2026 O’Leary Lecture

Fixed pheromones or flexible fingerprints? Exploring the complexity of mammalian social chemosensation

Julian P. Meeks, PhD
Associate Professor, Department of Neuroscience
Associate Professor, Department of Pediatrics – Joint
Associate Professor, Department of Pharmacology and Physiology – Joint
University of Rochester Medical Center

Each year, a former recipient of the James L. O’Leary Prize for Research in Neuroscience competition is invited to present the annual O’Leary Lecture and also be a guest judge at the prize competition.

Across the animal kingdom, chemical cues play central roles in supporting survival and reproduction. Chemosensory systems allow animals to sense excreted molecules that distinguish self from non-self, identify potential friends and foes, and evaluate potential mates. In vertebrates, the juxtaposition of strongly conserved aspects of physiology with each species’ need to interpret their chemical environments places chemosensory systems at an interesting neurobiological intersection. For example, all vertebrates utilize bile acids (digestive steroids) to absorb dietary lipids, and excrete bile acids in feces to prevent toxic buildup. Most vertebrates, including important preclinical model organisms (including zebrafish, mice, and rats) sense bile acids, but we do not yet understand how or why they evolved such a capacity. Using population Ca2+ imaging, mass spectrometry, and modeling, we investigated bile acid chemosensation in mice. We found that fecal bile acid patterns – and not species-bespoke molecules – support discrimination of vegetarian reptiles from rodent predators. We found that the mouse vomeronasal organ can use patterns of bile acid excretion (chemical “fingerprints”) to partially decode reptile species and diet. When we compared bile acid “fingerprints” of mice with different gut microbiomes to vomeronasal neuron sensitivities, we found tight coupling between the two, suggesting that the vomeronasal system is optimized for sensing conspecific gut health. Finally, we present early work investigating the potential for early life chemosensory experience to shape pheromone processing in adulthood. These studies suggest that the vomeronasal system, despite its reputation as a fixed pathway for detecting rare, unique molecules, is a flexible sensory system optimized to decode the chemical fingerprints of biologically relevant states.