Bottom-up and Top-down: Molecules and Circuits that Underlie Chemosensory Behaviors

This Research Topic highlights recent advancements in our understanding of how genes and neural circuits in the brain shape complex natural behaviors that are evolutionary conserved and essential for survival across species. How the brain balances critical extrinsic and intrinsic information to enable social behaviors is currently a major topic in neurobiology. All organisms rely on chemosensory systems to seek food, communicate, and avoid hazards and predators: e.g. the valence of tastants specifies its hedonic value and elicits selective behaviors. The link between chemosensory processing and behavior has been investigated in detail in both vertebrates and invertebrates. In mice, olfactory cues such as pheromones have been shown to elicit specific social forms of behavior.

In turn, chemosensation is shaped by internal cues, such as hunger, the drive to procreate, and fear. Internal brain states modulate the detection of external chemosensory stimuli. This requires neural circuits to adapt depending on the behavioral needs (wakefulness/sleep state, arousal, learning, metabolic demands, reproduction state, etc.). By making use of an advanced genetic toolset, mechanisms adapting chemosensory processing and perception to internal states such as hunger and reproductive state are currently a hot research topic in the field. In mice, hippocampal “top-down” projections to sensory centers have been shown to link memories of particular stimuli with place information and experiences.

Chemosensory information processing emerges from a complex interplay of ascending sensory inputs and descending fibers from higher brain areas. “Bottom-up” and “top-down” networks converge in early sensory areas and higher brain regions. For this reason, chemosensation is an excellent model system to investigate how the brain processes extrinsic and intrinsic information to ultimately shape behavior. Impairments can lead to neuropsychiatric disorders, communication disorders, and in the context of chemosensory systems, metabolic diseases. While the precise mechanisms leading to stimulus adaptations have not been fully elucidated, work from many labs has demonstrated that the activity of neurons at any stage of chemosensory information can be modulated to optimize stimulus processing and behavioral outputs.
This Research Topic will capture the current progress on our understanding of how changes in chemosensory neural circuits can have significant behavioral consequences.