Olfactory processing and odor specificity: a meta-analysis of menstrual cycle variation in olfactory sensitivity

Abstract Cycle-correlated variation in olfactory threshold, with women becoming more sensitive to odors mid-cycle, is somewhat supported by the literature but the evidence is not entirely consistent, with several studies finding no, or mixed, effects. It has been argued that cyclic shifts in olfactory threshold might be limited to odors relevant to the mating context. We aimed to test whether the evidence currently available points in the direction of odor-specific or, rather, general changes in olfactory sensitivity and, if the former is the case, to what group of odorants in particular. We carried out a meta-analysis of relevant studies which together used a variety of different odorants, including some found in food, body odor, and some that occur in neither of these. First we tested whether there appears to be an overall effect when all studies are included. Next, we hypothesised that if cyclic changes in olfactory processing are odor-specific and tuned to biologically relevant odors, we should find changes in detection thresholds only for odorants found in body odor, or for those that are perceptually similar to it. In contrast, if threshold patterns are linked to more general fluctuations in odor processing across the cycle, we would not expect changes in relation to any particular odorant group. The results support the view that there is significant cycle-correlated variation. Thresholds were in general significantly lower in the fertile than the non-fertile phases, with effect sizes consistently in this direction. This same conclusion applied to both ‘food’ and ‘musky’ odorants, despite their different evolutionary significance, and to the androgen steroids (androstadienone, androstenone, and androsterone), but could not be applied to phenyl-ethyl alcohol. The results indicate that olfactory sensitivity may be a non-adaptive by-product of the general physiological fluctuations or differences in neural processing experienced across the cycle to a broad spectrum of odorants, rather than being specifically selected for mate choice-related odors.

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Better Olfactory Performance and Larger Olfactory Bulbs in a Mouse Model of Congenital Blindness

Chemical Senses ◽

10.1093/chemse/bjaa052 ◽

2020 ◽

Vol 45 (7) ◽

pp. 523-531

Author(s):

Sara Touj ◽

Samie Cloutier ◽

Amel Jemâa ◽

Mathieu Piché ◽

Gilles Bronchti ◽

...

Keyword(s):

Performance Test ◽

Brain Plasticity ◽

Olfactory Threshold ◽

Olfactory Bulbs ◽

Threshold Test ◽

Anatomical Plasticity ◽

Sensory Modalities ◽

Olfactory Processing ◽

Granular Layers ◽

Early Blindness

Abstract It is well established that early blindness results in enhancement of the remaining nonvisual sensory modalities accompanied by functional and anatomical brain plasticity. While auditory and tactile functions have been largely investigated, the results regarding olfactory functions remained less explored and less consistent. In the present study, we investigated olfactory function in blind mice using 3 tests: the buried food test, the olfactory threshold test, and the olfactory performance test. The results indicated better performance of blind mice in the buried food test and odor performance test while there was no difference in the olfactory threshold test. Using histological measurements, we also investigated if there was anatomical plasticity in the olfactory bulbs (OB), the most salient site for olfactory processing. The results indicated a larger volume of the OB driven by larger glomerular and granular layers in blind mice compared with sighted mice. Structural plasticity in the OB may underlie the enhanced olfactory performance in blind mice.

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The Heritability of Behavior: A Meta-analysis

Journal of Heredity ◽

10.1093/jhered/esz023 ◽

2019 ◽

Vol 110 (4) ◽

pp. 403-410 ◽

Cited By ~ 22

Author(s):

Ned A Dochtermann ◽

Tori Schwab ◽

Monica Anderson Berdal ◽

Jeremy Dalos ◽

Raphaël Royauté

Keyword(s):

Genetic Variation ◽

Life History ◽

Life History Traits ◽

Meta Analysis ◽

Behavioral Responses ◽

Relative Effect ◽

Biologically Relevant ◽

Sources Of Variation ◽

High Heritability ◽

Relevant Factors

AbstractThe contribution of genetic variation to phenotypes is a central factor in whether and how populations respond to selection. The most common approach to estimating these influences is via the calculation of heritabilities, which summarize the contribution of genetic variation to phenotypic variation. Heritabilities also indicate the relative effect of genetic variation on phenotypes versus that of environmental sources of variation. For labile traits like behavioral responses, life history traits, and physiological responses, estimation of heritabilities is important as these traits are strongly influenced by the environment. Thus, knowing whether or not genetic variation is present within populations is necessary to understand whether or not these populations can evolve in response to selection. Here we report the results of a meta-analysis summarizing what we currently know about the heritability of behavior. Using phylogenetically controlled methods we assessed the average heritability of behavior (0.235)—which is similar to that reported in previous analyses of physiological and life history traits—and examined differences among taxa, behavioral classifications, and other biologically relevant factors. We found that there was considerable variation among behaviors as to how heritable they were, with migratory behaviors being the most heritable. Interestingly, we found no effect of phylogeny on estimates of heritability. These results suggest, first, that behavior may not be particularly unique in the degree to which it is influenced by factors other than genetics and, second, that those factors influencing whether a behavioral trait will have low or high heritability require further consideration.

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Human Chemosignals and Brain Activity: A Preliminary Meta-analysis of the Processing of Human Body Odors

Chemical Senses ◽

10.1093/chemse/bjaa067 ◽

2020 ◽

Vol 45 (9) ◽

pp. 855-864

Author(s):

Elisa Dal Bò ◽

Claudio Gentili ◽

Cinzia Cecchetto

Keyword(s):

Brain Activity ◽

Meta Analysis ◽

Inferior Frontal Gyrus ◽

Relevant Information ◽

Neural Correlates ◽

Specific Information ◽

Emotional States ◽

Body Odor ◽

The Right ◽

Body Odors

Abstract Across phyla, chemosignals are a widely used form of social communication and increasing evidence suggests that chemosensory communication is present also in humans. Chemosignals can transfer, via body odors, socially relevant information, such as specific information about identity or emotional states. However, findings on neural correlates of processing of body odors are divergent. The aims of this meta-analysis were to assess the brain areas involved in the perception of body odors (both neutral and emotional) and the specific activation patterns for the perception of neutral body odor (NBO) and emotional body odor (EBO). We conducted an activation likelihood estimation (ALE) meta-analysis on 16 experiments (13 studies) examining brain activity during body odors processing. We found that the contrast EBO versus NBO resulted in significant convergence in the right middle frontal gyrus and the left cerebellum, whereas the pooled meta-analysis combining all the studies of human odors showed significant convergence in the right inferior frontal gyrus. No significant cluster was found for NBOs. However, our findings also highlight methodological heterogeneity across the existing literature. Further neuroimaging studies are needed to clarify and support the existing findings on neural correlates of processing of body odors.

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The promise of a DNA taxonomy

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2003.1447 ◽

2004 ◽

Vol 359 (1444) ◽

pp. 669-679 ◽

Cited By ~ 307

Author(s):

Mark L. Blaxter

Keyword(s):

High Throughput ◽

Small Proportion ◽

High Throughput Sequencing ◽

Meta Analysis ◽

Molecular Data ◽

Similar Extent ◽

Molecular Barcoding ◽

Dna Taxonomy ◽

Biologically Relevant ◽

Operational Taxonomic Units

Not only is the number of described species a very small proportion of the estimated extant number of taxa, but it also appears that all concepts of the extent and boundaries of ‘species’ fail in many cases. Using conserved molecular sequences it is possible to define and diagnose molecular operational taxonomic units (MOTU) that have a similar extent to traditional ‘species’. Use of a MOTU system not only allows the rapid and effective identification of most taxa, including those not encountered before, but also allows investigation of the evolution of patterns of diversity. A MOTU approach is not without problems, particularly in the area of deciding what level of molecular difference defines a biologically relevant taxon, but has many benefits. Molecular data are extremely well suited to re–analysis and meta–analysis, and data from multiple independent studies can be readily collated and investigated by using new parameters and assumptions. Previous molecular taxonomic efforts have focused narrowly. Advances in high–throughput sequencing methodologies, however, place the idea of a universal, multi–locus molecular barcoding system in the realm of the possible.

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A Twin Study of Odor Identification and Olfactory Sensitivity

Acta geneticae medicae et gemellologiae twin research ◽

10.1017/s0001566000002312 ◽

1992 ◽

Vol 41 (2-3) ◽

pp. 113-121 ◽

Cited By ~ 7

Author(s):

N.L. Segal ◽

K.W. Brown ◽

T.D. Topolski

Keyword(s):

Twin Study ◽

Detection Threshold ◽

Odor Identification ◽

Interindividual Variation ◽

University Of Pennsylvania ◽

Olfactory Sensitivity ◽

Odor Detection Threshold ◽

Phenyl Ethyl Alcohol ◽

The University ◽

Smell Identification

AbstractInterindividual variation in odor identification and olfactory sensitivity has been explained primarily with reference to age, sex and/or experiential factors. A twin study of olfaction can, therefore, substantially contribute to current research in this area. Thirty-nine monozygotic and twenty dizygotic twin pairs have completed the University of Pennsylvania Smell Identification Test (UPSIT), an olfactory preference questionnaire, and two odor detection threshold tests (phenyl ethyl alcohol and butanol). A genetic influence on odor identification, as assessed by the UPSIT, has been demonstrated. Future plans and directions for this research program are discussed.

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Olfactory Co-Stimulation Influences Intranasal Somatosensory Perception

10.1101/519439 ◽

2019 ◽

Author(s):

Prasanna R. Karunanayaka ◽

Jiaming Lu ◽

Qing X. Yang ◽

K. Sathian

Keyword(s):

Ethyl Alcohol ◽

Visual Cues ◽

Human Subjects ◽

Olfactory Sensitivity ◽

Localization Task ◽

Healthy Human ◽

Somatosensory Stimulation ◽

Localization Accuracy ◽

Healthy Human Subjects ◽

Phenyl Ethyl Alcohol

ABSTRACTOlfactory sensitivity is influenced by intranasal trigeminal sensation. For instance, sniffing is central to how humans and animals perceive odorants. Here, we investigated the influence of olfactory co-stimulation on the perception of intranasal somatosensory stimulation. In this study, twenty-two healthy human subjects, with normal olfactory function, performed a localization task for weak air-puff stimuli, in the presence or absence of a pure odorant, phenyl ethyl alcohol (PEA; rose odor). Visual cues were used to inform participants to briefly hold their breath while weak, poorly localizable, air-puffs and/or PEA were delivered to either nostril. Although PEA alone could not be localized, when accompanied by a weak air-puff in the ipsilateral nostril, localization accuracy significantly improved, relative to presentation of the air-puff without the odorant. The enhancement of localization was absent when the air-puff and PEA were presented to opposite nostril. Since ipsilateral but not contralateral co-stimulation with PEA increased the accuracy of weak air-puff localization, the results argue against a non-specific alerting effect of PEA. These findings suggest an interaction between the olfactory and somatosensory trigeminal systems.

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Olfactory Costimulation Influences Intranasal Somatosensory Perception

Multisensory Research ◽

10.1163/22134808-bja10008 ◽

2020 ◽

Vol 33 (7) ◽

pp. 723-736

Author(s):

Prasanna R. Karunanayaka ◽

Jiaming Lu ◽

Qing X. Yang ◽

K. Sathian

Keyword(s):

Visual Cues ◽

Human Subjects ◽

Olfactory Sensitivity ◽

Localization Task ◽

Healthy Human ◽

Somatosensory Stimulation ◽

Localization Accuracy ◽

Healthy Human Subjects ◽

Phenyl Ethyl Alcohol ◽

Somatosensory Stimuli

Abstract Olfactory sensitivity is influenced by intranasal trigeminal sensation. For instance, sniffing is central to how humans and animals perceive odorants. Here, we investigated the influence of olfactory costimulation on the perception of intranasal somatosensory stimulation. In this study, 22 healthy human subjects, with normal olfactory function, performed a localization task for stimulation using weak air puffs, a pure odorant, phenyl ethyl alcohol (PEA; rose odor), or their combination. Visual cues were used to inform participants to briefly hold their breath while weak, poorly localizable, air puffs and/or PEA were delivered to either nostril. Although PEA alone could not be localized to the correct nostril, when it accompanied a weak air puff in the ipsilateral nostril, localization accuracy significantly improved, relative to presentation of the air puff without the odorant. The enhancement of localization was absent when the air puff and PEA were presented to opposite nostrils. Since ipsilateral but not contralateral costimulation with PEA increased the accuracy of weak air puff localization, the results argue against a non-specific alerting effect of PEA. These findings suggest an interaction between olfactory and intranasal somatosensory stimuli leading to their integration.

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Why do ecologists aim to get positive results? Once again, negative results are necessary for better knowledge accumulation

Animal Biodiversity and Conservation ◽

10.32800/abc.2013.36.0033 ◽

2013 ◽

Vol 36 (1) ◽

pp. 33-36

Author(s):

A. Martínez–Abraín ◽

Keyword(s):

Hypothesis Testing ◽

Meta Analysis ◽

A Priori ◽

Multiple Hypothesis Testing ◽

Population Parameter ◽

Statistical Population ◽

Biologically Relevant ◽

Negative Results ◽

Multiple Hypothesis ◽

Positive Results

Hypothesis testing is commonly used in ecology and conservation biology as a tool to test statistical–population parameter properties against null hypotheses. This tool was first invented by lab biologists and statisticians to deal with experimental data for which the magnitude of biologically relevant effects was known beforehand. The latter often makes the use of this tool inadequate in ecology because we field ecologists usually deal with observational data and seldom know the magnitude of biologically relevant effects. This precludes us from using hypothesis testing in the correct way, which is posing informed null hypotheses and making use of a priori power tests to calculate necessary sample sizes, and it forces us to use null hypotheses of equality to zero effects which are of little use for field ecologists because we know beforehand that zero effects do not exist in nature. This is why only ‘positive’ (statistically significant) results are sought by ecologists, because negative results always derive from a lack of power to detect small (usually biologically irrelevant) effects. Despite this, ‘negative’ results should be published, as they are important within the context of meta–analysis (which accounts for uncertainty when weighting individual studies by sample size) to allow proper decision–making. The use of multiple hypothesis testing and Bayesian statistics puts an end to this black or white dichotomy and moves us towards a more realistic continuum of grey tones.

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