Odor quality discrimination

Yee, K. K., Costanzo, R. M. 1998. "Changes in Odor Quality Discrimination Following Recovery from Olfactory Nerve Transection." Chemical Senses, 23 513-519. 

RA de Wijk, WS Cain. Odor quality Discrimination versus free and cued identification Percept Psychophys 56 12-18, 1994. 

MJ Olsson, WS Cain. Psychometrics of odor quality discrimination. Chem Senses 25 493 99, 2000. 

Newborns respond to odors by rapid breathing and activity changes. They can detect odors, rapidly develop their sensitivity over the first 4 days of life (Lipsitt etal, 1963), discriminate odor qualities and intensities, memorize odors for 1 day (and possibly for life), prefer odors they had experienced earlier, and localize odor sources (e.g. newborns aged 1 to 5.5 day olds turn away from a cotton swab with ammonia Rieser eta/., 1976). Neonates younger than 12 hours show olfactory preferences and aversions even before they experience their first food. 

If odor-evoked slow temporal patterns actually provide higher brain centers with information about the odor quality, identification and discrimination cannot be instantaneous as many of the temporal features in the response profiles appear late or even after offset of odor exposure. Honeybees need 500 ms for a response to (non-sexual pheromone) odors but at least 1 second of stimulation is required for a correct discrimination (J. Klein, unpublished, cited in Galizia el al., 2000a). Thus, it appears that time is an important factor in discrimination tasks involving non-pheromonal odors and the slow temporal patterns could theoretically contribute to an olfactory code. In contrast, these temporal patterns would be too slow to encode information about sexual pheromones. Male moths, for example, must be able to respond to rapid changes in stimulus intermittency when moving upwind in pheromone plumes in search of a calling female. 

Discrimination ability, that is, the capability of recognizing small differences in odor quality, can to some extent be learned. However, there are innate, permanent differences between people in the extent to which they can acquire this ability, and the perfumer must be very good at it. The beginning student will come to know his or her own potential ability only after some time. 

WISE, P.M., CAIN, W.S.., Latency and accuracy of discriminations of odor quality between binary mixtures and their components. Chem. Sens., 2000, 25, 247-265. 

These studies indicate that hamsters in at least two genera readily notice the difference between the odors of two individuals and remember these odor qualities over at least 15 minutes. Other experiments show that after 5 such habituation trials, golden hamsters remember the odor quality of the first donor and increase their investigation of a novel hamster s odor when tested 10 days later (Johnston, 1993). Since individuals of these two hamster species also distinguish between odors of individuals in another genus, this suggests that these discriminations are probably due to a generic ability to make distinctions between subtle differences in complex mixtures, rather than to perceptual mechanisms specialized for conspecific odors. 

Scholars have attempted to measure odor quality in a variety of ways [66], Others have provided thorough reviews (e.g., [67-69]). We provide a brief overview of four major techniques categorization, profiling, ratings of similarity, and discrimination. 

Some studies have examined the ability of animals to discriminate among odor stimuli and have attempted to correlate failures of discrimination with structural similarity among odor molecules. These studies may be used to form indices of the perceptual similarity of odors, and this may provide information about the way that a limited variety of chemical structures (e.g., alcohol groups or double-bonded oxygen moieties (ketones)) are used as features by the olfactory system Recent behavioral experiments using aliphatic alcohols, ketones, and aldehydes have shown that the perceptual qualities of odors are correlated with molecular features such as... 

To improve classification ability, the effect of environmental parameters in different data preprocessing algorithms was evaluated. The algorithm that allowed the least humidity, temperature, and day correlation was selected. PCA was used to determine discriminating ability. The results indicate that MOS sensors were much better at discriminating the different odors when compared with the conducting polymer sensors. It was also shown that the location of samples for MOS sensors depended on the quality of water. 

This advertisement of dominance through competitive scent marking also provides a mechanism that potential mates could use to assess and compare the relative competitive abilities of different territory owners or dominant individuals. Most importantly, this would allow potential mates to discriminate between those that advertise their apparent high quality through scent marking and the quality of their odor, to select a mate of proven high competitive ability. 

For now, discrimination seems most appropriate in two situations. First, discrimination is particularly appropriate in determining whether two odorants differ at all, rather than how much they differ. The study of enantiomers, molecules of identical composition that are structural mirror opposites, qualifies as a good example (e.g., [109,111,117-120]). Second, discrimination is particularly appropriate in the study of small differences in quality. The study of the effects of small and systematic changes in molecular properties qualifies as a good example [121-124]. 

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