The activity of the brain during sleep has long fascinated scientists, and now researchers from the University of California, Los Angeles (UCLA) think they have discovered something new about the part of the brain involved in learning and memory. While asleep or under anaesthesia, this part of the brain, known as the entorhinal cortex, behaves as though it is remembering something - much like when we concentrate to remember a phone number or follow directions, the researchers said. "The big surprise here is that this kind of persistent activity is happening during sleep, pretty much all the time. These results are entirely novel and surprising. In fact, this working memory-like persistent activity occurred in the entorhinal cortex even under anesthesia," said Mayank R Mehta, a professor of neurophysics at UCLA. It has been found previously that the neocortex and hippocampus communicate with one another during sleep, which is believed to play a vital role in establishing memories. This challenges the theory that the hippocampus drives the "conversation", suggesting instead that the entorhinal cortex is driving the hippocampus. "This is a whole new way of thinking about memory consolidation theory. We found there is a new player involved in this process and it’s having an enormous impact," added Dr Mehta.