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Objective: Cortical dynamics is driven by cortico-cortical connectivity and it characterizes cortical morphological features. These brain surface features complement volumetric changes and may offer improved understanding of disease pathophysiology. Hence, present study aims to investigate surface features; cortical thickness (CT) and gyrification index (GI) in Parkinson's disease (PD) patients of normal cognition (PD-CN), cognitively impaired patients with PD (PD-CI) in comparison with cognitively normal healthy controls (HC) to better elucidate cognition linked features in PD., Method: Anatomical MRI (3DT1) was carried out in 30 HC (56.53 ± 8.42 years), 30 PD-CN (58.8 ± 6.07 years), and 30 PD-CI (60.3 ± 6.43 years) subjects. Whole brain ROI based parcellation using Desikan-Killiany (DK-40) atlas followed by regional CT and GI differentiation [with 'age' and 'total intracranial volume' (TIV) correction], multiple linear regression (with 'age', 'TIV', and 'education' correction) with clinical variables, ROC analysis, and CT-GI correlation across the groups was used for data analysis., Results: Widespread cortical thinning with regional GI reduction was evident in PD-CI with respect to other two groups (HC and PD-CN), and with absence of such alterations in PD-CN compared to HC. Frontal, parietal, and temporal CT/GI significantly correlated with cognition and presented classification abilities for cognitive state in PD. Mean regional CT and GI were found negatively correlated across groups with heterogeneous regions., Conclusion: Fronto-parietal and temporal regions suffer cognition associated cortical thinning and GI reduction. CT may serve better discriminator properties and may be more consistent than GI in studying cognition in PD. Heterogeneous surface dynamics across the groups may signify neuro-developmental alterations in PD.

Mild cognitive impairment (MCI) affects nearly 20-50% patients with Parkinson's disease (PD). It may be the prodromal stage of dementia and impacts quality of life of the patient and caregiver. Characterizing PD cognition at the stage of MCI may help in understanding of cognitive pathophysiology. This study assessed and compared cognition in patients with PD and mild cognitive impairment (PD-MCI, n = 32, age = 61.09 ± 5.97 years), PD patients with normal cognition (PD-NC, n = 32, age = 58.81 ± 6.15 years) and healthy controls (HC, n = 38, age = 57.39 ± 7.14 years). Montreal Cognitive Assessment Test (MoCA) was used for categorization of subjects. Cognitive assessment of five domains: executive function, attention, visuospatial function, memory and language (using two tests in each domain) were performed. The effect of PD clinical scores on cognition and cognitive domain specificity in diagnosing PD-MCI were assessed by correlation and receiver operating curve (ROC) analyses, respectively. All the analyses followed removal of potential confounds (age, education and clinical scores). Attention, memory, executive and visuospatial functions were impaired in PD-MCI on comparison with HC and PD-NC groups. Performance in digit span forward and trail making tests for attention and memory (immediate recall) were comparable in both the PD groups. Both the PD groups revealed impairment in attention, memory and language with respect to HC, suggesting the fronto-striatal and posterior cortical syndrome in PD. Highly significant Visual-N-back correlation with UPDRS-III may implicate the shared motor-visuospatial neural pathways. Visual-N-back/PGI delayed recall domains are promising in characterizing PD-MCI stage., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)