Fooling the human brain

The human nose, with its hundreds of receptor types and complex biological machinery, can be viewed simply as a special case of a sniffer. Like any other sniffer, it takes an odorant (o; c) and represents it by an odorant vector d P (o; c).



However, mapping vectors from an artificial sniffer into the biological human “sniffer" will probably be far more challenging than mapping one e Nose into another. The difficulty is in the fact that the two systems, the biological and the artificial, are very different in the detection mechanism. The olfactory receptors (ORs) operate on very different principles than chemical sensors. As mentioned earlier biosensors for eNoses are being developed by several research groups. Once they are eventually incorporated in e Noses, this difficulty can be expected to be removed. Our point here is that even for “standard" e Noses that use conventional chemical sensors, there is evidence that the resulting fingerprints can be used to infer psychophysical data.

Over a wide range of concentrations between the threshold value and the saturation value, the intensity usually obeys a power law I (o; c) = kcn, with k and n being odor-specific constants. This is definitely not linear, but it has also been observed that n is usually close enough to 1 to allow for the linear approximationto hold in a reasonable range of low concentrations. As explained earlier, real world applications require only low concentrations, thus this linear approximation might very well be adequate for the kind of odor communication system we propose.