How Magic Mushrooms and Other Psychedelics Affect the Human Brain
What is the Default Mode Network?
The default mode network refers to an interconnected group of brain regions that are associated with introspective functions, internally directed thought, such as self-reflection, and self-criticism. Increased activity of the DMN is correlated with the experience of mind-wandering and our capacity to imagine mental states in others (i.e. theory of mind) as well as our ability to mentally “time travel”, projecting ourselves into the past or future.
The DMN is thought to be crucial to regular, everyday consciousness and is most active when a person is at rest and their attention isn’t focused on something happening in the outside world. For instance, if you place a person in an MRI scanner without giving them anything to do, their mind will begin to wander and you will notice the DMN’s component areas lighting up.
The DMN doesn’t become completely active until later in a child’s development, appearing around the age of five as the child develops a firm sense of narrative self or “ego.” The functional connections that make up the DMN expand from birth to maturity.
As we become older, we learn to react to life’s stimuli in predictable ways and form habitual communication channels across different brain regions, especially the DMN. As we grow, our brain gets more “constrained” because communication is restricted to certain pathways throughout time. Our ‘default mode’ of operation in the world, which shapes how we see the world, is actually these limited pathways of communication between brain areas.
According to evolutionary theory, the DMN aids in our survival by assisting us in developing a consistent sense of self and separating ourselves from the environment. According to psychiatrist Matthew Brown, the DMN is the area of the brain that “reminds you that you are you.”
