Study finds cognitive link between dopamine, Parkinson’s

An Australian study suggests that dopamine treatment could reduce apathy in Parkinson’s disease and other neurological disorders including dementia.

An Australian study suggests that dopamine treatment could reduce apathy in Parkinson’s disease and potentially other neurological disorders including dementia, a researcher says.

Trevor Chong

Dr Trevor Chong from the Monash Institute of Cognitive and Clinical Neurosciences led the study into dopamine and apathy in Parkinson’s patients, which is published in the current edition of the journal Brain.

Dopamine is a chemical that sends signals to the brain linked to movement, learning and emotional responses.

Parkinson’s disease is caused by the degeneration of dopamine-producing cells in the brain. As well as affecting movement, it can also cause apathy and a debilitating lack of motivation.

Dr Chong’s research suggests that dopamine can increase motivation by enhancing the willingness of people with Parkinson’s to engage in conitively demanding behavious.

About 40 per cent of Parkinson’s patients suffer from apathy, Dr Chong says.

“Traditionally Parkinson’s disease is thought of as a disorder of movement,” he told Community Care Review.

“But increasingly we’ve found that patients with Parkinson’s disease also suffer a lot of motivational impairments, like apathy. These traditionally have been quite under-recognised and there haven’t been very good ways of assessing it, measuring it and understanding its neurobiology.

“So we did in this most recent study was we took a sample of patients with Parkinson’s disease and examined the extent to which they .. couldn’t be bothered investing effort into a cognitive task.

“What we found was that compared to aged-matched controls, patients with Parkinson’s disease were less willing to invest cognitive or mental effort in pursuit of a particular goal.”

Earlier research has demonstrated the role of dopamine in motivating physically demanding actions, he says, but this study now provides evidence that it plays a crucial role in driving cognitive behaviour as well.

The team tested 20 patients, both on and off dopamine medication. The results showed the patients were less willing to invest in cognitive effort when they were off the medication.

“This is good news for patients with Parkinson’s disease, and emphasises the importance of dopamine medication in treating, not just the motor symptoms, but also the motivational problems that are a prominent part of the disease,” Dr Chong said.

Practical implications

Dr Chong says dopamine drugs are already used to treat motor symptoms in Parkinson’s, but his team’s research shows it was also important in treating cognitive factors.

“So it’s another reason to be on the dopamine treatment,” Dr Chong says.

However, the research suggested that dopamine could also be useful in treating other neurological conditions where apathy can be common, including dementia, traumatic  brain injury or stroke.

“We don’t have the data on that, but the implications of the study is that perhaps we should be looking more broadly at the role of dopamine in apathy in those settings as well,” he said.

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