Learning of odor timing

Abstract

Our olfactory senses are challenged to smell different odorants which vary in their physical and chemical characteristics. The odorants are often transported in turbulent plumes and depending on the source of origin, may arrive to our nose at different times. However, whether the mammalian olfactory system can extract temporal information of specific odorant from the varying olfactory environment is unknown. There has been an effort to understand if the olfactory system is capable to code odor timing. One such study in rodents using optogenetic stimulations have indicated that mice can discriminate the glomerular activations at different times (Smear et al., 2013). On the contrary, a recent study with human participants reported that humans are poor in discriminating temporal odor mixtures (Perl et al., 2020). To address if mice can discriminate odorant information arriving at different times, we developed a behavioral paradigm which, allowed us to deliver odor pulses of different durations in the background of another odorant. A series of behavioral assays were designed employing the go/no-go operant conditioning paradigm and animals were trained to detect target odorant with different temporal delays. Careful analysis of different behavioral readouts associated with the sampling and licking prove that mice can discriminate temporal delays associated with different odorants. However, mice showed slower learning pace while they were challenged to discriminate the delays associated with the same odorants and few of the animals were not able to learn this highly complex task. In conclusion, our results prove that the rodent olfactory system can discriminate the odor timings in complex olfactory environments.