Of the seven main brain networks, the dominant control networks are the most active. The CEN focuses on external goals and is responsible for active synthesis of memory with external activities2. The DMN, on the other hand, is the alternate network to the CEN. It is the most consistent network in the brain, and controls the brain’s passive, internal state for internal thinking and evaluating ideas2.
These two networks represent the mind’s internal and external states, and they work in tandem with other networks, such as the visual, sensorimotor, limbic, and attention networks. Together, they process external sights and sounds, internal emotions, or other stimuli that can lead either to internal thought or external active tasks.
Though the CEN and DMN are always active because of their dominant roles, they are not supposed to operate at the same time. The brain continually switches between the CEN and DMN as needed for external or internal processing.
The salience network is solely responsible for regulating the switch between these two control networks, and it determines which network is in control at any given moment. Additionally, the SN is also responsible for regulating emotion and pain from the other main networks. The SN regulates these changes so quickly and effectively that the process is typically imperceptible to the human mind.
However, the SN can have negative implications for the brain when it becomes overactive and abnormally handles network switching or emotional regulation. These irregularities can lead to mental illness, such as schizophrenia, depression, anxiety, and post-traumatic stress disorder. Analyzing the brain's neural networks opens up a range of possibilities to diagnose and treat these neuropsychiatric disorders.
