Objective: Our study assessed how nondemented patients with Parkinson's disease (PD) interpret the affective and mental states of others from spoken language (adopt a "theory of mind") in ecologically valid social contexts. A secondary goal was to examine the relationship between emotion processing, mentalizing, and executive functions in PD during interpersonal communication.
Method: Fifteen adults with PD and 16 healthy adults completed The Awareness of Social Inference Test, a standardized tool comprised of videotaped vignettes of everyday social interactions (McDonald, Flanagan, Rollins, & Kinch, 2003). Individual subtests assessed participants' ability to recognize basic emotions and to infer speaker intentions (sincerity, lies, sarcasm) from verbal and nonverbal cues, and to judge speaker knowledge, beliefs, and feelings. A comprehensive neuropsychological evaluation was also conducted.
Results: Patients with mild-moderate PD were impaired in the ability to infer "enriched" social intentions, such as sarcasm or lies, from nonliteral remarks; in contrast, adults with and without PD showed a similar capacity to recognize emotions and social intentions meant to be literal. In the PD group, difficulties using theory of mind to draw complex social inferences were significantly correlated with limitations in working memory and executive functioning.
Conclusions: In early PD, functional compromise of the frontal-striatal-dorsal system yields impairments in social perception and understanding nonliteral speaker intentions that draw upon cognitive theory of mind. Deficits in social perception in PD are exacerbated by a decline in executive resources, which could hamper the strategic deployment of attention to multiple information sources necessary to infer social intentions.
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