Brain Networks — The Large-Scale Networks of the Human Brain

What is a large-scale brain network?

A large-scale brain network, also called an intrinsic network, is a set of brain regions whose activity fluctuates together over time, even at rest. This coordinated activity is measured as functional connectivity, the statistical dependence between regions. Common parcellations of the human brain, such as the Yeo 2011 seven-network atlas, identify seven major networks, though finer parcellations can reveal up to 17 networks. These networks correspond to different functional domains.

Explore each network

• Default Mode Network — The Default Mode Network is a set of brain regions active at rest and during self-referential thought. Core hubs include the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus.
• Salience Network — The Salience Network is a set of brain regions—including the anterior insula, dorsal anterior cingulate cortex, and amygdala—that detects salient internal and external events and switches between the default mode and executive networks.
• Central Executive Network — The Central Executive Network is a frontoparietal brain system for goal-directed cognition. Core regions include the dorsolateral prefrontal cortex, posterior parietal cortex, and caudate, supporting working memory and cognitive control.
• Dorsal Attention Network — The Dorsal Attention Network is a set of brain areas including the frontal eye fields, dorsal posterior parietal cortex, and premotor cortex. It controls voluntary, goal-directed attention to spatial locations and features.
• Ventral Attention Network — The Ventral Attention Network is a brain system for detecting unexpected, behaviorally relevant stimuli and reorienting attention. Core regions include ventral posterior parietal cortex, insula, anterior cingulate cortex, and temporal cortex. It acts as a circuit breaker for focused attention.
• Language Network — The Language Network is a left-lateralized brain system for language. Core regions include Broca's area and Wernicke's area, with the arcuate fasciculus as a key connection, supporting speech, comprehension, and syntax.
• Sensorimotor Network — The Sensorimotor Network is a set of brain regions, including the motor cortex, somatosensory cortex, premotor cortex, and subcortical loops, that coordinates voluntary movement and integrates sensory feedback.
• Visual Network — The Visual Network is the brain system that processes visual information. Core regions include the occipital cortex, fusiform gyrus, and posterior parietal cortex. It handles object recognition and spatial vision.
• Limbic Network — The Limbic Network is a set of brain regions that includes the hippocampus, amygdala, and orbitofrontal cortex. It is central to emotion, memory, and motivated behavior.

The triple network model

Menon's triple network model proposes that three core networks—the salience network, default mode network, and central executive network—underlie many cognitive functions. The salience network detects salient stimuli and toggles between the default mode network, active during internally focused thought, and the central executive network, active during externally focused tasks. This dynamic switching is thought to be crucial for adaptive behavior, and disruptions in this balance are linked to several psychiatric conditions.

• Salience Network suppresses Default Mode Network — The anterior insula of the salience network deactivates the DMN when task-relevant external stimuli are detected, shifting the brain from internal mentation to externally focused processing.
• Salience Network activates Central Executive Network — The salience network engages the central executive network to allocate cognitive resources toward the detected salient stimulus, enabling goal-directed analysis and response planning.
• Default Mode Network anticorrelated Central Executive Network — The DMN and CEN show robust anticorrelation: when one increases activity, the other decreases. This reciprocal relationship ensures efficient toggling between internally and externally directed cognition.

How are brain networks measured?

Brain networks are typically measured using resting-state functional MRI, which records spontaneous brain activity while a person lies still. Functional connectivity between regions is estimated using seed-based correlation, where a region is chosen and its activity correlated with others, or independent component analysis (ICA), which separates the whole brain into distinct networks. A limitation is that resting-state measures are indirect and correlation does not imply causation.

Brain networks and mental health

Altered brain network connectivity has been associated with several mental health conditions. In depression, the default mode network often shows increased connectivity, while in ADHD, the salience and attention networks may be disrupted. Schizophrenia research finds abnormal connectivity in the central executive network, and Alzheimer's disease is linked to reduced default mode network activity. These findings are correlational and do not establish causality.

• Schizophrenia — Aberrant salience network switching leads to inappropriate DMN intrusion during task states, contributing to hallucinations and disorganized thought. CEN hypoconnectivity underlies cognitive deficits.
• Major Depressive Disorder — DMN hyperconnectivity drives persistent rumination. Reduced SN-CEN coupling impairs the ability to disengage from negative self-referential thought and engage with the external world.
• ADHD — Failure of the salience network to suppress the DMN during attention-demanding tasks causes mind-wandering and attentional lapses. CEN underactivation reduces sustained cognitive control.
• Autism Spectrum Disorder — Atypical salience network function alters how social stimuli are prioritized. Reduced DMN connectivity during social cognition tasks impairs theory of mind and self-other distinction.
• Frontotemporal Dementia — Progressive salience network degeneration (beginning with anterior insula atrophy) causes loss of empathy, social awareness, and emotional regulation. The DMN may become aberrantly dominant.