Waking up at night enhances your memory

Brief awakenings may be a sign you've slept well.

The study from the University of Copenhagen, done on mice, found that the stress transmitter noradrenaline wakes up the brain many times a night. These "microarousals" were linked to memory consolidation, meaning they help you remember the previous day's events. In fact, the more "awake" you are during a microarousal, the better the memory boost, the research suggests.

The findings add insight to what happens in the brain during sleep and may help pave the way for new treatments for those who have sleep disorders.

The noradrenaline levels rise and fall like waves every 30 seconds during non-rapid eye movement (NREM) sleep. At each "peak" the brain is briefly awake, and at each "valley" it is asleep. Typically, these awakenings are so brief that the sleeping subject does not notice. But the higher the rise, the longer the awakening - and the more likely the sleeper may notice.

During the valleys, or when norepinephrine drops, so-called sleep spindles occur.

The amount of the super-boosts of sleep spindles, and not REM sleep, defines how well you remember the experiences you had prior to going to sleep.

Deep valleys were followed by longer awakenings, the researchers observed. So, the longer the valley, the longer the awakening - and the better the memory boost. This means that, though restless sleep is not good, waking up briefly may be a natural part of memory-related sleep phases and may even mean you've slept well.