Fox, Grace Ellen; Department of Neuroscience and Regenerative Medicine (8/7/2018)
      Fear is an adaptive response that permits organisms to reduce or avoid danger. In many animal species, behavioral correlates of fear can be seen, which highlights its essential role in survival; conversely, inappropriate and exaggerated fears are a hallmark of psychiatric disorders, such as anxiety-related disorders. Recently, the retrosplenial cortex (RSC) has been implicated for long-term storage of fear-related memories. However, the basic physiological properties of RSC cells as well as their response to fearful events remained largely unexplored. Our experiments demonstrate that excitatory principal cells within RSC layers 2&3 and 5&6 contain multiple physiologically distinct sub-populations that are differentially affected by ketamine. We also demonstrate the novel finding that the RSC utilizes the specific-to-general cell-assembly logic for processing neural information about fearful experiences. Taken together, these results illustrate that the RSC generates a cell assembly-level representation of fear memory engrams and supports the pursuit of the RSC as a therapeutic target for anxiety-related disorders.