The Default Mode Network and Its Relationship with Consciousness

My name is Pierrette, and I am a Master's student studying Neuroscience at King's College London. A few months ago, I was introduced to the concept of the brain's "dark energy" during a lecture on neuroimaging. Deeply interested in this topic, I began to wonder about the origin and nature of consciousness and questioned whether the awareness of oneself resides in the body, or if our mind and body are two separate entities that converge to make us human.

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What is the Brain's Dark Energy?

It might be interesting to find out that our minds never really rest; instead, they are constantly busy even when we are not actively using them. The first to come to this deduction was Hans Berger in 1929. After noticing ceaseless recordings of electrical oscillations through the encephalogram (EEG), a device of his invention, he was able to record brain activity. He deduced that our central nervous system is always in an active state. The energy needed to keep our brain alive even when inactive has been defined as the ‘brain’s dark energy’.

The term ‘dark energy’ was borrowed from cosmology, where it is defined as a hypothetical energy that fills all of space.  It is believed to be responsible for the accelerating expansion of the universe. However, the term is used metaphorically in neuroscience to describe the seemingly spontaneous, random fluctuations in brain activity that are not directly related to any specific task or stimuli.

The brain’s dark energy seems to account for most of the brain’s energy use, around 60-80%, with only 5% being directed to goal-related neuronal responses. This form of intrinsic activity, and thus the energy used for it, is thought to be related to the brain’s default mode network (DMN).  

The Default Mode Network as the Possible Core of Consciousness

The DMN can be defined as a group of interconnected brain regions that are active when an individual's brain is at rest or not focused on their environment or external stimuli. Examples of behaviours activating the DMN include daydreaming, self-referential thinking, and mind-wandering.

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Self-referential thoughts are the basis of consciousness, as these involve the processing of how information relates to one’s own identity, experiences, and goals. In synthesis, we could say that such thoughts are what allow us to differentiate ourselves from others so that we are aware of who we are. There is a growing body of research that defines the DMN as the core of consciousness and aims to use it as a target to restore consciousness in the context of various pathologies.  

Since the recording of DMN activity through neuroimaging devices, we can hypothetically observe a reflection or proof of the existence of our consciousness. The DMN has been defined as 'the unifying thread that binds together humans’ perceptions and gives it continuity between present moments, past experiences, and future goals.'

The Mind-Body Problem

Throughout history, humans have always tried to understand the relationship between our psyches and our bodies, with speculations regarding the mind-body connection being made as early as the BC period. One of Aristole's most famous treatises, De Anima, otherwise known as On the Soul, described the mind and body as a 'synolon,' intended as two inseparable components of one being that complete each other as matter and form. However, the mind-body problem was officially outlined by Descartes in the 17th century, as he rejected Aristotle’s theory in favour of viewing the mind and body as two separate entities, giving rise to a theory known as dualism.  

Since then, humans have proposed different theories to resolve the mind-body problem, with the most dominant being the theory of physicalism. This theory sees the mind and body as one, basing its conclusion on the belief that the mind is, in fact, physical, and that every mental state can be explained by physical brain processes.

What Does This Mean for Science and Philosophy?

Viewing the DMN as the basis of consciousness would imply that the psyche and body are in fact, one and inseparable, a synolon. Despite this, the DMN could also be seen as the reflection of our consciousness and not the consciousness itself. This interpretation would link the DMN to the emergent theory that sees psyche processes as related but not solely limited to the mind. This assumption would thus disprove both the physicalism and dualism.

Photo by Vitaly Gariev

Viewing the psyche and body as one, fits the possibility of the DMN being the core of consciousness, as, according to this, the emergence of sentience is the result of the interaction of various brain regions.  This encapsulates what the DMN is, a network born from the interactions of regions such as the posterior cingulate cortex, medial prefrontal cortex, and the bilateral inferior parietal lobule, along with other associated regions. The amalgamation of these neurointeractions can generate those self-referential thoughts that are seen as the basis of consciousness, binding together one’s perception of themselves through time.

Nevertheless, it would be too simplistic to resolve the mind-body problem with the DMN. If we even decided to accredit the emergent theory, we would be faced with the limit of never being able to solve such a problem and only accept that consciousness is an emergent property of the brain, which cannot be explained or understood.

Although we cannot be overly reductionist when explaining the origin of consciousness, the DMN posits a great basis for speculation regarding the nature of consciousness and its association with the body.