Meeting Abstract
Sniffing and analogous sampling strategies are known from most classes of animals. Among mammals sniffing allows rapid and efficient odor sampling; initial responses and simple discriminations can occur after the first sniff (~ 200 ms). However, mammals often sniff in bouts lasting up to 10 seconds. Thus, although a single sniff may provide an initially useful odor “snapshot,” longer-term sniff dynamics likely play important roles in other behaviorally-relevant olfactory tasks, such as matching anodor to a known odor object, gleaning precise concentration information, or evaluating complex mixtures. In this project we investigate several mechanistic hypotheses for how sniffing contributes to early coding of olfactory information in the olfactory bulb of adult mice. We focus specifically on pre- and post-synaptic cells in the olfactory bulb, which is the first step in olfactory processing. To access these cell types we use genetically-encoded calcium indicators (primarily GCaMP) coupled with targeted mutant mouse lines, allowing us to image calcium activity (a proxy for neural activity) in the pre-synaptic olfactory sensory neurons (OSNs) and the post-synaptic mitral cells (MCs). Our initial experiments in anesthetized animals using an artificial sniff paradigmhave found differences in how OSNs and MCs respond to changes in sniff frequency. We have found some evidence that response patterns decorrelate rapidly over time in MCs, but have not found evidence for this in OSNs, though more experiments are needed to clarify this question. These experiments show that OSNs and MCs respond differently to changes in sniff frequency. More broadly our results suggest that mammals engage in extended sniffing bouts to filter out background odorants and form unique odor percepts, beyond the information that they can glean from a single sniff alone.
