Choosing your memories: How your brain decides which to keep.

When we sleep we encode all the information we have gathered during the day and store it as memory.

But how does our brain choose which are the memories best for us to keep? We store lots of memories initially, but many of them serve us little purpose to keep in longer term storage and are quickly discarded.

It turns out that our brain selectively retains that information that is more likely to be relevant or useful to us in the future, while we are asleep.

A team from Germany set up a study to look at the selection process the brain has in place to achieve this. A total of 191 participants were divided into two groups. The first group were given the task of learning 40 pairs of words. Those in the second group played a card game matching pictures of animals and objects and practised series of finger tapping.

In both groups, half were then advised they would be tested again after a 10-hour period. Actually all of the participants were tested. Some of the participants were allowed to sleep in the interval before being tested and not surprisingly, the sleepers performed better in the testing than those who hadn’t slept.

Of those given the option to sleep and be told they would be retested, scored the highest of all the participants.

EEG recording from the sleeping group who had the expectation of being retested showed an increase in brain activity in deep or “slow wave “ sleep.

The researchers believe that our prefrontal cortex (the executive suite of higher thinking skills) distinguishes our memories while we are awake into which are more relevant to us for future needs. During sleep our hippocampus (the specialised area of our brain involved in learning and memory) then consolidates the preselected memories.

Which means the difference in that we are more likely to remember a scheduled appointment or a change to our travel itinerary rather than what we discussed about the weather to a neighbour.

This study also serves to remind us of the enormous value sleep plays in helping us to learn more effectively.