What is the default mode brain network?
The default mode network (DMN) is the “internal mind.”
When you’re idly daydreaming or thinking about a new idea, the DMN is hard at work.
Though the default mode network is active during rest and sleep,1 it is most active when the mind engages in internal thought or contemplation. When you remember an event from your childhood, imagine a future vacation, or contemplate a family member’s thoughts or feelings, your internal mind drives these perceptions.
When the brain is in a resting state2 and isn’t actively engaged in focused, goal-oriented tasks, “default” or subconscious brain activity increases for internal thought processing,3 which likely evolved from evolutionary self-preservation.
Since we are nearly always thinking to ourselves or subconsciously processing the world around ourselves, the DMN is considered the most active and consistent4 of the seven main brain networks.
Disturbance in the DMN
Abnormal function in the default mode network is often associated with neuropsychiatric disorders.8 If the network becomes overactive, it can lead to intensified, self-referential thought as a symptom of schizophrenia or negative and disruptive thoughts associated with depression and post-traumatic stress disorder (PTSD).
Altered functional or structural organization of the DMN9 has also been implicated in autism spectrum disorder (ASD).10 Individuals with autism are often characterized by difficulty processing the emotions and feelings of others, in relationship to one’s self. Underlying DMN dysfunction may contribute to an individual’s difficulty processing social situations and information.
It has also been posited that higher functional connectivity between the DMN and other brain networks11 may be an underlying symptom of attention-deficit/hyperactivity disorder (ADHD). This abnormal connectivity may be linked to mind wandering and wavering attention.11 With regard to neurological disease, the earliest stages of Alzheimer’s disease often exhibit degradation of the posterior cingulate cortex.2 This key node in the default mode network is responsible for memory formation and retrieval,2 making it a common target of the disease.12 In some cases, individuals even experience disruption in the DMN prior to showing signs of Alzheimer’s disease.10 With the DMN being a relatively recent discovery for neuroscience, modern research is still uncovering its full implication on mental illness and physical disorders. Fortunately, there is a wide range of possibilities for new treatments and therapies.
As our internal mind, areas of the brain associated with the DMN likely have unique functions when they are active in a subconscious state.3 The PCC and the adjacent precuneus are thought to be tonically active regions3 that continually gain information about the external world, without conscious thought processing, but there is still much to explore about this network as the brain’s baseline state.
With the DMN’s prominence as a more recent discovery, as neuroscience continues to explore the subtle intricacies of the human brain, the DMN will offer a unique lens through which to view our own subconscious.
For the larger role the DMN plays in cognition, it will also be exciting to uncover how the DMN coordinates with other brain networks for internal thought processing. Other areas heavily interconnected with the limbic system3 are implicated in processing sensory information, both about the body and externally. With further research, there is potential to identify DMN-targeted therapies that will target the functional connectivity thought to cause mental health disorders and degenerative diseases.
It is our hope that analyzing the “internal mind” will aid in our journey to understand the relationship between our conscious and subconscious minds, as well as the nearly-imperceptible triggers that make up our human perceptions.
Uncover more cutting-edge discoveries about the key brain networks that function alongside the default mode network.