Modelling the Human Olfactory Stimulus-Response Function

Abstract

Two models, derived from the equations of Michaelis-Menten and Hill, were adapted to olfaction. Their ability to model human olfactory stimulus-response relationships was compared with that of the classical laws of Fechner and Stevens. First, these four models were systematically compared on data available in the literature concerning 20 pure odorous compounds. At the lower concentrations of the odorous compound, the model of Stevens was found to be as good as the model of Hill. However, when the concentration range was extended further and included the concentration at half the maximum intensity, the model of Hill was found to be better. Second, the four models were tested on different parts of a true stimulus-response sigmoid curve with 5% noise added. The comparison confirmed the results obtained when experimental data were used. Third, the hypothesis that the psychophysical response is the sum of sigmoidal responses generated at the more peripheral parts of the olfactory system was examined, assuming a binomial distribution of receptor affinities. Within a very large range of variation in their characteristics, the sums of several sigmoids are indeed correctly modelled by Hill equations with exponents reflecting the distribution of receptor affinities.

The Correlation and Prediction of VOC Thresholds for Nasal Pungency, Eye Irritation and Odour in Humans

“…Odor thresholds -There have been a number of early correlations of odor thresholds with various properties of odorants [27][28][29][30] but none have been very good statistically, and none have led to any conclusions of mechanistic significance. Two later studies 8 related ODT values to properties of homologous series of odorants.…”

Revisiting psychophysical work on the quantitative and qualitative odour properties of simple odour mixtures: a flavour chemistry view. Part 1: intensity and detectability. A review.

“…The saturation of the olfactory intensity at high levels of a single odorant solution is a well established fact [5,27,[31][32][33] which has as a consequence the inability to discriminate between solutions containing even very different levels of the odorant, a result similar to those aforementioned in multicomponent mixtures. The fact that this seems to happen in nearly all cases, irrespectively of the type of odorant, suggests that the suppression of the signal is not primarily caused by antagonist competition at the receptor level.…”

The Correlation and Prediction of VOC Thresholds for Nasal Pungency, Eye Irritation and Odour in Humans

“…There have been a number of early correlations of ODTs with various properties of odorants [27][28][29][30], but none have been very good statistically, and none have led to any conclusions of mechanistic significance. Two later studies related ODT values to properties of homologous series of odorants.…”