Positronic brain

A positronic brain, or positronic mind, was a form of artificial brain capable of supporting sentience.

Dalek technology
On Vulcan, the human space colonist Lesterson examined "dead" Daleks and, thinking of them as robots, conjectured they possessed a sort of positronic brain. (TV: The Power of the Daleks)

When the Second Doctor was forced to work for the Daleks in extracting the human factor from Jamie's emotions, he imprinted it into a positronic brain. This was to be implanted in the Daleks, which the Daleks hoped would have made them invincible. (TV: The Evil of the Daleks)

While stranded in the 1940s, a group of post-Time War Daleks created an android duplicate of the scientist Edwin Bracewell, filling his positronic brain with memories of the real Bracewell and leaving him unaware that he was not the original Bracewell. He was given fake memories of having developed the "Ironsides" war robots, allowing the Daleks to infiltrate the British war effort. (TV: Victory of the Daleks)

Human technology
The Dronebots used as maintenance robots on the Figaro Xll colonial supply base were provided with simple positronic brains. (COMIC: The Frankenstein Particle)

At one stage in human history, positronic minds were ubiquitous, and synonymous with human-developed artificial intelligence. The Sentiency Act of 2976 granted equal status with humans to "all Level 15 positronic minds", outlawing their sale as property or their mistreatment by human employers. However, even by 3909, bigotry against artificial minds still existed, as did illegal, unethical practices such as fleshing, the process of overwriting an existing positronic mind with the memories of a dead human as a way to bring the latter back from the dead, and adding mental blocks to prevent the thusly-resurrected person from noticing that they were now in an android body or from remembering their death. (PROSE: Cybergeddon)

The androids of EarthWorld had positronic brains. (PROSE: EarthWorld)

Other positronic technology
The Fourth Doctor recognised the labyrinth-like building complex that served as the lair of the Nimons as resembling both physically and functionally a "giant positronic circuit". (TV: The Horns of Nimon)

Kylex-12, an android once dated Tegan Jovanka, created by the Vorax Mach-Teldak, had a positronic brain (AUDIO: The Waters of Amsterdam)

The Seventh Doctor deduced that Qataka's cybernetic body had a positronic brain. (PROSE: Timewyrm: Genesys)

The dragons of Tír na n-Óg had positronic brains. The Seventh Doctor used a component from one brain to build a transmitter with which to contact Goibhnie. (PROSE: Cat's Cradle: Witch Mark)

Two positronic brains housed the twin artificial intelligences at the heart of the Cyberons' Cybernet, developed near the end of their Cyberon War against the Earth Alliance. After the Cyberons' apparent defeat, humans looted much of their technology including these two brains, which wound up being sold on the black market many centuries later. One still remembered his origins, while the other had her original programming wiped to become subject to fleshing. (PROSE: Cybergeddon)

Behind the scenes
A positronic brain is a fictional technological device, originally conceived by science fiction writer. Its role was to serve as a central computer for a robot, and, in some unspecified way, to provide it with a form of consciousness recognisable to humans. When Asimov wrote his first robot stories in 1939 and '40, the positron was a newly discovered particle and so the buzz word positronic — coined by analogy with electronic — added a contemporary gloss of popular science to the concept.