Emphasis added:

"This brain implant is a chip that can automatically sense dopamine levels through an electrode that measures the flow of the neurotransmitter through the brain and pH levels. An algorithm within the device calculates whether dopamine levels are within a predetermined range, and if not, the chip sends an electrical impulse to stimulate neurons to produce more. Someday, it might help patients with a variety of disorders including addiction, or Parkinson's disease..."

Source: http://spectrum.ieee.org/the-human-os/biom...
AuthorJordan Brown