B - 70 Left-Sided Motor Symptoms in Parkinson's Disease Are Associated with Impaired Social Cognition: a Preliminary Study.

Abstract

Disruption of frontostriatal pathways underlies working memory and executive function impairments in Parkinson's disease (PD), including theory of mind (ToM). PD symptoms appear on one side and remain lateralized, suggesting greater dysfunction in the contralateral basal ganglia. Previous studies have suggested the right hemisphere, particularly right frontal lobe, has greater involvement in ToM processing. We hypothesized PD subjects with left hemi-motor symptoms, indicating right hemisphere involvement, would show greater deficits on a ToM task. Fourteen PD subjects with lateralized symptoms (9 left, 5 right) and 12 controls were selected from an ongoing NIH-funded study. Participants were right-handed and free of other neurological conditions. Groups did not differ on age, education or sex. Participants completed a ToM story task, neuropsychological measures (Visual-Verbal test, verbal and design fluency, and digit span) and a depression scale. Relative to controls, PD subjects with left-sided symptoms had trouble deciding if the character was lying or joking (p = 0.001 95% CI[1.002, 4.277]) and trending difficulty discerning a character's second order belief (what another character was thinking) when the intent was humorous (p = 0.077; 95% CI[-0.122, 3.055]), after accounting for age. ToM story performance correlated with cognitive measures in PD subjects with right-sided symptoms, but not in those with left-sided symptoms or controls. Individuals with PD and demonstrating left hemi-motor symptoms may have greater difficulty in social cognition beyond executive function or working memory disorders, impacting interactions with caregivers and their quality of life. Investigation with a larger sample is needed to confirm these findings.