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.