Domain-driven verbal and non-verbal dissociations in cognition and social cognition in Parkinson's disease.

Introduction: Beyond motor symptoms, Parkinson's disease (PD) affects cognition and social cognition. This is already evident in cognitively intact PD, but is especially prominent in those with mild cognitive impairment (PD-MCI). The impact of processing modality (verbal vs. non-verbal) remains unclear. We examined differences across verbal and non-verbal components of cognition and Theory of Mind (ToM) in subjects with PD or PD-MCI compared to healthy controls (HC). Methods: Seventy-seven participants (HC = 26; PD = 28; PD-MCI = 23) completed a battery of neuropsychological tests to assess verbal and non-verbal cognition, verbal and non-verbal ToM. Data were analyzed using non-parametric statistics and multinomial logistic regression models. Results: Both PD groups showed statistically significant impairments compared to HC, with more pronounced deficits in PD-MCI. Verbal cognition was reduced in both PD groups (HC = 3.55 ± 0.59; PD = 2.76 ± 0.95; PD-MCI = 2.73 ± 0.95; χ Discussion: The pattern emerging from our findings is consistent with a framework in which domain-specific vulnerabilities are primary, while modality may influence performance in interaction with task complexity and executive demand. This 2 × 2 framework (domain X modality) refines our understanding of cognitive decline in PD and underscores the need for domain- and modality-sensitive assessments.