Rats replay scary memories during their sleep

Have you ever been warned not to watch a scary movie before going to bed, or risk having nightmares? New research may support this idea, but it may also explain why dreams can be useful for forming long-term memories. When rats are frightened in the day, the fear centers in their brains are re-activated during sleep - potentially helping to strengthen memories. When rats are frightened, the fear centers in their brains are re-activated during sleep - potentially helping to strengthen memories. The study, conducted by researchers at New York University, involved measuring the brain activity of rats as they ran around a maze.