" Why and how does this person switch gears, activating circuits in the dorsal prefrontal cortex connecting to adaptive basal ganglia circuits, rather than the OCD circuits connecting the orbital frontal cortex to the anterior cingulate and caudate? (See Figure 4.) At the instant of activation, both circuits—one encoding your walk to the garden to prune roses, the other a rush to the sink to wash—are ready to go. Yet something in the mind is choosing one brain circuit over another. Something is causing one circuit to become activated and one to remain quiescent. What is that something? William James posed the question this way: “We reach the heart of our inquiry into volition when we ask, by what process is it that the thought of any given action comes to prevail stably in the mind? "

― Jeffrey M. Schwartz , The Mind and the Brain: Neuroplasticity and the Power of Mental Force