Consciousness remains one of the most difficult mysteries in science, but researchers have uncovered new clues about how the brain produces it.

A study found that consciousness may depend on a delicate balance between self-awareness and awareness of the outside world. This balance appears to involve two major brain networks: the default mode network (DMN), which is more active when the brain is at rest, and the dorsal attention network (DAN), which becomes active when we focus on tasks or our surroundings.

Researchers analyzed hundreds of 3-D brain scans from healthy people, anesthetized patients, and individuals with unresponsive wakefulness syndrome. Using machine-learning methods, they identified eight major patterns of brain activity, including the DMN and DAN.

In people who were unconscious because of anesthesia or severe brain disorders, the normal interaction between these two networks was significantly reduced. This suggests that the constant back-and-forth between the brain’s internal thoughts and its awareness of the environment may be essential for maintaining consciousness.

The discovery doesn’t fully explain what consciousness is, but it provides an important new piece of the puzzle. In the future, understanding these brain networks could help doctors measure levels of consciousness, improve anesthesia monitoring, and develop treatments for people with disorders of consciousness.