NEXTUP and the Default Mode Network
In the last quarter of the twentieth century, two brain imaging techniques were developed that would dramatically change our understanding of how the brain works. Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have allowed scientists to look at brain activity while people are performing a whole range of mental tasks and create detailed 3-D maps of that brain activity. Using these new techniques, we have learned which brain areas are “turned on” during all sorts of mental activity—from staring at geometric patterns to viewing emotional pictures, reading, and memorizing word lists to having out-of-body experiences.
To produce these maps of brain activity, individuals are rolled into the center of a huge doughnut-shaped machine. Pictures of their brain activity are then taken, first while they’re just lying there resting and again while they’re doing some task. If we subtract the activity patterns ...
