There is now hope for people who are always losing their belongings.
It may be unorthodox, but jangling a set of keys next to someone as they sleep could help someone remember where they have put their own house keys or car key.
Playing them footsteps could help them remember where they left their shoes, and hearing a car engine could help them figure out where they parked the car when they got home last night.
Experts believe hearing sounds linked to objects helps reactivate the memory of where those objects are, storing that knowledge more efficiently in the brain.
There is now hope for people who are always losing their belongings. It may be unorthodox, but jangling a set of keys next to someone as they sleep could help someone remember where they have put their own house keys or car key
A small study of five people tested the theory by showing people objects like shoes and cars on a screen while playing them related sounds.
When they were played the same sounds as they slept, they remembered the location of the objects far better the next morning.
Their memory of where things were was 36 per cent better on average when they were played a sound prompt in their sleep compared to a random sound.
Brain scans showed activity in the hippocampus and cortex, as people were played the sounds, which suggested their memory was being resurrected and strengthened.
Professor Ken Paller, senior author of the study, from Northwestern University, said: ‘Whereas this method helped people remember locations of things — cars, shoes, and various other objects we’ve used in prior studies, like keys — the evidence is that sleep helps people with remembering all sorts of facts and events.
‘That is because memories are revisited when we sleep, even though we wake up not knowing it happened.’
The study, published in the journal Proceedings of the National Academy of Sciences, looked at five people with epilepsy, who had electrodes implanted in their brain to investigate their seizures.
This showed the effect on the brain of trying to re-trigger memories with sounds at night.
Generally, people forget things after several hours have passed, which is why it can be so hard to locate an item the next morning after putting it down at night.
Indeed, people asked to remember where objects were on a screen were accurate within 4.4cm after learning their position at night, but accurate only within 5.1cm on average the next morning.
However people replayed sounds linked to the objects, like the sound of shoes, saw a three per cent improvement on average in their memory of where those objects were the next day.
That compared to a 33 per cent reduction in memory, on average, when played random sounds as they slept.
The researchers played 10 to 20 sounds quietly, so as not to wake people up.
They found an increase in brainwaves within the gamma frequency, suggesting these brainwaves play a crucial role in helping sleeping people remember where they have put their belongings.
The research was conducted to understand how important sleep is for consolidating memories and making them stronger and longer lasting.
