Registering a memory for the long haul doesn’t happen all at once, according to new studies of how people learn perceptual and motor skills. Instead, building memory is a three-pronged process that rests on sleep.
First, knowledge accrues during training and dips immediately afterward. A good night’s sleep then revives much of what was forgotten, the researchers find. Finally, recalling the learned skill the next day destabilizes the memory of it, setting the stage for an individual either to reinforce prior knowledge or lose it.
These findings, published in the Oct. 9 Nature, contrast with the long-standing psychological theory that lasting memories essentially form all at once and don’t require sleep.
“Memory seems to be a process of storage and restorage,” says neuroscientist Karim Nader of McGill University in Montreal in a commentary published with the new studies.
In this vein, one of the new investigations, directed by psychologist Daniel Margoliash of the University of Chicago, examined the first two proposed prongs of memory formation. The results indicate that sleep rescues memories that had begun to deteriorate the previous day.
The scientists trained 84 college students to identify a series of similar-sounding words produced by a synthetic-speech machine. Improvement in discerning new words depended on participants’ ability to recognize novel combinations of previously heard synthetic sounds.
In one set of experiments, participants underwent training in the morning. In subsequent tests that morning, the learners performed well, but tests later in the day showed that their word-recognition skill had declined. The next morning, after a full night’s sleep, however, the volunteers performed at their original levels.
Further testing revealed…