A new study has found that a drug used to treat Parkinson’s Disease can help reverse age-related impairment in decision making in some older people.
The study from researchers at the Wellcome Trust Centre for Neuroimaging also describes changes in the patterns of brain activity of adults in their 70s that may help explain why they are worse at making decisions than younger people.
According to researchers, poor decision-making is a natural part of the aging process. It stems from a decline in our brain’s ability to learn from our experiences. Part of the decision-making process involves learning to predict the likelihood of getting a reward from the choices we make.
An area of the brain called the nucleus accumbens is responsible for interpreting the difference between the reward we’re expecting to get from a decision and the reward that is actually received. These “prediction errors” reported by the brain chemical dopamine help us learn from our actions and modify our behavior to make better choices the next time.
“We know that dopamine decline is part of the normal aging process, so we wanted to see whether it had any effect on reward-based decision making,” explained Dr. Rumana Chowdhury, who led the study at the Wellcome Trust Centre for Neuroimaging at University College London.
“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 20s and enabled them to make better decisions.”
The researchers used a combination of behavioral testing and brain imaging techniques to investigate the decision-making process in 32 healthy volunteers in their early 70s compared with 22 volunteers in their mid-20s.
The 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 behavioral learning task called the 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. Their performance before and after drug treatment was assessed by the amount of money they won in the task.
“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 researchers then looked at brain activity as the participants played the game using functional Magnetic Resonance Imaging (fMRI). They measured connections between areas of the brain that are involved in reward prediction using a technique called Diffusor Tensor Imaging (DTI).
The findings revealed that the older adults who performed best in the gambling game before drug treatment had greater integrity of their dopamine pathways, according to the researcher. Those who performed poorly before drug treatment were not able to adequately signal reward expectation in the brain. When this was corrected by L-DOPA, their performance improved.
“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,” said Dr. John Williams, head of Neuroscience and Mental Health at the Wellcome Trust.
“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.”
The study was published in the journal Nature Neuroscience.
Source: Wellcome Trust