Elucidating Noradrenergic Neuroadaptations of the Central Amygdala in Alcohol Use Disorder.

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 communication 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 responses. 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 (). In this special issue of we focus on the
anatomical and functional organization of brain–body circuits across species and
behaviors. The collection of articles featured here explores how brain–body
circuits regulate thermal and metabolic homeostasis, coordinate animal movements, give
rise to the experience of self-awareness, and adapt to internal challenges such as
sickness or nutrient deprivation. Together, they reveal the fundamental neural
principles underlying how the brain interacts with the body to guide sensory perception,
decision-making, and internal physiology. Recently, comparative analyses of brain–body circuits across diverse
species have begun to shed light on the evolutionary origins of this bidirectional
communication. These studies have revealed that the core functional principles of
brain–body circuits are broadly conserved across species. For example, the vagus
nerve that connects the brain to internal organs in vertebrates has both sensory and
motor functions. It regulates the heart rate and digestion through its motor branch and
provides feedback to the brain about the metabolic state of the body through its sensory
branch . Insects regulate their feeding and reproductive behaviors by
analogous sensory-motor pathways that transmit visceral and metabolic signals to the
central brain. Similar pathways have
also been observed in annelids (e.g., earthworms), where central ganglia and neurons
surrounding the gut interact to control secretory activity and peristalsis, which in
turn controls digestion. Taken
together, these findings suggest that brain–body communication has ancient
evolutionary origins and conserved functions across the animal kingdom. Yet their
developmental and anatomical organization varies widely across animals, reflecting
lineage-specific innovations.