The human brain does not operate as a collection of isolated parts. Instead, it functions through intricate connections and coordinated activity across various regions. These interconnected systems are known as brain networks, and they play a role in nearly every aspect of our cognitive abilities, emotions, and behaviors. Understanding these networks offers insight into how the brain processes information and orchestrates diverse functions.
What are Brain Networks
Brain networks consist of distinct brain regions, or “nodes,” linked by “connections” that transmit signals. The brain’s processing is distributed, meaning complex tasks emerge from the coordinated activity of multiple regions rather than being confined to a single area.
This allows for efficiency and flexibility in brain function. Even a simple action involves the seamless interplay of many brain areas, each contributing to the overall outcome. The strength and efficiency of these connections determine how effectively different brain regions can collaborate, underpinning all cognitive processes.
Major Functional Networks
The brain organizes itself into several major functional networks, each specialized for different types of mental activity. Three prominent examples include the Default Mode Network (DMN), the Central Executive Network (CEN), and the Salience Network (SN). These networks interact dynamically, switching roles depending on the task at hand.
The Default Mode Network (DMN) becomes active when an individual is at rest and not focused on external tasks, often engaging in introspection, mind-wandering, or planning for the future. It plays a role in self-referential thinking and constructing a sense of self. Key regions of the DMN are involved.
Conversely, the Central Executive Network (CEN), also known as the frontoparietal network, is active during tasks requiring focused attention, problem-solving, decision-making, and working memory. This network allows for controlled processing of information and the integration of inputs from other brain networks. It helps manage thoughts and actions, supporting high-level cognitive functions.
The Salience Network (SN) acts as a “moderator” between the DMN and CEN, detecting and filtering relevant stimuli from the environment. It signals when to shift focus based on the importance of sensory inputs, determining which network should be active at any given moment. Its main components are involved in emotion regulation and conflict monitoring. The SN ensures that the brain prioritizes important information and directs attention effectively.
How Brain Networks Adapt and Change
Brain networks are not static; they adapt and change throughout life, a phenomenon known as neuroplasticity. This adaptability allows networks to strengthen or weaken existing connections, form new ones, or even reorganize in response to new experiences, learning, development, and injury. Neuroplasticity underlies learning and memory.
As individuals learn new skills, the frequently used neural pathways within these networks become stronger and more efficient. For instance, learning to juggle can lead to changes in brain connections. This continuous rewiring allows the brain to optimize its functions. Neuroplasticity also plays a role in recovery from brain damage, as the brain can reorganize its activity to compensate for injured areas.
Networks and Brain Disorders
Disruptions or alterations in the connectivity and activity of brain networks are implicated in various neurological and psychiatric conditions. Understanding these network changes can offer insights into the underlying mechanisms of these disorders.
In Alzheimer’s disease, for example, changes in large-scale functional brain network organization are observed, with reduced efficiency in long-distance connections. Similarly, depression is associated with widespread network dysconnectivity, including alterations in the Default Mode Network and the Salience Network. Studies have shown that an enlarged Salience Network may be linked to depression risk.
Schizophrenia is often conceptualized as a disorder of brain network dysfunction, involving abnormal interactions between distributed networks. Individuals with schizophrenia tend to have less integrated functional connectivity. In autism spectrum disorder, differences in brain network structure and connectivity patterns are observed, with some studies suggesting reduced connectivity between distant regions and altered interactions between networks like the Default Mode Network and Salience Network. Research into these network dysfunctions continues to advance, potentially leading to new diagnostic tools and approaches.