How sleep helps us learn and memorize

Sleep is important for long lasting memories, particularly during this exam season. Research publishing in PLOS Computational Biology suggests that sleeping triggers the synapses in our brain to both strengthen and weaken, which prompts the forgetting, strengthening or modification of our memories in a process known as long-term potentiation (LTP).

Researchers led by Sidarta Ribeiro at the Brain Institute of the Federal University of Rio Grande do Norte, Brazil, measured the levels of a protein related to LTP during the sleep cycle of rats. The authors then used the data to build models of sleep-dependent synaptic plasticity.

The results show that sleep can have completely different effects depending on whether LTP is present or not. A lack of LTP leads to memory erasure, while the presence of LTP can either strengthen memories or prompt the emergence of new ones.

The research provides an empirical and theoretical framework to understand the mechanisms underlying the complex role of sleep for learning, which involves selective remembering as well as creativity.

A good night’s sleep helps modify deeply rooted attitudes

Long-held social biases can be reduced during sleep, a new report suggests.

It adds further support to recent research that has shown that memories can be selectively reactivated and strengthened during slumber.

Scientists have known that sleep boosts memory formation by resuscitating faint neuron activity shaped during earlier periods, when an individual was awake. This process can be experimentally stimulated by giving a sleeping individual cues related to an earlier period of learning.

Now, Xiaoqing Hu and colleagues extend these findings to show that this method not only works for recently learned information but also to influence implicit attitudes learned during childhood.

The researchers focused on prejudices of race and gender.

In a series of exercises designed to counter typical racial and gender biases, participants were shown pictures of men and women of different races. They learned to associate races and genders with opposing features (female faces with science-related words, for example, and black men with "good" words). A distinctive sound was associated with each type of counter-bias. The participants then took a 90-minute nap during which one sound, by random assignment, was repeatedly played to cue and reactivate a newly learned association. Shortly after waking, and again one week later, the researchers found that implicit social biases were reduced preferentially for the counter-bias training reactivated during sleep (but not for counter-biases not reactivated).

Given the implications of this research for societal change, Gordon Feld and Jan Born say in a related Perspective, the study should inspire research to solve remaining issues of targeted memory reactivation during sleep so that its mechanisms are fully understood.

Sleeping Your Way out of a Bad Attitude
This image shows sleeping your way out of a bad attitude. Implicit social bias scores could be improved by applying a counterbias intervention comprising two tasks: counterbias training with sound feedback and retrieval of the sound - counterbias association. This training - i nduced improvement was then stabilized by re - presenting the sound cue during sleep. (A) On the counterbias training, participants were shown separate pictures of men and women of different racial groups together with words from the opposing categories "sci ence/art" and "good/bad". When seeing an "incongruous" pair (e.g., face of a woman and the word "math"), participants had to respond by pressing a button. "Correct" and timely responses received a feedback sound. Congruent trials afforded no response. (B) On the sound - counterbias retrieval task, participants were instructed to drag and drop a face (e.g., a female face) onto the incongruous word (e.g., "math") whenever they heard the sound that was associated with this specific counterbias during the precedi ng counterbias training. (C) The sound was then used to cue, and thereby reactivate, the memory of the newly learned counterbias association when the participant entered slow - wave sleep during a subsequent 90 - min nap. (D) A stable reduction of implicit soc ial bias, persisting 1 week later, was only achieved if the counterbias intervention was cued during the nap.
Credit: P. Huey/Science