Cognitive, Emotional, and Neural Responses to Acute Inflammation

The inflammatory response of the immune system is responsive to stress and it impacts brain function. Animal studies have shown that inflammation appears to alter threat- and reward-related brain activity. Accumulating evidence points to inflammatory proteins, specifically cytokines, as key players in this relationship. Although cytokines are typically too large to pass through the blood brain barrier (BBB), they can influence brain function and structure by transmitting signals from peripheral systems to the brain. The administration of endotoxin within the polysaccharide form of Salmonella typhi vaccination provides an ideal model for studying the causal effects of short-term inflammation on thinking patterns (i.e., cognition) and emotions in the brain. Endotoxin is a component of the cell walls of Gram-negative bacteria, which promotes the production of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) via toll-like receptor-4 (TLR-4) activation and nuclear factor- κB (NF-κB) signaling. To examine the effects of acute inflammation on brain functioning, 24 healthy participants will be recruited. The investigators will will randomize participants to placebo or inflammatory challenge using polysaccharide typhoid vaccine (i.e., endotoxin) and will use validated behavioral tasks and questionnaires to assess threat and reward sensitivity. They will assess chronic resting levels of inflammation as well as the inflammatory response to Salmonella typhi vaccination.