THE ANTERIOR OLFACTORY NUCLEUS IS ESSENTIAL FOR MEDIATING EXPLORATORY BEHAVIORS INDUCED BY NOVEL OLFACTORY STIMULI.

When novel stimuli are detected, humans and animals react with exploratory behaviors driven by sensory input. Mice exposed to novel odorants respond with an increase in respiration frequency and pupil dilatation, which reflects the adaptive value of exploring unfamiliar stimuli in complex environments.
How the brain discriminates novel odors is poorly understood. We used a spontaneous novelty detection paradigm to examine behavioral and neuronal responses to novel and familiar odors. We found stronger neural responses to novel odors in the AON, compared to the PCx. We hypothesized that the AON, but not the PCx, is crucially involved in processing stimulus novelty. To verify this, we inhibited these regions using muscimol infusions; inhibiting the AON, but not the PCx, reduced sniffing and pupil dilation in response to novel odors.
Following questions remained: a) did AON inhibition selectively influence novelty detection, or odor discrimination in general b) was the effect mediated by AON feedforward or feedback projections. We therefore inhibited the AON neurons that project back to the OB using DREADDs. We found that inhibiting those projections caused a reduction in response to novel odors. We observed that feedforward projections from the AON to the PCx were also labeled. We could not conclude whether the feedback projection (AON-OB) or the feedforward projection (AON-PCx) is primarily important for discriminating between novel and familiar odors. We are now inhibiting AON-PCx feedforward projections, which will provide insight into the potential involvement of this projection in novel odor processing.

Abbreviation	Early olfactory region
OB	Olfactory Bulb
AON	Anterior Olfactory Nucleus
PCx	Piriform Cortex