Findings from the University of Geneva could benefit educators.

A new study suggests that receiving rewards as you learn can help cement new facts and skills in your memory, particularly when combined with a daytime nap.

The findings from the University of Geneva, to be published in the journal eLife, reveal that memories associated with a reward are preferentially reinforced by sleep. Even a short nap after a period of learning is beneficial.

“Rewards may act as a kind of tag, sealing information in the brain during learning,” says lead researcher Dr Kinga Igloi from the University of Geneva.

“During sleep, that information is favourably consolidated over information associated with a low reward and is transferred to areas of the brain associated with long-term memory.”

“Our findings are relevant for understanding the devastating effects that lack of sleep can have on achievement,” she says.

Thirty-one healthy volunteers were randomly assigned to either a sleep group or a ‘wake’ group and the sensitivity of both groups to reward was assessed as being equal. Participants’ brains were scanned while they were trained to remember pairs of pictures. Eight series of pictures were shown and volunteers were told that remembering pairs in four of them would elicit a higher reward.

Following a 90-minute break of either sleep or rest, they were tested on their memory for the pairs and asked to rate how confident they were about giving a correct answer. Participants were also asked to take part in a surprise test of exactly the same nature three months later.

Both groups’ performance was better for highly rewarded picture pairs, but the sleep group performed better overall. Strikingly, during the surprise test three months later participants who had slept after learning were selectively better for the highly rewarded pairs.

The people who slept were also more confident of achieving a correct answer during the memory tests, even after three months.

The MRI scans revealed that the sleep group experienced greater activity of the hippocampus, a small area of the brain critical for forming memories. This correlated with a higher number of bursts of brain activity called slow spindles. After three months, the sleep group also showed increased connectivity between the hippocampus, the medial prefrontal cortex and the striatum, areas of the brain implicated in memory consolidation and reward processing.

“We already knew that sleep helps strengthens memories, but we now also know that it helps us select and retain those that have a rewarding value,” says Igloi.

“It makes adaptive sense that the consolidation of memory should work to prioritise information that is critical to our success and survival.”

About this neuroscience and learning research

Source: Zoe Dunford – eLife

Image Credit: The image is credited to Psy3330 W10 and is licensed CC BY-SA 3.0

Original Research: Abstract for “A nap to recap or how reward regulates hippocampal-prefrontal memory networks during daytime sleep in humans” by Kinga Igloi, Giulia Gaggioni, Virginie Sterpenich, and Sophie Schwartz in eLife. Published online October 16 2015 doi:10.7554/eLife.07903

Abstract

A nap to recap or how reward regulates hippocampal-prefrontal memory networks during daytime sleep in humans

Sleep plays a crucial role in the consolidation of newly acquired memories. Yet, how our brain selects the noteworthy information that will be consolidated during sleep remains largely unknown. Here we show that post-learning sleep favors the selectivity of long-term consolidation: when tested three months after initial encoding, the most important (i.e., rewarded, strongly encoded) memories are better retained, and also remembered with higher subjective confidence. Our brain imaging data reveals that the functional interplay between dopaminergic reward regions, the prefrontal cortex and the hippocampus contributes to the integration of rewarded associative memories. We further show that sleep spindles strengthen memory representations based on reward values, suggesting a privileged replay of information yielding positive outcomes. These findings demonstrate that post-learning sleep determines the neural fate of motivationally-relevant memories and promotes a value-based stratification of long-term memory stores.

“A nap to recap or how reward regulates hippocampal-prefrontal memory networks during daytime sleep in humans” by Kinga Igloi, Giulia Gaggioni, Virginie Sterpenich, and Sophie Schwartz in eLife. Published online October 16 2015 doi:10.7554/eLife.07903

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