Research in the Fonken lab broadly focuses on how interactions between the immune, nervous, and endocrine systems can regulate complex behavioral processes such as cognitive and mood related behaviors. Resident immune cells, called microglia, were first identified in the brain by Del Rio-Horetga over 100 years ago. These cells were initially thought to have a passive role in the healthy brain and only become active during CNS injury. However, we now know that glial cells have a diverse array of functional roles in maintaining brain homeostasis and in responding to CNS pathology. For example, microglia are involved in synaptic development and pruning, neuronal migration, and progenitor cell differentiation. Microglia form and function are tightly regulated in the CNS to help regain homeostasis following activation. However, the neuroimmune system is sensitive to a number of environmental challenges and dysregulation of neuroimmune function is implicated in neuropsychiatric disorders including depression, schizophrenia, and cognitive dysfunction. Thus, our current research focuses on understanding how endogenous (e.g. circadian rhythms and aging) and exogenous (e.g. environmental pollutants, infection, and injury) factors that influence neuroimmune function drive cognitive and affective behavioral changes.