by University of Jyväskylä

Credit: CC0 Public Domain

Soon we will once again switch to winter time, that is, we set the clocks back an hour. Switching to winter time is considered the easier of the two annual clock transitions, as we gain an hour of sleep. Some people may find the one-hour change challenging, as our sleep patterns can be momentarily disturbed.

Researchers at the Department of Psychology of the University of Jyväskylä in Finland have studied how sleep deprivation can affect an individual's learning processes. Their research focused on the hippocampus, which is especially responsible for our long-term memory.

"Certain brain phenomena related to long-term memory are most common during sleep," says associate professor Miriam Nokia. "Our interest in studying functions related to the consolidation of memory traces finally led us to examine the hippocampus during the first periods of rest and sleep following learning."

Brain activity varies in different stages of sleep

Sleep can be roughly divided into two main stages: Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep. NREM sleep takes place early in the night, while REM sleep is more common in the early morning hours. When the quality of sleep is ordinary, the different stages of sleep are repeated in cycles of about one and a half hours several times a night.

"Brain activity is very different during the NREM and REM sleep stages: during REM sleep the electroencephalogram (EEG) partly resembles wakefulness, whereas during NREM sleep, the brain mainly exhibits phenomena typical of this state, such as slow rhythmic activity," says Nokia.

Sleep disturbances affect memory performance

Several research groups internationally have tried to identify the connection between the stages of sleep and learning. Since the brain activity during NREM and REM sleep differ from each other, it has been reasonable to assume NREM and REM sleep would have different, diverging effects on the consolidation of memory traces also during rest.

The phenomenon has been studied with the help of several experiments in which people have first been taught various tasks, and then either early night (NREM) sleep or early morning hours (REM) sleep has been disturbed, and after this, the participant's memory performance has been observed. The results have been contradictory, but it seems that both stages of sleep are needed for learning different things.

One thing, however, has become obvious based on research: sleep deprivation clearly impairs learning.

"If sleep is disturbed or sleep is deprived altogether," says Nokia, "things we have previously learned will not be stored in memory as efficiently as usually."

A well-rested brain is able to meet everyday challenges more flexibly

Sleep helps us maintain our neural plasticity, and, consequently, our behavioral flexibility. Sleep affects not only the processing of past experiences, but also the way in which people are prepared to face challenges in the next waking period. A good night's rest and a well-rested brain help us find more effective solutions to everyday challenges.

Even though changing the clocks may affect our alertness and learning ability in the days that follow, Nokia and her research group have a comforting message:

"The temporary effects can be dramatic, but one or more nights of bad sleep do not permanently impair our learning ability."

Provided by University of Jyväskylä