Event:

The olfactory system is essential for a wide range of behaviors, yet how the brain processes odor information to drive and modulate behavior remains poorly understood. Odor information is transmitted from the olfactory bulb (OB) to distributed, parallel circuits in the higher olfactory system, which route it to decision-making and motor coordination centers via largely uncharacterized pathways. Using larval zebrafish, a model with unique advantages such as optical transparency and advanced genetic tools, we investigated brain-wide neuronal dynamics and behaviors in response to appetitive and aversive chemosensory stimuli. Our findings reveal reliable stimulus-evoked behaviors despite inter-individual variability, conserved in partially immobilized fish. Brain-wide responses were strongest in the forebrain but extended to mid- and hindbrain areas. Within the higher olfactory system, distinct target areas exhibited specialized responses, with the posterior tuberculum showing the most pronounced transformations of OB inputs. Notably, valence-encoding neurons were concentrated in the forebrain, forming networks potentially independent of behavioral execution. Neurons correlated with behavioral output were predominantly located in the mid- and hindbrain. This study provides a comprehensive map of neuronal activity related to the processing of behaviorally relevant odors, providing critical insights into distributed processing strategies in the brain.