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Concept: Unpleasant odor


Internal action models (IAMs) are brain templates for sensory-motor coordination underlying diverse behaviors [1]. An emerging theory suggests that impaired IAMs are a common theme in autism spectrum disorder (ASD) [2-4]. However, whether impaired IAMs occur across sensory systems and how they relate to the major phenotype of ASD, namely impaired social communication [5], remains unclear. Olfaction relies on an IAM known as the sniff response, where sniff magnitude is automatically modulated to account for odor valence [6-12]. To test the failed IAM theory in olfaction, we precisely measured the non-verbal non-task-dependent sniff response concurrent with pleasant and unpleasant odors in 36 children-18 with ASD and 18 matched typically developing (TD) controls. We found that whereas TD children generated a typical adult-like sniff response within 305 ms of odor onset, ASD children had a profoundly altered sniff response, sniffing equally regardless of odor valance. This difference persisted despite equal reported odor perception and allowed for 81% correct ASD classification based on the sniff response alone (binomial, p < 0.001). Moreover, increasingly aberrant sniffing was associated with increasingly severe ASD (r = -0.75, p < 0.001), specifically with social (r = -0.72, p < 0.001), but not motor (r < -0.38, p > 0.18), impairment. These results uncover a novel ASD marker implying a mechanistic link between the underpinnings of olfaction and ASD and directly linking an impaired IAM with impaired social abilities.

Concepts: Autism, Pervasive developmental disorder, Sense, Olfaction, Asperger syndrome, Autism spectrum, Odor, Unpleasant odor


The current study investigated the extent to which the concurrent presentation of pleasant and unpleasant odors could modulate the perceptual saliency of happy facial expressions in an emotional visual search task. Whilst a search advantage for happy faces was found in the no odor and unpleasant odor conditions, it was abolished under the pleasant odor condition. Furthermore, phasic properties of visual search performance revealed the malleable nature of this happiness advantage. Specifically, attention towards happy faces was optimized at the start of the visual search task for participants presented with pleasant odors, but diminished towards the end. This pattern was reversed for participants in the unpleasant odor condition. These patterns occur through the emotion-inducing capacities of odors and highlight the circumstances in which top-down factors can override perceptually salient facial features in emotional visual search.

Concepts: Psychology, Olfaction, Odor, Emotion, Paul Ekman, Happiness, Visual search, Unpleasant odor


Concentration levels and seasonal variation of odorous gases at landfill site and in surrounding areas within the city of Incheon, South Korea were investigated. Sampling was conducted at 11 points (5 at landfill site and 6 in surrounding areas). The highest concentrations of odorous gases (complex odor, ammonia, acetaldehyde, and VOCs) at landfill site were found in summer, probably due to fast decomposition of waste in high temperature related with more release of ammonia. In addition, specific weather condition of dominant wind direction, humidity and higher atmospheric pressure with no or lower wind speed caused positive effect of higher aldehyde compounds and VOCs concentration. Similar to other studies, sludge-related sampling site S-2, where a couple of odor generating facilities including sludge mixing and drying treatment process are located, showed the highest concentration levels of odorous gases compared to other sites. Odor generation frequency was in the order of acetaldehyde (68.8%) > ammonia (39.4%) > propionaldehyde (21.9%), which means the main substances generating the unpleasant odor at landfill site was recognized as aldehydes and ammonia due to combined effect of sludge-related facilities and meteorological conditions. Offensive odor was not a big pollution issue in most surrounding areas which are located within a circle of 5 km radius of the landfill except high odor generation frequency of acetaldehyde and propionaldehyde. Relative percentage differences (RPD) of odorous gases between day and night times at landfill site were below 10%, which indicates that the concentration differences in day and night were not severe. The relationship between concentrations of complex odor and designated offensive odor substances was analyzed statistically. At landfill site, the analysis shows that the correlation coefficient between the concentration of complex odor and ammonia was quite high (0.833), but it was much lower (0.129) in the surrounding areas due to considerably lower concentrations of these substances.

Concepts: Pollution, Olfaction, Pressure, Atmosphere, Odor, Acetaldehyde, Wind, Unpleasant odor


The prompt recognition of pleasant and unpleasant odors is a crucial regulatory and adaptive need of humans. Reactive answers to unpleasant odors ensure survival in many threatening situations. Notably, although humans typically react to certain odors by modulating their distance from the olfactory source, the effect of odor pleasantness over the orienting of visuospatial attention is still unknown. To address this issue, we first trained participants to associate visual shapes with pleasant and unpleasant odors, and then we assessed the impact of this association on a visuospatial task. Results showed that the use of trained shapes as flankers modulates performance in a line bisection task. Specifically, it was found that the estimated midpoint was shifted away from the visual shape associated with the unpleasant odor, whereas it was moved toward the shape associated with the pleasant odor. This finding demonstrates that odor pleasantness selectively shifts human attention in the surrounding space. (PsycINFO Database Record

Concepts: Olfaction, Primate, Odor, Olfactory fatigue, Electronic nose, Olfactometer, Elementary geometry, Unpleasant odor


Unpleasant odor emissions have traditionally occupied an important role in environmental concern. In this paper, twin biotrickling filters (BTFs) packed with different packing materials, seeded with Bacillus cereus GIGAN2, were successfully constructed to purify gaseous dimethyl disulfide (DMDS). The maifanite-packed BTF showed superior biodegradation capability to the ceramic-packed counterpart in terms of removal efficiency and elimination capacity under similar conditions. At an empty bed residence time of 123s, 100% of DMDS could be removed by maifanite-packed BTF when DMDS inlet concentration was below 0.41gm(-3). To achieve same effect, the inlet concentration must be lower than 0.25gm(-3) for ceramic-packed BTF. The bacterial communities analyses found higher relative abundance of GIGAN2 in the maifanite-packed BTF, suggesting that maifanite is more suitable for GIGAN2 immobilization and for subsequent DMDS removal. This work indicates maifanite is a promising packing material for real odorous gases purification.

Concepts: Oxygen, Bacteria, Microbiology, Fluid dynamics, Olfaction, Bacillus, Odor, Unpleasant odor


Basic neuroscience research provides strong evidence for the role of oxytocin in olfactory processes and social affiliation in rodents. Given prior indication of olfactory impairments that are linked to greater severity of asociality in schizophrenia, we examined the association between plasma oxytocin levels and measures of olfaction and social outcome in a sample of outpatients with schizophrenia (n=39) and demographically matched healthy controls (n=21). Participants completed the 40-item University of Pennsylvania Smell Identification Test (UPSIT), and rated each odor for how positive and how negative it made them feel. Results indicated that individuals with schizophrenia had higher plasma oxytocin levels and lower overall accuracy for UPSIT items than controls. Individuals with schizophrenia also reported experiencing more negative emotionality than controls in response to the olfactory stimuli. Lower plasma oxytocin levels were associated with poorer accuracy for pleasant and unpleasant odors and greater severity of asociality in individuals with schizophrenia. These findings suggest that endogenous oxytocin levels may be an important predictor of olfactory identification deficits and negative symptoms in schizophrenia.

Concepts: Neuroscience, Olfaction, Odor, Olfactory fatigue, Electronic nose, Olfactometer, Smell, Unpleasant odor


The anterior medial temporal lobe (TL), including the amygdala, has been implicated in olfactory processing, e.g., coding for intensity and valence, and seems also involved in memory. With this background, the present study evaluated whether anterior medial TL-resections in TL epilepsy affected intensity and valence ratings, as well as free and cued identification of odors. These aspects of odor perception were assessed in 31 patients with unilateral anterior medial TL-resections (17 left, 14 right) and 16 healthy controls. Results suggest that the anterior medial TL is in particular necessary for free, but also cued, odor identification. TL resection was also found to impair odor valence, but not intensity ratings. Left resected patients rated nominally pleasant and unpleasant odors as more neutral suggesting a special role for the left anterior TL in coding for emotional saliency in response to odors.

Concepts: Temporal lobe, Cerebrum, Hippocampus, Olfaction, Odor, Temporal lobe epilepsy, Lobe, Unpleasant odor


Loss aversion is the tendency to prefer avoiding losses over acquiring gains of equal nominal values. Unpleasant odors not only influence affective state but have also been shown to activate brain regions similar to those mediating loss aversion. Therefore, we hypothesized a stronger loss aversion in a monetary gamble task if gambles were associated with an unpleasant as opposed to pleasant odor. In thirty human subjects, unpleasant (methylmercaptan), pleasant (jasmine), and neutral (clean air) odors were presented for 4 s. At the same time, uncertain gambles offering an equal chance of gain or loss of a variable amount of money, or a prospect of an assured win were displayed. One hundred different gambles were presented three times, each time paired with a different odor. Loss aversion, risk aversion, and logit sensitivity were evaluated using non-linear fitting of individual gamble decisions. Loss aversion was larger when prospects were displayed in the presence of methylmercaptan compared to jasmine or clean air. Moreover, individual differences in changes in loss aversion to the unpleasant as compared to pleasant odor correlated with odor pleasantness but not with odor intensity. Skin conductance responses to losses during the outcome period were larger when gambles were associated with methylmercaptan compared to jasmine. Increased loss aversion while perceiving an unpleasant odor suggests a dynamic adjustment of loss aversion towards greater sensitivity to losses. Given that odors are biological signals of hazards, such adjustment of loss aversion may have adaptive value in situations entailing threat or danger.

Concepts: Risk, Olfaction, Perfume, Odor, Risk aversion, Pleasure, Hedonism, Unpleasant odor


Human body odor, which contains several volatile organic compounds, possesses various odor qualities. To identify key volatile compounds responsible for the common unpleasant odors derived from human axillae and feet, the odor quality and intensity of 118 human axillae and feet were directly evaluated by sniffing, and odor compounds obtained from the subjects were identified. Furthermore, the sensory differences in odor intensity and quality with and without addition of butane-2,3-dione were evaluated by using the visual analog scale (VAS). An acidic odor was a common unpleasant note in human axillae and feet. Butane-2,3-dione was identified as a key compound associated with this odor. Strong positive correlations between the amount of butane-2,3-dione, and the odor intensities of axillae and feet were observed, and the addition of butane-2,3-dione solution to blended short-chain fatty-acid solutions caused significantly increased VAS values of axillary-like odor, unpleasantness, and odor intensity compared to those of each solution without added butane-2,3-dione.

Concepts: Foot, Pain, Odor, Morality, Volatile organic compound, Volatile, Body odor, Unpleasant odor


We behaviorally explore the link between olfaction, emotion and memory by testing the hypothesis that the emotion carried by odors facilitates the memory of specific unique events. To investigate this idea, we used a novel behavioral approach inspired by a paradigm developed by our team to study episodic memory in a controlled and as ecological as possible way in humans. The participants freely explored three unique and rich laboratory episodes; each episode consisted of three unfamiliar odors (What) positioned at three specific locations (Where) within a visual context (Which context). During the retrieval test, which occurred 24-72 h after the encoding, odors were used to trigger the retrieval of the complex episodes. The participants were proficient in recognizing the target odors among distractors and retrieving the visuospatial context in which they were encountered. The episodic nature of the task generated high and stable memory performances, which were accompanied by faster responses and slower and deeper breathing. Successful odor recognition and episodic memory were not related to differences in odor investigation at encoding. However, memory performances were influenced by the emotional content of the odors, regardless of odor valence, with both pleasant and unpleasant odors generating higher recognition and episodic retrieval than neutral odors. Finally, the present study also suggested that when the binding between the odors and the spatio-contextual features of the episode was successful, the odor recognition and the episodic retrieval collapsed into a unique memory process that began as soon as the participants smelled the odors.

Concepts: Psychology, Memory, Hippocampus, Olfaction, Emotion, Episodic memory, Emotion and memory, Unpleasant odor