In the neurons that produce Fundamental Consciousness- particle-level freestanding events. The swells of feeling produced by the aggregates of these formed as they affect each other both due to field effects and neural connectivity are the will and the essence of human consciousness, the rest being attached representations of information.
If you are searching for this region to performe a BCI, you can work in the associated cortex, the part related to control the human movements. Otherwise findind the origin of our intentions is not an easy job.