Neural mechanisms of experience-dependent learning of likes or dislikes of odors in mice

Abstract

Odors elicit many kinds of emotion and emotion-based behaviors. While some odors induce genetically-inherited behaviors, many odors are initially neutral and odor responses are learned through experience. Odor information received in the olfactory epithelium is transferred to the olfactory cortex. Olfactory cortex can be divided into several areas, and we are interested in one area, olfactory tubercle (OT). When mice associate a particular odor to food reward and become liking the odor, anteromedial subarea of the OT is activated. On the other hand, when mice associate the same odor to electrical shock punishment and become disliking the odor, lateral subarea of the OT is activated. Given that activation of brain areas depends on synaptic inputs, plastic property of synaptic inputs to the OT was examined. By associating optogenetically-stimulated synaptic inputs to the OT with either reward or punishment, the synaptic inputs were strengthened in an OT subarea-specific manner. Further, the OT expresses a variety of neuromodulatory signal molecules, and manipulation of the signals altered olfactory behaviors. Through these topics I wish to introduce the highly plastic and adaptive nature of the olfactory system to determine olfactory behaviors by experience. A possible relation between odor, emotion and pain is also discussed.