Default Mode Network

Abstract

The default mode network is a set of brain regions that are most active when a person is left alone with their thoughts and least active when they turn to an external task. First noticed as the tissue that consistently deactivated whenever a demanding task began, it was recognized as a coherent system when its regions were found to fluctuate together at rest — the medial prefrontal cortex, the posterior cingulate and precuneus, the angular gyrus, the lateral temporal cortex and the hippocampal formation. The network is the neural signature of internally directed thought: remembering the past, imagining the future, thinking about oneself and other people. This article traces the default mode network from its accidental discovery in task deactivations, through the resting-state connectivity that defined it, to what its activity means for the wandering, self-referential mind.

Keywords: default mode network, resting-state connectivity, mind-wandering, self-referential thought, task-negative network

The default mode network is a large-scale brain system — a set of distributed cortical regions whose activity is correlated at rest and which MeSH classifies among the brain's neural pathways (Raichle et al., 2001). It was found by accident: functional-imaging studies kept reporting the same regions decreasing their activity whenever a subject engaged an attention-demanding task, and the puzzle of why a resting brain should have a consistent, organized baseline of activity became the question that named the network. Its regions are not a random collection but a functionally connected system, and what unites them is a class of mental activity — thought directed inward, at the self, the remembered past and the imagined future, rather than outward at the sensory world.

What the Default Mode Network Is

The default mode network is a set of brain regions that behave as a unit: their spontaneous activity rises and falls together, and it does so most strongly when the brain is not engaged in a demanding external task. The name comes from the idea of a default mode of brain function — a baseline state the brain falls into when it is not doing anything in particular, which turns out to be neither quiet nor idle but a distinct, organized pattern of activity (Raichle et al., 2001). Rather than switching off during rest, these regions are more active at rest than during many tasks, and it was this counterintuitive rest-greater-than-task profile that first marked them out.

What makes the collection a network, and not merely a list of regions that happen to quiet down during tasks, is that their activity is correlated over time even in the absence of any stimulus. Measured with resting-state functional MRI, the slow spontaneous fluctuations of the medial prefrontal cortex, the posterior cingulate and the other members track one another closely, indicating that they form a functionally connected system (Greicius et al., 2003). The network is therefore defined two ways that agree: by the regions that deactivate together during tasks, and by the regions that correlate together at rest.

Figure 1

The core regions of the default mode network on a schematic midline and lateral view of the brain: the medial prefrontal cortex at the front, the posterior cingulate cortex and precuneus at the rear midline, and the lateral angular gyrus and temporal cortex.

Core Regions and Subsystems

The network has two principal hubs, both on the cortical midline: the medial prefrontal cortex at the front and the posterior cingulate cortex, extending into the precuneus, at the back. These are the most reliably identified and most densely connected members, and they anchor the network. Radiating from them are the inferior parietal lobule — chiefly the angular gyrus — the lateral temporal cortex, and the hippocampal formation in the medial temporal lobe (Buckner et al., 2008). The hippocampus and its neighbours tie the network to memory, and the prefrontal cortex hub ties it to self-referential and evaluative thought.

The network is not monolithic. Andrews-Hanna and colleagues showed that it fractionates into subsystems that couple through the midline hubs: a dorsal medial prefrontal subsystem, engaged when people reflect on their own and others' mental states, and a medial temporal subsystem, engaged when they draw on memory to construct scenes and imagine the future — with the posterior cingulate and anterior medial prefrontal cortex acting as connector hubs that both subsystems share (Andrews-Hanna, 2012). This internal structure matters because it explains how one network can serve tasks as different as thinking about a friend's intentions and remembering last summer: different subsystems carry different components of internal thought.

Table 1. The core regions of the default mode network and their principal associations. The medial hubs bind the network; the lateral and medial-temporal regions link it to memory, social and self-referential cognition.

Discovery: From Task Deactivations to a Network

The default mode network was not sought; it was stumbled upon. Across many positron-emission-tomography studies, researchers noticed that certain regions showed decreases in blood flow whenever a task was performed, no matter what the task was. Shulman and colleagues, pooling nine such studies, identified a consistent set of regions that reliably reduced their activity during visual tasks compared with passive viewing — the first systematic map of what would become the default mode network, seen at that point only as a pattern of task-induced deactivation (Shulman et al., 1997). The regions were the same across tasks, which meant the deactivation reflected something about the resting state being interrupted, not about any particular task.

Raichle and colleagues supplied the interpretation. They argued that the brain has a default mode of function — an organized baseline of activity that the resting brain maintains and that tasks suspend — and showed that these regions have a high metabolic rate at rest that falls when attention turns outward, giving the network its name and its defining rest-greater-than-task signature (Raichle et al., 2001). Gusnard and Raichle then set out the conceptual problem the finding raised: what does it mean for the brain to have a baseline, and how should imaging studies treat a resting state that is anything but inactive (Gusnard & Raichle, 2001)? The decisive step to calling it a network came from Greicius and colleagues, who used resting-state functional connectivity to show that these regions' spontaneous fluctuations are correlated with one another at rest, confirming that they form an integrated system rather than a set of regions that merely happen to deactivate together (Greicius et al., 2003).

Functional Connectivity and Anticorrelation

Once the network could be mapped from resting activity alone, its relationship to the rest of the brain came into view. Fox and colleagues showed that the brain's spontaneous activity is organized into two broad, opposed systems: a task-positive network of regions that increase activity during attention-demanding tasks, and a task-negative network (the default mode network) that decreases during them, and that the two are anticorrelated, so that when activity in one rises, activity in the other tends to fall (Fox et al., 2005). This anticorrelation is intrinsic: it is present in the spontaneous fluctuations of the resting brain, not merely imposed by a task. It captures a fundamental tension in the brain's organization between attention directed outward at the world and thought directed inward.

Functional connectivity is measured as the correlation between the activity time courses of two regions. Placing a seed in one hub — commonly the posterior cingulate cortex — and correlating its time course with every other point in the brain recovers the whole default mode network as the set of regions positively correlated with the seed, and recovers the task-positive network as the set negatively correlated with it. The Worked Example below computes such a correlation from a short time series, and the third demonstration lets the reader move a seed and watch the connectivity pattern change. Raichle's review of the field consolidates this picture, treating the default mode network as an intrinsic system defined by its correlated resting activity rather than by any single task (Raichle, 2015).

Functions: The Internally Directed Mind

What the default mode network does follows from when it is active: it engages when the mind turns away from the external world and toward internally generated thought. Buckner and colleagues, synthesizing the anatomy and function, argued that the network supports a family of internal mental activities built on memory — remembering the personal past, envisioning the future, and constructing mental scenes — and drew the link to episodic memory and prospection through the hippocampal subsystem (Buckner et al., 2008). Much of this depends on the capacity for episodic memory, which the network recombines to simulate events that have not happened.

A second strand of function is self-referential and social. The network is engaged when people think about themselves, reflect on their own traits, and reason about the mental states of others — the province of theory of mind — and Yeshurun and colleagues argued that the network's higher-order regions integrate the idiosyncratic contents of one's own mind with the shared meanings of the social world, positioning it at the meeting point of the personal and the interpersonal (Yeshurun et al., 2021). The most everyday expression of the network's activity is mind-wandering. Mason and colleagues linked the network directly to stimulus-independent thought — the drift of the mind away from the task at hand toward unrelated inner content — showing that default-network activity tracks the tendency of the mind to wander (Mason et al., 2007). Christoff and colleagues later reframed mind-wandering within a broader dynamic framework of spontaneous thought, in which the default network's contribution is shaped by how much the flow of thought is constrained (Christoff et al., 2016), and Smallwood and colleagues integrated the network's varied roles under a topographical account in which its location — sitting at the greatest distance from sensory and motor cortex — lets it support cognition decoupled from the immediate environment (Smallwood et al., 2021).

Worked Example

Functional connectivity between two brain regions is the Pearson correlation of their activity time courses, the same quantity the third demonstration displays. Consider a short resting-state run in which the posterior cingulate cortex (PCC) seed and a within-network node, the medial prefrontal cortex (mPFC), give these six BOLD samples (arbitrary units):

PCC: 2, 4, 3, 5, 6, 4 — mean = (2 + 4 + 3 + 5 + 6 + 4) / 6 = 24 / 6 = 4.0. mPFC: 3, 5, 4, 5, 7, 6 — mean = (3 + 5 + 4 + 5 + 7 + 6) / 6 = 30 / 6 = 5.0.

The deviations from the mean for PCC are −2, 0, −1, 1, 2, 0 and for mPFC are −2, 0, −1, 0, 2, 1. The sum of their products is (−2)(−2) + 0 + (−1)(−1) + (1)(0) + (2)(2) + 0 = 4 + 0 + 1 + 0 + 4 + 0 = 9. The sum of squared PCC deviations is 4 + 0 + 1 + 1 + 4 + 0 = 10; for mPFC, 4 + 0 + 1 + 0 + 4 + 1 = 10. The correlation is therefore r = 9 / √(10 × 10) = 9 / 10 = 0.90 — a strong positive coupling, the mark of two nodes in the same network.

Now take a task-positive node, the intraparietal sulcus (IPS), with samples 7, 5, 6, 4, 3, 5 — mean = 30 / 6 = 5.0, deviations 2, 0, 1, −1, −2, 0. Its product-sum with the PCC seed is (−2)(2) + 0 + (−1)(1) + (1)(−1) + (2)(−2) + 0 = −4 + 0 − 1 − 1 − 4 + 0 = −10, and its squared-deviation sum is 4 + 0 + 1 + 1 + 4 + 0 = 10, so r = −10 / √(10 × 10) = −10 / 10 = −1.00. The seed correlates positively with its network partner and negatively with the task-positive node — the anticorrelation that separates the two systems, computed from the same formula the demonstration uses.

Discussion

The default mode network reframed a nuisance into a discovery. The regions that kept deactivating were, for years, treated as an artifact to be subtracted away; recognizing that they form an organized, intrinsically connected system turned the resting brain into an object of study in its own right and showed that the brain devotes substantial resources to activity untied to any external demand. That the network's signature is deactivation during tasks — and anticorrelation with the attention systems — captures a basic trade-off: the brain seems unable to attend fully outward and think fully inward at once, and the balance between the two is a dimension along which cognition, and its disorders, vary.

The network's value as a construct is that it links an anatomy to a psychology. Its regions overlap those long implicated in autobiographical memory, prospection and social cognition, and its fractionation into a self-and-other subsystem and a memory-based subsystem maps onto real distinctions in the kinds of internal thought people generate. This is also the source of the main cautions. The network is defined by correlation, not by a single function, and the same regions participate in more than one network depending on state and task; treating default mode network activity as synonymous with any one mental act — mind-wandering, say — overreaches the evidence.

Much of the network's clinical interest follows from the same anatomy. Its core hubs overlap the regions earliest and most affected in Alzheimer's disease, and Greicius and colleagues showed that resting default-mode connectivity is reduced in Alzheimer's patients relative to healthy older adults, well enough to distinguish the groups from functional MRI alone (Greicius et al., 2004). Altered default-network activity has since been reported across depression, schizophrenia and other conditions, which is why the network is now a standard target of clinical imaging: because it can be measured at rest, without a task a patient might perform differently, it offers a comparable index of intrinsic brain organization across populations.

Current Directions

Two decades on, the network is being reconceived from a task-negative default into an active contributor to cognition. Menon's synthesis of twenty years of research places the default mode network within a triple-network model — alongside the salience and central-executive networks — and argues that its dynamic interactions with those systems, rather than its activity in isolation, underlie both healthy cognition and psychopathology (Menon, 2023). Smallwood and colleagues' topographical account reframes the network's defining feature as its physical and connectional distance from sensory and motor systems, which is what allows it to support thought decoupled from the here-and-now (Smallwood et al., 2021). And work on shared cognition, exemplified by Yeshurun and colleagues, is extending the network beyond the individual mind to how brains align during communication, so that the same regions that host the idiosyncratic self also carry the meanings people hold in common (Yeshurun et al., 2021). The common thread is a move away from asking when the network switches off toward asking what computation it performs — and how its coupling with the rest of the brain shapes the stream of thought.

Common Misconceptions

The default mode network is the brain at rest doing nothing.

The opposite: these regions are highly active at rest, maintaining an organized baseline of internally directed activity that tasks suspend (#ref-raichle-2001).

The default mode network is just the mind-wandering network.

Mind-wandering engages it, but the network also supports autobiographical memory, future thinking, self-reference and social cognition; equating it with any single function overreaches the evidence (#ref-andrews-hanna-2012).

Its regions turn off completely during any task.

Deactivation is relative, not absolute, and the network is engaged rather than suppressed by internally focused tasks such as remembering or imagining (#ref-buckner-2008).

Glossary

Anticorrelation.

A negative correlation between two regions' activity, such that when one rises the other falls; the relationship between the default mode and task-positive networks.

Autobiographical memory.

Memory for the events and facts of one's own life, a core internally directed function the network supports through its hippocampal subsystem.

Default mode.

The organized baseline pattern of brain activity present at rest, which attention-demanding tasks interrupt.

Functional connectivity.

The statistical dependence, usually measured as a correlation, between the activity time courses of different brain regions.

Medial prefrontal cortex.

The anterior midline hub of the network, engaged in self-referential and evaluative thought.

Mind-wandering.

The drift of attention away from an external task toward stimulus-independent, internally generated thought.

Posterior cingulate cortex.

The posterior midline hub of the network, extending into the precuneus; its most metabolically active core node and a connector between subsystems.

Precuneus.

The medial parietal region adjoining the posterior cingulate, part of the network's posterior hub.

Prospection.

The mental simulation of future events, built by recombining stored episodic memory, and a core function the network supports.

Resting-state fMRI.

Functional MRI acquired while the subject lies at rest without a task, used to map networks from spontaneous activity.

Seed-based connectivity.

A method that correlates the time course of a chosen seed region with every other point in the brain to map a network.

Self-referential processing.

Thought directed at oneself, one's traits, and one's mental states, engaging the medial prefrontal hub of the network.

Task-positive network.

The set of regions that increase activity during attention-demanding external tasks, anticorrelated with the default mode network.

Triple-network model.

A framework organizing cognition around the interaction of the default mode, salience and central-executive networks.

Key Researchers

Jessica R. Andrews-Hanna

Cognitive neuroscientist at the University of Arizona whose work fractionated the default mode network into interacting subsystems and detailed its role in internal mentation. ORCID - Google Scholar - Arizona faculty

Randy L. Buckner

(born 1970). Harvard neuroscientist who mapped the network's anatomy and its relevance to memory, prospection and disease. ORCID - Wikipedia - Wikidata

Michael D. Greicius

Stanford neurologist who produced the first resting-state functional-connectivity mapping of the default mode network, establishing it as a coherent system. Google Scholar - Stanford faculty

Vinod Menon

Stanford neuroscientist whose triple-network model situates the default mode network among interacting large-scale systems and who authored a twenty-year synthesis of the field. Google Scholar - Stanford faculty

Marcus E. Raichle

(born 1937). Washington University neurologist who coined the default mode of brain function and pioneered its study with PET and fMRI. ORCID - Wikipedia - Wikidata

Daniel L. Schacter

(born 1952). Harvard psychologist whose work established the default network's role in episodic memory, prospection and mental simulation. ORCID - Wikipedia - Wikidata

Jonathan Smallwood

(1975-2025). Psychologist whose work tied the default mode network to mind-wandering and advanced the topographical account of its role in cognition. ORCID - Wikipedia - Wikidata

Frequently Asked Questions

What is the default mode network?

It is a set of brain regions, chiefly the medial prefrontal cortex and the posterior cingulate cortex, together with the angular gyrus, lateral temporal cortex and hippocampal formation, whose activity is correlated at rest and which is most active when a person is engaged in internally directed thought rather than an external task.

Why is it called the default mode?

Because it reflects a baseline or default state the brain settles into when it is not doing a demanding task. Rather than switching off at rest, these regions stay active, so rest is the brain's default mode of function.

When is the default mode network active?

During rest and during internally focused mental activity: remembering the past, imagining the future, thinking about oneself, reasoning about other people, and letting the mind wander. It is suppressed when attention turns to a demanding external task.

How was the default mode network discovered?

It was found accidentally, as a set of regions that consistently reduced their activity whenever subjects performed tasks in imaging studies. It was later confirmed as a genuine network when its regions were shown to fluctuate together at rest.

What does anticorrelated mean for the network?

The default mode network and the task-positive attention networks tend to move in opposite directions: when the attention networks become more active, the default mode network becomes less active, and vice versa. This opposition is present even in the resting brain.

What functions does the default mode network support?

Autobiographical memory, envisioning future events, self-referential thought, social cognition and theory of mind, and mind-wandering. These are unified as internally directed thought, decoupled from the immediate environment.

Is the default mode network linked to any disorders?

Yes. Altered default-network activity and connectivity have been reported in Alzheimer's disease, depression, schizophrenia and other conditions, which is one reason the network is intensively studied clinically.

Does the default mode network relate to consciousness?

It is closely tied to self-referential awareness and the ongoing inner narrative, and its activity changes with states such as sleep, anaesthesia and meditation, but it is not simply the seat of consciousness; it is one system among several whose interactions matter.

References