Neural processing of the reward value of pleasant odorants.

Pleasant odorants are represented in the posterior olfactory bulb (pOB) in mice. How does this hedonic information generate odor-motivated behaviors? Using optogenetics, we report here that stimulating the representation of pleasant odorants in a sensory structure, the pOB, can be rewarding, self-motivating, and is accompanied by ventral tegmental area activation. To explore the underlying neural circuitry downstream of the olfactory bulb (OB), we use 3D high-resolution imaging and optogenetics and determine that the pOB preferentially projects to the olfactory tubercle, whose increased activity is related to odorant attraction. We further show that attractive odorants act as reinforcers in dopamine-dependent place preference learning. Finally, we extend those findings to humans, who exhibit place preference learning and an increase BOLD signal in the olfactory tubercle in response to attractive odorants. Thus, strong and persistent attraction induced by some odorants is due to a direct gateway from the pOB to the reward system. • The posterior olfactory bulb is a site of intracranial self-stimulation • Olfactory tubercle receives heavy projections from the posterior olfactory bulb • Olfactory tubercle activity is related to odorant pleasantness in mice and humans • Attractive odorants are natural rewards in both mice and humans Midroit et al. reveal that the odorants act as natural rewards. The olfactory tubercle gates olfactory information from the posterior olfactory bulb to the reward system to encode spontaneous odor-driven attraction. [ABSTRACT FROM AUTHOR]