Decisive despite Parkinson’s
Dopamine regulates our motivation, mood, and drive — and thus also our learning and decision-making abilities. In Parkinson's disease, a progressive dopamine deficiency plays a central role. In a new study, researchers from HMU Health and Medical University and TU Darmstadt have now examined the connection between decision-making processes and the administration of dopamine-enhancing medications in more detail. Their findings have been published in the renowned journal Science Advances.
Parkinson's disease is not only characterized by motor symptoms; as the disease progresses, a person's ability to make decisions and learn is also impaired. Picture: javier - stock.adobe.com
Bernstein member involved: Matthias Guggenmos
The starting point for the study was the bachelor’s thesis of HMU graduate Martha Sterf. Together with her,Prof. Dr. Björn Meder, Prof. Dr. Matthias Guggenmos (both HMU) and Prof. Dr. Charley Wu (TU Darmstadt) investigated why people with Parkinson’s disease apparently have particular difficulty deciding when to explore a new possibility and when it is better to rely on known options based on experience.
The study draws on TU Darmstadt’s strengths in the field of computer-aided modelling to address key societal questions regarding the mechanisms and potential treatments for Parkinson’s disease. This expertise also shapes the Cluster of Excellence ‘The Adaptive Mind’ (TAM), which explores the balance between stability and adaptation and seeks new approaches to understanding and computationally modelling human perception, thinking, decision-making, action and learning.
Effect of dopaminergic medication on decision-making processes
“Parkinson’s disease not only causes motor symptoms, but also impairs decision-making and learning abilities as the disease progresses. In our study, we investigated whether Parkinson’s medications such as levodopa can support cognitive processes beyond treating motor symptoms, processes that are important for goal-oriented learning and decision-making,” explains Martha Sterf.
Performance enhancement through levodopa
The study participants were tasked with accumulating as many points as possible on a virtual game board through repeated decisions. They could either reselect previously successful options or explore new, unknown options. Three groups were compared: Parkinson’s patients after taking the medication levodopa, patients immediately before their next medication dose, and an age-matched control group. Björn Meder explained: “We found that the group without current medication chose an excessive number of new options and underutilized previously identified good options. In contrast, patients who had taken the medication performed significantly better and exhibited decision-making behavior more closely resembling that of the control group.”
Dopamine is an important indicator
Computer-aided model analyses suggest that this behavior cannot be explained simply by random decisions. Rather, it appears that patients without medication overestimated the potential value of uncertain, unknown options and used the task structure less effectively to draw conclusions about new situations from past experiences. Charley Wu from TU Darmstadt explains: “We all experience this tension in numerous everyday decisions. For example: Should I stick with my favorite pizza or choose a new dish? Dopamine is an important indicator in these decisions. Those who cling too tightly to the familiar may overlook better alternatives. Conversely, those who try too many new things don’t make sufficient use of successful experiences.”
Matthias Guggenmos concludes: “The study shows that dopamine plays an important role in weighing up new and familiar decision options. Parkinson’s medications such as levodopa can therefore also support important cognitive processes.”
