Mental State Recognition Deficits Linked to Brain Changes in Parkinson's Disease Without Dementia

Recent studies have reported social cognitive deficits, particularly in emotional processing, in Parkinson's disease (PD). However, a comprehensive characterization of these deficits and their underlying neural correlates remains elusive. Therefore, this study aims to investigate the association between deficits in the recognition of complex mental states and structural/functional brain changes in non-demented PD individuals. To reach this aim, 24 PD participants underwent clinical assessment, neuropsychological testing and the FAcial Complex Expressions (FACE) test, a novel test of complex mental state recognition from faces. Patients were classified as clinically impaired (n = 8) or unimpaired (n = 16) based on performance on this test. Magnetic resonance imaging data were acquired to investigate the association between FACE test performance and both resting-state functional connectivity and grey matter volume, within the emotion understanding network and at the whole-brain level. Statistical analyses also included the comparison of imaging metrics between the impaired and unimpaired groups. Results showed that complex mental state recognition in PD was significantly associated with both defective and compensatory mechanisms at the functional and anatomical level within the emotion understanding network, particularly involving the amygdala, dorsomedial prefrontal cortex, primary/secondary somatosensory cortices, and right anterior temporal cortex. Whole-brain results extended the network to temporal and medial frontal areas. In conclusion, reduced recognition of complex mental states in non-demented PD patients is associated with alterations in the emotion understanding network A comprehensive characterization of early emotional deficits in these patients may have significant implications in the characterization of the cognitive phenotype, with potential benefit for tailored non-pharmacological intervention.