Researchers from Uppsala University, Sweden, investigated the role of sleep duration for memory transfer, and how long-term memories formed by sleep remain accessible after acute cognitive stress.
They discovered sleep not only helps to form long-term memory but it also ensures access to memories during times of cognitive stress.
The study, by sleep researchers Drs. Jonathan Cedernaes and Christian Benedict, appears in the journal SLEEP.
The novel experiment included a learning session in the evening during which 15 participants learned 15 card pair locations on a computer screen. Following this, one group of experimental session subjects slept for half a night (four hour) while another group slept for a full night (eight hour).
The next morning subjects were asked to recall as many card pair locations as possible.
Perhaps as a surprise, researchers discovered half a night of sleep (four hour) was as powerful as a full night of sleep (eight hour) to form long-term memories for the learned card pair locations.
However, the study also revealed that stress had an impact on the participants’ ability to recall these memories.
This was demonstrated in another part of study in which the men were acutely stressed for 30 minutes in the morning after a half or full night of sleep (for example by having to recall a newly learnt list of words while exposed to noise). Afterwards, researchers discovered this stress reduced participants ability to recall these card pair locations by around 10 percent.
In contrast, no such stress-induced impairment was seen when the same men were allowed to sleep for a full night.
“On the basis of our study findings, we have two important take home messages: First, even though losing half a night of sleep may not impair memory functions under baseline conditions, the addition of acute cognitive stress may be enough to lead to significant impairments, which can possibly be detrimental in real-world scenarios.
“Second, interventions such as delaying school start times and greater use of flexible work schedules, that increase available snooze time for those who are on habitual short sleep, may improve their academic and occupational performance by ensuring optimal access to memories under stressful conditions,” said Cedernaes.
“An important next step will be to investigate how chronic sleep loss and or more chronic stress may interact to impair the ability to retrieve memories that are consolidated during sleep,” he said.
Source: Uppsala University/EurekAlert