How sleeping helps us learn
Most scientists believe that sleep plays an important role in memory. Getting a good night’s sleep after learning something new seems to help you remember it later, whether it is a new motor skill (like a series of repetitive movements) or a new cognitive skill (like memorizing a poem). The way the brain processes and stores these two types of learning (implicit or explicit) is important to understanding how our brains work with implications for learning, education, and the treatment of diseases involving memory loss.
Knowing that sleep plays a role in all of this is one thing. Understanding exactly how this happens in the brain is another. New research from Edwin Robertson at the University of Glasgow and Jocelyn Breton at the University of California, Berkeley helps clarify the role sleep plays in these two different types of learning.
Participants in the study were asked to play a game like the electronic memory game Simon. They had to push a button on a keyboard that corresponded to one of 4 possible positions of a circle on their screen. All participants received the same 12-item long repeating sequence. In the first group (the explicit learning group), the participants were told that they should try to learn the sequence and were given clues to when the sequence would begin again. In the second group (the implicit learning group) the participants were simply told to push the keys correctly as quickly as possible.
The researchers then used a technique called Transcranial Magnetic Stimulation (TMS) that allows them to temporarily turn off specific neural circuits in the brain to test the role of two circuits in storing the sequence in the brain. After a night of sleep, the participants were then tested to recall as much of the sequence as possible. The researchers found that two independent brain circuits mediate the improvement in explicit and implicit learning that typically occurs with sleep. When the participants learned a skill through the repetitive motion alone, the memory was learned through a circuit in the inferior parietal lobe. When they learned by consciously trying to remember the sequences, the learning was stored through a different circuit in the primary motor cortex. This suggests that awareness of learning, even the same sequence, can alter the circuit supporting learning and subsequent memory enhancement over sleep. Overall, the same memory enhancement over a night of sleep can be achieved through different circuits.
This work was published this week in Nature Human Behaviour.