- See Flashback for the Voyager episode / novel.
A flashback is a phenomenon in which a person has a sudden, intense recollection of a past experience. The experiences recalled are often traumatic in nature, and are so vivid that the person having the flashback relieves the experience.
Doctor Audrea Benar, who had survived Romulan captivity once suffered a flashback on the surface of Temaris. In this flashback, she believed that she was back at the Romulan prison camp, attempting to escape, and that the Romulan approaching her was Reelan, who was the commander of the prison camp. She was stopped by Hikaru Sulu before she could seriously injure Dajan. (TOS novel: Probe)
The Banean people of the Delta Quadrant had a very advanced medical technology. This enabled them to implant memories into the minds of others. The technique was employed as a method of punishment, requiring convicted murders to relieve the last moments of their victim's life for the remainder of their lives. The person would have flashbacks of these memories every 14 hours. (VOY episode: "Ex Post Facto")
While infected with a virus that disguised itself as a memory engram, Tuvok suffered from flashbacks of himself as a child, holding on to another child hanging over the edge of a cliff. The Doctor soon discovered the virus, and used radiation to eliminate it from Tuvok's system. (VOY episode: "Flashback")