The Brain, DMN and Consciousness
Of the virtually unlimited information available in the world around us, approximately ten billion bits per second arrive on the retina at the back of our eye. The optic nerve attached to the retina sending impulses back to the visual cortex, has only one million output connections. This means that only six million bits per second can leave the retina, and only ten thousand bits per second make it to the visual cortex. After further processing, visual information feeds into the brain regions responsible for forming our conscious perception. Surprisingly, the amount of information this conscious perception is made of amounts to less than 100 bits per second. From ten billion (10,000,000,000) to 100 bits per second – if that was all the brain took into account, this thin stream of data would hardly produce a perception. To add to this picture, of all the synapses in the visual cortex, only ten percent are devoted to incoming visual information from the retina, so that the vast majority of visual cortex connections must represent internal connections among neurons in that brain region. This shows how little information from the senses actually reaches the brain’s internal processing areas, and how extensive the processing of information through internal connections within the brain really must be. What you see is mostly what your brain constructs from scant data coming from the outside world. I guess Shakespeare hit the nail on its head: “Sir, what you see is not what you see!”
You may think that the brain lights up in different ways when you perform different tasks, and that it turns off when you are at rest. Far from it. There is a persistent level of background activity, called the default mode, that is critical for overall brain functioning and the planning of future actions. When your mind is at rest (daydreaming, meditating, sleeping), dispersed brain areas chatter away to one another, and the energy consumed by this ever-active messaging is twenty times higher than the energy the brain uses to accomplish specific tasks. Everything we do marks a departure from the brain’s default mode, and the energy used for such specific activities is only about five percent more than what the brain already consumes in this highly active default mode. During specific activities, the default mode continues underneath. Because this background default mode of high energy consumption is difficult to see and was difficult to find, brain scientists gave a reverential nod to dark energy in astronomy and called it the brain’s dark energy. This dark energy was later found to be predominant in four widely separated areas of the brain, the lateral parietal cortex, the lateral temporal cortex, the medial parietal cortex and (no surprise) the medial prefrontal cortex (MPFC). Together, these areas constitute the default mode network (DMN), thought to behave like an orchestra conductor issuing timing signals to coordinate activity among different brain regions. Damage to the DMN may be involved with a whole series of mental and physical disorders. In this way, the brain integrates all its regions in a way that allows them to function and react in concert to stimuli. Integration is the key.
Moving from neuron to narrative, I write about neurons in order to shed light on the story of meditation. We only use very little information residing in the outside world to know that world. Instead, we mostly construct a perception of that world by means of a staggering amount of internal brain processing involving neural networks that are widely distributed throughout the nervous system. To do that effectively, it is essential that the integrative function of the DMN be intact and unfold in optimal ways. Proper brain hygiene, which includes time for play, goal-oriented focusing, sleeping, physical activity, connecting with others, non-focused day-dreamy downtime and time for inner reflection, ensures such brain health.
Central to these aspects of brain hygiene is time for inner reflection, also called ‘time in’. This is what we hone through mindfulness meditation. We harness the power of the master integrator of the brain, the middle prefrontal cortex (MPC), to create a still point, different from, but not unlike sleep, a state of concentrated and ultimately effortless rest. This allows the brain to get out of its own way. Were I to put my money on something, I would put it on the hypothesis that this concentrated rest optimally activates the DMN for its sweeping integrative function throughout the body-brain. Integration is the linkage of differentiated parts and stands at the core of health. For integration to occur, the ability to differentiate between the parts of the whole system and then connect them by holding them in awareness is key, not problem-solving. Open awareness of the details of the mind’s landscape discovered through focused attention changes everything it becomes aware of. Relative to neurons, we are talking about the differentiation and linkage between widely distributed brain regions, neural networks and neurocircuits; relative to narratives, we differentiate between the different somatic sensations, feelings and thoughts, between embodied and cognitive self-awareness, and ultimately between the different narrative threads we weave about our lives. Holding all that in awareness, after having gained a clear and detailed view of our energy flow through focused attention and kind intention, we then allow the DMN sweep to creatively reconnect in ever new ways all these parts moment-by-moment, thus forever changing everything in its wave-like repetitive surf movement.
Following the principle of the DMN sweep, and with the same ease we try to move from neurons to narratives, from science to subjective experience, in examining the intricacies of our internal world we need to learn not to focus too much on solving problems, but on finding new connections instead. This is the hallmark of creativity and health. If you are depressed, it is more important to stop fighting the obvious, deeply examine the space of darkness and find out how you create a dark reality devoid of connections to other possible ways of constructing reality, than it is to try to solve the problem by substituting negativity with positive thoughts. This latter project usually only partially works, because positivity that tries to replace negativity without exploration of the relationship between the two, only leads to the repression of darkness, which then lurks in the unconscious depths waiting to return with a vengeance at the first opportunity that arises.
What makes us sick is the combination of lack of clarity about the differentiated details of our internal sea and lack of connection between these details. What paralyzes people in depressive states is the lack of connection between the darkness and the larger context of the living organism, not the presence of darkness itself; for darkness is always around as a matter of course in human life. It is not about here and not wanting to be here, nor is it about there and wishing one was there, but about the ways here and there are connected or not. It is the nature of transitions from one mental state to the other that is crucial for integration and healing. Like in the Tango, with its unique aspect of improvisation also so prevalent in brain functioning, the excellence of either dancer is secondary to the couple’s ability to move in mutual attunement. Without the latter, no amount of expertise will put you in awe of the dance’s inspired aspirations. We need great curiosity and acceptance in simply being, as we closely examine the complex intrigues that make up the story of the mental state we don’t desire – more so than the conscious problem-solving wish to get rid of the undesired state. In approaching our inner world this way, we stimulate the brain’s creative propensity to find and create new connections, and that very process is the one that will lift us out from underneath the wreckage of chaos or rigidity.
The DMN works largely below the radar of consciousness. In order to reach the non-conscious realm, or more accurately, to become permeable to the constant flow of energy and information from non-conscious body and mind processes, we have to surrender to the unknown. The most powerful forces that influence our lives are not the ones we know about and are conscious of, but the ones we don’t know our mind has decided to adopt and work with as its own.
Copyright © 2019 by Dr. Stéphane Treyvaud. All rights reserved.