Autopilot by Andrew Smart Read Free Book Online Page B

just lay there doing nothing. It turned out that the brain’s noise wasn’t “noise” at all.
    What Raichle found so striking was that many scientists still doubt that it is possible. They argue that it’s a measurement error, some technical problem, or an artifact of how fMRI data is analyzed. When subjects just lie in the MRI scanner and let their minds wander, the exact same network that deactivated during experimental tasks begins to hum with activity.
    Additionally, during mind-wandering the activity in the nodes in this network becomes highly correlated. This means that each part of the default mode network behaves the same way. Crucially, the default network that activates during idleness is almost perfectly “anti-correlated” with the network that activates during tasks that require your attention. You can probably guess what an anti-correlation is: the opposite of correlation. Something “X” which is anti-correlated with “Y” means that when the value of X goes up, the value of Y goes down, and vice versa.
    Using fMRI data, the signal that neuroscientists use to measure the activity of a certain brain region is called the Blood-Oxygen-Level-Dependent (BOLD) contrast. Without going into the complicated details, this signal tells you roughly how much blood and oxygen is flowing to an active brain region. When neurons increase their activity, they use more blood and oxygen (just like your muscles). A rise in the BOLD signal indicates an increase in brain activity.
    Even though the network your brain uses to actively pay attention only requires a small fraction of your brain’s total energy, when this attention network activates, your default mode network reduces its activity. This is what is meant by anti-correlated: when your attention network activates, your default mode deactivates. While you run around like a decapitated chicken in your daily life, trying to manage your schedule, trying to keep up with all your mobile devices, posting to your Twitter and Facebook accounts, receiving text messages, composing emails, and checking off to-do lists, you are suppressing the activity of perhaps the most important network in your brain.
    The two networks I have been describing are also referred to as the “task positive network” (TPN) and the “task negative network” (TNN). The task negative network is the same as the default mode network. The task positive network is the one that becomes active when you are frantically trying to manage your time.
    What all this means is that as you lie there letting your mind wander—or in the awkward language of neuroscientific writing, having Stimulus Independent Thoughts—your brain becomes more organized than if you are trying to concentrate on some task like color coding your Outlook calendar. Thus, when you space out, information begins to flow between the nodes in the default mode network. The activity in these regions and in the network as a whole increases. We shall see later why this might be so crucial to your creative mind, and to your health in general.
    ----
    Where and what exactly is the default mode network? The default mode network arises from a set of posterior, medial, anterior medial, and lateral parietal brain regions. Posterior means “behind,” medial means “middle,” anterior medial means “middle front,” and lateral parietal means regions that are on both sides toward the top and back of your head. The specific regions that form the default mode network are called: medial prefrontal cortex, the anterior cingulate cortex, the precuneous, the hippocampus, and the lateral parietal cortex.
    What is important is to realize that these regions form nodes in the very large widespread network that is your default mode. These nodes are brain hubs. It is as if the default mode network comprises O’Hare, JFK, Heathrow, and Frankfurt airports. Together these nodes form the