Mammalian behavioral discrimination and neural processing of naturalistic odor plumes based on intermittency

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PROJECT SUMMARY Mammals use odor navigation to avoid noxious environmental dangers, find food sources, locate mates, and escape predators- critical behaviors for survival. Odors in nature are often carried by turbulent air flow, producing odor plumes with complex spatiotemporal structure. Intermittency is a fluid dynamics parameter that quantifies this fluctuating nature as the fraction of time odor is present at a point within the plume. Intermittency decreases with increased distance from an odor source and may provide important information about source proximity. Such odor information must be sampled by animals, integrated by the olfactory system, and ultimately, drive navigation. Mammals modulate odor sampling through sniffing, and rapid sampling can possibly support the detection of sparse odor whiffs at low intermittency sections of a plume. In addition, olfactory sensory neurons (OSNs) are capable of rapid response properties that are beneficial for detection of fleeting odor presentation as well as response adaptation to persistent odor presentation that allows for detection of changes in the odor landscape. Although dynamic odor plumes are prevalent in nature, most studies have focused on olfactory processing of static odors. The objective of this proposal is to examine if mice can use temporal properties of odor plumes for navigation and to determine their neurobehavioral responses to these dynamic odor sequences. This proposal will test the hypothesis that mice can use intermittency to navigate odor plumes and that modulation of sniffing and OSN response properties enable detection of odor presence at the plume periphery and changes in the odor environment close to the source. In preliminary work, mice were trained on a task in which they discriminate between odor sequences, some directly sampled from an odor plume, using intermittency. The sampling strategies they use to perform this task are hypothesized as an increase in sniff frequency during odor presentation at low intermittencies to detect sparse odor whiffs. This will be determined by measuring sniff frequency during the task. Moreover, OSN responses will be quantified to test the hypothesis that at low intermittencies, robust responses to each odor whiff are needed for intermittency discrimination (Aim 1). To define OSN response adaptation to fluctuating odors, decreases in OSN response amplitude to consecutive odor whiffs across increasing intermittency will be quantified in mice displaying a range of sniff frequencies (Aim 2). If navigation depends on reliable detection of odor presence at the periphery and changes in odor environment close to the source, OSN response to low intermittency stimuli may be sensitive across many whiffs and adaptation may only occur with high intermittency stimuli. This proposal will provide insight into how mammals interpret olfactory information to localize essential odor sources. This work is well-aligned with the NIDCD mission to understand the normal processes of smell as it is critical to countless everyday functions.