluation. In this article, we lay out evidence underlying the subjective-objective disjunction and discuss potential methodological and psychological issues that may explain this phenomenon.

APOE-\u025b4 effects on longitudinal decline in olfactory and non-olfactory cognitive abilities in middle-aged and old adults

Characterizing aging-related decline trajectories in mental abilities, and relationships of the ɛ4 allele of the Apolipoprotein gene, helps to identify individuals at high risk for dementia. However, longitudinal changes in olfactory and non-olfactory cognitive abilities have not been investigated in relation to the ɛ4 allele. In the present study, participants from a large population-based study (657 middle-aged and 556 old) were tested over 10 years on their performance on an odor identification task and three non-olfactory cognitive tasks; MMSE, episodic memory, and semantic memory. Our key finding is that in middle-aged participants, odor identification declined twice as fast for ɛ4/4 homozygotes, compared to non-carriers. However, in old participants, the ɛ4/4 homozygotes showed an impaired odor identification ability, but they declined at a similar rate as the non-carriers. Furthermore, in old participants all assessments displayed aging-related declines, but exaggerated declines in ɛ4-carriers were found only in MMSE and episodic memory assessments. In sum, we present evidence that odor identification ability starts to decline already in middle-aged, and that carriers of ɛ4/4, who are at highest risk of developing dementia, decline twice as fast. Our results may have implications for use of odor identification assessment in detection of early-stage dementia.

Differences in peripheral sensory input to the olfactory bulb between male and female mice

Female mammals generally have a superior sense of smell than males, but the biological basis of this difference is unknown. Here, we demonstrate sexually dimorphic neural coding of odorants by olfactory sensory neurons (OSNs), primary sensory neurons that physically contact odor molecules in the nose and provide the initial sensory input to the brain’s olfactory bulb. We performed in vivo optical neurophysiology to visualize odorant-evoked OSN synaptic output into olfactory bub glomeruli in unmanipulated (gonad-intact) adult mice from both sexes, and found that in females odorant presentation evoked more rapid OSN signaling over a broader range of OSNs than in males. These spatiotemporal differences enhanced the contrast between the neural representations of chemically related odorants in females compared to males during stimulus presentation. Removing circulating sex hormones makes these signals slower and less discriminable in females, while in males they become faster and more discriminable, suggesting opposite roles for gonadal hormones in influencing male and female olfactory function. These results demonstrate that the famous sex difference in olfactory abilities likely originates in the primary sensory neurons, and suggest that hormonal modulation of the peripheral olfactory system could underlie differences in how males and females experience the olfactory world.