Olfactory evoked responses to odorous stimuli of different intensities

In comparison to other senses, the electrophysiology of olfaction has been little studied in man. Some of the basic paradigms used in the study of the other senses have not yet been widely applied to olfaction. Fundamental information such as the effect of stimuli of different intensities on the olfactory evoked potential (OEP) has yet to be presented. To this end, 12 subjects received olfactometrically delivered odorant pulses of toluene at three intensity levels—1600, 8000 and 16 000 p.p.m. Data were obtained from three electrode sites—Fz, Cz and Pz. An ANOVA revealed significant stimulus intensity and site effects. There was no difference in amplitude at the lowest intensities, although a significant increase in amplitude evoked by the 16 000 p.p.m. stimulus was observed. The amplitude recorded from Fz differed from that recorded from Pz. No latency differences were found, although there was a trend toward briefer latency with greater stimulus concentration. The OEP responds with increased amplitude to increased stimulus intensity, as do evoked responses in other sensory modalities. Stimulus control over the OEP amplitude can be obtained by varying the stimulus intensity. These data are evidence that the common principles of sensory processing may be extended to include the sense of smell.