The ancient dialogue between brain and body.

The brain rarely works alone to control our behavior or physiology. From the rhythm of our heartbeat to the flutter of 'butterflies' in our stomach, it is in constant dialogue with our body. This connection affects how we feel, influences what we pay attention to in our environment and ultimately affects the choices we make. Over the past several decades, research in model organisms has uncovered brain-body circuits that detect and interpret interoceptive (internal) and exteroceptive (external) signals. These studies have revealed how nervous systems integrate sensory inputs with essential homeostatic processes, such as hunger, thirst, reproduction and immune responses1,2,3,4,5,6,7. We now know that our brain continuously monitors the physiological and metabolic state of our body through both direct neural pathways and indirect neuroendocrine routes. In turn, the body influences our cognitive and metabolic states through a dynamic interplay of hormonal, neural and metabolic signals. This bidirectional communication between the brain and body regulates our sensory perception, modulates our motivation and cognition, and ultimately guides our behavior (Figure 1).