A team of researchers experimented with fruit flies and found that by genetically engineering some flies, they were able to give those flies the "memory" of pain that they never actually experienced. It's kind of complicated and kind of creepy.
Basically, and I use the word loosely, the researchers understand that fruit flies are able, to a degree, to avoid things that have caused them pain in the past (in this case, they were electrically shocked when flying into a specific area). But then the researchers genetically engineered some flies so that their dopamine-producing brain cells manufacture a laser-sensitive protein. When shone with a laser in a particular area, though the stimulation produced no pain, the flies avoided that area with almost the exact same frequency as they had when there was pain involved. Says one of the researchers:
Miesenböck concludes that stimulating dopamine release in these 12 neurons has the same effect as applying electric shocks to flies. In other words, these flies feared that [area] as if they had been conditioned to associate an electric shock with it. "Stimulating just these neurons gives the flies a memory of an unpleasant event that never happened," he says.
And as for what I know you're all wondering: Can this experiment be extended to humans? Well, maybe, and maybe not. A biochemical researcher named Wayne Sossin points out that it's sort of unethical to genetically engineer humans, making the hypothesis pretty difficult to test, and that the original fruit fly test only works for short-term, not long-term, memory. So false memories of the sort we expect from sci-fi (or should I say syfy? Answer: I should not) may not be immediately forthcoming. [NewScientist]