Representations of carbon dioxide in the mosquito antennal lobe

Carbon dioxide (CO2) is one of the prominent sensory cues used by mosquitoes to find hosts for blood-feeding. CO2is detected on the maxillary palps by capitate peg sensory neurons, whose axons project to the antennal lobe in the brain. Behavioral studies have shown that mosquitoes prefer non-homogenous plumes of CO2over homogenous plumes and CO2greatly enhances the attractiveness of lactic acid, a skin volatile. However, the neural mechanisms underlying these behavioral preferences are not known. Usingin vivointracellular recordings from projection neurons and local neurons in the antennal lobe, along with single sensillum recordings from the maxillary palps, we checked the representations of CO2in the first two layers of theAedes aegyptiolfactory system. We found that the preference to non-homogeneous plumes of CO2and its synergistic attraction with lactic acid are encoded in the PN population responses. Our results provide a foundation for understanding CO2-mediated host-attraction in mosquitoes.