Discrimination of Complex Odor Mixtures: A Study Using Wine Aroma Models

There are key unanswered questions when it comes to multi-component odor discrimination. This study was designed to assess discrimination of odorant mixtures that elicit a singular percept. We collected data to address the following two questions: 1) What odor features do humans notice when attempting to discriminate between subtly different odor mixtures? 2) Are odor mixtures easier to discriminate when an odorant is added, compared to when a component is removed? Using modern aroma chemistry techniques, an odor mixture resembling a generic white wine was constructed. This wine odor mixture was modified using a series of 3 esters which are commonly found in white wines that vary in chain length and branching. Participants performed a sequence of discrimination tasks for the addition / subtraction of modifiers to the base wine at different concentrations. Only one of the esters (ethyl-propanoate) led to a discriminable odor mixture. As concentration of the modifying odorant was increased, discrimination of odor mixtures was first reported because of changes in odor mixture familiarity and then intensity. We found similar sensitivity to changes in odor mixtures regardless whether the modifying compound was added or subtracted, suggesting that perceptual stability of odor mixtures is equally dependent on both imputing missing information (pattern completion) and disregarding extraneous information.

Adaptive weighting of taste and odor cues during flavor choice

The authors demonstrate that rats make choices about which flavor solution (i.e., taste-odor mixture) to consume by weighting the individual taste and odor components according to the reliability of the information they provide about which solution is the preferred one. A similar weighting operation underlies multisensory cue combination in other domains and offers novel insight into the computations underlying multisensory flavor perception and food choice behavior.

Discrimination of Complex Odor Mixtures: A Study Using Wine Aroma Models

There are key unanswered questions when it comes to odor mixture discrimination. This study was designed to assess some of those questions regarding configural odor mixture discrimination in humans. We collected data to address the following two questions: 1) What odor features do humans notice when attempting to discriminate between subtly different odor mixtures? 2) Are odor mixtures easier to discriminate when an odorant is added, compared to when a component is removed? Using modern aroma chemistry techniques, an odor mixture resembling a generic white wine was constructed. This wine odor mixture was modified using a series of 3 esters which are commonly found in white wines that vary in chain length and branching. Participants performed a sequence of discrimination tasks for the addition / subtraction of modifiers to the base wine at different concentrations. Only one of the esters (ethyl-propanoate) led to a discriminable odor mixture. As concentration of the modifying odorant was increased, discrimination of odor mixtures was first reported because of changes in odor mixture familiarity and then intensity. We found similar sensitivity odor mixture discrimination regardless of addition or subtraction of modifying compounds, suggesting that perceptual stability of odor mixtures is equally dependent on both imputing missing information (pattern completion) and disregarding extraneous information.

Odor mixture perception: can molecular complexity be a factor determining elemental or configural perception?

Odor mixtures can evoke smells that differ from those of their individual odor components. Research has revealed the existence of two perceptual modes, in which a mixture can be perceived as either the original smells of its individual components (elemental) or as a novel smell (configural). However, the factors underlying the perceptual transformation that occurs when smelling a mixture versus its original components remain unclear. Therefore, the present study aimed to identify the properties of odorants that affect olfactory perception of odor mixtures, focusing on the structural complexity of an odorant. We conducted psychophysical experiments in which different groups of participants were instructed to provide olfactory perceptual descriptions of low-, medium-, and high-complexity odor mixtures or components, respectively. To investigate the perceptual modes induced by the mixtures, we compared the participants’ evaluations between mixtures and components via two types of analyses. First, we compared each olfactory description following quantification via principal component analysis. We then compared data based on seven major olfactory perceptual groups. We observed that odor mixtures composed of low-complexity odorants were perceived as relatively novel smells with regard to both minor (olfactory descriptions) and major (perceptual community) odor qualities than medium- and high-complexity mixtures. Such information may further our understanding of the olfactory perceptual modes of odor mixtures.

Increased accuracy of signaling by hyperbolic odorant mixtures in a beneficial insect-plant relationship

Animals use odors in many natural contexts, for example, for finding mates or food, or signaling danger. Analyses of natural odors search for either the most meaningful components of a natural odor mixture, or they use linear metrics to analyze the mixture compositions. Both analyses assume that the odor space itself is Euclidian, like visual and auditory spaces. However, we have recently shown that the physical space for complex mixtures is ‘hyperbolic’ – curved – because of the correlations that arise in biosynthetic pathways. Here we shown that the shape of the space for flowers (Brassica rapa) using an existing data set can also be better described with a hyperbolic rather than a linear shape, and that components in the space correlate to the nectar and pollen resource sought by bee pollinators. We also show that honey bee and bumble bee antennae can detect most components of the B. rapa odor space. We argue that further investigation of the implications of hyperbolic space can have important implications for how sensory systems have evolved to encode the space.

Antagonistic odor interactions in olfactory sensory neurons are widespread in freely breathing mice

Odor landscapes contain complex blends of discrete molecules that each activate unique, overlapping populations of olfactory sensory neurons (OSNs). Despite the presence of hundreds of OSN subtypes in many animals, the overlapping nature of odor inputs may lead to saturation of neural responses at the early stages of stimulus encoding. Information loss due to saturation could be mitigated by normalizing mechanisms such as antagonism at the level of receptor-ligand interactions, whose existence and prevalence remains uncertain. By imaging OSN axon terminals in olfactory bulb glomeruli as well as OSN cell bodies within the olfactory epithelium in freely breathing mice, we found widespread antagonistic interactions in binary odor mixtures. In complex mixtures of up to 12 odorants, antagonistic interactions became stronger and more prevalent with increasing mixture complexity. Therefore, antagonism is a remarkably common feature of odor mixture encoding in olfactory sensory neurons and helps in normalizing activity to reduce saturation.

163 Treatment of Odor-Induced Anxiogenesis With Odor-Induced Anxiolysis

Study ObjectiveTo understand the effects of odor on anxiety.IntroductionReduction of odor-induced anxiety through a presentation of an odor has not heretofore been described.MethodCase report: A 69-year-old right-handed male with a five year history of generalized anxiety disorder, presented with a one and a half month history of hypersensitivity to odors of multiple synthetic chemicals manifest by the perception that these odors were more intense and unpleasant inducing nausea, abdominal cramping, coughing, a need to “get away from the smell”, and panic with intense anxiety. These symptoms would occur whenever he was exposed to these smells, 20 to 25 times a day, and would persist for 10 to 15 minutes after the exposure. When odors induced the above symptoms, exposure to the aroma of cinnamon immediately alleviated these symptoms. He now continues using cinnamon odor whenever the odor induced anxiety and associated symptoms arise. This remedy has been effective over the course of treatment, for almost two years.ResultsAbnormalities on examination: Three per second titubation. Archimedean Spiral Test: Saw tooth pattern with macrographia. Anxious, circumstantial, overly inclusive. Unable to determine how to put on shoe covers. Impaired voluntary upward gave, but intact vertical doll’s eyes. Left torticollis. Bilateral finger to nose dysmetria. Low amplitude, high frequency tremor on extension of both upper extremities. Areflexic. Olfactory Testing: hyposmic. MRI of brain with and without infusion: mild generalized volume loss.ConclusionsThere are myriad mechanisms whereby odor may have reduced the odor-induced anxiety. Since aroma induced anxiogeneis is usually confined to a specific odor, it does not preclude other odors from acting in an anxiolytic manner. The combination of exposure simultaneously of anxiolytic and anxiogenic odors may have acted to increase the threshold of the anxiety producing odor, inhibiting perception of the anxiogenic odor and thus precipitation of anxiety. The two odors could have combined in an additive fashion, changing the olfactory characteristics of the anxiety provoking odor such that it no longer was perceived as the same odor and thus no anxiety. The anxiolytic/anxiogenic odor mixture could have overwhelmed the anxiogenic odor, thus creating the perception of only anxiolytic odor. On a central basis, the anxiolysis and anxiogenesis may have been induced to occur coincidently with anxiolysis superseding anxiogenesis. Alternatively, the odors may have acted as a distractor, changing the focus of attention from anxiogenic odor to a different odor which does not have the same anxiety provoking effect. Maybe because the patient already has demonstrated a heightened odor emotion linkage, he may be more susceptible to any other odor emotion effects. Trial of odors in those with odor induced anxiety warrants consideration.Funding AcknowledgementsNo funding.