Mice spontaneously gather information about their environment through exploratory sniffing. Identifying smells and localizing their source is not only essential for navigation, but also to obtain food and avoid danger.
To find out how mice perceive the spatial localization of different airborne chemicals, José Esquivelzeta Rabell and his colleagues at the Haesler lab developed a new method to measure the high-frequency respiration that characterizes sniffing behaviour. Using infrared thermography, they registered inhalation and exhalation patterns in a non-invasive manner and compared what happened when mice were presented with either novel or familiar smells. They found that mice actively orient their nostrils toward previously unexperienced smells at a remarkable speed: within the very first sniff.
How does the brain accomplish such a rapid response? “Our data show that mice compare the strength of the smell obtained through the two nostrils for locating the direction of the odor source,” explains Prof. Sebastian Haesler. “This comparison involves information transfer between the two brain hemispheres.” Using an optogenetic approach, the team further demonstrated that the anterior olfactory cortex, the first site of convergence between left and right olfactory inputs, plays a key role in the orientation process.