Neuroscience: Default Mode Network

From yee Wiki: In neuroscience, the default mode network (DMN), also default network, or default state network, is a large scale brain network of interacting brain regions known to have activity highly correlated with each other and distinct from other networks in the brain.

The default mode network is most commonly shown to be active when a person is not focused on the outside world and the brain is at wakeful rest, such as during daydreaming and mind-wandering. But it is also active when the individual is thinking about others, thinking about themselves, remembering the past, and planning for the future. The network activates "by default" when a person is not involved in a task. Though the DMN was originally noticed to be deactivated in certain goal-oriented tasks and is sometimes referred to as the task-negative network,mit can be active in other goal-oriented tasks such as social working memory or autobiographical tasks.The DMN has been shown to be negatively correlated with other networks in the brain such as attention networks.

Evidence has pointed to disruptions in the DMN of people with Alzheimer's and autism spectrum.

The default mode network is known to be involved in many seemingly different functions:

It is the neurological basis for the self:

Autobiographical information: Memories of collection of events and facts about one's self

Self-reference: Referring to traits and descriptions of one's self

Emotion of one's self: Reflecting about one's own emotional state

Thinking about others:

Theory of Mind: Thinking about the thoughts of others and what they might or might not know

Emotions of other: Understanding the emotions of other people and empathizing with their feelings

Moral reasoning: Determining just and unjust result of an action

Social evaluations: Good-bad attitude judgments about social concepts

Social evaluations: Good-bad attitude judgments about social concepts

Social categories: Reflecting on important social characteristics and status of a group

Remembering the past and thinking about the future:

Remembering the past: Recalling events that happened in the past

Imagining the future: Envisioning events that might happen in the future

Episodic memory: Detailed memory related to specific events in time

Story comprehension: Understanding and remembering a narrative

The default mode network is active during passive rest and mind-wandering. Mind-wandering usually involves thinking about others, thinking about one's self, remembering the past, and envisioning the future.

Electrocorticography studies (which involve placing electrodes on the surface of a subject's scalp) have shown the default mode network becomes activated within a fraction of a second after participants finish a task.

Studies have shown that when people watch a movie, listen to a story, or read a story, their DMNs are highly correlated with each other. DMNs are not correlated if the stories are scrambled or are in a language the person does not understand, suggesting that the network is highly involved in the comprehension and the subsequent memory formation of that story. The DMN is shown to even be correlated if the same story is presented to different people in different languages, further suggesting the DMN is truly involved in the comprehension aspect of the story and not the auditory or language aspect.

The default mode network has shown to deactivate during external goal-oriented tasks such as visual attention or cognitive working memory tasks, thus leading some researchers to label the network as the task-negative network. However, when the tasks are external goal-oriented tasks that are known to be a role of the DMN, such as social working memory or an autobiographical task, the DMN is positively activated with the task and correlates with other networks such as the network involved in executive function.

A hitherto unsuspected possibility is that the default network is activated by the immobilization inherent in the testing procedure (the patient is strapped supine on a stretcher and inserted by a narrow tunnel into a massive metallic structure). This procedure creates a sense of entrapment and, not surprisingly, the most commonly reported side-effect is claustrophobia. This alternative view is suggested by a recent article that links theory of mind to immobilization.