Next Friday, Matt Damon returns for a fourth outing in the film “Jason Bourne,” as the superspy continues to investigate his fuzzy past and piece together all the terrible things he’s done.

Bourne’s amnesia has always been central to the character’s story. The ex-black ops soldier has spent years (and three previous films) trying to elude the authorities and uncover exactly how the CIA manipulated him.

And while “Jason Bourne” includes several ripped-from-the-headlines details — austerity protests in Greece, a battle over cyberprivacy — Bourne’s memory loss seems more like the stuff of fiction. But it’s actually based on fact.

The CIA experimented extensively with brainwashing during the 1950s and 1960s, honing techniques that could force someone to kill, then have no recollection afterward. Code-named MKUltra, the program involved some 149 separate experiments — many on unwitting Americans, including a Kentucky mental patient who was dosed with LSD for 179 days straight.

MKUltra was officially launched in 1953 to develop better interrogation techniques, as well as to explore the possibility of creating a programmable assassin. The CIA also wondered if it would be possible to mind-control hostile foreign leaders, such as Fidel Castro.

Some 44 universities, 12 hospitals and three prisons helped out with the experiments, though many were apparently not aware they were working for the CIA. The spy agency sometimes funded the work through anonymous grants that the organizations believed were from private individuals. The institutions that did know “acted in good faith and with the belief they were aiding their government,” per a 1977 Senate report.

So what exactly went on? Were subjects really subjected to Bourne-style brainwashing?

Many of the documents pertaining to MKUltra were destroyed in 1973 on the CIA’s orders, but some survived and were revealed in the late ’70s.

The details read like something straight out of a Robert Ludlum novel.

A disturbing 1954 document details an experiment during which two women were hypnotized and one was made to try to wake the other. When the first woman didn’t stir, the other woman was ordered to “fly into a rage and shoot her.” The entranced woman picked up an (intentionally unloaded) pistol, pointed it at the other woman and pulled the trigger before falling into a “deep sleep.” Upon waking, neither woman remembered anything about the sequence.

Another time, a hypnotized woman was told to wait by a phone to receive a call. The person on the other end would mention a code word in the course of a normal conversation, causing the woman to pass into an undetectable trance state. The woman would then proceed to a location and plant an incendiary device hidden in a briefcase.

The potential for abuse seemed nearly limitless.

One hypnotist told the CIA in 1951 that he had used his powers to induce “young girls to engage in sexual intercourse with him.” In 1952, another specialist said that with the correct conditioning, “Individuals could be taught to do anything, including murder.”

The program was reduced in scope in the late ’60s and stopped completely in 1973.

The man who presided over the program, Sidney Gottlieb, concluded in 1972, shortly before he retired, that the experiments had been “useless” — though Hollywood screenwriters might beg to differ.