Picture: A jigsaw 
To see how the separate pieces
are associated a good night´s
sleep is helpful; © SXC

“Relational memory is a bit like solving a jigsaw puzzle,” explains senior author Matthew Walker, PhD, Director of the Sleep and Neuroimaging Laboratory at Beth Israel Deaconess Medical Center (BIDMC). “It’s not enough to have all the puzzle pieces – you also have to understand how they fit together.”

The researchers tested 56 healthy college students, each of whom was shown five pairs of unfamiliar abstract patterns – colourful oval shapes resembling Faberge’ eggs. The students were then told that some of the patterns were correct while others were incorrect. All of the students learned the individual pairs but were not told that there was a hidden “hierarchy” linking all five of the pairs together.

After a 30-minute study period, the students were separated into three groups to test their understanding of the larger “big picture” relationship between the individual patterns: Group One was tested after a period of 20 minutes; Group Two was tested after a 12-hour period; and Group Three was tested after a 24-hour time span. In addition, approximately half of the students in Group Two slept during the 12-hour period, while the other half remained awake. All of the students in Group Three had a full night’s sleep.

“Group One, the students who were tested soon after their initial learning period, performed the worst,” says Walker. “They could not discern the hierarchical relationships between the pieces.” Groups Two and Three, on the other hand, demonstrated a clear understanding of the interrelationship between the pairs of shapes.

“This strongly implies that sleep is actively engaged in the cognitive processing of our memories,” notes lead author Jeffrey Ellenbogen. “Knowledge appears to expand both over time and with sleep. Sleep not only strengthens a person’s individual memories, it appears to actually knit them together and help realize how they are associated with one another.”

MEDICA.de; Source: Beth Israel Deaconess Medical Center