A Redefinition of Odor Mixture Quality.

Odor mixtures are perceived as different from (configural) or the same as (elemental) their components. Recent studies (L. M. Kay, C. A. Lowry, & H. A. Jacobs, 2003; C. Wiltrout, S. Dogra, & C. Linster, 2003) propose that component structural or perceptual similarities predict configural properties of binary mixtures. The authors evaluated this in rats using 4 binary mixtures with varying structural similarity (eucalyptol-benzaldehyde, eugenol-benzaldehyde, octanol-octanal, and [+/-]-limonene). The range of tested ratios for each mixture was determined by the components' vapor pressures. Three results are presented: (a) No mixture maintains purely elemental or configural properties for all concentration ratios, (b) structural similarity or dissimilarity does not predict configural or elemental perception, and (c) overshadowing is significant in responses to all odor sets. The authors offer more precise definitions of elemental and configural properties and overshadowing as they relate to odor mixture perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A critical test of the overlap hypothesis for odor mixture perception.

The overlap hypothesis of mixture perception is based on the observation that mixtures of perceptually similar odorants tend to smell different from their components (configural), whereas mixtures of dissimilar odorants smell like their components (elemental). Because input patterns of perceptually similar odorants tend to overlap more than dissimilar ones, it has been hypothesized that component pattern overlap can predict a mixture's perceptual quality, with high overlap predicting a configural response and low overlap an elemental response. The authors used 7 pairs of odorants chosen for different degrees of overlap in their monomolecular 2-deoxyglucose activation patterns to test the theory in a go/no-go behavioral assay that measured generalization from binary mixtures to components. The authors show that individual component odorant input patterns are not sufficient to predict mixture quality, falsifying the overlap hypothesis. An important finding is that different odorant pairs with similar glomerular overlap showed opposite behavioral–perceptual responses, suggesting nonlinear effects at the receptor or glomerular level or the critical involvement of higher order areas. Thus, the authors posit that imaging the mixtures themselves may provide additional information needed to reliably predict mixture quality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binary mixture perception is affected by concentration of odor components.

Some controversy still exists as to how binary odorant mixtures are behaviorally perceived, despite many studies aimed at understanding this phenomenon. Binary mixture perception by rodents is a first step in elucidating how more complex odor blends may be perceived. Research thus far has examined how the degree of component similarity, olfactory receptor overlap, relative concentration of components, and even olfactory enrichment affect the behavioral perception of binary mixtures. These studies have aimed to categorize binary mixtures into 1 of 3 rigid categories, but often the results conflict as to which category a particular mixture belongs. In the present article, the authors used a habituation/discrimination paradigm to determine whether rats' perception of one component of a binary mixture of either perceptually similar or dissimilar components changed when the concentration of both components was varied together. The authors found that perception of a binary mixture changed with changing component concentration, such that one binary mixture could be categorized differently depending on component intensity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Configurational and nonconfigurational interactions between odorants in binary mixtures.

Studies on odor mixture perception suggest that although odor components can often be identified in mixtures, mixtures can also give rise to novel perceptual qualities that are not present in the components. Using an olfactory habituation task, the authors evaluated how the perceptual similarity between components in a mixture affects the perceptual quality of the mixture itself. Rats perceived binary mixtures composed of similar components as different from their 2 components, whereas binary mixtures composed of dissimilar components were perceived as very similar to their components. Results show that for both types of mixtures, pretraining to Component A reduces subsequent learning about Component B in rats trained in the presence of A. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discriminating the stimulus elements during human odor–taste learning: A successful analytic stance does not eliminate learning.

Odor “sweetness” may arise from experiencing odors and tastes together, resulting in a flavor memory that is later reaccessed by the odor. Forming a flavor memory may be impaired if the taste and odor elements are apparent during exposure, suggesting that configural processing may underpin learning. Using a new procedure, participants made actual flavor discriminations for one odor–taste pair (e.g., Taste A vs. Odor X–Taste A) and mock discriminations for another (e.g., Odor Y–Taste B vs. Odor Y–Taste B). Participants, who were successful at detecting the actual flavor discriminations, demonstrated equal amounts of learning for both odor–taste pairings. These results suggest that although a capacity to discriminate flavor into its elements may be necessary to support learning, whether participants experience a configural or elemental flavor representation may not. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Inhibition of matrix metalloproteinases attenuates anti-Thy1.1 nephritis

An understanding of the olfactory system of any animal must account for how odor mixtures are perceived and processed. The present experiments apply associationist models to the study of how elements are processed in binary odorant mixtures. Using experimental designs for Proboscis Extension Conditioning of honey bees, I show that learning about a pure odorant element is frequently affected by its occurrence in a mixture with a second odorant. Presence of a background odor when an odorant is associated with sucrose reinforcement decreases the rate and/or asymptotic level of associative strength that accumulates to that odorant. This interaction is in part due to synthetic qualities that arise in sensory transduction and initial processing. In addition, it involves an attention-like processing system like that involved in overshadowing. Therefore, a model that includes representations of the component and configural qualities of odorants in mixtures is needed to provide a more complete account of learning about odor mixtures.     

Influence of training and experience on the perception of multicomponent odor mixtures.

This study examined whether a previously established (D. G. Laing and G. W. Francis; see record 1990-11967-001) limited capacity to discriminate and identify the components of olfactory mixtures resulted from the participants' lack of familiarity with the task, training designed to optimize cognitive and perceptual performance, or professional experience in odor discrimination. The participants were a trained panel of 10 women (23–43 years old), and an expert panel of 8 male professional perfumers and flavorists (25–55 years old). The individual chemical stimuli were 7 common dissimilar odorants of equal moderate intensity. An air dilution olfactometer delivered a single odorant or a mixture containing up to 5 odorants. The results indicated that for both panels only 3 or 4 components of a complex mixture could be discriminated and identified and that this capacity could not be increased by training. Therefore, the limit may be imposed physiologically or by processing constraints. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multicomponent kinetic determinations using artificial neural networks

Neural networks were successfully used for multicomponent kinetic determinations of species with rate constant ratios approaching unity without the aid of spectral discrimination. The ensuing method relies on two inputs describing the profile of the kinetic curve for each mixture, which is obtained by preprocessing kinetic data using nonlinear least-squares regression. A straightforward network architecture (2:4s:21) was used to resolve mixtures of 2- and 3-chlorophenol; the trained network estimated the concentrations of both components in the mixture with a relative standard error of prediction of approximately 5%, which is much lower than that obtained with Kalman filtering. The effect of some variables such as the rate constant and analyte concentration ratios on the proposed multicomponent determination is discussed.     

Odor of Taste Stimuli in Conditioned "Taste" Aversion Learning.

The present research addresses whether rats can express odor aversions to the odor of taste stimuli. In Experiment 1, saccharin or salt were either mixed in distilled water, so the rats could taste and smell them, or presented on disks attached to the tubes' metal spouts so the rats could only smell them. Aversions were established to taste stimuli under both conditions. The results of Experiment 2 indicate that conditioning was to the odor of the tastes when they were presented on disks in Experiment 1, hence both taste and odor aversions were established by means of "taste" stimuli. Taste aversion learning thus may more properly be termed flavor aversion learning, with flavor referring to both taste and odor components. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acute illness induces the release of aversive odor cues from adult, but not prepubertal, male rats and suppresses social investigation by conspecifics.

The present study examined odorant communication during acute illness provoked by injection of lipopolysaccharide (LPS; 100 μg/kg) and how these effects vary between prepubertal and adult conspecifics. Exposure to odor of LPS-treated adult male rats produced increased avoidance in both sexes of adults and prepubertal male partners. This response was not found when they were exposed to odor of LPS-treated prepubertal males. Even a 2.5-fold higher load of LPS in prepubertal males failed to produce aversive odor cues, suggesting that the difference in the odor is not a simple issue of dose/body volume. Both estradiol benzoate (20 μg/kg) and testosterone propionate (500 μg/kg), but not dihydrotestosterone (500 μg/kg) pretreatment in prepubertal males administered LPS restored the expression of aversive odor. These hormone treatments per se did not influence odor properties of prepubertal males, indicating that estrogen receptors may play a key regulatory role in the expression of aversive odor in LPS-treated prepubertal rats. These data suggest that the expression of sickness-related odor emerges through puberty, and likely involves a complex interaction between inflammation and sex steroids across development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfaction and the "data" memory system in rats.

Conducted studies to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radical maze; 1 of the arms contained a water reward. After training on 4 to 5 pairs of odors Ss learned to discriminate the members of a new pair in 5–20 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the Ss learn both positive and negative odors, rather than ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Animals trained on 3 component odors with 2 in common did not recognize the elements that were unshared when these were presented by themselves. Even when 1 of the 2 shared components was combined with the differentiating component into a cue the new cue was treated as a novel odor. Inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor. Findings, combined with those of previous studies in which lesions were used, suggest that learning that a series of odor discriminations involves a version of the "data" memory system described by cognitive psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An empirical test of Olsson's interaction model using mixtures of tastants

In 1994, Olsson published a model predicting the intensity and quality of an odor mixture percept on the basis of the intensities of the unmixed components. Whether this model can also be used for mixtures of dissimilar tasting substances was investigated for sucrose/citric acid mixtures. The identification data revealed asymmetrical mixture suppression, which does not support the model. The intensity responses were in accordance with the definitions employed for level independence and hypo-additivity. However, the intensity judgements suggest deviations from symmetry and exhibited compromise, which violates two other principles. A comparison with previously published data shows that these violations probably occur for other mixture types, too. It is concluded that the Olsson interaction model cannot describe interactions in mixtures of dissimilar tasting components accurately.     

Importance of retronasal and orthonasal olfaction for odor aversion memory in rats.

The role of odors in food memory formation, especially for aversions, has long been considered secondary to taste. However, the importance of odor ingestion in conditioned odor aversion (COA) has recently challenged this assumption (B. M. Slotnick, F. Westbrook, & F. M. C. Darling, 1997). The aim of the present study was to evaluate the respective role of orthonasal and retronasal olfactory experience in COA acquisition, long-term retention, extinction, and spontaneous recovery. To this end, the odor was presented either close to the drinking spout (orthonasal stimulation) or close to and mixed with the drinking water (eliciting both orthonasal and retronasal stimulation). The authors brought evidence that odor ingestion was crucial for COA acquisition, especially when odor presentation and gastric malaise were separated by long delays. On the contrary, once formed, a distal (orthonasal) odor recognition was sufficient for COA to be retrieved. COA was odor specific and long lasting (more than 50 days). Moreover, results brought evidence for a spontaneous recovery of odor aversion tested 57 days after its extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine D? receptor activation modulates perceived odor intensity.

Dopaminergic modulation affects odor detection thresholds and olfactory discrimination capabilities in rats. The authors show that dopamine D? receptor modulation affects odor discrimination capabilities in a manner similar to the modulation of stimulus intensity. Performance in a simultaneous odor discrimination task was systematically altered by manipulations of both odorant concentration and D? receptor activation (agonist quinpirole, 0.025-0.5 mg/kg; antagonist spiperone, 0.5 mg/kg). Rats' discrimination performance systematically improved at higher odor concentrations. Blockade of D? receptors improved performance equivalent to increasing odor concentration by 2 log units, whereas activation of D? receptors reduced odor discrimination performance in a dose-dependent manner. Bulbar dopamine release may serve a gain control function in the olfactory system, optimizing its sensitivity to changes in the chemosensory environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pattern memory involves both elemental and configural processes: Evidence from the effects of hippocampal lesions.

The formation of an integrated memory for a pattern of stimulation could be based on the elements of that pattern becoming directly linked to one another, or by each of the elements becoming linked to a shared separate configural representation. These 2 accounts have proven difficult to discriminate between. Here, rats received exposure to four patterns of stimulation, each consisting of an auditory stimulus, a visual context, and a time of day; and we examined whether pre-training lesions to the hippocampus influenced memory for the patterns. These lesions abolished pattern memory that required configural processes (Experiments 1A and 1B) but had no effect on pattern memory that could be supported by elemental processes (Experiment 2). This dissociation provides support for the views that elemental and configural processes ordinarily support pattern memory and that rats with lesions to the hippocampus are left reliant on elemental processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of brain lesions on taste-potentiated odor aversion in rats.

Rats failed to acquire aversions to odor stimulus, which was followed 30 min later by an unconditioned stimulus (US). However, when the odor stimulus was accompanied by a taste stimulus, they acquired odor aversions as well as taste aversions. In this phenomenon, referred to as a taste-potentiated odor aversion, lesions of the amygdala disrupted both taste and odor aversions, whereas lesions of the parvicellular part of ventroposteromedial thalamic nucleus (VPMpc) or insular cortex (IC) disrupted taste aversion but attenuated only odor aversion. These results suggest that both taste and odor stimuli are associated with US in the amygdala and that taste inputs delivered to the amygdala through the IC and/or VPMpc play an important role in potentiation of odor aversion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning theory and neuropsychology: Configuring their disparate elements in the hippocampus.

Using the contrast of elemental and configural theories of learning, some of the major differences in the assumptions that underlie neuropsychological approaches to memory and learning theoretical approaches are illustrated. Both strategies are shown to have different advantages and shortcomings. It is argued that future progress will succeed best by synthesizing features of both types of analysis. To provide evidence for this argument, it is suggested that both elemental and configural conditional stimuli processing systems exist and that they interact by competitive associational rules. This type of approach receives convergent support from both environmental manipulations; neuroanatomy and examination of brain-damaged subjects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

不同改性剂改善填埋污泥臭度的实验研究

未经生物稳定化的污泥处置于填埋场时存在着恶臭污染的问题,从废物利用、以废治废的宗旨出发,选用粉煤灰、矿化垃圾和建筑垃圾三种改性剂并以泥土为对照,与污泥混合,可有效地降低污泥的臭度,对污泥臭度的改善能力由强到弱的顺序是粉煤灰、矿化垃圾、建筑垃圾和泥土。其中矿化垃圾具有易于就地取材,数量充足,不额外占用填埋空间的优点,将污泥处置于已有垃圾填埋场时,可优先考虑矿化垃圾与污泥混合填埋的方法,矿化垃圾混合比例的增大,有利于改性污泥的臭度降低,但污泥臭气中硫化氢浓度的降低幅度越来越小,添加量为7:10时,硫化氢的去除率达96%,按满足填埋强度要求的最低混合比例添加四种改性剂后,污泥的臭度降低到三级以下,符合填埋场恶臭污染物排放标准。     

Assessment of Olfactory Function and Androstenone Odor Thresholds in Humans With or Without Functional Occlusion of the Vomeronasal Duct.

To obtain information on the possible role of the vomeronasal duct (VND) in odor perception and human pheromone detection, the present study investigated different aspects of olfactory function, including thresholds for androstenone in adults with or without detectable VNDs. The study also examined correlations between detection thresholds of androstenone odor and general olfactory function. Subjects' olfaction was assessed with tests for odor identification, odor discrimination, and phenyl ethyl alcohol odor threshold. Measurements were performed on 1 side only, with and without covering the VND. Subjects with or without detectable VNDs did not differ in olfactory sensitivity or androstenone odor thresholds. A small but significant correlation was found between detection thresholds of androstenone and general olfactory function. Finally, covering of the VND did not affect olfactory function or androstenone sensitivity. Results suggest that the human VND does not play a major role in sensitivity toward odorants or the preception of androstenone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)