Detection versus perception: physiological and behavioral analysis of olfactory sensitivity in the moth (Manduca sexta).

The precise relationship between olfactory transduction sensitivity and sensitivity at the level of sensory perception is poorly understood. The goal of this work was to correlate neurophysiological measures of sensory transduction and psychophysical measures of salient odor perception using the moth (Manduca sexta). Moths were conditioned to respond to a single monomolecular odor and then tested across a dilution series. Resulting concentration-response functions were dependent on the conditioning odor and its concentration but not on the moth's sex. Comparison of responsiveness to odor versus an odorless blank provided a statistical indicator of detection threshold. Separate control experiments revealed that conditioned responsiveness to odor was a function of test concentration and independent of the conditioning concentration. Next, electroantennogram (EAG) responses to these odorants and concentrations were recorded. EAG responses were highly correlated with the behavioral results but typically identified lower detection thresholds. Furthermore, significant effects of sex, Sex x Odor, and Sex x Odor x Concentration were observed only within the EAG data, suggesting a mismatch across methods. Possible reasons for and implications of this mismatch are discussed.