A 2007 study called "Mindfulness meditation reveals distinct neural modes of self-reference" by Norman Farb at the University of Toronto, along with six other scientists, broke new ground in our understanding of mindfulness from a neuroscience perspective.
Farb and his colleagues worked out a way to study how human beings experience their own moment-to-moment experience. They discovered that people have two distinct ways of interacting with the world, using two different sets of networks. One network for experiencing your experience involves what is called the "default network", which includes regions of the medial prefrontal cortex, along with memory regions such as the hippocampus. This network is called default because it becomes active when not much else is happening, and you think about yourself. If you are sitting on the edge of a jetty in summer, a nice breeze blowing in your hair and a cold beer in your hand, instead of taking in the beautiful day you might find yourself thinking about what to cook for dinner tonight, and whether you will make a mess of the meal to the amusement of your partner. This is your default network in action. It's the network involved in planning, daydreaming and ruminating.
This default network also become active when you think about yourself or other people, it holds together a "narrative". A narrative is a story line with characters interacting with each other over time. The brain holds vast stores of information about your own and other people's history. When the default network is active, you are thinking about your history and future and all the people you know, including yourself, and how this giant tapestry of information weaves together. In this way, in the Farb study they like to call the default network the ‘narrative' circuitry. (I like the ‘narrative circuit' term for every-day usage as it's easier to remember and a bit more elegant than ‘default' when talking about mindfulness.)
Continue reading at Psychology Today