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. Author manuscript; available in PMC: 2010 Oct 2.
Published in final edited form as: Cell. 2009 Oct 2;139(1):45–59. doi: 10.1016/j.cell.2009.09.015

Figure 4. Representations of odor space.

Figure 4

(A) Chemical structures of three odorants. It is difficult to compare the degree of relatedness between odorants by visual inspection. (B) A physical odor space constructed using 32 optimized descriptors of odorant structure (Haddad et al., 2008), for the odor panel used in Hallem and Carlson, 2006. The Euclidean distance between hexyl hexanoate (green) and ethyl decanoate (blue) is smaller than the distance of either odorant to methyl hexanoate (magenta), indicating that hexyl hexanoate and ethyl decanoate are more structurally similar. The first three principal components (PC) are shown. Similarly, hexyl hexanoate and ethyl decanoate map closer to each other than to methyl hexanoate in a neural odor space (C), based on the functional data reported in Hallem and Carlson, 2006.