Mechanisms for survival: vagal control of goal-directed behavior.

Vagal afferents have long been thought to convey mostly negative homeostatic feedback to the brain. Recent studies stimulating vagal afferents in animals and humans have fundamentally extended this view by pointing towards a crucial role in the adaptive control of goal-directed behavior. Based on recent insights on the vagal afferent pathway, we review how basic modes of survival are regulated through brainstem circuits. By integrating ascending signals from the body, these circuits are well equipped to switch between complementary survival modes. Tuning of goal-directed behavior, as indicated by increased reward-seeking or effort invigoration following vagal afferent stimulation, may arise from a greater weight on interoceptive signals of need that are gated via the brainstem. This highlights how vagal projections to the brain could provide an intricate link between energy homeostasis and adaptive behavior. Survival is a fundamental physiological drive, and neural circuits have evolved to prioritize actions that meet the energy demands of the body. This fine-tuning of goal-directed actions based on metabolic states ('allostasis') is deeply rooted in our brain, and hindbrain nuclei orchestrate the vital communication between the brain and body through the vagus nerve. Despite mounting evidence for vagal control of allostatic behavior in animals, its broader function in humans is still contested. Based on stimulation studies, we propose that the vagal afferent pathway supports transitions between survival modes by gating the integration of ascending bodily signals, thereby regulating reward-seeking. By reconceptualizing vagal signals as catalysts for goal-directed behavior, our perspective opens new avenues for theory-driven translational work in mental disorders. [ABSTRACT FROM AUTHOR]