In 2001, (not the film, although that features heavily in my writings for various reasons), Marcus Raichle coined the term that refers to what is deemed to be the brain’s default state at rest. The application of neuroimaging techniques was logically focused on scrutinising brain activation when a given task is performed by the ‘lab-rat’ (often a peculiar species of rodent termed ‘undergraduate student). This makes perfect sense – which bit of the brain ‘lights up’ when I get participant X to perform task Y? such that region Z can be localised and hey presto we have a nicely coloured map of regional functionality.
But we are all taught in science 101 from an early age that in order to understand an experimental effect we ought to have a control condition. In the case of typical fMRI studies, this will involve lying quietly in the scanner doing little else other than listen to the humming noise of the contraption in which one is lying, and the steady hum of one’s own internal monologue chattering away. Some bright spark took a closer look at brain activation data in that period of rest, and rather than throw out the baby with the bathwater, noticed something interesting. It is fairly obvious that the brain, with it’s disproportionate thirst for metabolic energy, and its constant crackle of electrical activity, even at rest is a busy organ. It is working constantly to keep the organism regulated, monitoring it’s internal state, ready to alert the ‘owner’ to any aberrant signals that might require jumping into action to rectify any survival threatening incidents. But what was interesting was the degree of what is termed ‘functional connectivity’ observed when the participant was ‘at rest’.
In this so called resting or ‘default’ state, actually there is a high level of metabolic activity, with attention directed inwards, and in fact this activity ‘falls off’ when attention becomes more directed outwards. This ‘functional connectivity’ in fact serves a purpose with respect to generating internal cognition that may involve diverse modes of thought including thinking about one’s ‘self’ and emotional state, recalling facts and instances from one’s own past, or ruminating about the future, or others’ states of mind. Or simply, to indulge in a state of thinking termed ‘mind-wandering’ (daydreaming by a more ‘scientific’ name). For a comprehensive review of the functional anatomy, history of ‘discovery’ and pertinence to normal and ‘aberrant’ mental functioning, see Buckner et al. (2008).
In short, the default mode network (from hereonin ‘DMN’), could be construed as being the seat of ‘self’. Bereft of a specific task to concentrate upon, the mind turns inwards, a parade of thoughts, memories, fantasies, ruminations progresses. It is quite remarkable how much energy is consumed by this ‘resting’ state, with the ‘ego’ as it were being given the floor to pontificate upon it’s own sense of worth. And how easily this ego can run away with itself. Any insomniac will be painfully aware of how this unfettered mind will whip a still pond into a whirpool of turmoil, spiralling in on itself in torment. The night is anything but restful…Aside from debating what is the ‘self’, it is interesting to couch it in terms of the brain activation and blood flow to specific connected areas of the brain. And moreover to consider how that ‘basis’ is ‘easily’ disrupted by a ‘simple’ neurophysiological diversion of energy, blood flow, electrical activity to other parts of the brain. What I am referring to is the interesting supposition that in the same way a network such as the DMN can be connected to such meaningful cognitive experience leading to a (often painful) awareness of a ‘self’, equally can such a network be ‘turned off’. For remember, the evidence for a so-called default network arose from observations that the ‘control’ state in experimental studies called for the subject to NOT engage in a task during that ‘rest’ period. Which means that when engaged in a task, a different set of regions, betrayed by elevated local activity is / was in evidence. The so-called ‘task positive network’ (TPN) encompasses a set of brain areas that ‘functionally connect’ when engaged in a goal-directed task. This is also known as the central executive network (CEN), and as the name alludes to, involves regions that deal with executive control and governance of attentional resources relating to cognitive performance.
So what we have here is at least two different networks of brain regions that subserve different purposes if you like. And which can be represented by different activity and metabolic energy distribution. There are certainly more than two differentiated networks in the brain but for now and to keep things more comprehensible I will restrict discussion to these. The really interesting part of this equation is the notion that these two networks are anticorrelated. This term essentially describes the mutually exclusive status that when one is ‘on’ the other is ‘off’. Or more correctly, one may exhibit greater functional connectivity (i.e. stronger activation when engaged in it’s own ‘purpose’) than when the other takes precedence. For instance, when engaged in a directed task, the TPN will show strong functional connectivity within it’s network of regions, whilst at the same time the DMN will show reduced levels of activation and consequently lower functional connectivity.
Concomitant with this neurophysiological index is the cognitive functioning and perceived experience that relates to one or the other network. In the case of the DMN this may involve patterns of thought that associate with a sense of self, be that fantasy based flights of fancy, or depressive ruminations, or just wandering thoughts about past, present or future. But this also means any task related performance will suffer, as the mind really is not focusing on that task at hand. One is internally distracted. On the other hand, when the TPN is active, engaged and functionally connected, by virtue of the anticorrelated state of affairs, the DMN will not be given leeway to ruminate about it’s ‘self’. Therefore there will be little awareness of self. By definition this TPN dominant state becomes selfless. And as with a selfless state of being, if we allow for a little zen-style analogy, performance should be on point.
This leads in future directions into discussion of optimal functioning, and the so-called flow-state. For that state is frequently alluded to when talking about high performing situations when one loses all awareness of self, of time passing (logically the sense of time calibrates to an awareness of self-involvement in proceedings). The positive mental health benefits, and creative innovation output that may arise from such a state of optimised brain functioning are multifarious. This is intended as a primer to the DMN and associated brain networks. This is an introduction to slowly bring in the complexity of a systems neuroscience approach to unpacking the neurocognitive factors that underlie perceived experience. For it will be seen that this is not so black and white a case. Mittner and colleages (2016) argue for a role of the DMN in certain task focused states which do require internally focused cognition for example, and postulate phasic fluctuation in functional connectivity dependent on an integrative framework between DMN and the locus-coeruleus-norepinephrine system. This has relevance to levels of alert and arousal, and sustained attention pertinent to task performance. I will explore that in later pieces.
The thrust of this piece though is to lodge in mind that the brain has specific functional capacity, localised to various networks. Also, that these networks associate with different types of cognitive functioning, and with that comes variation in subjective perception. This is linked to attentional control, and effectively when one network is active the other is significantly reduced in its activity, essentially tuned down. There are wide ranging philosophical ramifications with respect to the notion of self awareness, and ultimately where ego and identity and sense of one’s own control or agency is ‘located’. It is fascinating to think that one could feasibly alter blood flow preferentially from out of the DMN and into the TPN (simplifying massively!) in order to ultimately harness control over one’s self. At the very least this gives pause for thought with respect to how one can strategically alter one’s subservience to the ruminating self by focusing one’s attention wholly on a task, or at least attempting to engage in a task if one is plagued by self-rumination.
Another strand of discussion to be had at a later stage involves implications of research into the pharmacological and neurophysiological effects of psychedelic compounds on functional brain connectivity. And with that comes a whole load of interesting associations with perceived phenonoma and disrupted cognition. The DMN plays a significant role in that research regarding functional connectivity, ‘mind-expansion’, and the dissolution of ego…
To bring this back to ‘CognitvExploration’, a purpose of this site is to forge links between subjective perceptions of environments / adventurous experiences and the science of brain functioning. By discussing topics such as functional brain networks we can start to understand how it is that the brain as a physical system is affected by the physical environment in which it operates. In turn, the cognitive demands of operating in a given environment then impinge upon the metabolic energy required for given cognitive states to be managed. This before we get into a discussion on the homeostasis management requirements of maintaining an organism’s physiological equilibrium in response to environmental stresses. I will diverge into that at a later stage and introduce a compensatory framework that links cognitive resources to biological priorities for survival.
For now, we can see that there are at least two clear and distinct states of being that favour either self-negating absorption in performing a task (perhaps that is a focus on getting from A to B in an adventurous landscape) or else a self-aware (all consuming?) state in which one is distracted by internal status and less aware of the surrounds (perhaps consumed by the beauty and significance of a vista, and in a contemplative mood that pays less heed to any hazards or functional requirements of the environment). But let us ruminate further on the Default Mode Network, and the importance of task focus in adventurous environments to help us figure out ways for self-transformation and personal growth! That is one to ‘allow’ the DMN to ponder on in the depths of the night…
Andrews-Hanna JR. (2012). The brain's default network and its adaptive role in internal mentation. Neuroscientist. 2012 Jun;18(3):251-70. doi: 10.1177/1073858411403316. Epub 2011 Jun 15.
Buckner, R.L., Andrews-Hanna, J.R. and Schacter, D.L. (2008). The Brain’s Default Network Anatomy, Function, and Relevance to Disease. Ann. N.Y. Acad. Sci. 1124: 1–38
Mittner M1, Hawkins GE2, Boekel W2, Forstmann BU (2016). A Neural Model of Mind Wandering.Trends Cogn Sci. 2016 Aug;20(8):570-578. doi: 10.1016/j.tics.2016.06.004. Epub 2016 Jun 25.
Raichle ME, MacLeod AM, Snyder AZ, Powers WJ, Gusnard D, and Shulman, G.L. (2001). A default mode of brain function. Proc Natl Acad Sci U S A 98:676–82.
Uddin LQ, Kelly AM, Biswal BB, Castellanos FX, Milham MP. (2009). Functional connectivity of default mode network components: correlation, anticorrelation, and causality. Hum Brain Mapp. 2009 February ; 30(2): . doi:10.1002/hbm.20531.
The science of cognition and perception in context
This is where I elaborate upon brain science relating to cognitive functioning dependent on environmental context.