It’s a bit like sorting out photos and videos on your phone. Storing images requires a lot of memory, so when your phone starts to get full, you have to edit them. Removing dud videos and photos leaves space for new ones.
Even compared to a modern computer, your brain can store an extraordinary amount of data; a recent estimate puts its storage capacity at around 1000 terabytes, which is a billion megabytes. A computer with that capacity could store around 2 billion books or 500,000 films. Yet while you have an awesome capacity to remember things, you don’t want to store more junk up top than necessary. So during the night, the memories that are considered important are shifted from the hippocampus (the short-term storage area of the brain) to the safety of the prefrontal cortex (the long-term storage area of the
