Stimulus-response relationships of insect olfaction: Correlations among neurophysiological and behavioral measures of response

The inter-relationships among parameters of odorant concentration, the responses evoked in single olfactory receptor neurons, the whole-animal behavioral threshold, and the intensity of the behavioral response are examined for insect olfaction from the perspective of a new phenomenological model of the perceived intensity of single odorants. Electrophysiological and behavioral data compiled from diverse insect studies are analyzed in detail to determine the utility of the model for interpreting these studies and for designing new studies. The analysis of electrophysiological data indicates that the response of olfactory receptor neurons can be expressed as a power function of the odorant concentration. The behavioral thresholds to sex pheromone, predicted by the model from direct calculations using phenomenological parameters, are in good agreement with thresholds measured by bioassay. It is also shown that the interpretation of behavioral bioassay data in terms of concepts introduced by the model provides more information about the behavioral response than provided by the currently popular probit analysis. In addition, aspects of the physiological significance of power functions are discussed, and new methods are presented for distinguishing background activity from activity evoked in single olfactory neurons by an odor at threshold levels.