A widely used Parkinson's drug may help older people to make up their minds, research suggests.
Poor decision-making is a recognised problem of ageing that stems from an inability to learn from experiences.
Part of the decision-making process involves learning to predict the likelihood of a rewarding outcome.
That in turn implicates dopamine, a brain chemical associated both with reward responses and Parkinson's disease.
Study leader Dr Rumana Chowdhury, from the Wellcome Trust Centre for Neuroimaging at University College London, said: "We know that dopamine decline is part of the normal ageing process so we wanted to see whether it had any effect on reward-based decision-making.
"We found that when we treated older people who were particularly bad at making decisions with a drug that increases dopamine in the brain, their ability to learn from rewards improved to a level comparable to somebody in their twenties and enabled them to make better decisions."
The team, who report their findings in the journal Nature Neuroscience, used a combination of behaviour testing and brain imaging to study decision-making in 32 volunteers aged in their seventies.
Their results were compared with those from 22 individuals in their mid-20s.
Participants were asked to complete a behavioural learning task called "two-arm bandit", which mimics the decisions gamblers make while playing slot machines.
Players were shown two images and had to choose the one that they thought would give them the biggest reward. Performance was assessed by the amount of money won in the task.
Before some sessions, older volunteers were given the Parkinson's disease drug Levodopa which increases dopamine levels in the brain.
"The older volunteers who were less able to predict the likelihood of a reward from their decisions, and so performed worst in the task, showed a significant improvement following drug treatment," said Dr Chowdhury.
Brain scans showed that older participants who performed best in the gambling game before treatment had a better dopamine response.
Those who performed poorly could not adequately signal reward expectation in the brain. When this was corrected by Levodopa, their performance improved.
Dr John Williams, head of neuroscience and mental health at the Wellcome Trust, said: "This careful investigation into the subtle cognitive changes that take place as we age offers important insights into what may happen at both a functional and anatomical level in older people who have problems with making decisions.
"That the team were able to reverse these changes by manipulating dopamine levels offers the hope of therapeutic approaches that could allow older people to function more effectively in the wider community."