Cognitive effects of Parkinson's disease: Automated tasks easier, but task switching difficult

"We often think of Parkinson's disease as being a disorder of motor function," says Douglas Munoz, director of the Queen's Centre for Neuroscience Studies and a Canada Research Chair in Neuroscience. "But the issue is that the same circuit can affect more cognitive functions like planning and decision-making."

The researchers conducted an experiment using a sample of Parkinson's patients and a control group. When asked to look at a light when it came on, people with Parkinson's responded with greater accuracy than people without the disease. But when asked to change that behavior -- to look away from the light, for instance -- Parkinson's patients struggled. Even when asked to simply prepare to change their behaviour, people with the disease found it incredibly difficult to adjust their plans.

PhD student Ian Cameron, lead author of the study, says the findings are significant because they highlight how biased Parkinson's patients are towards performing an automated response. It also suggests that medications currently prescribed to treat the symptoms of the disease that affect motor functioning could further upset a patient's cognitive balance.

Mr. Cameron is now conducting functional brain imaging in Parkinson's patients to determine which parts of the brain are affected by medications currently used to treat the symptoms of the disease.

The findings were recently published in Neuropsychologia, an international interdisciplinary journal of cognitive and behavioural neuroscience.