The memory of older people has been returned to the state of someone in their 20s for the first time by applying electrical stimulation to the brain to reconnect faulty circuits.

Scientists at Boston University in the US have proven it is possible to restore working memory by ‘recoupling’ areas of the brain which have become out-of-sync as people grow older.

Short-term working memory is crucial for everyday life, storing information for around 10 - 15 seconds to allow problem solving, reasoning, planning and decision making, allowing someone, for example, to keep a telephone number in mind while writing it down.

Sometimes described as being ‘mentally online’ working memory forms the basis of consciousness, but declines with age and is the reason elderly people struggle with basic tasks, such as remembering why they entered a room.

Now scientists believe they have uncovered what causes the decline and how to reverse it. Two areas in the brain, the prefrontal and temporal cortex must be talking to each other correctly for working memory to function well.

When they fired electrical currents of the same frequency at the areas, older people were able to carry out working memory tasks with an accuracy comparable with people in their 20s.