April 13, 2017

How are Odors Linked to Innate Behaviors?

Using a mechanism that is likely much more complicated that we thought! Check out the lab's most recent paper, from the inimitable Giuliano Iurilli, who performed the first systematic in vivo recordings ever in a part of the brain called the posterolateral cortical amygdala (plCoA), which couples odors (like fox odor or the scent of peanut butter) to different innate behaviors like attraction and aversion. Based upon anatomic and functional data (including from Sosulski et al), we and others predicted that odor representations in the plCoA should be pretty simple - probably labeled lines that either identified particular odors (i.e., we'd find that neurons in plCoA responded only to single innately relevant odors, so some neurons would respond only to fox odor while other neurons would respond only to peanut butter) or categorized odors based upon their behavioral meaning (i.e., we'd find some plCoA neurons that respond to all odors that are appetitive and other that respond to all odors that are aversive). Instead what Giuliano found was that individual neurons in the plCoA do not encode information about odor identity or odor category. Ensembles of neurons in plCoA appear to collectively convey information about the identity of odor objects in the world, and the structure of these ensembles is similar regardless of the identity or behavioral meaning of the odor object being encoded - at least in psuedopopulations of neurons assembled from multiple animals. In other words, odor representations in plCoA, which is known to be involved in innate behaviors, look just like those in the piriform cortex, which is involved in odor learning. This surprise suggests a dual role for the plCoA in both innate and learned behaviors, and new models for how the olfactory system can flexibly generate behaviors to innately-relevant odor cues in the environment. These data don't definitively rule out labeled lines, but strongly suggest that the plCoA is doing much more than just acting as a relay. Check out his provocative - and exciting - paper here! Yoram Ben Shaul also wrote a great preview of the paper here (for those who want a little more context), and the paper was recently covered by the Simons Foundation (the work was supported in part by the Simons Collaboration on the Global Brain) here. Congrats, Giuliano!