The Development of Novel Methods for Assessing Human Olfaction Ability and the Odor Intensity of Samples

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Description
Olfactory perception is a complex and multifaceted process that involves the detection of volatile organic compounds by olfactory receptor neurons in the nasal neuroepithelium. Different odorants can elicit different perceived intensities at the same concentration, while direct intensity ratings are

Olfactory perception is a complex and multifaceted process that involves the detection of volatile organic compounds by olfactory receptor neurons in the nasal neuroepithelium. Different odorants can elicit different perceived intensities at the same concentration, while direct intensity ratings are vulnerable to framing effects and inconsistent scale usage. Odor perception is genetically determined, with each individual having a unique olfaction "footprint" and sensitivity levels. Genetic factors, age, gender, race, and environmental factors influence olfactory acuity. The olfactory system's complexity makes it challenging to create a standardized comparison system for olfactory perception tests. The COVID-19 pandemic has underscored the importance of olfactory dysfunction, particularly the loss of smell and taste as common symptoms. Research has demonstrated the widespread occurrence of olfactory impairment in various populations, often stemming from post-viral origins, which is the leading cause of permanent smell loss. Utilizing quantitative ranking on a qualitative scale enhances the precision and accuracy when evaluating and drawing conclusions about odor perception and how to mitigate problems caused by external factors. Pairwise comparisons enhance the accuracy and consistency of results and provide a more intuitive way of comparing items. Such ranking techniques can lead to early detection of olfactory disorders and improved diagnostic tools. The COVID-19 pandemic has shed light on the significance of olfactory dysfunction, emphasizing the need for further research and standardized testing methods in olfactory perception.
Date Created
2023
Agent

Odor Divergence of Enantiomers

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Description

Enantiomers are pairs of non-superimposable mirror-image molecules. One molecule in the pair is the clockwise version (+) while the other is the counterclockwise version (-). Some pairs have divergent odor qualities, e.g. L-carvone (“spearmint”) vs. D-carvone (“caraway”), while other pairs

Enantiomers are pairs of non-superimposable mirror-image molecules. One molecule in the pair is the clockwise version (+) while the other is the counterclockwise version (-). Some pairs have divergent odor qualities, e.g. L-carvone (“spearmint”) vs. D-carvone (“caraway”), while other pairs do not. Existing theory about the origin of such differences is largely qualitative (Friedman and Miller, 1971; Bentley, 2006; Brookes et al., 2008). While quantitative models based on intrinsic molecular features predict some structure–odor relationships (Keller et al., 2017), they cannot identify, e.g. the more intense enantiomer in a pair; the mathematical operations underlying such features are invariant under symmetry (Shadmany et al., 2018). Only the olfactory receptor (OR) can break this symmetry because each molecule within an enantiomeric pair will have a different binding configuration with a receptor. However, features that predict odor divergence within a pair may be identifiable; for example, six-membered ring flexibility has been offered as a candidate (Brookes et al., 2008). To address this problem, we collected detection threshold data for >400 molecules (organized into enantiomeric pairs) from a variety of public data sources and academic literature. From each pair, we computed the within-pair divergence in odor detection threshold, as well as Mordred descriptors (molecular features derived from the structure of a molecule) and Morgan fingerprints (mathematical representations of molecule structure). While these molecular features are identical within-pair (due to symmetry), they remain distinct across pairs. The resulting structure+perception dataset was used to build a predictive model of odor detection threshold divergence. It predicted a modest fraction of variance in odor detection threshold divergence (r 2 ~ 0.3 in cross-validation). We speculate that most of the remaining variance could be explained by a better understanding of the ligand-receptor binding process.

Date Created
2023-05
Agent

Characterization of Odor-Evoked Olfactory Sensory Neuron Responses in the Ant Camponotus
floridanus

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Description

Insects are able to navigate their environments because they can detect hydrocarbons and volatile odors, but it is not clear which one has the fastest reaction when detected, or how much of a response can be produced due to either

Insects are able to navigate their environments because they can detect hydrocarbons and volatile odors, but it is not clear which one has the fastest reaction when detected, or how much of a response can be produced due to either one. In order to determine which category of odorant is detected first as well as which one causes the highest response rate, data on electrophysiological responses from ants was analyzed. While the statistical tests can be done to understand and answer the questions raised by the study, there are various hydrocarbons and volatile odors that were not used in the data. Conclusive evidence only applies to the odorants used in the experiments.

Date Created
2021-05
Agent

Chemical Cues Impact Zebrafish Response to Visual Cues

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Description

Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how

Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how the presence of chemical cues affect the perception of visual cues. Zebrafish (Danio rerio) often use both chemical cues and visual cues to communicate with shoal mates, to assess predation risk, and to locate food. For example, zebrafish rely on both olfactory cues and visual cues for kin recognition, and they frequently use both chemical and visual cues to search for and to capture prey. In zebrafish, the terminal nerve (TN) constitutes the olfacto-visual centrifugal pathway and connects the olfactory bulb with the retina, thus allowing olfactory perception also to activate visual receptors. Past studies have found that the presence of an olfactory cue can modulate visual sensitivity in zebrafish through the terminal nerve pathway. Alternatively, given that zebrafish are highly social, the presence of social chemical cues may distract individuals from responding to other visual cues, such as food and predator visual cues. Foraging and predator chemical cues, including chemical food cues and alarm cues, may also distract individuals from responding to non-essential visual cues. Here, we test whether the response to a visual cue either increases or decreases when presented in concert with alanine, an amino acid that represents the olfactory cues of zebrafish prey. We found that the presence of chemical cues did not affect whether zebrafish responded to visual cues, but that the fish took longer to respond to visual cues when chemical cues were also present. These findings suggest that different aspects of behavior could be affected by the interaction between sensory modalities. We also found that this impact of delayed response was significant only when the visual cue<br/>was weak compared to the strength of the chemical cue, suggesting that the salience of interacting cues may also have an influence on determining the outcomes of the interactions. Overall, the interactive effects of chemicals on an animal’s response to visual cues may also have wide-ranging impacts on behavior including foraging, mating, and evading predators, and the interaction of cues may affect different aspects of the same behavior.

Date Created
2021-05
Agent

Mice Olfaction and Habituation on Strawberries through Utilization of an Odorized Hole-Board Arena

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Description
The mammalian olfactory system is commonly studied by using the mouse as a model system. Odor habituation is used to investigate odor perception and learning processes. Most previous experimental preparations have been tedious, requiring a researcher to manually change odorants,

The mammalian olfactory system is commonly studied by using the mouse as a model system. Odor habituation is used to investigate odor perception and learning processes. Most previous experimental preparations have been tedious, requiring a researcher to manually change odorants, record investigation time and duration at each odorant, or physical alteration on the mice to enable video tracking. These limitations were overcame by creating an odorized hole-board to allow for systematic and automatic recording of olfactory behavior in mice. A cohort of five male mice were utilized in these experiments and the responses to the odor of strawberries, a diet staple of wile mice, were examined. Experiment 1 showed that free-feeding mice exhibit a preference to locations with strawberry (over control locations), even when these locations can only be identified using olfaction. This preference habituates within a trial but not across days. Experiment 2 showed that strawberry odor without reward causes habituation or extinction to the odor both within trials and across days. From these experiments, it can be concluded that mice innately explore strawberry odor and this can be exploited to the study odor habituation using an odorized hole-board.
Date Created
2016-12
Agent

The Number of Olfactory Stimuli That Humans Can Discriminate is Still Unknown

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Description

It was recently proposed (Bushdid et al., 2014) that humans can discriminate between at least a trillion olfactory stimuli. Here we show that this claim is the result of a fragile estimation framework capable of producing nearly any result from

It was recently proposed (Bushdid et al., 2014) that humans can discriminate between at least a trillion olfactory stimuli. Here we show that this claim is the result of a fragile estimation framework capable of producing nearly any result from the reported data, including values tens of orders of magnitude larger or smaller than the one originally reported in (Bushdid et al., 2014). Additionally, the formula used to derive this estimate is well-known to provide an upper bound, not a lower bound as reported. That is to say, the actual claim supported by the calculation is in fact that humans can discriminate at most one trillion olfactory stimuli. We conclude that there is no evidence for the original claim.

Date Created
2015-07-07
Agent

High-Speed Odor Transduction and Pulse Tracking by Insect Olfactory Receptor Neurons

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Description

Sensory systems encode both the static quality of a stimulus (e.g., color or shape) and its kinetics (e.g., speed and direction). The limits with which stimulus kinetics can be resolved are well understood in vision, audition, and somatosensation. However, the

Sensory systems encode both the static quality of a stimulus (e.g., color or shape) and its kinetics (e.g., speed and direction). The limits with which stimulus kinetics can be resolved are well understood in vision, audition, and somatosensation. However, the maximum temporal resolution of olfactory systems has not been accurately determined. Here, we probe the limits of temporal resolution in insect olfaction by delivering high frequency odor pulses and measuring sensory responses in the antennae. We show that transduction times and pulse tracking capabilities of olfactory receptor neurons are faster than previously reported. Once an odorant arrives at the boundary layer of the antenna, odor transduction can occur within less than 2 ms and fluctuating odor stimuli can be resolved at frequencies more than 100 Hz. Thus, insect olfactory receptor neurons can track stimuli of very short duration, as occur when their antennae encounter narrow filaments in an odor plume. These results provide a new upper bound to the kinetics of odor tracking in insect olfactory receptor neurons and to the latency of initial transduction events in olfaction.

Date Created
2014-11-25
Agent

Homeostatic Regulation of Spontaneous and Evoked Synaptic Transmission in Two Steps

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Description

Background: During development both Hebbian and homeostatic mechanisms regulate synaptic efficacy, usually working in opposite directions in response to neuronal activity. Homeostatic plasticity has often been investigated by assaying changes in spontaneous synaptic transmission resulting from chronic circuit inactivation. However,

Background: During development both Hebbian and homeostatic mechanisms regulate synaptic efficacy, usually working in opposite directions in response to neuronal activity. Homeostatic plasticity has often been investigated by assaying changes in spontaneous synaptic transmission resulting from chronic circuit inactivation. However, effects of inactivation on evoked transmission have been less frequently reported. Importantly, contributions from the effects of circuit inactivation and reactivation on synaptic efficacy have not been individuated.

Results: Here we show for developing hippocampal neurons in primary culture that chronic inactivation with TTX results in increased mean amplitude of miniature synaptic currents (mEPSCs), but not evoked synaptic currents (eEPSCs). However, changes in quantal properties of transmission, partially reflected in mEPSCs, accurately predicted higher-order statistical properties of eEPSCs. The classical prediction of homeostasis--increased strength of evoked transmission--was realized after explicit circuit reactivation, in the form of cells' pairwise connection probability. In contrast, distributions of eEPSC amplitudes for control and inactivated-then-reactivated groups matched throughout.

Conclusions: Homeostatic up-regulation of evoked synaptic transmission in developing hippocampal neurons in primary culture requires both the inactivation and reactivation stages, leading to a net increase in functional circuit connectivity.

Date Created
2013-09-22
Agent