Modelling analysis of centroid curves of olfactory habituation in humans.

Previously published experiments established the time-course of olfactory habituation in humans, and extracted 3 centroid curves from clustering analysis that reflected high, middle and low habituation. The aim of the current theoretical study was to further analyse these previous experimental data by developing a mathematical modelling analysis designed for fitting the 3 curves from a general equation. After adjusting equation parameters for each curve, fitting equation outcomes on experimental data yielded high correlation coefficients of 0.9997 - 0.9995 - 0.9962, respectively. A model-based interpretation of olfactory-habituation centroid curves is proposed suggesting that they result from the effect of 2 separate processes that act simultaneously. We suggest that the first process is unlikely related to the olfactory habituation itself, and, rather, is of unclear origin. The second process seems to play a major role in the degree of OH and cannot be assigned, a priori, to either peripheral or central adaptation, respectively.