What does the sleeping brain think about?

Using an artificial intelligence approach capable of decoding brain activity during sleep, scientists were able to glimpse what we think about when we are asleep. By combining fMRI and EEG, they provide unprecedented evidence that the work of sorting out the thousands of pieces of information processed during the day takes place during deep sleep. Indeed, the brain can evaluate all of these memories in order to retain only the most useful ones.

source https://www.sciencedaily.com/releases/2021/07/210715124527.htm