Poster Session D, Monday, March 25, 8:00 – 10:00 am, Pacific Concourse
Use of Bayesian Priors in Perceptual Decision-Making in Clinical Subtypes of Parkinson’s Disease
Barbara Knowlton1, Vaibhav Thakur1, Alessandra Perugini1, Aasef Shaikh2, Michele Basso1; 1UCLA, 2Case Western Reserve University
Patients with Parkinson’s disease (PD) have been shown to be impaired at incorporating priors in perceptual decision-making. Because PD is a heterogeneous disorder, we investigated whether this impairment is consistent across two major subtypes of the disease, Bradykinetic and Tremor Dominant. In the perceptual decision-making task, participants were shown a pattern on the screen on each trial and decided if the dots were oriented leftward or rightward. The coherence of the orientation signal varied across stimuli, affecting the difficulty of the trial. Stimuli were presented in green or red, and each color had different prior probabilities. For one color, the stimuli were equally likely to be leftward or rightward oriented, and for the other, the prior probabilities were unequal (e.g. 75% leftward, 25% rightward). Each subject performed the task twice, off and on prescribed dopaminergic medication to examine its effect on their performance. To assess whether priors were applied, we examined the value of the psychometric function at the zero coherence condition when the stimulus was fully ambiguous. We found that both groups showed an impairment in applying priors when off medication, as choice probability at zero coherence was unaffected by the prior probabilities. However, on medication, Bradykinetic patients were able to incorporate the priors such that choice probability at zero coherence differed for the equal and unequal prior conditions. However, Tremor Dominant patients in the “on” state showed no such improvement. These results suggest that the relationship between dopaminergic tone and cognition differs for PD subtypes.
Topic Area: PERCEPTION & ACTION: Other