Default Mode Network - Neurological Emptiness?

What does emptiness of mind mean neurologically?

Recently (2001) a group of regions in the brain have been identified that are generally active at times of rest and deactivate when external circumstances require that a task be undertaken. This ‘default network - see video’ has been shown to be active during internal thoughts of the past and future and likely daydreaming as well. One of these regions is the medial prefrontal cortex which has been associated with self-referential processing. Two other regions include temporal-parietal junction (TOM- interpreting others minds) and the posterior cingulate cortex (autobiographic and emotional memory).

Abnormalities in the functional connectivity of this network can be seen in many mental disorders including Alzheimers, Schizophrenia, Depression, Anxiety, Epilepsy, Autism, and ADHD.

For example in patients with major depression the subgenual cingulate (area 25), and the thalamus become overactive and part of the default network.  The subgenual cingulate may be the hub of this network in depressed patients and the source of internal rumination. Deep brain stimulation of BA 25 has led patients to report the lifting of a ‘void’ or ‘painful emptiness’. Interestingly this area is also active when making altruistic (selfless) choices.

"donating to societal causes recruited two types of reward systems: the VTA–striatum mesolimbic network, which also was involved in pure monetary rewards, and the subgenual area, which was specific for donations and plays key roles in social attachment and affiliative reward mechanisms in humans  and other animals." 

This study also shows how walking in nature improves depression through it's action on the subgenual cingulat.

Narrative (NF) & experiential focus (EF)

A recent study of mindfulness meditation (Farb et al., 2007), examined the neural correlates of a narrative focus compared to an experiential focus. The paper describes narrative focus compared to an experiential focus based on the philosophy of William James.

"Since William James’ early conceptualization, the ‘self ’ has been characterised as a source of permanence beneath the constantly shifting set of experiences that constitute conscious life. This permanence is often related to the construction of narratives that weave together the threads of temporally disparate experiences into a cohesive fabric. To account for this continuity, William James posited an explanatory ‘me’ to make sense of the ‘I’ acting in the present moment (James, 1890). "

  Narrative focus ('me') is characterized as a language mediated conceptual-analytic mode of evaluation, and resulted in activation of cortical regions implicated in conceptual self-representation (ventral and dorsal MPFC, PCC) and language processing (left inferior frontal gyrus, middle temporal gyrus). In trained mindfulness meditation participants, experiential focus ('I') resulted in more marked and pervasive reductions in the mPFC, and increased engagement of a right lateralised network, comprising the lateral PFC and viscera-somatic areas such as the insula, secondary somatosensory cortex and inferior parietal lobule.

"These results suggest a fundamental neural dissociation between two distinct forms of self-awareness that are habitually integrated but can be dissociated through attentional training: the self across time and in the present moment."

Also see this interesting FMRI study of Jazz improvisation.  The MPFC becomes activated in improv relatative to the DLPFC.

Another study showed that experienced meditators have decreased (quieter) DMN activity, stronger self-monitoring& cognitive control (Judson Brewer, 2011).

"Meditation isn't a cure for mental illness, Brewer said, but he said his study suggests that there may be a neurological basis for the benefits that many meditators report -- increased awareness, improved concentration, and a better ability to deal with the cognitive and emotional stresses of modern life."

The paradox may be that an overactive default tendency towards self-focus and rumination has the potential to self-implode leading to a sense of ‘painful emptiness’. In contrast mindful practices that empty the narrative mind from time to time help us connect to experience and may help us avoid the creation of our own narrative prisons. .

Update: New and interesting research study indicates the involvement of the default mode network during intense aesthetic experiences.

This is interesting because the default mode network is not generally involved when we are actively engaged with the outside world. The researches concluded:

"Our results suggest that aesthetic experience involves the integration of sensory and emotional reactions in a manner linked with their personal relevance."

Another way to frame the result would be related to the way we conceive of 'Heart-Mind' in tai chi practice. The 'Heart-Mind' subtle awareness presents itself when what is normally conceived of as 'outside' ourselves is integrated with what we conceive of as 'inside' ourselves, and thus separation of self and environment is transcended.

And this From Zhuangzi:

"Emptiness and stillness, calm and indifference, quiescence, Doing Nothing, are the even level of heaven and earth, the utmost reach of the Way and the Power; therefore emperor, king or sage finds rest in them. At rest he empties, emptying he is filled, and what fills him sorts itself out. Emptying he is still, in stillness he is moved, and when he moves he succeeds. In stillness he does nothing; and if he does nothing, those charged with affairs are put to the test. If he does nothing he is serene; and in whoever is serene, cares and misfortunes cannot settle, his years will be long."

Chuang-Tzu (2001-03-15). The Inner Chapters (Hackett Classics) (Kindle Locations 5521-5525). Hackett Publishing Company, Inc.. Kindle Edition.