Dopamine found to restore motivation in Parkinson's sufferers

Monash University researchers have for the first time found evidence that dopamine levels in the brain can help people with Parkinson’s disease overcome cognitive apathy and achieve levels of cognitive motivation equivalent to healthy individuals.

This new research shows that dopamine can improve apathy in Parkinson’s disease by increasing the willingness of patients to engage in cognitively demanding behaviour.

Dopamine is one of the brain’s neurotransmitters – a chemical that sends signals to other nerve cells – which helps to regulate movement, learning and emotional responses to reward cues.

Parkinson’s disease is a common neurological disease that is caused by the degeneration of dopamine-producing cells in the brain. Although it is usually thought of as a disorder of movement, patients also suffer from debilitating disorders of motivation, such as apathy.

In light of World Parkinson’s Day on Thursday 11 April, Dr Trevor Chong from the Monash Institute of Cognitive and Clinical Neurosciences (MICCN) said this news is encouraging for both the medical industry and the 80,000 Australians with Parkinson’s disease.

“About 40% of patients with Parkinson’s disease suffer from apathy,” Dr Chong said.

“Our earlier work showed that dopamine plays an important part in motivating physically demanding actions. Now, we have evidence that dopamine plays a crucial role in driving cognitively effortful behaviour as well. This provides us with an important insight into the multifaceted role that dopamine plays in motivation.”

The team tested 20 patients with Parkinson’s disease on a cost-benefit decision-making task, in which they had to decide how much cognitive effort they were willing to invest in return for reward. These patients were tested across two sessions – on and off dopaminergic medication – and their performance compared to 20 healthy controls.

The aim was to explore whether patients with Parkinson’s disease were less cognitively motivated than controls and, if so, whether and how dopamine therapy impacted these outcomes.

Results showed that patients with Parkinson’s disease were less willing to invest cognitive effort when off medication relative to healthy controls. However, when the same patients were tested on dopaminergic therapy, their levels of cognitive motivation were restored to healthy levels.

“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.

The study, published in Brain, was produced by Ms Sara McGuigan, Dr Shou-Han Zhou, Dr Meadhbh Brosnan, Professor Dominic Thyagarajan, Professor Mark Bellgrove and Dr Trevor Chong.