Brain networks are large scale circuits of brain regions that interact to support thought, perception and behavior. Modern neuroscience shows that the brain is not organized into isolated modules, but into overlapping, dynamic networks that continuously reconfigure.

A central example is the default mode network, active when we daydream, remember the past, imagine the future or reflect on ourselves. It involves midline and parietal regions and typically decreases activity during demanding external tasks. In contrast, the dorsal attention network supports focused, goal directed attention toward the outside world, while the ventral attention or salience network detects behaviorally relevant events and helps shift attention.

Executive control networks, often centered in lateral prefrontal and parietal cortices, coordinate complex cognition such as problem solving and decision making. Visual and motor networks handle sensory input and movement. These networks are identified using techniques such as resting state and task based functional MRI, which measure correlations in activity across distant brain regions.

Brain networks are not static. Their connectivity patterns change across development, aging and sleep, and are altered in many disorders, including depression, schizophrenia and Alzheimer’s disease. Rather than being caused by a single damaged spot, symptoms often reflect disrupted communication within or between networks.

The brain can reorganize its networks after injury or training, a property known as plasticity. Understanding these network level mechanisms is reshaping basic and clinical neuroscience, guiding new diagnostic tools and inspiring treatments that aim to restore healthy patterns of connectivity instead of focusing only on individual brain regions.