You know people, or perhaps you are one yourself, that continually replays an event from the past. Sometime it can lead to alcohol or drug abuse, but even when it doesn't, that type of fixation is unhealthy. My advice to friends and colleagues troubled with such thoughts is to not think about it unless there is something you can do about it.
Mental Replay in Memory and Learning tells that neurons replay previous experiences in short bursts called sharp-wave ripples (SWRs). These occur during periods of brain inactivity such as sleep or texting. These SWRs primarily occur in the brain's hippocampus.
Researchers at the University of California - San Francisco, experimented with rats exposed to a testing track. Proper decisions through the maze were rewarded. The rats were implanted with electrodes to determine when periods of SWRs would occur. One group of rats had their SWRs interrupted, whereas the other group did not.
The rats without the benefit of SWRs performed displayed much poorer memory and performance in negotiating the maze. Researchers plan to continue their testing to discover more about memory and learning.