The mechanisms that underlie a wine lover's ability to identify a favorite
vintage and a dog's ability to track the scent of a lost child are still de
ep mysteries. Our understanding of these olfactory phenomena is confounded
by the difficulty encountered when at-tempting to identify the parameters t
hat define odor stimuli, by the broad tuning and variability of neurons in
the olfactory pathway, and by the distributed nature of olfactory encoding,
These issues pertain to both biological systems and to newly developed 'ar
tificial noses' that seek to mimic these natural processes. Information the
ory, which quantifies explicitly the extent to which the state of one syste
m (for example, the universe of all odors) relates to the state of another
(for example, the responses of an odor-sensing device), can serve as a basi
s for analysing both natural and engineered odor sensors. This analytical a
pproach can be used tcs explore the problems of defining stimulus dimension
s, assessing strategies of neuronal processing, and examining the propertie
s of biological systems that emerge from interactions among their complex c
omponents. It can also serve to optimize the design of artificial olfactory
devices for a variety of applications, which include process control, medi
cal diagnostics and the detection of explosives.