Neuroscience: Impaired Decision-Making in Parkinson's Disease

Abstract

When making decisions we combine previously acquired knowledge with the available current information to optimize our choices. A new study shows that Parkinson patients are impaired in using their prior knowledge leading to suboptimal decisions when current information is ambiguous.

Figure 1. Biased decision-making.

A: The drift diffusion model [6] can explain behaviour (reaction times and accuracy rates) during simple decisions between two alternatives. Evidence accumulates from a starting point (SP) towards the boundary for choice A where the sensory evidence favours choice A over choice B. Once one of the boundaries is crossed, the decision process is terminated and the respective choice is executed. B: When there is no clear sensory evidence for either of the choices and no prior knowledge of one of the choices being more likely to be correct, participants chose option A or B with equal probability. When past experience dictates that one choice is more likely to be correct, healthy participants chose this option more frequently, even if the presented stimulus is not informative. PD patients, on the other hand, fail to implement such a bias. C: Applying the drift diffusion model indicated that healthy persons both adjusted their starting point and drift rate in order to bias their response towards the choice which was more likely to be correct. D: PD patients only adjusted their drift rate, which was insufficient to properly bias decisions according to prior knowledge when clear sensory evidence was lacking.