Default Mode Network: How Meditation Affects Brain Function

The default mode network (DMN) refers to the brain regions that are more active during a resting state—the default mode of brain function. Conversely, the DMN experiences deactivation when specific attention-focused tasks are performed. In 1929, German psychiatrist Hans Berger proposed that the brain is continuously working, even as we rest. Berger had previously invented the electroencephalogram, the machine that detects brain activity via electroencephalography (EEG). Though his ideas were not taken seriously at the time, further advancements in neuroscience have shown that there is much credibility to this theory.

The term “default mode” was not coined until 2001, when neurologist Marcus E. Raichle confirmed that the brain’s energy consumption baseline did not increase by more than five percent when switching from a resting state to active tasks. This finding essentially proved that the brain must continuously operate at a high level of energy consumption. By 2003, neurologist Michael Greicius determined, from a series of functional magnetic resonance imaging studies (fMRI), that the same network connectivity occurred in specific brain regions when performing similar tasks, proving a correlation within the DMN regions.

The main hubs of functional connectivity consist of the posterior cingulate cortex (PCC), the medial prefrontal cortex (mPFC), and the angular gyrus, located in the parietal lobe. These brain areas correlate with the default mode network (though most regions overlap in function). Here is an anatomical breakdown of the default mode network:

• Posterior cingulate cortex: The posterior cingulate cortex (PCC) is a key node in the DMN. This brain region’s network activity is engaged when one thinks about themselves or others, the past and the future, or processes spatial navigation. The dorsal region of the PCC deals with involuntary awareness and arousal, which impacts attentional focus.
• Precuneus: Located right above the PCC, the ventral portion of this brain region is involved in “unconscious attention” and visual and sensorimotor information. The precuneus involves various functions, including mental imagery, pain response, and recollection.
• Dorsomedial prefrontal cortex: Scientists have yet to determine the exact role of the dmPFC in the default mode network, though some suggest that the area helps analyze social behavior, like when we consider the motivations of other people.
• Medial temporal lobe: Housing the hippocampus, the temporal lobe is one of the four lobes of the cerebral cortex, with the MTL connected to the default mode cortical network through the parahippocampal gyrus. The hippocampal region is involved in our autobiographical memory and certain phases of working memory, visions for the future, and the formation of new memories.
• Temporoparietal junction: The TPJ is located where the temporal and parietal lobes meet and is mainly composed of the inferior parietal lobule and superior temporal sulcus. The TPJ takes in information from the limbic system, thalamus, and other sensory regions, allowing the brain to engage in reflections about others, also known as the theory of mind.
• Lateral temporal cortex: This brain region helps retrieve conceptual knowledge—long-term memory associated with objects, facts, and word meanings.

The default mode network has many vital functions, such as:

• Self-reflection: The DMN is a hub for self-referential activity—where we think about ourselves, our personality traits, and our emotional state. The DMN shows activity during rumination about who we are and how we feel.
• Social evaluations: The DMN is also active when we think about others. Empathy, morality, and consideration of other people’s feelings occur in our default network, along with the social concepts and characteristics of a social group.
• Memories: The DMN plays a role in our recollection of the past and helps us comprehend story narratives. It allows us to retain our episodic memories, which are detailed accounts of events that have happened during specific moments in time (like your first day of school or first kiss).
• Envisioning the future: DMN activation is also present during meditation, when we daydream, or think about the future.

A meta-analysis of resting-state neuroimaging studies has revealed that abnormalities within the DMN may contribute to a disruption in cognitive processes, leading to impairment or the occurrence of brain disorders such as autism, ADHD, Alzheimer’s, schizophrenia, or anxiety. “The Brain's Default Network: Anatomy, Function, and Relevance to Disease,” a scientific paper by Harvard neuroscientists Randy Buckner, Jessica Andrews-Hanna, and Daniel Schacter, further explores the relationship between the DMN, internal cognition efficiency, and its relation to disease.

Meditation affects the default mode network by altering the way we process our thoughts while our minds wander. The DMN is closely connected to our feelings and self-perception, and plays a role in our overall happiness. Mindfulness meditation is an effective way to reduce DMN activity. It can help refocus the brain and keep the mind from wandering into stressful territory, like reliving traumatic events from the past or anxieties about the future. Other forms of meditation, like loving-kindness meditation, can help with DMN modulation by decreasing negative emotions and feelings relating to the self, promoting more self-esteem and confidence, which, in turn, can help make us happier.

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