Basically, what they noticed was that during freestyle, there were significant changes in the prefrontal cortex (credit where credit is due: Jonah Lehrer was spot on about this part of the brain being integral to the creative process). The areas implicated in processes like organization and drive were marked by an increase in activity, while those parts responsible for close self-monitoring and editing were deactivated. In this context, the authors explain, "self-generated action is freed from the conventional constraints of supervisory attention and executive control," allowing sudden insights, seemingly unbidden, to emerge. 

In other words, in order to turn on their creative flow, the rappers had to switch off their inner critic. And in fact, the researchers believe that when they're freestyling, the artists are actually occupying an altered state of mind. A closer look at their brain activity reveals that an entire, unique network emerges during the process, one in which motivation, language, emotion, motor function, sensory processing and the representation of the artists' subject experience all interact in unusual ways to create the flow state. 

And it's not just rappers: The authors believe that their findings can be extrapolated to explain creativity itself. Specifically, they point to the first phase of any artist's process, in which unrestrained bursts of inspiration and ideas are brought forth. In other forms of art, like writing, those ideas are later edited and revised.

The idea of studying creativity's roots in freestyle is actually a takeoff from a similar study done with improvisational jazz, in which six musicians played a specially designed keyboard from within the bowels of an fMRI machine. For these artists, playing a one octave C-major scale in quarter notes was also associated markedly different brain activity than when they were allowed to start improvising within those parameters. 

PLoS ONE

Here, the researchers called special attention to increased activity that was observed in the part of the brain associated with the inner self, the subjective perspective unmediated by outside stimuli. That improvisation is the expression of an artist's musical voice, they argue, further strengthens these associations. It raises the question: Could this mean that we're most genuine during the  first stage of the creative process, later to be mediated during the revision stage by outside constraints?

In the absence of self-editing, the researchers further noted of the freestyle experience, "ongoing actions, moment to moment decisions and adjustments in performance may be experienced as having occurred outside of conscious awareness." This, they suggest, could explain why artists sometimes claim the guiding influence of some outside agency on their creative process. But, as they insist they've demonstrated with the jazz musicians, "the process is neither mysterious nor obscure, but is instead predicated on novel combinations of ordinary mental processes."

Which is not, they might do well to add, to diminish the wonder we experience during a burst of creative expression, or our appreciation of seeing (or, more accurately, hearing) it occur in others. That changes in brain activity are so clear, and so obviously powerful, only confirms the extraordinary nature of the creative mind.