Odor space

Canonical correlation analysis was used to relate small subsets of physicochemical parameters to the MDS space. Small subsets were necessary because in canonical correlation analysis, the number of stimuli should be greater than the number of dimensions and physicochemical parameters combined. The analysis revealed that a linear combination of two ADAPT parameters in Table 3 (number of oxygen atoms and chemical environment of substructure (7)) in addition to a concentration variable accounted for 63% of the arrangement of the pyrazine odor space. 

See also R R. Reed. Opening the window to odor space. Science, 279,193, 1998. 

Acree T, Am H. Flavomet and Human Odor Space. http./Avww. Jlavornet.org. 

Perception of Odor Quality Odor Similarity and Odor Space.209... 

Due to the complex structure of odor space, it is an extremely interesting and challenging question whether the olfactory system has a correlate of retinotopic maps in vision or frequency maps in audition. And if it does, what would be the organizing principle of such an odor map Furthermore, can we learn from this organization of biological olfactory systems to build artificial chemosensor systems that perform at levels comparable to the performance of the former in general olfactory sensing tasks ... 

Before presenting our results on structural implications of the observed and predicted levels of activity in the MB and of the requirement of lossless information transmission, some explanation of our probabilistic approach seems warranted. The probability Ppn of activity in a given PN mainly reflects properties of the input space (odor space) and different patterns of PN activity are diced out for every LFP cycle. The connection probabilities pn->kc and kc bkc, on the other hand, refer to the random connectivity of each locust, i.e., the connectivity is determined only once for each animal. In building distributions (and taking averages) with respect to both probability spaces, we are making statements about the distribution of (and the typical value of) properties for all locusts in response to all possible odors, in a sense. 

Hopfield, J.J. Odor space and olfactory processing collective algorithms and neural implementation. P. Natl. Acad. Sci. USA 96, 12506-12511 (1999)... 

Flavomet database [20, 21]. Flavomet is a compilation of aroma compotmds foimd in human odor space, meaning at suprathreshold concentrations where they are likely to stimulate human olfactory receptor neurons [22]. Access to the online database (sponsored by DATU, Inc.) is freely available in the public domain. 

Acree, T., Am, H. (2004) Flavomet and human odor space, http //www.flavomet.org/index. html Accessed 10 Jan. 2008... 

Multidimensional analyses of ratings of similarity typically yield a dominant hedonic dimension pleasant odors cluster on one side of an odor space and unpleasant odors cluster on the other ([75,97,99,102 104,106] cf, [96]). Analyses often yield an intensity dimension as well, and occasionally one or two others that are unimportant in statistieal terms and defy clear interpretation. 

As mentioned, at suprathreshold levels subjects differ greatly both in the kind and in the number of verbal descriptors they apply to a given odor [78,79,81]. Some differences probably stem from the way subjects use labels, but some may reflect true individual differences in perceived quahty [126]. To determine exactly how the odor spaces of two subjects might differ, some test of performance (a task based on discrimination) might serve best [69]. 

By contrast, flavor space is difficult to define. Taste, of course, has its traditional four qualities—sweet, salt, sour, and bitter—and possibly a fifth, umami. However, smell seems to have a virtually limitless odor space. It is common to say that a human can identify up to 10,000 different odors, but that number as far as I can determine is only a speculation. Since odors are the main component of most flavors, flavor space is correspondingly difficult to define. This underlines the reason why no description of brain mechanisms in flavor can arise until there is a better understanding of the complex roles of the mechanisms in smell. 

The neural basis of the sense of smell begins with the action of an odor molecule on receptors on the sensory neurons in the nose. An important first step in the analysis is to characterize the odor molecules that make up odor space. ... 

This is an extremely useful step in revealing order within odor space and how it is represented within neural spaee. However, it must be kept in mind that natural stimuli usually occur in the form of eomplex combina-... 

III. STRUCTURE-ACTIVITY RELATIONS BETWEEN ODORS AND RECEPTORS TRANSDUCING ODOR SPACE INTO BRAIN SPACE... 

IV. COMPARING THE ODOR SPACES OF HUMANS AND OTHER SPECIES... 

How does human odor space compare with that of other primates and other mammals One way to characterize this space is by the odor molecules themselves, but as already noted it is impossible to catalogue all the potential members. Another way is by characterizing the olfactory receptors. 

ODOR IMAGES IN MICE AND HUMANS MAPPING ODOR SPACE WITHIN BRAIN SPACE... 

Sensory transduction involves the transfer of information carried in the stimulus to information carried in the receptor cells. For smell, one can refer to this as transfer from odor space to neural space. 

After the initial transduction of odor space into neural space by the olfactory receptors, a second messenger cascade amplifies the response in each cell, leading to activation of a cyclic nucleotide gated (CNG) ionic channel. The resulting ion flows depolarize the membrane, generating the receptor potential, which spreads to the site of action potential initiation [19]. 

---