The Neural Basis of Coordination in Social Decision-Making: Evidence from Lewy Body Spectrum Disorder (IN4-1.010)

Abstract

Objective: Demonstrate that patients with Lewy body spectrum disorder (LBSD), including Parkinson9s disease (PD), PD dementia (PDD), and dementia with Lewy bodies (DLB), have impaired decision-making related to frontal/executive dysfunction. Background Individuals often coordinate with each other when making decisions. For example, we provide a less typical boy9s name in a random list ( John =9%) than when instructed to coordinate responses with another participant ( John =50%; Mehta, 1994). We propose that coordination is supported by a probabilistic mechanism that evaluates the likelihood of a response (e.g., John is more frequent than Alfred ) and a hierarchical control mechanism that models a partner9s response (e.g., I think my partner will respond John ). Areas of dorsolateral and rostral prefrontal cortex (PFC) have been implicated in probabilistic and hierarchical control mechanisms, respectively. Design/Methods: LBSD patients (PD=9; PDD/DLB=12) and healthy elderly controls (N=22) answered 10 questions probing various semantic categories (e.g., a boy9s name). In the Survey condition, participants could provide any response. In the Coordination condition, participants were instructed to respond with the same answer they think an anonymous partner would give. Responses were quantified using a measure of semantic representativeness, the focal index (FI; e.g., Alfred has a lower FI than John ). Patients underwent neuropsychological testing. Volumetric MRI analysis related cortical thinning to coordination performance. Results: An FI-difference score (Coordination-Survey) confirmed that while PD patients coordinate similarly to seniors, PDD/DLB patients are significantly impaired when asked to coordinate their responses [t(32)=2.54, p Conclusions: PDD/DLB patients have impaired coordination related to frontal/executive dysfunction. We suggest a degraded decision-making network in these patients involving areas of PFC related to probability estimation and hierarchical control mechanisms. Supported by: NIH grants NS44266, NS53488, AG15116, AG17586, AG32953, and HD060406, as well as the Wyncote Foundation. Disclosure: Dr. Goldmann Gross has nothing to disclose. Dr. McMillan has nothing to disclose. Dr. Kitain has nothing to disclose. Dr. Rascovsky has nothing to disclose. Dr. Clark has nothing to disclose. Dr. Grossman has nothing to disclose.