The activation of default mode and multiple demand networks: an fMRI study on intentional and unintentional mind wandering

Abstract

Mind wandering or task-unrelated, self-generated thoughts happen every day in life. These thoughts can either be Unintentional or Intentional. The brain’s Default Mode (DMN) and Multiple Demand (MD) networks integrate during Mind Wandering. In this study, we conducted a functional magnetic resonance imaging (fMRI) experiment where Mind Wandering was the task. During this task’s think part, an Intentional form of Mind Wandering occurred. Meanwhile, Unintentional Mind Wandering took place during the rest part where participants rested in the fMRI machine. We aimed to see the difference in the pattern of activity in both the Default Mode and Multiple Demand Networks during the Intentional and Unintentional Mind Wandering. Our results showed that, in the Posterior Cingulate Cortex (PCC) and the left Temporoparietal Junction (TPJ) regions of the Default Mode Network, the think part provokes a stronger response than the rest part. On the other hand, the Multiple Demand network regions responded differently to the different forms of Mind Wandering. Some Multiple Demand regions, such as the left Inferior Frontal Sulcus (IFS) and the pre-Supplementary Motor Area (pre-SMA), represented a more robust response in the think part than the rest part. Meanwhile, the bi-lateral Intraparietal Sulcus (IPS) regions showed stronger activation in response to the rest part. In addition, we showed that the Language regions have a more pronounced activation in the think part than the rest part. Consequently, the Default Mode Network’s regions, some of the Multiple Demand regions, and Language regions respond more robustly to the Intentional form of Mind Wandering than the Unintentional Mind Wandering.