In 2371, the USS Voyager was struck by a kinoplasmic radiation surge from a subspace anomaly. This caused a malfunction in The Doctor's program, causing him to experience an elaborate delusion in which he was Lewis Zimmerman, and Voyager was the hologram.
In the delusion, Reginald Barclay claimed that Zimmerman had become trapped in the Voyager program due to a kinoplasmic surge on Jupiter Station, and that the radiation was causing neurocellular deterioration in his brain. Thus, Barclay urged Zimmerman to destroy Voyager, to end the program and save his life. (VOY: "Projections")