ORIGINAL

Abstract

Animals use social behaviors to communicate their needs within and across species. Interest in conspecific aggression as a popular and effective way of mediating this compound dynamic has revealed the ventromedial hypothalamus ventrolateral area (VMHvl) as a critical node for this survival behavior. This region in the brain acts as a hub for complex inputs, responding to motivational, sensory, and action-oriented components of peer interactions. However, despite our understanding of areas involved in aggression, there has yet to be research that explains the interactions between upstream and downstream players, in other words, how a complex multidimensional input is processed and transformed into a coordinated attack behavior. Our findings suggest that external stimuli is hierarchically organized in a hypothalamic-midbrain circuit. We use genetic tools to capture the glutamatergic line involved in attack behavior that extends from the neurons in the VMHvl to those in the lateral and dorsomedial columns of the periaqueductal gray area (PAG). However, the abundance of direct projections in this circuit seem to vary by area. We use chemogenetic tools on the resident-intruder paradigm to reveal that inactivation of the lPAG produces action-selective deficits and hypothesize that inactivation of dmPAG might also yield similar but more muted results. The results of this thesis adds to the growing literature of systems and circuit level understanding of aggression and has important implications on how we navigate aggressive behavior in the human world.