Mixture Perception of Straight Chain Aldehydes C6-C11
Physiological studies examining the binding properties of the olfactory receptor I-7 (OR-I7) has identified octanal (C8) as the primary agonist for this receptor. However, the molecular range of the receptor has been shown also bind odorants straight chain aldehydes C7-C10. Free-choice profiling of odorants C6-C12 identified as striking difference between the qualitative differences of C6 and odorants C7-C12. Identifying C6 as grassy/green and odorants C7-C12 as more citrus in character. An adaptation study of odorants C6, C8, C10, and C11 was conducted in order to examine the cross-adaptation properties of these odorants and determine whether odorants which do not bind with OR-I7 cross-adapt. Prior studies have shown cross-adaptation in influenced by odorant quality similarity as well as chemical functionality similarity. Furthermore, odorants sharing common receptor sites are known to cause cross-adaptation. It was hypothesized that C6 would not cross-adapt with odorants C8, C10, and C11. But the odorants characterized as citrus (C8, C10, C11) would readily cross-adapt. In order to evaluate changes in intensity due to adaptation, a methodology using odor reference matching was devised. All odorant pairs were tested for cross-adaptation and results determined that C6 did not cross-adapt with the citrus odorants C8, C10, and C11. This project also examined the odor mixture perception and the ability of the individual to detect components within a mixture. There are two theories supporting odor mixture perception. One theory states that the components comprising an odor mixture are detectable; while the other theory suggests that the components within a mixture combine to create a novel odor making the individual components impossible to detect. Odorants with dissimilar odor qualities are known to be easier to detect within an odor mixture. From the previous study it had been shown that C6 and C8 have very different odor qualities and do not cross-adapt. A series of binary odor mixtures of C6 and C8 were examined where the ratios of the intensities of each of the components was varied. Subjects were trained by using a reference matching task to identify the intensities of the individual components within the mixtures. Furthermore, subjects were asked to identify a single component within the binary mixture and determine the intensity of that component. Subjects made quick decisions of the perception of the intensities of the components within the mixture through a gestalt. The reference odorant was the figure, the subject was asked to find the figure within the mixture and determine it?s intensity. The other odorant present within the mixture was the ground. As hypothesized as the ground odorant increased in intensity, the ability to properly identify the intensity of the figure odorant became increasingly more difficult due to the effects of mixture suppression resulting in figure suppression. From the first experiment it is understood that C6 and C8 do not cross-adapt; however, results from the second experiment suggest that C6 and C8 demonstrate the effects of mixture suppression. These results suggest mixture suppression and adaptation must occur at two different stages of odorant processing within the olfactory process.
dissertation or thesis