User blog comment:Commdor/Gamestop Spills From Ashes screenshots/@comment-4118072-20120224202309/@comment-2094653-20120225204448

I tend to agree with Commdor here. While I would have liked to continuously blast collectors in the face in addition to all the new husk like enemies (still sad about adjutants being cut but I digress), the flashback theory does indeed seem the most probable. A prothean artifact triggers a vision in Shepard's mind of The Prothean fighting off Collectors(Prothean Husks)  and the fight results in The Prothean  going into his deep sleep.