07 November 2011

To Be a Zombie, or Not to Be a Zombie: That is the Question

Default Mode Network Background

The "default mode network" of the brain is particularly active when the brain is resting, waiting for something "important" to do. The brain never goes completely idle, but instead goes into a stand-by mode. When we pay particular attention to things, the stand-by network goes idle to allow other parts of the brain to work. But what happens when the stand-by network is allowed to push the other brain networks around?.
A study carried out by a team at the Centre de Recherche en Neurosciences de Lyon (led by Tomas Ossandon and managed by Jean-Philippe Lachaux, Research Director at Inserm and Karim Jerbi, Research Leader at Inserm) has just revealed how this network interferes with our ability to pay attention, by assessing the activity of the human brain's default-mode network neurons on a millisecond scale for the first time ever, in collaboration with Philippe Kahane's epilepsy department in Grenoble.

The results unambiguously illustrate that whenever we look for an object in the area around us, the neurons of this default-mode network stop their activity. Yet, this interruption only lasts for the amount of time required to find the object: in less than a tenth of a second, after the object has been found, the default-mode network resumes its activity as before. And if our default-mode network is not sufficiently deactivated, then we will need more time to find the object. These results show that there is fierce competition for our attentional resources inside our brain which, when they are not used to actively analyse our sensorial environment, are instantaneously redirected towards more internal mental processes. _SD
Jnl Neuroscience Abstract
DMN [Default Mode Network] deactivation encodes the extent and efficiency of our engagement with the external world. Furthermore, our findings reveal a pivotal role for broadband gamma modulations in the interplay between task-positive and task-negative networks mediating efficient goal-directed behavior and facilitate our understanding of the relationship between electrophysiology and neuroimaging studies of intrinsic brain networks.

We are learning more about the perpetual tug-of-war that goes on between the networks of the brain. The brain is an insatiable consumer of the body's energy -- consuming 20% of O2 and glucose supplies. But if you actually think -- unlike most humans -- your brain will consume more. It is easier for the brain to do nothing, although even to do nothing the brain must still consume a lot of energy. The thinking networks of the brain require training and regular exercise, just as the muscles of the body require regular upkeep. If one does not continually train the cognitive networks, the default mode network will assume more influence.
Meta-Analysis of the default mode network Connectivity patterns

DocStoc Default Mode Network embed

The default mode is extremely important, in terms of saving energy and in terms of "resetting" or clearing the mind for whatever new situations may come up. At its best, the DMN opens the door to creative mental activity such as "lateral thinking." At its worst, when indulged too much, the DMN can make humans indistinguishable from zombies.

But when the situation calls for immediate planning or focus, the default mode may get in the way of your ability to achieve a clear conception of your situation or to formulate workable plans. Before that happens, one needs to make the choice whether to exercise the cognitive, planning, and decision-making networks of the brain, or to allow the default mode to occupy more and more of one's time. That choice is usually made very early in life, based upon a wide range of genetic and environmental factors.

For many things in our lives, we have no meaningful choice. That is why it is important to exercise choice when we can.

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