Search This Blog

Wednesday, November 5, 2014

DEFAULT MODE NETWORK: What took 'em so long?

It is quite astonishing that all those neuroscience researchers, for all those years, doing all those fMRIs were actually clueless as to what was going on in this vital DMN network within the brain.
The term “default mode” was first used by Dr. Marcus Raichle in 2001 to describe resting brain function. It had previously been noted that a “resting” brain uses hardly less energy than a brain doing an “active” task, suggesting that perhaps the brain doesn’t “rest” so much as it changes the type of activity in which it is actively engaged.
The default mode network (DMN) involves low frequency oscillations of about one fluctuation per second. The network is most active when the brain is at rest. When the brain is directed towards a task or goal, the default network deactivates.
Areas of the brain included in the default mode network include the medial temporal lobe , the medial prefrontal cortex, and the posterior cingulate cortex, as well as the ventral precuneus and parts of the parietal cortex. All of these regions have been associated with some aspect of internal thought. For example, the medial temporal lobe is associated with memory. The medial prefrontal cortex has been associated with theory of mind, the ability to recognize others as having thoughts and feelings similar to one’s own. The posterior cingulate is thought to involve integrating different kinds of internal thoughts. Mirror neurons have also been posited to interact with the DMN.
Most critically, this work has called attention to the importance of intrinsic functional activity in assessing brain behavior relationships. It appears to be a vital connection to understanding the concept of self insofar as it is directly involved in the switching of "interest" or attention from "task orientation" in the outside world to some "internal" orientation 
For those puzzling over the paradoxes of "consciousness" (really in our mind just a use of a nonsense word that only leads to more nonsense), here is a place where the brain does make its own distinctions between the tangled notions of "consciousness" and "self consciousness".
Essentially, among its many other aspects, the DMN currently already appears to be an essential means of modulating parasympathetic/sympathetic balance
It has been implicated, just in the past couple of years, in such crucial aspects of our daily being as being able to go to sleep and switch from awake to sleep mode, ADHD function, depression and affective disorders, daydreaming, the benefits of both acupuncture and meditation and hypnosis, and the modulation of respiratory and cardiovascular maintenance and more.
The concept of a default mode of brain function arose out of a focused need to explain the appearance of activity decreases in functional neuroimaging data when the control state was passive visual fixation or eyes closed resting.
The problem was particularly compelling because these activity decreases were remarkably consistent across a wide variety of task conditions. It was determined that these activity decreases did not arise from activations in the resting state.
Hence, their presence implied the existence of a default mode. While the unique constellation of brain areas provoking this analysis has come to be known as the default system, all areas of the brain have a high level of organized default functional activity.