Positronic brain

A positronic brain is a fictional technological device, originally postulated by science fiction writer Isaac Asimov, that performs "thinking" activities for a robot. The Star Trek character Data is also reported to have a positronic brain. In Asimov's writing, robots possessed a positronic brain rather than electronic, because each positronic thought would be negated by electrons in a moment, making the thought unique. In a positronic brain Asimov's Three Laws of Robotics would usually be implemented:

1. A robot shall not harm a human, nor shall it allow any harm to come to a human through its inaction.
2. A robot shall obey the commandments given by a human, unless in conflict with the first law.
3. A robot shall protect its own existence, unless in conflict with the first or second law.

Later an additional law, the Zeroth Law, was conceived by the robot Giscard:

0. A robot shall not harm HUMANITY, nor shall it allow any harm to come to humanity through its inaction.

If Data was ruled by these Laws remains a matter of debate. Data's evil brother Lore was not ruled by any of these laws with a possible exception to the third.

In the universe of Asimov, the gravitonic brain was invented in the final days of the robot era. Robots harboring this brain could obey the Three Laws, or any other Laws, or none. This brain was used to weaken the Three Laws into the Four Laws or Robotics.