Color enhances orthonasal olfactory intensity and reduces retronasal olfactory intensity

The effect of color on orthonasal and retronasal odor intensities was investigated. When odorants were smelled orthonasally (i.e., through the nostrils), color enhanced odor intensity ratings, consistent with previous reports. However, when odorants were smelled retronasally (i.e., the odorous solution was put in the mouth), color reduced odor intensity ratings. These different effects of color on odor intensity (i.e., enhancement orthonasally and suppression retronasally) appear to be the result of route of olfactory stimulation rather than of any procedural artifact. This supports previous reports that retronasal and orthonasal odors are perceived differently.     

Olfactory discrimination of short chain fatty acids in rats with large bilateral lesions of the olfactory bulbs

Rats trained preoperatively to discriminate between acetic acid and caproic acid and between acetic acid and propionic acid were tested for their memory of these tasks and ability to discriminate between these odorants and between the enantiomers of carvone after receiving large bilateral bulbar lesions that included most of the fatty acid responsive areas identified in prior physiological studies. Concentrations of acid odorants were varied to insure that discrimination was based on the qualitative difference between acids. Experimental rats performed somewhat poorer than controls on the memory test but had no significant deficits in performing the acid discrimination tasks or discriminating between the enantiomers of carvone. These results demonstrate that removal of most bulbar sites identified as responsive to fatty acids and the consequent disruption of patterned input to the bulb is largely without effect on discriminating odor qualities of structurally similar acids.     

Sniff magnitude test: relationship to odor identification, detection, and memory tests in a clinic population

Recently a novel measure of olfactory function, the Sniff Magnitude Test (SMT), was developed that relies on changes in inhalation in response to an odor. The relationship of this unique test to that of other olfactory tests has received little investigation. In this study, we assessed, in 132 patients presenting to a chemosensory disorders clinic, the relationship of SMT scores to those from 3 standardized psychophysical tests: the University of Pennsylvania Smell Identification Test (UPSIT), a phenyl ethyl alcohol odor detection threshold test, and a short-term odor memory/discrimination test. SMT scores were roughly related to olfactory dysfunction categories defined for the UPSIT and correlated moderately with the other tests. Malodors (1% and 3% methylthiobutyrate [MTB], 1% ethyl 3-mercaptoproprionate) exhibited stronger correlations than nonmalodors (3% phenyl ethyl alcohol [PEA], 3% amyl acetate, 3% n-butanol) and elicited greater sniff suppression. In a principal component analysis, the SMT measures loaded on components different from those of the other tests, which loaded on a separate component. Anticipatory responses (i.e., smaller sniffs) occurred across trials for the first malodor (1% MTB), but not for the first nonmalodor (3% PEA), that was encountered. These results, along with those of an earlier factor analysis, suggest that sniff magnitude is influenced by odorant quality and intensity, as well as by cognitive factors.     

Response accuracy and odor sampling time in mice trained to discriminate between enantiomers of carvone and those of terpinen-4-ol

Response accuracy and odor-sampling times were used to compare the ability of mice to detect (+)-carvone and (+)-terpinen-4-ol and to discriminate between enantiomers of carvone and of terpinen-4-ol. Except for increased odor sampling when mice were first exposed to the (+)-carvone odor, there was no difference in odor-sampling time or response accuracy in tests of odor detection or in discriminating between enantiomers of these odorants. These results fail to support the suggestion that odorants that produce different patterns of olfactory bulb activation should be easier to discriminate than those that produce much more similar patterns of bulbar activation.     

植食性昆虫寄主植物嗅觉搜寻述介

植食性昆虫与寄主植物关系的本质是化学。植食性昆虫搜寻寄主的嗅觉媒介是植物气味即化学信息物质。在介绍植物气味构成及其扩散模型基础上,阐述了植物气味在地上植食性昆虫成虫、幼虫和地下植食性昆虫搜寻寄主过程中的嗅觉导向作用,并指出了今后相关研究需要注意的问题。从植物与环境因子的关系来看,植物气味包括构成性气味和诱发性气味两类,这两类气味的概念既相联系而又不同。构成性气味组分及构成因植物分类地位等而不同。诱发性气味组分因植食性昆虫取食、植物病原微生物、机械致伤等因子的胁迫而变化,这种变化性状随植物属和/或种、植株生长发育阶段、胁迫因子性质及其作用方式而不同。无论是哪种植物气味,其释放均具有节律性。气味扩散过程比较复杂,扩散状态可用数学模型表征。对于地上植食性昆虫成虫,植物气味对其寄主搜寻行为具有导向特异性,重点分析了这种特异性形成的两个假说;鳞翅目昆虫幼虫,能够利用植物化学信息物质趋向寄主植物或回避非寄主植物;地下植食性昆虫搜寻寄主,既与寄主植物地下组织释放或分泌的次级代谢物有关,又与一些初级代谢物有关。初级代谢物中的CO₂,起着“搜寻触发器”作用。有助于增强人们对昆虫与植...     

Odor-sampling time of mice under different conditions

Response accuracy and odor sample times on positive (S+) and negative (S-) trials were recorded for mice trained on a variety of go, no-go odor detection and discrimination tasks. Odor sample time was relatively stable over extended training on the same task, increased during acquisition of difficult tasks, relatively insensitive to reinforcement magnitude, and, in some cases, provided more information regarding task difficulty and discrimination than did response accuracy. Mice generally sampled longer on S- trials in simple odor detection tasks but longer on S+ trials in odor discrimination tasks.     

The acoustic startle reflex as a tool for assessment of odor environment effects on affective states in laboratory mice

Apart from self and conspecific odors, odors from other species also influence the affective states in laboratory mice (Mus musculus musculus) in their home cages and during experimental procedures, possibly inducing confusion and inconsistency in experimental data. Thus, it is important to detect the types of animal odors associated with housing, husbandry, and laboratory practice that can arouse different types of affective changes in mice. Here, we aimed to test the effectiveness of the acoustic startle reflex (ASR) in detecting changes in the affective states of laboratory mice due to animal-derived-odor as it has a non-zero baseline, and can be enhanced or attenuated by positive or negative affective shifts, respectively. We used ASR to examine the affective changes in mice that were induced by bedding odors and an alarm pheromone. The odor of bedding obtained from the mice’ home cages significantly attenuated the ASR, suggesting positive affective shifts in the test mice, whereas that from bedding obtained from rat cages significantly enhanced the ASR, suggesting negative affective shifts. No significant changes in ASR were observed in mice presented with the odor of bedding obtained from cages of unfamiliar conspecifics. In contrast, there was significant ASR enhancement in mice exposed to volatile components of alarm pheromones trapped in water, suggesting negative affective shifts. Thus, our findings show that ASR may be a valuable tool in assessing the effects of odors on the affective states in laboratory mice.     

Behavioral responses to odorants in drosophila require nervous system expression of the beta integrin gene myospheroid

Integrins are cell adhesion molecules that mediate numerous developmental processes in addition to a variety of acute physiological events. Two reports implicate a Drosophila beta integrin, betaPS, in olfactory behavior. To further investigate the role of integrins in Drosophila olfaction, we used Gal4-driven expression of RNA interference (RNAi) transgenes to knock down expression of myospheroid (mys), the gene that encodes betaPS. Expression of mys-RNAi transgenes in the wing reduced betaPS immunostaining and produced morphological defects associated with loss-of-function mutations in mys, demonstrating that this strategy knocked down mys function. Expression of mys-RNAi transgenes in the antennae, antennal lobes, and mushroom bodies via two Gal4 lines, H24 and MT14, disrupted olfactory behavior but did not alter locomotor abilities or central nervous system structure. Olfactory behavior was normal in flies that expressed mys-RNAi transgenes via other Gal4 lines that specifically targeted the antennae, the projection neurons, the mushroom bodies, bitter and sweet gustatory neurons, or Pox neuro neurons. Our studies confirm that mys is important for the development or function of the Drosophila olfactory system. Additionally, our studies demonstrate that mys is required for normal behavioral responses to both aversive and attractive odorants. Our results are consistent with a model in which betaPS mediates events within the antennal lobes that influence odorant sensitivity.     

Olfactory deficits in patients affected by minimal hepatic encephalopathy: a pilot study

Minimal hepatic encephalopathy (MHE) is the earliest stage of hepatic encephalopathy and is associated with changes in cognitive functions, in electrophysiological parameters, and in cerebral neurochemical/neurotransmitter homeostasis. MHE can be observed in patients with cirrhosis who have no clinical evidence of hepatic encephalopathy (HE). At present, no data are available on a possible olfactory dysfunction in such a syndrome, although the pathophysiology of HE may alter olfactory functions since some of the neurotransmitters impaired in the syndrome are involved in the transmission of olfactory information. In the present paper, we performed a preliminary study aimed at detecting whether identification and recognition odor memory is altered in patients with MHE. Twelve patients diagnosed as MHE on the basis of their scores at the portosystemic encephalopathy (PSE)-syndrome test battery, and 12 age-matched controls were studied. Consistent with the hypothesis, patients performed significantly worse than controls for both odor identification and recognition tasks. In addition, a significant correlation between the two olfactory tests and the PSE-syndrome test score was found. This pattern supports the notion that olfactory alterations related to cognitive dysfunction in patients with MHE may be linked to the pathophysiology of HE.     

SURE,why not? The SUbstitution-REciprocity method for measurement of odor quality discrimination thresholds: replication and extension to nonhuman primates

Recently, Olsson and Cain (2000, Chem. Senses, 25: 493) introduced a psychometric method which, for the first time, allows the standardized determination of odor quality discrimination (OQD) thresholds. The method defines a threshold value that is an average fraction by which one odorant has to be substituted with another to reach a criterion level of discrimination. This measure of discrimination is reciprocal in the sense that it is a result of two separate psychometric functions involving two different standards but the same comparison stimuli. Using the same odor stimuli as Olsson and Cain, with six human subjects but adopting a slightly different experimental design, we were able to replicate their finding that the proportion of correct discriminations changes monotonically with the proportion of adulterant in mixtures of eugenol and citral. As the SURE (SUbstitution-REciprocity) method is based on discriminative responses, it should also be applicable with nonhuman species which can be trained to give unequivocal discriminative responses at the behavioral level. Using an olfactory conditioning paradigm, we therefore trained four squirrel monkeys to discriminate between exactly the same pairs of odor stimuli as our human subjects. We found the psychometric functions of the monkeys to be similar to those of the human subjects. Our results show that the SURE method can successfully be employed with nonhuman primates and thus offers a new approach to study the odor spaces of nonhuman species. Future studies should elucidate whether the SURE method allows for direct comparisons of OQD thresholds and of similarities and differences between odor quality perception of different species.     

Perceptual interactions between characteristic notes smelled above aqueous solutions of odorant mixtures

Twenty-two experienced panelists rated odor intensity of aqueous solutions of citral, octen-1-ol-3, and hexanal. The panel assessed unmixed components and mixtures (9 binary and 4 ternary). In sensory sessions dedicated to mixtures (n = 6), evaluation was focused on one target odor, presented at a fixed concentration. All components had lower odor intensity on mixed presentations. In many cases, information obtained from simpler systems was not extended to complex mixtures. In a mixture, the competition between odorant molecules on qualitative aspects (dominance/suppression) imbalanced components contribution, anticipated from the quantitative distribution. Hexanal appeared to be the potentially weaker odorant in paired combinations, whereas octen-1-ol-3 had a lower relative impact on ternary systems. Suppression of the odor of octen-1-ol-3 and a concomitant increase in the odor of hexanal was common to all ternary mixtures. Reciprocal inhibition of octen-1-ol-3 and citral odors through perceptual interactions was suspected. Mutual suppression is suspected to have eased the perception of hexanal intensity.     

The sniff is part of the olfactory percept

In this review, we use data obtained primarily from humans to argue that sniffs are not merely a stimulus carrier but are rather a central component of the olfactory percept. We argue that sniffs 1) are necessary for the olfactory percept, 2) affect odorant intensity perception and identity perception, 3) drive activity in olfactory cortex, 4) are rapidly modulated in an odorant-dependent fashion by a dedicated olfactomotor system, and 5) are sufficient to generate an olfactory percept of some sort even in the absence of odor.     

Fear-like behavioral responses in mice in different odorant environments: Trigeminal versus olfactory mediation under low doses

Odors can have repulsive effects on rodents based on two complementary adaptive behaviors: the avoidance of predator odors (potentially dangerous) and the avoidance of trigeminal stimulants (potentially noxious). The present study aimed to compare the behavioral effects on mice of odors according to their trigeminal properties and ecological significance. We used three different odors: 2,4,5-trimethylthiazoline (TMT: a fox feces odor frequently used to elicit fear-induced behaviors), toluene (a strong stimulant of the trigeminal system) and phenyl ethyl alcohol (PEA: a selective stimulant of the olfactory system). First, we checked preference and avoidance behaviors in mice with and without anosmia towards these odors to ensure their olfactory/trigeminal properties. Secondly, we used a standard test (open-field and elevated plus-maze) to assess the behaviors of mice when exposed to these odors. The results show that the anosmic and control mice both avoided TMT and toluene odors. In the open-field and the elevated plus-maze, mice exhibited "anxious" behaviors when exposed to TMT. Conversely, exposure to PEA induced "anxiolytic" effects confirmed by low blood corticosterone levels resulting from completion of the elevated plus-maze. Compared with TMT exposure, toluene exposure induced moderate "anxious" effects.     

Asymmetric suppression of components in binary aldehyde mixtures: behavioral studies in the laboratory rat

The aim of the present study was to assess component interaction in the perception of the 2 aldehydes butanal and heptanal when presented in binary mixtures to rats. A further aim was to develop a behavioral paradigm for testing suppression of components in mixtures using rodent subjects. Thirsty rats were initially trained to discriminate between the 2 aldehydes butanal and heptanal in an olfactometer using a go/no-go discrimination task. This involved rats learning to place their noses in a sniff port where odors were presented and to lick a tube for water reward when one of the aldehydes was presented (S+) while withholding licking at the tube to the other, unrewarded, aldehyde (S-). A mixture condition was then introduced into the task, whereby a proportion of trials involved presentation of a combination of the 2 aldehydes as an additional unrewarded condition. Rats readily learned to withhold licking on trials when the mixture was presented. The concentration of the nonrewarded (S-) aldehyde in the mixture was then systematically decreased, whereas the concentration of the S+ component was held constant. This eventually caused the S+ component in the mixture to suppress detection of the S-, as shown by an increasing number of lick responses (false alarms) on trials when the mixture was presented. These suppressing effects occurred well above the detection threshold for the S- aldehyde presented alone. Results showed asymmetric suppression in the mixture condition such that butanal suppressed detection of heptanal at much lower concentrations than vice versa. A second experiment showed that when both butanal and heptanal were present in a binary mixture at the same concentration (10(-6) volume %), then rats responded to the mixture as if only butanal was present. These findings are discussed in terms of butanal having higher mobility and being able to compete more effectively than heptanal for occupation of shared receptor sites.     

Analog synthesis of DAMASCENOLIDETM,an important aroma component of roses,and their odor properties

ABSTRACT

DAMASCENOLIDE^TM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of double-bond isomers of 1 and concluded that the position and the geometric isomerism of the double-bond had a significant effect on the odor. For the purpose of deepening knowledge about structure–odor relationships, we synthesized 13 analogs of compound 1 and evaluated their odors. As a result, it was found that the presence of two double-bonds and branched methyl group at the terminal position in the side chain was essential in order to have a citrus-like odor. Substitution of the side chain with appropriate length at the appropriate 4-position of the 2(5H)-furanone ring was also an important factor in determining the quality of the odor.     

Butane‐2,3‐dione: the Key Contributor to Axillary and Foot Odor Associated with an Acidic Note

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.     

Odor, taste, and flavor perception of some flavoring agents

Psychophysical functions for the odor, taste, and flavor offive common flavorings were obtained by the method of magnitudeestimation. The stimuli included three simple compounds (vanillin,piperonal, and benzaldehyde) and two complex ones (natural vanillaextract and artificial almond essence). The odor intensity ofall the flavorings grew much less rapidly with concentrationthan did taste intensity. The growth of flavor for the complexsubstances and piperonal behaved very much like taste. For vanillinand benzaldehyde, the flavor functions resembled taste functionsat high concentrations but showed a tendency to flatten at lowerconcentrations. These findings implied that, at least for someflavorings, the growth of flavor reflects the most salient featureon the particular concentration range studied. At low concentrationsodor seems to be the most important feature and so flavor functionsare generally flat, but at high concentrations taste becomesthe salient feature and so flavor functions steepen.     

Can ambient odors influence the recognition of emotional words? A behavioral and event-related potentials study

Odor context can affect the recognition of facial expressions. However, there is no evidence to date that odor can regulate the processing of emotional words conveyed by visual words. An emotional word recognition task was combined with event-related potential technology. Briefly, 49 adults were randomly divided into three odor contexts (pleasant odor, unpleasant odor, and no odor) to judge the valence of emotional words (positive, negative, and neutral). Both behavioral and Electroencephalography (EEG) data were collected. Both the pleasant odor and unpleasant odor contexts shortened the response time of the subjects to emotional words. In addition, negative words induced greater amplitudes of early posterior negativity (EPN) and late positive potential (LPP) than the positive and neutral words. However, the neutral words induced a larger N400 amplitude than the positive and negative words. More importantly, the processing of emotional words was found to be modulated by external odor contexts. For example, during the earlier (P2) processing stages, pleasant and unpleasant odor contexts induced greater P2 amplitudes than the no odor context. In the unpleasant odor context, negative words with the same odor valence induced greater P2 amplitudes than the positive words. During the later (N400) stages, various regions of the brain regions exhibited different results. For example, in the left and right frontal areas of the brain, exposure to positive words in a pleasant odor context resulted in a smaller N400 amplitude than exposure to neutral words in the same context. Meanwhile, in the left and right central regions, emotional words with the same valence as pleasant or unpleasant odor contexts elicited the minimum N400 amplitude. Individuals are very sensitive to emotional information. With deeper processing, different cognitive processes are reflected and they can be modulated by external odors. In the early and late stages of word processing, both pleasant and unpleasant odor contexts exhibited an undifferentiated dominance effect and could specifically modulate affectively congruent words.     

Development of a smell identification test using a novel stick-type odor presentation kit

The odor identification is strongly influenced by the social and cultural factors; therefore, the odorants used in a smell identification test should be familiar to the test population. In addition, the device used in the test is desired to be simply handled and retain odor quality over time. We developed a novel stick-type odor presentation kit that consists of microcapsules of odorant incorporated into stable cream and the smell identification test using it. Thirteen odorants were selected to be familiar to the test population. In the test, we used two identification methods: one was a modified forced-choice paradigm with "detectable but not recognizable" and "no smell detected" added as choices and the other was a two-step identification paradigm where the participant first selected one of eight odor categories and then chose the specific odor name from the selected category. We verified the performance of the odor stick and the test by stability, using a test-retest paradigm, comparing this test with another smell test, and testing Japanese people from a range of age groups. We conclude that this kit is a useful odor presentation device, and the test using it works effectively as a smell identification test.