The Neural Correlates of Sickness

The brain protects animals during infection by detecting immune activity, coordinating behavioral and physiological defenses, anticipating potential infectious threats, and limiting excessive inflammation. Collectively termed sickness, these centrally organized responses include changes in body temperature, activity, energy balance, appetite, fluid intake, social behavior, neuroendocrine function, and autonomic output. Rather than constituting a single uniform state, sickness is generated by distributed and partially dissociable neural pathways that translate immune signals into responses appropriate to the nature and stage of an infection. Work presented at a symposium at the 2026 Society for Neuroscience meeting highlights how humoral and cranial sensory pathways detect ongoing immune responses; how social cues, expectations, and prior experience prepare the organism for anticipated threats; and how endocrine and autonomic circuits constrain inflammation and promote recovery. Together, these findings establish the brain as an active regulator of immunity across the full course of illness.