The Role of Neuromodulation in Social Learning

earning plays a broad role shaping behavior in animals with imposed social structures. We humans attach personal meaning to the simple smell of coffee, or a perfume, or the aroma of a great white wine, because we inhaled them off of a loved one or shared them with a special friend. For other mammalian species, ascribing social meaning to an initially neutral stimulus may have more paramount importance; for a male, remembering the ideal location to find a suitable mate -- but not a more dominant male – may be essential to obtaining resources, food and partners. Even for humans with disorders like autism, the inability to associate stimuli with social behaviors is incredibly debilitating. To understand and affect social learning, we must understand the circuits that underlie it. Thus we are modeling the behavioral process of social learning – putting together non-social odors or ensembles of piriform neurons, with social stimuli to afford a social status to the former – and functionally dissecting the circuit components involved.

But neural circuits, and the components of those circuits, do not provide a full picture of how the brain produces behavioral responses from sensory stimuli. Superimposed on the connectivity patterns between neurons is another layer of control mediated by the neuromodulatory environment. Neuromodulators are thought to reshape circuits to transform behavioral outputs while maintaining the functional integrity of the underlying circuits. In addition to the usual suspects, like dopamine and norepinephrine, particularly interesting neuromodulators with regard to social behaviors are oxytocin and vasopressin. They regulate multiple social behaviors, including social preference, maternal care and aggression, sexual behavior, social cognition and inter-male aggression.

A set of experiments in our laboratory also suggests they have roles in odor-driven social learning. Thus, our laboratory utilizes olfactory circuits centered on the piriform cortex to understand how social learning emerges from interactions between neural circuits and the modulatory cues of oxytocin and vasopressin. We are achieving this goal by identifying the cells responsible for OT and AVP release, the cells that detect OT and AVP and their effects on these cells, as well as the behavioral effects of OT and AVP realized through the downstream circuitry of these neurons. These efforts will lead to the full characterization of an odor-driven social circuit, including a minimal structure provided by the anatomical connectome and nuanced control provided by characterization of the overlying neuromodulatory environment.