Parkinson's drug helps older people to make decisions

A drug widely used to treat Parkinson's disease can help reverse age-related impairments in decision making in some older people, a new study has found.

UK researchers described changes in the patterns of brain activity of adults in their seventies that help to explain why they are worse at making decisions than younger people.

Poorer decision-making is a natural part of the ageing process that stems from a decline in our brains' ability to learn from our experiences.

An area of the brain called the nucleus accumbens is responsible for interpreting the difference between the reward that we're expecting to get from a decision and the reward that is actually received.

These so called 'prediction errors', reported by a brain chemical called dopamine, help us to learn from our actions and modify our behaviour to make better choices the next time.

"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," said Dr Rumana Chowdhury, who led the study at the Wellcome Trust Centre for Neuroimaging at University College London (UCL).

"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," she said.

The team used a combination of behavioural testing and brain imaging techniques, to investigate the decision-making process in 32 healthy volunteers aged in their early seventies compared with 22 volunteers in their mid-twenties.

Older participants were tested on and off L-DOPA, a drug that increases levels of dopamine in the brain. L-DOPA, more commonly known as Levodopa, is widely used in the clinic to treat Parkinson's.

The participants were asked to complete a behavioural learning task called the two-arm bandit, which mimics the decisions that 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.

"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," Chowdhury said.

The findings published in the journal Nature Neuroscience, reveal that the older adults who performed best in the gambling game before drug treatment had greater integrity of their dopamine pathways.

Older adults who performed poorly before drug treatment were not able to adequately signal reward expectation in the brain - this was corrected by L-DOPA and their performance improved on the drug.