Associations of Gray Matter Volume and Perceived Intensity of Bitter Taste: a Voxel-Based Morphometry Study Abstract Introduction Two recent brain morphological studies reported inconsistent results on the neuroanatomical correlates of taste intensity rating among healthy populations. The current study re-visited this issue with a large and more homogeneous sample size. It was hypothesized that the orbitofrontal cortex, the sole region commonly reported by the two studies together with olfactory studies, had its gray matter volume (GMV) correlated to taste intensity rating. Methods The open data from the Human Connectome Project (HCP, S1200 release dataset) was used. Data from 213 subjects were analyzed. They were aged 22–25, completed 3-Tesla structural brain scan, and were asked to taste a bitter solution (0.001 M quinine) and rate the perceived intensity with a general Labelled Magnitude Scale. The age-adjusted taste intensity rating was used for the current analysis. Voxel-based morphometry (VBM) using CAT12 toolbox implemented in SPM12 was conducted with the default procedures and settings. Whole brain analysis was performed at a threshold of cluster p < 0.05, familywise error corrected (FWE), with a primary cluster-forming threshold of uncorrected voxel p < 0.001. Results Voxel-wise GMV was significantly correlated to taste intensity rating in the right angular gyrus. OFC was insignificant even with a more liberal threshold of uncorrected voxel p < 0.001. Conclusions The current results were again different from previously published reports. This might be due to heterogeneous population, data processing, and analytical methods. Implications At the current stage, the morphometric finding from brain imaging is not yet a simple and reliable biomarker for assessing taste intensity perception.

Sommelier Students Display Superior Abilities to Identify but Not to Detect or Discriminate Odors Early in their Training Abstract Introduction Experts acquire superior abilities in their specific domains by training. Sommelier students, who are future olfaction experts, could be an excellent model to study the effects of olfactory training. Methods We tested whether sommelier students display superior olfactory abilities early in their education: within the first 2 months of education, we examined the olfactory function, i.e., discrimination and identification of odors as well as olfactory threshold and olfactory memory, of n = 25 sommelier students and compared them to n = 29 control students. We also tested episodic and working memory. Results We found that sommelier students outperformed controls in free and cued identification, but we did not observe any difference in discrimination or threshold tasks. There was also no difference in memory tasks. Conclusions Early in their education, sommelier students appear to be better at identifying odors, but do not display other superior olfactory abilities. Implications Results suggest that sommeliers are better at identifying odors than the average person, either because they enter into training with superior identifications skills or are able to learn to identify odors at a very fast rate.

Olfaction During Pregnancy and Postpartum Period Abstract Introduction Studies of the effect of pregnancy on olfactory function are contradictory—some report reduced function, others hypersensitivity, and still others no change at all. Our objectives were to quantify olfactory function in women during gestational and puerperal periods, to compare the olfactory test scores to those of non-pregnant women, and to explore the potential influence of rhinitis on olfactory function during these periods. Methods We evaluated olfactory function in 206 women with and without rhinitis—47 in the first trimester of pregnancy, 33 in the second, 44 in the third, 32 in the postpartum period, and 50 who were non-pregnant. Olfactory assessment was performed using the University of Pennsylvania Smell Identification Test (UPSIT) and ratings of the pleasantness and intensity of four common odors. Results Although total UPSIT scores did not differ among the study groups, pregnant and postpartum women identified some odors less well than did the controls. Pregnant women, especially in the first trimester, tended to consider some smells less pleasant. Rhinitis was adversely associated with the olfactory test scores of the pregnant and postpartum women. Conclusions The overall olfactory function of postpartum and pregnant women did not differ compared to controls; however, detection of some individual UPSIT items was adversely impacted (e.g., menthol, gingerbread, gasoline). Rhinitis was associated with reduced olfaction during pregnancy and puerperium. Implications These findings support the view that pregnancy-related alterations in smell are idiosyncratic, present only for some odorants, and may be impacted by the presence of rhinitis that commonly occurs during pregnancy.

Examination and Validation of Classification Schema for Determining Thermal Taste Status Abstract Introduction Thermal taster status (TTS) is determined when the tongue is cooled or warmed, whereby thermal tasters (TT) experience a taste sensation while thermal nontasters (TnT) do not. The literature suggests that TT experience greater responsiveness (higher intensity ratings) to orosensory stimuli; however, small sample sizes and differences in classification schemes between studies confound our understanding of TTS. In addition, up to 50% of individuals (nonclassifiables, NC) have been excluded from previous studies and have yet to be characterized. Methods Raw responses to the thermal-elicitation procedure were used to determine the TTS of the same participants using four published classification schemes, and concordance between the schemes was examined using Fleiss’ kappa. Using a large convenience sample (n = 708), we tested for differences in orosensory (ANOVA) and temperature (Mann-Whitney U) responsiveness between TT, TnT, and NC. Results TT are more responsive than TnT to both orosensations and temperature changes, regardless of the classification method used despite only moderate concordance between the schemes. Overall, the orosensory and temperature responsiveness of NC is intermediate to that of TT and TnT. However, the responses of NC are not homogeneous and subgroups are identified. Conclusions The trend of TT being more responsive to orosensory and temperature stimuli is confirmed. The responsiveness patterns of NC subgroups suggest they are misclassified TT and TnT, and can be included in future studies examining thermal tasting. Implications TTS is an important source of individual differences in orosensory responsiveness, and our findings inform best practices for thermal elicitation and classification.

Association Between Olfactory Performance and Affective Symptoms in Children Abstract Introduction Correlations between olfactory performance and particular personality traits (e.g., disgust proneness), as well as symptoms of specific mental disorders (e.g., depression) have been found in numerous studies with adults. The present questionnaire study examined whether similar associations already exist in childhood. Method The olfactory discrimination ability of 66 children (32 boys and 34 girls aged between 7 and 11 years) was tested. In addition, the children filled out screening questionnaires to assess the severity of symptoms related to depression, various anxiety disorders (e.g., panic disorder, social anxiety disorder), and disgust proneness. A multiple regression analysis was calculated with olfactory performance as criterion variable and questionnaire scores as predictor variables. Results The results showed that depression and disgust proneness were negatively associated with olfactory discrimination ability. Moreover, high levels of social anxiety and low levels of panic symptoms were found to be positive predictors of olfactory performance. Conclusion This investigation identified specific associations between olfactory performance and affective symptoms in children. Implications Future tests with pediatric samples (children with anxiety disorders, depression) are recommended.

Alcohol and Taste Intensity Abstract Introduction Although most US adults drink alcoholic beverages, little is known about the association between drinking and taste. We hypothesized that the ability to distinguish differing intensities of bitter and salt solutions would be poorer among drinkers than nondrinkers. Methods We used cross-sectional data from 4990 participants aged 40+ from a large, national survey of the US population (National Health and Nutrition Examination Survey, 2012–2014). The validated generalized Labeled Magnitude Scale (gLMS) was used to rate participants’ perception of the intensities of a series of bitter (1 mM quinine) and salt (0.32 M and 1 M NaCl) solutions. Statistical analyses, weighted to produce nationally representative estimates, were adjusted for factors including race/ethnicity, education, marital status, income, body mass index (BMI), smoking, physical activity, self-reported health status, diabetes, depression, and use of medications known to affect taste. Results In adjusted analyses, ability to distinguish intensity of a salt solution (0.32 M) was poorer among older (aged 60+) female current drinkers than their nondrinking counterparts (p = 0.001). Ability was also poorer among drinkers who consumed wine in the past 24 h compared to drinkers who consumed no alcohol during that time (p = 0.016). Ability to distinguish different intensities of the bitter solution was poorer among more frequent wine consumers (p = 0.034). Conclusions We found few significant associations. However, the result for older women is potentially interesting given recent increases in drinking within that population. Implications Taste is a novel consideration in research on alcohol consumption. We encourage further exploration in this area.

Odors Are More Sensitive to Evaluative Conditioning than Sounds Abstract Introduction Stimuli of different modalities can acquire an affective value via evaluative conditioning. This process describes a shift in perceived affective quality of a neutral stimulus towards the hedonics of an associated affective stimulus. The olfactory system, as compared to other modalities, might be especially prone to attributing affective value to an odor due to its close neuroanatomical connectivity with brain regions processing emotion. Methods In the present study, we investigated whether perceived affective quality of odors is more sensitive to evaluative conditioning than that of sounds. For this purpose, 48 healthy participants (50% male) rated unfamiliar and emotionally neutral odors and sounds before and after pairing with either aversive or neutral pictures. Results Our results show a stronger decrease in odor valence and stronger increases in arousal and dominance ratings for odors paired with aversive compared to neutral pictures. For sounds, ratings of valence, arousal, and dominance were independent of picture emotionality. Conclusion Odors appear to be more sensitive to evaluative conditioning than sounds. Our findings extend existing modality comparisons mainly focusing on characteristics of odor-associated memories by specifically looking at affective quality of the odor itself in associative learning. Implications Perceived affective quality of a stimulus goes along with the tendency to approach or avoid this stimulus. For odors, it is especially prone to change into an aversive direction. This may have implications for food and fragrance choices but also for the understanding of clinical conditions in which odors become highly aversive, such as post-traumatic stress disorder.

Development of a Regional Taste Test that Uses Edible Circles for Stimulus Delivery Abstract Introduction Measurements of chemosensory function within specific regions of the tongue can yield important information about the sensitivity of lingual areas to chemosensory stimuli and may identify possible nerve damage. A novel regional chemosensory test that uses thin edible circles was developed for human testing. Methods Edible circles placed at six different regions of the tongue were used to examine regional sensitivity to quinine for bitter taste, NaCl for salt taste, sucralose for sweet taste, and capsaicin for pungency. The six regions included the anterior tip of the tongue, the left and right lateral margins of the tongue (anterior and posterior), and the circumvallate region. Testing was completed with the mouth open, and the mouth closed. Results Intensity ratings at all sites were higher in the closed mouth condition for the three taste stimuli. Quinine intensity was highest at the circumvallate region with the mouth closed. NaCl and sucralose intensity were highest at the anterior tip and circumvallate regions. Capsaicin intensity was most highly perceived at the anterior tip of the tongue, but open and closed mouth intensity ratings showed no significant differences. Conclusions Regional differences in chemosensory perception were observed on the tongue, and these differences were dependent on the chemosensory stimulus, tongue region, and tasting mode. Implications Edible circles show minimal diffusion with saliva, can be used to examine both taste and irritation, and may be used to identify regional papillae counts on the tongue. Finally, edible circles should be invaluable for examining damage to the oral cavity.

Investigating the Putative Impact of Odors Purported to Have Beneficial Effects on Sleep: Neural and Perceptual Processes Abstract Introduction Olfaction has an important role in physiological and affective processes, as well as the potential to have profound effects on activities such as sleep and learning. We investigated two commercially manufactured odors (“Deep Sleep” and “Oriental,” from This Works) purported to promote sleep, compared with control odor, where we aimed to explore whether neural and behavioral differences existed after odor inhalation. Methods In a neuroimaging study, 30 healthy participants were exposed to the odors via an olfactometer during functional magnetic resonance imaging (fMRI). In a further behavioral study using 12 chronic insomniacs, we investigated whether the commercial odors showed effects on sleep during a double-blind, randomized home evaluation. Results In the neuroimaging, the odors were related to activation of olfactory-relevant areas, such as the orbitofrontal cortex, and we found positive connectivity between the piriform cortex and the hippocampus, amygdala, insula, and middle cingulate cortex. Deep Sleep specifically activated the superior temporal gyrus, whereas Oriental activated the caudate. Further, these commercial odors showed some beneficial impact on sleep. Conclusions The perceptual and neural impacts of the commercial odors showed that olfactory stimulation can potentially aid sleep and modify affective processes in a number of ways. Implications The present work opens up opportunities for further investigations into how different odors may lead to specific behavioral and physiological modifications, such as their impact on sleep and well-being, which may provide non-pharmacological alternative approaches.

Different Brain Activation in Response to Repeated Odors of Pleasantness and Unpleasantness Abstract Introduction Brain activation in response to olfactory stimuli has been studied using functional magnetic resonance imaging (fMRI), but there is little knowledge about processing repeated olfactory information which is usual in daily life. Methods This fMRI study was designed to investigate brain response to repeated odorant stimulation with positive and negative valences in 12 healthy right-handed volunteers. There was a 25-min rest interval between two fMRI runs with identical stimulation paradigms with two odors, as phenylethyl alcohol (PEA) and isovaleric acid (IVA), and the two odors were released alternately. Results There was a similar activation pattern in regions of primary and secondary olfactory cortex induced by odors of both valences, especially by negative odor. Weakened activation of the brain is responsive to repeated both pleasant and unpleasant smell. Nevertheless, the repeated unpleasant odor has a more intimate relationship with the piriform cortex, amygdala, and hippocampus. Conclusion We conclude that asymmetric brain activation in response to repeated odorant stimulation depended on valences and that the unpleasant odor can evoke more negative emotion and profound memory. Implications We explore the central processing about repeated olfactory information applied fMRI for the first time, revealing asymmetric brain activation in response to repeated odors of pleasantness and unpleasantness.