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Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) not only differ for the time of onset of cognitive deficits but also present variability in affected functions which are relevant in understanding underlying pathology. Cognitive performance of two global cognitive screening scales, the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA), as well as of a neuropsychological test battery, was evaluated in 18 DLB and 21 PDD patients. Feasibility for each cognitive test was investigated. Both MMSE and MoCA are feasible assessments in PDD and DLB patients. MoCA was more sensitive in discriminating groups as higher number of DLB patients showed pathological performances on the Digit Span Forward subitem (p = 0.049). The Stroop test in PDD and the Trail Making Tests-A and B, and the Benton's judgment of line orientation tests in both groups were considered not feasible. Among feasible cognitive tests in at least one group, Rey-Osterrieth complex figure test copy (p = 0.013) and semantic fluency (p = 0.038) are sensitive in discriminating DLB from PDD cognitive profile. Trail Making Tests-A and B, the Benton's judgment of line orientation and the Stroop tests are not feasible for assessing patients with frank dementia. Longitudinal studies should not include those tasks to reduce the risk of missing data once disease progresses and dementia develops. DLB patients present more severe and widespread cognitive dysfunction than PDD, particularly in attentive, visuospatial, and language domains.

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Dynamic functional connectivity captures temporal variations of functional connectivity during MRI acquisition and it may be a suitable method to detect cognitive changes in Parkinson's disease. In this study, we evaluated 118 patients with Parkinson's disease matched for age, sex and education with 35 healthy control subjects. Patients with Parkinson's disease were classified with normal cognition (n = 52), mild cognitive impairment (n = 46), and dementia (n = 20) based on an extensive neuropsychological evaluation. Resting state functional MRI and a sliding-window approach were used to study the dynamic functional connectivity. Dynamic analysis suggested two distinct connectivity 'States' across the entire group: a more frequent, segregated brain state characterized by the predominance of within-network connections, State I, and a less frequent, integrated state with strongly connected functional internetwork components, State II. In Parkinson's disease, State I occurred 13.89% more often than in healthy control subjects, paralleled by a proportional reduction of State II. Parkinson's disease subgroups analyses showed the segregated state occurred more frequently in Parkinson's disease dementia than in mild cognitive impairment and normal cognition groups. Further, patients with Parkinson's disease dementia dwelled significantly longer in the segregated State I, and showed a significant lower number of transitions to the strongly interconnected State II compared to the other subgroups. Our study indicates that dementia in Parkinson's disease is characterized by altered temporal properties in dynamic connectivity. In addition, our results show that increased dwell time in the segregated state and reduced number of transitions between states are associated with presence of dementia in Parkinson's disease. Further studies on dynamic functional connectivity changes could help to better understand the progressive dysfunction of networks between Parkinson's disease cognitive states.

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Background: Impulse control disorders (ICDs) and related behaviors are frequent in Parkinson's disease (PD). Mild cognitive impairment (PD-MCI) and dementia (PDD), both characterized by heterogeneous cognitive phenotypes, are also commonly reported in PD. However, the frequency and severity of ICD within PD cognitive states is unknown. Methods: Three hundred and twenty-six PD patients completed a comprehensive neuropsychological assessment and were classified as PD-MCI, PDD, or without cognitive alterations (PD-NC). The Minnesota impulsive disorders interview was used to ascertain the presence (ICD+) or absence (ICD-) of ICD. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale was used to assess ICD severity. A subsample of 286 patients evaluated with the same cognitive tasks was selected in order to investigate the characteristics of ICD in PD cognitive phenotypes. Results: ICDs were present in 55% of PD-NC, in 50% of PD-MCI, and in 42% of PDD patients. Frequencies of ICD+ with attentive (ICD+: 20% vs. ICD-: 4%; p = 0.031) and executive impairments (ICD+: 44% vs. ICD-: 30%; p = 0.027) were higher in the PD-MCI and PDD subgroups, respectively. As expected, no differences were observed in the PD-NC. PD-MCI with attentive impairments presented higher percentage of ICD+ with deficits in the Trail Making Test B-A but not in the Digit Span Sequencing task. In PDD, executive failures concerned Similarities task (ICD+: 67%; ICD-: 29%; p = 0.035), with no differences between ICD+ and ICD- in the Stroop task. Conclusions: Prevalence and severity of ICDs and related behaviors do not differ in PD with different cognitive states. However, ICD+ are more likely to show deficits, respectively in attentive and in executive domains, specifically in the Trail Making Test B-A task for the attention and working memory domain in PD-MCI and in the Similarities task for the executive function domain in PDD. Prospective studies should evaluate if these tests can be used as screening tool for ICDs in PD.