London, July 14 (IANS): Sleep deprivation for half a night can make it hard for you to access memories in stressful situations the next day, says a study.

Apart from helping form long-term memory, sleep also ensures access to it during times of cognitive stress, the results said.

It is well known that during sleep newly-learned information is transferred from short-term to long-term memory stores in humans.

"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," said Jonathan Cedernaes, researcher at the Department of Neuroscience, Uppsala University.

In the study published in the journal SLEEP, researchers probed the role of nocturnal sleep duration for this memory transfer, and how long-term memories formed by sleep remain accessible after acute cognitive stress.

Following a learning session in the evening during which 15 participants learned 15 card pair locations on a computer screen, in one experimental session subjects slept for half a night (4-hour) and in the other for a full night (8-hour).

Next morning, the researchers found that half a night of sleep (4-hour) was as powerful as a full night of sleep (8-hour) to form long-term memories for the learned card pair locations.

Stress had an impact on the participants' ability to recall these memories.

The men were acutely stressed for 30 minutes in the morning after a half or full night of sleep.

Following short sleep, this stress exposure reduced their 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.

"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," Cedernaes said.