OWSum: algorithmic odor prediction and insight into structure-odor relationships.

We derived and implemented a linear classification algorithm for the prediction of a molecule's odor, called Olfactory Weighted Sum (OWSum). Our approach relies solely on structural patterns of the molecules as features for algorithmic treatment and uses conditional probabilities combined with tf-idf values. In addition to the prediction of molecular odor, OWSum provides insights into properties of the dataset and allows to understand how algorithmic classifications are reached by quantitatively assigning structural patterns to odors. This provides chemists with an intuitive understanding of underlying interactions. To deal with ambiguities of the natural language used to describe odor, we introduced descriptor overlap as a metric for the quantification of semantic overlap between descriptors. Thus, grouping of descriptors and derivation of higher-level descriptors becomes possible. Our approach poses a large leap forward in our capabilities to understand and predict molecular features.

Nutrition claims influence expectations about food attributes, attenuate activity in reward-associated brain regions during tasting, but do not impact pleasantness.

INTRODUCTION: Nutrition claims are one of the most common tools used to improve food decisions. Previous research has shown that nutrition claims impact expectations; however, their effects on perceived pleasantness, valuation, and their neural correlates are not well understood. These claims may have both intended and unintended effects on food perception and valuation, which may compromise their effect on food decisions. METHODS: We investigated the effects of nutrition claims on expectations, perceptions, and valuation of milk-mix drinks in a behavioral (n = 110) and an fMRI (n = 39) study. In the behavioral study, we assessed the effects of a "fat-reduced" and a "protein-rich" nutrition claim on expected and perceived food attributes of otherwise equal food products. In the fMRI study, we investigated the effect of a "protein-rich" claim on taste pleasantness perception and valuation, and on their neural correlates during tasting and swallowing. RESULTS: We found that both nutrition claims increased expected and perceived healthiness and decreased expected but not perceived taste pleasantness. The "protein-rich" claim increased expected but not perceived satiating quality ratings, while the "fat-reduced" claim decreased both expected and perceived satiating quality ratings. In the absence vs. presence of the "protein-rich" claim, we observed an increased activity in a cluster extending to the left nucleus accumbens during tasting and an increased functional connectivity between this cluster and a cluster in right middle frontal gyrus during swallowing. CONCLUSION: Altogether, we found that nutrition claims impacted expectations and attenuated reward-related responses during tasting but did not negatively affect perceived pleasantness. Our findings support highlighting the presence of nutrients with positive associations and exposure to foods with nutrition claims to increase their acceptance. Our study offers insights that may be valuable in designing and optimizing the use of nutrition claims.

Bloody olfaction? Confounding associations of sex and age on the influence of blood parameters and body weight on odor identification performance in healthy adults.

Olfactory function and nutrition are closely related and may influence each other via metabolic parameters. However, the relationship between nutritional blood parameters and olfactory performance is still unclear. Inconclusive findings exist for specific blood parameters. In this extensive analysis, we examined the relationship between olfactory performance, measured with MONEX-40, as well as intensity and pleasantness ratings with 38 metabolic blood parameters, age, sex, and the anthropometric measurements body mass index (BMI) and body fat percentage (BFP). Therefore, we included data of 418 healthy, well-phenotyped Caucasians of the Enable cohort. We replicated age-dependent olfactory identification scores (p < 0.001) and found slight evidence for a body fat dependence measured with BFP (BF10 = 10.466). We further identified a sex difference only in middle-aged adults (p < 0.001) that could be explained by environmental factors. Several blood parameters correlated significantly with the MONEX-40 score (p < 0.05 - p < 0.001). However, these effects diminished after adjusting for sex and age (p > 0.9) that were identified as confounders. The same applies for BFP. In addition, no parameters were identified to correlate significantly with perceived olfactory intensity or pleasantness score if controlled for sex and age (p > 0.08). Our results suggest that metabolic blood parameters are not related to olfactory identification performance in a relevant manner and highlight the importance of controlling for sex and age in chemosensory research.

Less is more: Removing a modality of an expected olfactory-visual stimulation enhances brain activation.

In recent years, multisensory integration of visual and olfactory stimuli has extensively been explored resulting in the identification of responsible brain areas. As the experimental designs of previous research often include alternating presentations of unimodal and bimodal stimuli, the conditions cannot be regarded as completely independent. This could lead to effects of an expected but surprisingly missing sensory modality. In our experiment, we used a common functional magnetic resonance imaging (fMRI) study design with alternating strong unimodal and bimodal olfactory-visual food stimuli, in addition to a slight overhang of the bimodal stimuli in an effort to examine the effects of removing a visual or olfactory congruent stimulus for older people (41-83 years). Our results suggest that the processing of olfactory and visual stimuli stays intact over a wide age-range and that the utilization of strong stimuli does not lead to superadditive multisensory integration in accordance with the principle of inverse effectiveness. However, our results demonstrate that the removal of a stimulus modality leads to an activation of additional brain areas. For example, when the visual stimulus modality is missing, the right posterior superior temporal gyrus shows higher activation, whereas the removal of the olfactory stimulus modality leads to higher activation in the amygdala/hippocampus and the postcentral gyrus. These brain areas are related to attention, memory, and the search of the missing stimulus. Consequently, careful attention must be paid to the design of a valid, multimodal sensory experiment while also controlling for cognitive expectancy effects that might confound multimodal results.