Petrulis Lab Research

The aim of our current project is to understand how social information is encoded by brain structures critical for social communication and behavior in mice. Specifically, these experiments will assess how several interconnected socially-responsive and reward-related brain regions (e.g. medial amygdala (MA); bed nucleus of the stria terminalis (BNST); medial preoptic/anterior hypothalamus (MPOA/AH); ventral striatum (VS)) code and process male and female odor cues that ultimately drive social behavior in mammals. In particular, we wish to identify the chemical nature and connectivity of neurons that process social odors and thereby alter communicative (scent marking, ultrasonic vocalizations) and social behaviors (copulation, aggression). To do this ,we take advantage of the combinatorial possibilities of combining genetically-modified mice (that express a non-native enzyme (cre recombinase) under the control of genes that code for specific neural transmitters) combined with brain region-specific injections of viral vectors that only insert their genetic code (for light- or designer drug-sensitive molecules) in neurons in the presence of this non-native enzyme. Thus, we can excite or inhibit a particular type of neuron in a particular brain region by using designer-drug injections (either systemic or intracranial) or intracranial light stimulation. This allows us to evaluate the necessity and sufficiency of these chemically-defined neurons for odor-guided social and communicative behaviors.

We wish to understand how social information is encoded by brain structures critical for social behavior. Specifically, these experiments will assess how the mouse brain encodes and analyzes same- and opposite-sex odor stimuli produced by conspecifics. We use house mice as a model species for understanding social odor processing because: (1) mice are almost completely dependent on odor information to guide their social behavior; (2) much information is already available about the neural systems involved in mouse social behavior and communication and (3) the availability of genetically-modified mice makes the fine neurochemical dissection of social circuits possible. Even though humans do not generally use odors to guide their social behavior, many of the same neural structures (e.g. amygdala, hypothalamus) involved in social odor processing are involved in normative human social and emotional regulation. Importantly, several psychiatric disorders have impaired social and emotional behaviors as primary or core symptoms (autism, depression, anxiety) and many of these problems have been linked to dysfunction of brain structures that we study in mice. Consequently, the detailed experimental analysis that is afforded by studying neural processing of social odors in mice will allow us to identify general rules or processes that govern social behavior across all mammals, including humans and how they break down in social psychopathology.