[From the Wikipedia entry on the default mode network]
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, it 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 disorder.
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 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.
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[From “A Wandering Mind is an Unhappy Mind,” a 2010 Science research article by Killingsworth and Gilbert:]
We developed a smartphone technology to sample people’s ongoing thoughts, feelings, and actions and found (i) that people are thinking about what is not happening almost as often as they are thinking about what is and (ii) found that doing so typically makes them unhappy…
Although negative moods are known to cause mind wandering, time-lag analyses strongly suggested that mind wandering in our sample was generally the cause, and not merely the consequence, of unhappiness.
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[From How to Change Your Mind: What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence, a 2018 book by Michael Pollan:]
Perhaps the most striking discovery of Carhart-Harris’s first experiment [to study the effect of psilocybin on the brain] was that the steepest drops in default mode network activity occurred with the volunteers’ subjective experience of “ego dissolution.” (“I existed only as an idea or concept,” one volunteer reported. Recalled another, “I didn’t know where I ended and my surroundings began.” The more precipitous the drop-off in blood flow and oxygen consumption in the default network, the more likely a volunteer was to report the loss of a sense of self…
The transcendence of self reported by expert mediators showed up on fMRIs as a quieting of the default mode network. It appears that when activity in the default mode network falls off precipitously, the ego temporarily vanishes, and the usual boundaries we experience between self and world, subject and object, all melt away…
In its normal state, the brain’s various networks talk mostly to themselves, with a relatively few heavily trafficked pathways among them. But when the brain operates under the influence of psilocybin, thousands of new connections form, linking far-flung brain regions that during normal waking consciousness don’t exchange much information. In effect, traffic is rerouted from a relatively small number of interstate highways onto myriad smaller roads linking a great many more destinations. The brain appears to become less specialized and more globally interconnected, with considerably more intercourse, or “cross talk,” among its various neighborhoods.
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[From “The Yard Boy,” a 1977 short story by Joy Williams:]
The yard boy was a spiritual materialist. He lived in the Now. He was free from the karmic chain. Being enlightened wasn’t easy. It was very hard work. It was manual labor, actually.
The enlightened being is free. He feels the sorrow and sadness of those around him but does not necessarily feel his own. The yard boy felt that he had been enlightened for about two months, at the most.
The yard boy had two possessions. One was a pickup truck. The other was a stuffed and mounted plover he had found in the take-it-or-leave-it shed at the dump. The bird was now in the room he rented…
The yard boy is disgusted with himself. The spider’s web is woven into wanting, he thinks. He has desire for his girlfriend. His mind is shuttling between thoughts of the future and thoughts of the past. He is out of touch with the sharp simplicity and wonderfulness of the moment. He looks around him. He opens his eyes wide. The yard boy’s jeans are filthy. A green insect crawls in and out of the scapular feathers of the plover.
The yard boy goes downstairs. He gives the plover to his landlady. She seems delighted. She puts it on a shelf in the pantry with her milk-glass collection. The landlady has white hair, a wen and old legs that end in sneakers. She wants the yard boy to look at a plant she has just bought. It is in a big green plastic pot in the sunshine of her kitchen. Nothing is more obvious than the hidden, the yard boy thinks.
“This plant is insane,” the yard boy says.