Progress towards understanding mammalian olfactory coding has been hindered by: 1) our inability to identify receptors that make a measurable impact on odor perception and 2) the highly complex and distributed nature of higher order olfactory projections in the brain. Volatile odorants are detected by a large family o olfactory receptor genes in the mouse. This includes two families of canonical odorant receptors (ORs) containing over 1,000 members, and a small family of 14 Trace Amine-Associated Receptors (TAARs). We have shown that the TAARs play a critical role in the detection of amines-a class of compounds that elicits avoidance behavior in nave (untrained) mice. Moreover, the TAARs are required for the aversive quality of the amines. Because a majority of TAARs project to a cluster of glomeruli in the dorsal olfactory bulb, the neural circuitry underlying amine aversion can be traced from a genetically identifiable starting point. Here I propose to identify projections from TAAR glomeruli to higher brain regions, and to define their functions in odor processing.
Specific Aim 1 will map the projections of olfactory bulb output neurons that get input from the TAAR glomeruli.
Specific Aim 2 will optogenetically silence TAAR specific input to individual olfactory regions in order to determine their role in amine detection and aversion. Achieving these aims will be a key first step in identifying higher order neural circuitry that contributes to odor valence and olfactory perception in mammals.
The olfactory system contributes significantly to overall health and quality of life by allowing humans to evaluate food sources and avoid harmful chemicals. Relatively little is known about higher order brain structures that process olfactory information i mammals. The goal of this proposal is to use advanced anatomical tracing and optogenetic methods to elucidate the organization and better understand the function of central olfactory structures in mammals.
