Olfactory lateralization: odor intensity but not the hedonic estimation is lateralized.

An earlier study in humans comparing the olfactory sensitivity of both nostrils revealed a small but significant advantage of the right nostril for detection and for olfactory quality discrimination. However lateralization was not evaluated for the perception of odor intensity and hedonic evaluation (pleasantness/unpleasantness). Thus we investigated lateralization of olfactory intensity and hedonic evaluation in right-handed healthy volunteers (n=186) from the HeDoS-F database (Hedonic Database of Smell-Franconia). For olfactory evaluation the Sniffin' Stick Test was employed with the parameters detection, discrimination, identification and extended by analogue hedonic and intensity rating scales. Over all odors subjects rated the perceived intensity significantly higher following stimulation of the right compared to the left nostril. The analysis of the single odors of the Sniffin' Stick Test consistently confirmed higher intensity ratings for the right compared to the left nostril reaching a statistically significant difference for 10 out of 16 odors. In contrast we found no significant differences between the nostrils for the hedonic estimates over all odors. Differences in odor detection, discrimination and identification did not reach a statistically significant level, but for all these parameters the scores of the right nostril were slightly higher compared to the left nostril. For odor identification, however, a statistical tendency was observed. Based on our results we concluded that olfactory intensity estimates represent the most sensitive parameter of olfactory lateralization.

Good news for elderly persons: olfactory pleasure increases at later stages of the life span.

BACKGROUND: Numerous studies have been conducted collecting normative values dependent on age for the three major components of the Sniffin' Stick Test (threshold of n-butanol, and identification and discrimination of odors). Less is known about the influence of age on the hedonic and intensity evaluation of odors. Thus, the objective of this study was to analyze the influence of age on the hedonic and intensity estimates in a large human population. METHODS: Two hundred one single data sets established the Hedonic Database of Smell-Franconia (HeDoS-F) with the parameters age, gender, odor threshold, odor discrimination, oder identification, intensity estimates, and hedonic estimates (median age: 39 years, interquartile range: 28, minimum age: 19, maximum age: 83, men: 103, women: 98). For olfactory testing the Sniffin' Stick Test was used, and hedonic and intensity estimates were registered using visual analogue rating scales. For statistical analysis, we separated the study population into three age groups (19-39 years, 40-59 years, and > or = 60 years), and parametric and nonparametric tests were calculated. RESULTS: We found a significant influence of age on threshold, discrimination, and identification with a decrease in the higher age class. Over all odors the summed intensity estimates did not depend on age, whereas the summed relative hedonic estimates increased with the beginning of the fifth decade. CONCLUSION: Our study suggests that, for perceived odors, olfactory pleasure increases at later stages of the life span, whereas the perceived intensity of odors remains stable.

The influence of mecamylamine on trigeminal and olfactory chemoreception of nicotine.

Nicotine presented to the nasal cavity at low concentrations evokes 'odorous' sensations, and at higher concentrations 'burning' and 'stinging' sensations. A study in smokers and nonsmokers provided evidence of a relationship between the experience with the pharmacological action of S-(-)-nicotine and the perceived pleasantness/unpleasantness following nasal stimulation with S-(-)-nicotine. Mecamylamine, a nicotinic acetylcholine-receptor-(nAch-R) antagonist, was able to block painful responses following chemical stimulation of the human tongue and to block responses from the rat's ethmoidal nerve. The aim of our study in humans was to investigate the effects of mecamylamine on the olfactory and the trigeminal chemoreception of nicotine enantiomers. In order to achieve this aim, we determined-before and after mecamylamine-(1) detection thresholds, trigeminal thresholds, and intensity estimates (stimulus intensity) and (2) recorded the negative mucosal potential (NMP) following nasal stimulation with nicotine in a placebo-controlled double blind study (n = 15). CO(2) was used as a trigeminal and H(2)S as an olfactory control stimulus. Mecamylamine significantly increased trigeminal thresholds of S-(-)-nicotine and reduced intensity estimates and NMPs following stimulation with nicotine enantiomers, whereas mecamylamine did not influence NMPs and trigeminal intensity estimates following stimulation with CO(2). In contrast, mecamylamine did neither influence detection thresholds nor olfactory intensity estimates following stimulation with olfactory nicotine concentrations. These results demonstrate that the trigeminal nasal chemoreception of nicotine enantiomers, in contrast to CO(2), is mediated by nAch-Receptors and give evidence that the olfactory chemoreception of nicotine is independent from peripheral nAch-Receptors.

Emotional reactivity to odors: olfactory sensitivity and the span of emotional evaluation separate the genders.

Numerous studies report gender differences in emotional reactivity in health and disease and the perception of odors is closely linked to the limbic system. In order to investigate gender differences in the emotional perception of odors we extended the Sniffin' Stick Test with analogue rating scales for hedonic (pleasantness/unpleasantness) and intensity estimates. We matched 172 healthy subjects (86 females and 86 males) on age in order to balance the study population for three age strata (A: 19-39 years, B: 40-59, C: 60 years and above). Overall odors in our statistical analysis demonstrated significant gender differences for the absolute hedonic estimates but not for the relative hedonic and not for the intensity estimates. These findings demonstrate that women evaluate the pleasantness of perceived odors in a more extreme manner than men without significant differences in hedonic polarity (pleasantness/unpleasantness). Thus, we report a singular significant effect of gender on the dimension valence (hedonic estimation) independent from the dimension intensity. Our findings are in accordance with gender differences in facial reactivity to auditory stimuli and differences in the evaluation of emotional pictures. Investigating olfactory sensitivity females detected n-butanol and discriminated the 16 odors of the test significantly better than males. These results indicate that females possess higher olfactory sensitivity.

The myth of the birthday blues: a population-based study about the association between birthday and suicide.

PURPOSE: The problem of time distribution of suicide has aroused the interest of various investigators in the past. A population-based study on the association of the birthday in relation to the time of suicide taking into account sex and the chosen suicide method was conducted. METHODS: The study included all residents of Bavaria who died between 1998 and 2003 and whose death was classified as suicide by the death certificate. In sum, 11378 deaths from suicide were included. The suicide ratios in various time frames around the individuals' birthdays were compared with expected suicide ratios. RESULTS: The occurrence of suicide did not vary around the birthday. Different time frames (3, 7, 14, 30, and 90 days) before as well as after the individuals' birthdays were taken into account. Even after dichotomization regarding the chosen method as well as sex differences, no significant association between birthdays and dates of suicide could be found. CONCLUSION: There is no evidence for a "birthday blues" effect on suicide.