Yuka Sasaki, Brown University – Sleep and Learning

How have you been sleeping?

Yuka Sasaki, research professor in the department of cognitive, linguistic and psychological sciences at Brown University, examines how sleep and learning are connected.

Yuka Sasaki, PhD is a research Professor in Cognitive, Linguistic & Psychological Sciences at Brown University. Her research aims to understand functions and sleep and the human brain plasticity.

Yuka earned her PhD in psychology from Waseda University in Japan.

Sleep and Learning

Our lab studies how beneficial sleep is to brain functions. We all know sleep is important. But how important it is remains mysterious. 

Sleep is divided into two stages, non-rapid eye movement sleep, or non-REM sleep, and REM sleep.

Our recent studies investigated whether non-REM sleep and REM sleep play the same role in learning. We asked young volunteers to do training to improve vision and then to have a nap for about an hour. While they were asleep, we measured their brain activation using both polysomnography and magnetic resonance spectroscopy.

Polysomnography shows whether volunteers are asleep and if so, whether they are in non-REM sleep or REM sleep.

Magnetic resonance spectroscopy measures the concentrations of excitatory and inhibitory neurotransmitters in the visual cortex.

This information is crucial for us because the balance between the excitatory and inhibitory neurotransmitters would tell us whether the brain is plastic, that is in a state of being easy to change, or stable, in a state of being hard to change.

We found that during non-REM sleep, the brain became more plastic than during wakefulness, the amount of learning on the visual task was larger after sleep, compared to before sleep, without any additional training. In contrast, during REM sleep, the brain became more stable and made the learning protected from being replaced by new learning. When volunteers did not experience REM sleep after non-REM sleep, learning was not protected and replaced by new learning.

In summary, non-REM sleep and REM sleep play different but complementary roles in making learning better and stronger.