April 21 : A recent study has found that relational memory is dependent on taking a break from studies and learning, and particularly getting a good night’s sleep.

Relational memory is the capability to make logical “big picture” inferences from dissimilar pieces of information.

The study was conducted by researchers at Beth Israel Deaconess Medical Center (BIDMC) and Brigham and Women’s Hospital (BWH).

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

Adds lead author Jeffrey Ellenbogen, MD, a postdoctoral fellow at HMS and sleep neurologist at BWH, “People often assume that we know all of what we know because we learned it directly. In fact, that’s only partly true. We actually learn individual bits of information and then apply them in novel, flexible ways.”

Earlier research by Walker and colleagues had shown that sleep dynamically recovers task-oriented “procedural memory”, for instance, learning to talk, to coordinate limbs, musicianship, or to play sports.

The researchers examined 56 healthy college students, each of whom was given five pairs of unknown abstract patterns – colourful oval shapes resembling Faberge’ eggs.

The students were then told that some of the patterns were “correct” while others were “incorrect,” for example, Shape A wins over Shape B, Shape B wins over Shape C, and so on. All of the students learned the individual pairs but were not told that there was a secreted “hierarchy” linking all five of the pairs together.

After a 30-minute study period, the students were separated into three groups to assess 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. Additionally, around half of the students in Group Two slept during the 12-hour period, while the other half remained awake, while all of the students in Group Three had a full night’s sleep.

The test results showed remarkable disparity among the three groups, particularly between the students who slept for a while and those who remained awake.

“Group One, the students who were tested soon after their initial learning period, performed the worst,” says Walker. “While they were able to learn and recall the component pieces [for example, Shape A is greater than Shape B, Shape B is greater than Shape C] they could not discern the hierarchical relationships between the pieces [Shape A is greater than Shape C] – they couldn’t yet see ‘the big picture.’”

Conversely, Groups Two and Three, established a comprehensible understanding of the interrelationship between the pairs of shapes.

“These individuals were able to make leaps of inferential judgment just by letting the brain have time to unconsciously mull things over,” he says.

But, perhaps the most noteworthy fact, he adds, was when the inferences were predominantly complicated; the students who had had periods of sleep in between learning and testing, considerably outperformed the other groups.

“This strongly implies that sleep is actively engaged in the cognitive processing of our memories,” notes Ellenbogen. “Knowledge appears to expand both over time and with sleep.”

“These findings point to an important benefit [of sleep] that we had not previously considered. 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. And this may, in fact, turn out to be the primary goal of sleep: You go to bed with pieces of the memory puzzle, and awaken with the jigsaw completed,” Walker concluded. (ANI)