Reference Matching of Dissimilar Binary Odor Mixtures

Abstract

Hexanal (C6) and octanal (C8) exhibit two different odor qualities at all concentrations: C6 is perceived as green, while C8 is perceived as citrus. This paper examines the odor perception (quality+intensity) of C6-C8 binary mixtures by varying the concentration ratios within the mixtures and using an odor reference-matching task to estimate perceived intensity. Three perceptible concentrations of C6 and C8, low (L), medium (M), and high (H), were prepared. Subjects were trained to match the quality and intensity of blind samples of these standards with their appropriate reference. Mixtures were composed of a focal or "figure" odorant (indicated below in bold) of the same odor quality as the references and a second odorant defined as the "ground" odorant. In subsequent sessions, subjects were asked to evaluate their perception of the quality of the focal odorant in a C6-C8 mixture. Stimuli for C6 matching tasks, where C6 was both the reference and the figure, were: 6L-8M, 6M-8L, 6M-8M, 6M-8H, and 6H-8M. The C8 matching tasks were the same, except that the roles of C6 and C8 were reversed. When the figure odorant was stronger than or iso-intense to the ground odorant, mixtures were often matched to a less intense reference, indicating suppression (compensation) of the figure by the ground odorant.

Chemesthesis, Thermogenesis, and Nutrition

“…The compounds can only mask each other (Cain et al, 1995;Marshall et al, 2006). The masking gets worse if configural learning is prevented by training to attend to one of the compounds (Kurtz, Lawless & Acree, 2009;Prescott & Murphy, 2009). …”

Mixture Perception of rORI7 Agonists with Similar Odors

“…1 and 2. In addition to the three L, M, and H references used in Kurtz et al 2009, a fourth reference containing only PEG (Ø) was added. Concentration levels defined as L, M, and H were chosen to be clearly suprathreshold (> 5% detection), statistically distinguishable, and to cover most of the range of the intensity scores given.…”

“…There were five binary mixture stimuli: 8M-10L, 8M-10M, 8M-10H, 8L-10M, and 8H-10M. All stimuli were prepared using the same procedure outlined in Kurtz et al (2009).…”

“…Although we do not examine this theory experimentally in this study, the approach seems unlikely to produce less analytic data than the use of an external standard. This is the fourth in a series of papers (Kittel et al 2008;Kurtz et al 2009Kurtz et al , 2010 examining the human psychophysics of the primary agonists of the rat olfactory receptor ORI7, the first mammalian deorphanized olfactory receptor (Zhao et al 1998). The primary agonists of rORI7 are the normal aldehydes C7-C11 and have a similar "citrus-like" odor quality for humans.…”

“…Our second paper demonstrated cross-adaptation in humans between the rORI7 agonists (C7-C11), while antagonist hexanal (C6) did not cross-adapt with C7-C11. The final two experiments examined the perceived intensity of three of these compounds, C6, C8, and C10, in binary mixtures using an analytical protocol that uses reference matching instead of scaling (Kurtz et al 2010(Kurtz et al , 2009. Other studies (Köster 1968;Berglund et al 1973;Cain and Drexler 1974;Laing and Francis 1989) show reproducible patterns of odor processing of mixtures from the psychophysics of single odorants that are not the same for all odorants in mixtures.…”