Based on their findings, it would appear the suspected memory consolidation researchers were looking for what occurs in deep sleep. And part of that is figuring out which memories are worth saving, based on rewards.
In deep sleep, the hippocampus replays the day’s memories, sending them to the cerebral cortex, reinforcing those neural pathways. And the brain took much more interest in the game participants won than the one they lost.
As lead author Virginie Sterpenich explains in a news release, while the volunteers slept, they “started to ‘think’ about both games again, and then almost exclusively about the game they won when they went into deep sleep.”
As a follow-up, the participants had to recognize faces from one game, as well as get out of the maze from the other. Unsurprisingly, the more their brain imaging while sleeping showed memory consolidation, the better they performed on this follow-up task—meaning the “rewarding” memories that the brain stored were easier to recall.