A sniff in humans typically lasts 1-2 seconds and is considered to produce a "snapshot" of the chemical environment that also sets the temporal resolution of olfactory perception. To examine whether the temporal order of events within a sniff influences the perceptual "snapshot", we devised an apparatus that enabled us to phase-lock odor delivery to sniff onset and precisely manipulate onset asynchronies of odorants in humans. Psychophysical testing showed that participants were able to tell apart two odorants presented in the same or different order when the onset asynchrony was as low as 40 milliseconds. The performance improved with longer onset asynchronies and was not based on the molar ratio difference of the two odorants. Meanwhile, they were consistently at chance in reporting which odorant arrived first. These results provide behavioral evidence that human olfaction is sensitive to temporal patterns within a single sniff and indicate that timing of odor-evoked responses in relation to the sniff contributes to the perceived odor quality.
bioRxiv Subject Collection: Neuroscience