When people first began to think about human nature, one of the
first questions that they asked is whether or not experience is created by the
process of sensing the environment. That is, whether or not our minds would shut
down without the energy from the things we sense.
Since then, it has been found that many parts of the nervous
system produce patterns independent of their sensory input. Neural circuits
that produce self-sustaining patterns of behavior are called central pattern
generators.