Cognitive impairment in nondemented Parkinson's disease

Effect of Proprioceptive Training Compared With Other Interventions for Upper Limb Deficits in People With Parkinson Disease: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

This systematic review and meta-analysis aimed to determine the efficacy of proprioceptive training on hand dexterity, upper limb function, and quality of life (QoL) in people with Parkinson disease (PD) compared with no or other active interventions.

DATA SOURCES

Medline PubMed, Cochrane Library, CINAHL, PEDro, and Web of Science databases were searched to identify published studies until February 2023.

STUDY SELECTION

Peer-reviewed English publications of randomized controlled trials (RCTs) of proprioceptive training conducted among people with PD.

DATA EXTRACTION

Study characteristics, exercise program type and dosage, outcome of interest, and between-group comparisons of post-test results of intervention and comparison groups.

DATA SYNTHESIS

Eight RCTs were included, involving 344 people with PD. Six RCTs contributed to meta-analyses. There was very low certainty of evidence that proprioceptive training may improve dominant hand (standard mean difference [SMD] 0.34, 95% CI 0.08-0.60, P=.01) and non-dominant hand (SMD 0.36, 95% CI 0.10-0.63, P<.01) fine motor dexterity, and dominant hand gross manual dexterity (SMD 1.73, 95% CI 0.30-3.16, P=.02), following 2-8 weeks of proprioceptive training. There was no evidence of effects on non-dominant hand gross manual dexterity, upper limb function, and QoL after proprioceptive training.

CONCLUSIONS

Findings regarding the effect of proprioceptive training on hand dexterity in the short-term are inconclusive. The small sample size likely limited effect detection. Future large RCTs should compare proprioceptive training with no intervention and perform comprehensive biomechanical analysis to gain a clearer idea of its effects. Incorporating longer-duration proprioceptive training programs is also recommended to investigate long-lasting effects.

Functional and structural gradients reveal atypical hierarchical organization of Parkinson's disease

Parkinson's disease (PD) patients exhibit deficits in primary sensorimotor and higher-order executive functions. The gradient reflects the functional spectrum in sensorimotor-associated areas of the brain. We aimed to determine whether the gradient is disrupted in PD patients and how this disruption is associated with treatment outcome. Seventy-six patients (mean age, 59.2 ± 12.4 years [standard deviation], 44 women) and 34 controls participants (mean age, 58.1 ± 10.0 years [standard deviation], 19 women) were evaluated. We explored functional and structural gradients in PD patients and control participants. Patients were followed during 2 weeks of multidisciplinary intensive rehabilitation therapy (MIRT). The Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) was administered to patients before and after treatment. We investigated PD-related alterations in the principal functional and structural gradients. We further used a support vector machine (SVM) and correlation analysis to assess the classification ability and treatment outcomes related to PD gradient alterations, respectively. The gradients showed significant differences between patients and control participants, mainly in somatosensory and visual networks involved in primary function, and higher-level association networks (dorsal attentional network (DAN) and default mode network (DMN)) related to motor control and execution. On the basis of the combined functional and structural gradient features of these networks, the SVM achieved an accuracy of 91.2% in discriminating patients from control participants. Treatment reduced the gradient difference. The altered gradient exhibited a significant correlation with motor improvement and was mainly distributed across the visual network, DAN and DMN. This study revealed damage to gradients in the brain characterized by sensorimotor and executive control deficits in PD patients. The application of gradient features to neurological disorders could lead to the development of potential diagnostic and treatment markers for PD.

Functional alterations in resting-state networks for Theory of Mind in Parkinson's disease

In Parkinson's disease (PD), impairment of Theory of Mind (ToM) has recently attracted an increasing number of neuroscientific investigations. If and how functional connectivity of the ToM network is altered in PD is still an open question. First, we explored whether ToM network connectivity shows potential PD-specific functional alterations when compared to healthy controls (HC). Second, we tested the role of the duration of PD in the evolution of functional alterations in the ToM network. Between-group connectivity alterations were computed adopting resting-state functional magnetic resonance imaging (rs-fMRI) data of four groups: PD patients with short disease duration (PD-1, n = 72); PD patients with long disease duration (PD-2, n = 22); healthy controls for PD-1 (HC-1, n = 69); healthy controls for PD-2 (HC-2, n = 22). We explored connectivity differences in the ToM network within and between its three subnetworks: Affective, Cognitive and Core. PD-1 presented a global pattern of decreased functional connectivity within the ToM network, compared to HC-1. The alterations mainly involved the Cognitive and Affective ToM subnetworks and their reciprocal connections. PD-2-those with longer disease duration-showed an increased connectivity spanning the entire ToM network, albeit less consistently in the Core ToM network, compared to both the PD-1 and the HC-2 groups. Functional connectivity within the ToM network is altered in PD. The alterations follow a graded pattern, with decreased connectivity at short disease duration, which broadens to a generalized increase with longer disease duration. The alterations involve both the Cognitive and Affective subnetworks of ToM.

The effects of rivastigmine on neuropsychiatric symptoms in the early stages of Parkinson's disease: A systematic review

BACKGROUND AND PURPOSE

Neuropsychiatric symptoms including depression, apathy and psychosis occur frequently in patients with Parkinson's disease. A subgroup of patients develop cognitive impairment, which may increase the risk of falls due to reduced attention. The acetylcholinesterase inhibitor rivastigmine is beneficial in Parkinson's disease dementia, but whether the use of rivastigmine is effective earlier in the disease course is unclear. The aim of this systematic review was to assess the evidence for rivastigmine in the treatment of neuropsychiatric symptoms in Parkinson's disease without dementia.

METHODS

Embase, Medline, PsychINFO, Cochrane CENTRAL, NGLC, National Institute for Health and Care Excellence Evidence and medRxiv.org were searched for studies with terms relating to population (Parkinson's disease) and intervention (rivastigmine). Of 1922 references identified, 358 were duplications. Following title and abstract review, 1331 articles were excluded. After full-text review, nine articles remained.

RESULTS

Outcomes were heterogenous, therefore, the results are presented in narrative form. The articles included six randomized controlled trials, two open-label trials and one case series. Outcome measures included: time to develop psychosis; frequency of rapid eye movement sleep behaviour disorder (RBD) episodes; apathy; gait variability; falls; cognitive ability; Neuropsychiatric Inventory score; and regional spontaneous brain activity.

CONCLUSIONS

There is evidence that rivastigmine is beneficial for RBD and apathy in Parkinson's disease patients without dementia. There is high level evidence that rivastigmine reduces falls, which may be due to improved attention. The impact of rivastigmine on psychotic symptoms is less clear, but is supported by current theoretical models which involve acetylcholine dysfunction in the generation of visual hallucinations in Parkinson's disease.

Pathobiology of Cognitive Impairment in Parkinson Disease: Challenges and Outlooks

Cognitive impairment (CI) is a characteristic non-motor feature of Parkinson disease (PD) that poses a severe burden on the patients and caregivers, yet relatively little is known about its pathobiology. Cognitive deficits are evident throughout the course of PD, with around 25% of subtle cognitive decline and mild CI (MCI) at the time of diagnosis and up to 83% of patients developing dementia after 20 years. The heterogeneity of cognitive phenotypes suggests that a common neuropathological process, characterized by progressive degeneration of the dopaminergic striatonigral system and of many other neuronal systems, results not only in structural deficits but also extensive changes of functional neuronal network activities and neurotransmitter dysfunctions. Modern neuroimaging studies revealed multilocular cortical and subcortical atrophies and alterations in intrinsic neuronal connectivities. The decreased functional connectivity (FC) of the default mode network (DMN) in the bilateral prefrontal cortex is affected already before the development of clinical CI and in the absence of structural changes. Longitudinal cognitive decline is associated with frontostriatal and limbic affections, white matter microlesions and changes between multiple functional neuronal networks, including thalamo-insular, frontoparietal and attention networks, the cholinergic forebrain and the noradrenergic system. Superimposed Alzheimer-related (and other concomitant) pathologies due to interactions between α-synuclein, tau-protein and β-amyloid contribute to dementia pathogenesis in both PD and dementia with Lewy bodies (DLB). To further elucidate the interaction of the pathomechanisms responsible for CI in PD, well-designed longitudinal clinico-pathological studies are warranted that are supported by fluid and sophisticated imaging biomarkers as a basis for better early diagnosis and future disease-modifying therapies.

Genetic variation in the dopamine system is associated with mixed-strategy decision-making in patients with Parkinson's disease

Decision-making during mixed-strategy games requires flexibly adapting choice strategies in response to others' actions and dynamically tracking outcomes. Such decisions involve diverse cognitive processes, including reinforcement learning, which are affected by disruptions to the striatal dopamine system. We therefore investigated how genetic variation in dopamine function affected mixed-strategy decision-making in Parkinson's disease (PD), which involves striatal dopamine pathology. Sixty-six PD patients (ages 49-85, Hoehn and Yahr Stages 1-3) and 22 healthy controls (ages 54-75) competed in a mixed-strategy game where successful performance depended on minimizing choice biases (i.e., flexibly adapting choices trial by trial). Participants also completed a fixed-strategy task that was matched for sensory input, motor outputs and overall reward rate. Factor analyses were used to disentangle cognitive from motor aspects within both tasks. Using a within-subject, multi-centre design, patients were examined on and off dopaminergic therapy, and genetic variation was examined via a multilocus genetic profile score representing the additive effects of three single nucleotide polymorphisms (SNPs) that influence dopamine transmission: rs4680 (COMT Val158 Met), rs6277 (C957T) and rs907094 (encoding DARPP-32). PD and control participants displayed comparable mixed-strategy choice behaviour (overall); however, PD patients with genetic profile scores indicating higher dopamine transmission showed improved performance relative to those with low scores. Exploratory follow-up tests across individual SNPs revealed better performance in individuals with the C957T polymorphism, reflecting higher striatal D2/D3 receptor density. Importantly, genetic variation modulated cognitive aspects of performance, above and beyond motor function, suggesting that genetic variation in dopamine signalling may underlie individual differences in cognitive function in PD.

Early identification of subjective cognitive functional decline among patients with Parkinson's disease: a longitudinal pilot study

Practical methods for early identification of Parkinson's disease (PD) mild cognitive impairment (PD-MCI) through changes in real-life daily functioning are scarce. The aim of the study was to examine whether the cognitive functional (CF) feature, comprising of seven self-reported Movement Disorder Society's (MDS) Unified Parkinson's Disease Rating Scale (UPDRS) items, predicts PD patients' cognitive functional status after a year. We conducted a 1-year follow-up of 34 PD patients (50-78 year; 70.6% men) suspected of MCI using the following measures: the MDS-UPDRS, UPDRS-CF feature, Beck Depression Inventory (BDI), Montreal Cognitive Assessment (MoCA), Trail Making Test (TMT), Parkinson's Disease Cognitive Functional Rating Scale (PD-CFRS), and Daily Living Questionnaire (DLQ). The first and second UPDRS-CF feature scores, and additional measures at the 1-year follow-up significantly correlated. Hierarchical regression revealed that the initial MoCA, TMT, and BDI scores predicted the second UPDRS-CF, and the first UPDRS-CF predicted 31% of the second PD-CFRS score variance. Depression moderated the relationship between the first UPDRS-CF score and the DLQ Part A. These results suggest practical, self-reported, daily functional markers for identifying gradual decline in PD patients. They consider the patients' heterogeneity, underlying cognitive pathology, and implications on daily functioning, health, and well-being.

The Intranigral Infusion of Human-Alpha Synuclein Oligomers Induces a Cognitive Impairment in Rats Associated with Changes in Neuronal Firing and Neuroinflammation in the Anterior Cingulate Cortex

Parkinson’s disease (PD) is a complex pathology causing a plethora of non-motor symptoms besides classical motor impairments, including cognitive disturbances. Recent studies in the PD human brain have reported microgliosis in limbic and neocortical structures, suggesting a role for neuroinflammation in the development of cognitive decline. Yet, the mechanism underlying the cognitive pathology is under investigated, mainly for the lack of a valid preclinical neuropathological model reproducing the disease’s motor and non-motor aspects. Here, we show that the bilateral intracerebral infusion of pre-formed human alpha synuclein oligomers (H-αSynOs) within the substantia nigra pars compacta (SNpc) offers a valid model for studying the cognitive symptoms of PD, which adds to the classical motor aspects previously described in the same model. Indeed, H-αSynOs-infused rats displayed memory deficits in the two-trial recognition task in a Y maze and the novel object recognition (NOR) test performed three months after the oligomer infusion. In the anterior cingulate cortex (ACC) of H-αSynOs-infused rats the in vivo electrophysiological activity was altered and the expression of the neuron-specific immediate early gene (IEG) Npas4 (Neuronal PAS domain protein 4) and the AMPA receptor subunit GluR1 were decreased. The histological analysis of the brain of cognitively impaired rats showed a neuroinflammatory response in cognition-related regions such as the ACC and discrete subareas of the hippocampus, in the absence of any evident neuronal loss, supporting a role of neuroinflammation in cognitive decline. We found an increased GFAP reactivity and the acquisition of a proinflammatory phenotype by microglia, as indicated by the increased levels of microglial Tumor Necrosis Factor alpha (TNF-α) as compared to vehicle-infused rats. Moreover, diffused deposits of phospho-alpha synuclein (p-αSyn) and Lewy neurite-like aggregates were found in the SNpc and striatum, suggesting the spreading of toxic protein within anatomically interconnected areas. Altogether, we present a neuropathological rat model of PD that is relevant for the study of cognitive dysfunction featuring the disease. The intranigral infusion of toxic oligomeric species of alpha-synuclein (α-Syn) induced spreading and neuroinflammation in distant cognition-relevant regions, which may drive the altered neuronal activity underlying cognitive deficits.

Morphological basis of Parkinson disease-associated cognitive impairment: an update

Cognitive impairment is one of the most salient non-motor symptoms of Parkinson disease (PD) that poses a significant burden on the patients and carers as well as being a risk factor for early mortality. People with PD show a wide spectrum of cognitive dysfunctions ranging from subjective cognitive decline and mild cognitive impairment (MCI) to frank dementia. The mean frequency of PD with MCI (PD-MCI) is 25.8% and the pooled dementia frequency is 26.3% increasing up to 83% 20 years after diagnosis. A better understanding of the underlying pathological processes will aid in directing disease-specific treatment. Modern neuroimaging studies revealed considerable changes in gray and white matter in PD patients with cognitive impairment, cortical atrophy, hypometabolism, dopamine/cholinergic or other neurotransmitter dysfunction and increased amyloid burden, but multiple mechanism are likely involved. Combined analysis of imaging and fluid markers is the most promising method for identifying PD-MCI and Parkinson disease dementia (PDD). Morphological substrates are a combination of Lewy- and Alzheimer-associated and other concomitant pathologies with aggregation of α-synuclein, amyloid, tau and other pathological proteins in cortical and subcortical regions causing destruction of essential neuronal networks. Significant pathological heterogeneity within PD-MCI reflects deficits in various cognitive domains. This review highlights the essential neuroimaging data and neuropathological changes in PD with cognitive impairment, the amount and topographical distribution of pathological protein aggregates and their pathophysiological relevance. Large-scale clinicopathological correlative studies are warranted to further elucidate the exact neuropathological correlates of cognitive impairment in PD and related synucleinopathies as a basis for early diagnosis and future disease-modifying therapies.

Cognitive function and blood pressure control in elderly hypertensive individuals

This article aims to estimate the prevalence of cognitive impairment and analyze its association with blood pressure control in elderly hypertensive individuals. Cross-sectional study of 383 elderly hypertensive individuals in the state of Piauí, Brazil. The authors collected sociodemographic and clinical data, performed blood pressure measurement, and assessed cognitive function using the Montreal Cognitive Assessment (MoCA) test. Poisson regression with robust variance was used. Overall prevalence of cognitive impairment was 74.4%, higher in the age group 80 years and over and among older persons with less schooling. Prevalence of uncontrolled blood pressure was 61.6%, with a higher proportion in the elderly with cognitive impairment. An association was observed between cognitive impairment and uncontrolled blood pressure (aPR: 3.98; 95%CI = 2.51-6.33). The significant association between cognitive function and blood pressure control suggest that cognitive impairment is an important risk factor for uncontrolled blood pressure in older persons. The inclusion of screening measures for possible cognitive deficits may be useful for better monitoring blood pressure levels among elderly hypertensive individuals.

Mild Cognitive Impairment Subtypes Are Associated With Peculiar Gait Patterns in Parkinson's Disease

Background

Mild cognitive impairment (MCI) is frequent in Parkinson's disease (PD) and represents a risk factor for the development of dementia associated with PD (PDD). Since PDD has been associated with disability, caregiver burden, and an increase in health-related costs, early detection of MCI associated with PD (PD-MCI) and its biomarkers is crucial.

Objective

Given that gait is considered a surrogate marker for cognitive decline in PD, the aim of this study was to compare gait patterns in PD-MCI subtypes in order to verify the existence of an association between specific gait features and particular MCI subtypes.

Methods

A total of 67 patients with PD were consecutively enrolled and assessed by an extensive clinical and cognitive examination. Based on the neuropsychological examination, patients were diagnosed as patients with MCI (PD-MCI) and without MCI (no-PD-MCI) and categorized in MCI subtypes. All patients were evaluated using a motion capture system of a BTS Bioengineering equipped with six IR digital cameras. Gait of the patients was assessed in the ON-state under three different tasks (a single task and two dual tasks). Statistical analysis included the t-test, the Kruskal-Wallis test with post hoc analysis, and the exploratory correlation analysis.

Results

Gait pattern was poorer in PD-MCI vs. no-PD-MCI in all tasks. Among PD-MCI subtypes, multiple-domain PD-MCI and amnestic PD-MCI were coupled with worse gait patterns, notably in the dual task.

Conclusion

Both the magnitude of cognitive impairment and the presence of memory dysfunction are associated with increased measures of dynamic unbalance, especially in dual-task conditions, likely mirroring the progressive involvement of posterior cortical networks.

Motor–Cognitive Treadmill Training With Virtual Reality in Parkinson’s Disease: The Effect of Training Duration

Treadmill training with virtual reality (TT + VR) has been shown to improve gait performance and to reduce fall risk in Parkinson’s disease (PD). However, there is no consensus on the optimal training duration. This study is a sub-study of the V-TIME randomized clinical trial (NCT01732653). In this study, we explored the effect of the duration of training based on the motor–cognitive interaction on motor and cognitive performance and on fall risk in subjects with PD. Patients in Hoehn and Yahr stages II–III, aged between 40 and 70 years, were included. In total, 96 patients with PD were assigned to 6 or 12 weeks of TT + VR intervention, and 77 patients completed the full protocol. Outcome measures for gait and cognitive performance were assessed at baseline, immediately after training, and at 1- and 6-month follow-up. The incident rate of falls in the 6-month pre-intervention was compared with that in the 6-month post-intervention. Dual-task gait performance (gait speed, gait speed variability and stride length under cognitive dual task and obstacle negotiation, and the leading foot clearance in obstacle negotiation) improved similarly in both groups with gains sustained at 6-month follow-up. A higher decrease in fall rate and fear of falling were observed in participants assigned to the 12-week intervention than the 6-week intervention. Improvements in cognitive functions (i.e., executive functions, visuospatial ability, and attention) were seen only in participants enrolled in 12-week training up to 1-month follow-up but vanished at the 6-month evaluation. Our results suggest that a longer TT + VR training leads to greater improvements in cognitive functions especially those directly addressed by the virtual environment.

Longitudinal Healthcare Utilization and Costs in Parkinson's Disease: Pre-Diagnosis to 9 Years After

BACKGROUND

There is currently insufficient long-term data on costs of treatment in patients with Parkinson's disease (PD), which is chronic and progressive, and associated with substantial healthcare costs. Identifying patterns in healthcare utilization and cost may illuminate further discussion on early intervention.

OBJECTIVE

To characterize long-term healthcare utilization and costs of PD in newly diagnosed patients managed by movement disorder specialists.

METHODS

Using a longitudinal matched-cohort study of linked data from the National Neuroscience Institute Parkinson's disease and Movement Disorder and healthcare administrative databases in Singapore from 2008-2017, we compared healthcare utilization and costs between patients and controls matched on age, sex, race, and Charlson Comorbidity Index score.

RESULTS

1,162 patients met study inclusion criteria and 1,157 matched controls were identified. The total mean annual healthcare cost (at 2017 costs) was significantly increased in patients compared to controls from years 1-9 post-diagnosis. The increased cost was observed 2 years before diagnosis (USD2322 vs. 2052; p < 0.001). Mean annual cost attributable to PD increased from USD1854 at 1-year post-diagnosis to USD2652 at 9 years. Over 9 years, average costs were significantly higher across all domains of healthcare utilization except primary care-cost of intermediate and long-term care was increased by a factor of 2.5, specialist care by 2.3, emergency department visits by 1.6, and hospital admissions by 1.3.

CONCLUSION

PD results in higher healthcare utilization and costs. Pre-diagnosis increase in healthcare utilization observed in patients supports the presence of prodromal PD symptoms and may present an opportunity for early diagnosis.

Myrtenol complexed with β-cyclodextrin ameliorates behavioural deficits and reduces oxidative stress in the reserpine-induced animal model of Parkinsonism

Current pharmacological approaches to treat Parkinson's disease have low long-term efficacy and important adverse side effects. The development of new pharmacological therapies has focused on novel plant-derived phytochemicals. The alcoholic monoterpene myrtenol has been isolated from several plant species, and has anxiolytic, analgesic, anti-inflammatory and antioxidant actions. Our study evaluated the neuroprotective potential of myrtenol complexed with β-cyclodextrin (MYR) on a progressive parkinsonism model induced by reserpine (RES) in mice. The complexation with cyclodextrins enhances the pharmacological action of monoterpenes. Male Swiss mice were treated daily with MYR (5 mg/kg, p.o.) and with RES (0.1 mg/kg, s.c.) every other day during 28 days. Behavioural evaluations were conducted across treatment. At the end of the treatment, immunohistochemistry for tyrosine hydroxylase (TH) and oxidative stress parameters were evaluated. Chronic MYR-treatment protected against olfactory sensibility loss, restored short-term memory and decreased RES-induced motor impairments. Moreover, this treatment prevented dopaminergic depletion and reduced the oxidative status index in the dorsal striatum. Therefore, MYR ameliorated motor and non-motor impairments in the progressive animal model of parkinsonism, possibly by an antioxidant action. Additional research is needed to investigate the mechanisms involved in this neuroprotective effect.

Cognitive Decline in Parkinson's Disease: A Subgroup of Extreme Decliners Revealed by a Data-Driven Analysis of Longitudinal Progression

Cognitive impairment is an important symptom of Parkinson’s disease (PD) and predicting future cognitive decline is crucial for clinical practice. Here, we aim to identify latent sub-groups of longitudinal trajectories of cognitive change in PD patients, and explore predictors of differences in cognitive change. Longitudinal cognitive performance data from 349 newly diagnosed PD patients and 145 healthy controls from the Parkinson Progression Marker Initiative were modeled using a multivariate latent class linear mixed model. Resultant latent classes were compared on a number of baseline demographics and clinical variables, as well as cerebrospinal fluid (CSF) biomarkers and striatal dopamine transporter (DAT) density markers of neuropathology. Trajectories of cognitive change in PD were best described by two latent classes. A large subgroup (90%), which showed a subtle impairment in cognitive performance compared to controls but remained stable over the course of the study, and a small subgroup (10%) which rapidly declined in all cognitive performance measures. Rapid decliners did not differ significantly from the larger group in terms of disease duration, severity, or motor symptoms at baseline. However, rapid decliners had lower CSF amyloidß42 levels, a higher prevalence of sleep disorder and pronounced loss of caudate DAT density at baseline. These data suggest the existence of a distinct minority sub-type of PD in which rapid cognitive change in PD can occur uncoupled from motor symptoms or disease severity, likely reflecting early pathological change that extends from motor areas of the striatum into associative compartments and cortex.

Semantic Memory and Lexical Availability in Parkinson's Disease: A Statistical Learning Study

Parkinson’s disease (PD) is a neurodegenerative disorder that causes a progressive impairment in motor and cognitive functions. Although semantic fluency deficits have been described in PD, more specific semantic memory (SM) and lexical availability (LA) domains have not been previously addressed. Here, we aimed to characterize the cognitive performance of PD patients in a set of SM and LA measures and determine the smallest set of neuropsychological (lexical, semantic, or executive) variables that most accurately classify groups. Thirty early-stage non-demented PD patients (age 35–75, 10 females) and thirty healthy controls (age 36–76, 12 females) were assessed via general cognitive, SM [three subtests of the CaGi battery including living (i.e., elephant) and non-living things (i.e., fork)], and LA (eliciting words from 10 semantic categories related to everyday life) measures. Results showed that PD patients performed lower than controls in two SM global scores (picture naming and naming in response to an oral description). This impairment was particularly pronounced in the non-living things subscale. Also, the number of words in the LA measure was inferior in PD patients than controls, in both larger and smaller semantic fields, showing a more inadequate recall strategy. Notably, the classification algorithms indicated that the SM task had high classification accuracy. In particular, the denomination of non-living things had a classification accuracy of ∼80%. These results suggest that frontostriatal deterioration in PD leads to search strategy deficits in SF and the potential disruption in semantic categorization. These findings are consistent with the embodied view of cognition.

The influence of white matter hyperintensity on cognitive impairment in Parkinson's disease

The aim of this meta‐analysis was to review systematically and to identify the relationship between the severity and location of white matter hyperintensities (WMHs) and the degree of cognitive decline in patients with Parkinson’s disease (PD). We searched the PubMed, EMBASE, Web of Science, Ovid, and Cochrane Library databases for clinical trials of the severity and location of WMHs on the degree of cognitive impairment in PD through October 2020. We conducted the survey to compare the association of WMH burden in patients with PD with mild cognitive impairment (PD‐MCI) versus those with normal cognition (PD‐NC) and in patients with PD with dementia (PDD) versus those with PD without dementia (PD‐ND). Nine studies with PD‐MCI versus PD‐NC and 10 studies with PDD versus PD‐ND comparisons were included. The WMH burden in PD‐MCI patients was significantly different compared to that in PD‐NC patients (standard mean difference, SMD = 0.39, 95% CI: 0.12 to 0.66, p = 0.005), while there was no correlation shown in the age‐matched subgroup of the comparison. In addition, PDD patients had a significantly higher burden of WMHs (SMD = 0.8, 95% CI: 0.44 to 1.71, p < 0.0001), especially deep white matter hyperintensities (SMD = 0.54, 95% CI: 0.36 to 0.73, p < 0.00001) and periventricular hyperintensities (SMD = 0.70, 95% CI: 0.36 to 1.04, p < 0.0001), than PD‐NC patients, regardless of the adjustment of age. WMHs might be imaging markers for cognitive impairment in PDD but not in PD‐MCI, regardless of age, vascular risk factors, or race. Further prospective studies are needed to validate the conclusions.

Impaired Executive Function and Depression as Independent Risk Factors for Reported Delirium Symptoms: An Observational Cohort Study Over 8 Years

Background

Acute medical illnesses, surgical interventions, or admissions to hospital in older individuals are frequently associated with a delirium. In this cohort study, we investigated the impact of specific cognitive domains and depression before the occurrence of delirium symptoms in an 8-year observation of older non-hospitalized individuals.

Methods

In total, we included 807 participants (48–83 years). Deficits in specific cognitive domains were measured using the CERAD test battery, and depressive symptoms were measured using Beck Depression Inventory and the Geriatric Depression Scale (GDS) before the onset of a delirium. Delirium symptoms were retrospectively assessed by a questionnaire based on the established Nursing Delirium Screening Scale.

Results

Fifty-eight of eight hundred seven participants (7.2%) reported delirium symptoms over the 8-year course of the study. Sixty-nine percent (n = 40) of reported delirium symptoms were related to surgeries. In multivariate regression analysis, impaired executive function was an independent risk factor (p = 0.034) for the occurrence of delirium symptoms. Furthermore, age (p = 0.014), comorbidities [captured by the Charlson Comorbidity Index (CCI)] (p < 0.001), and depression (p = 0.012) were significantly associated with reported delirium symptoms.

Conclusion

Especially prior to elective surgery or medical interventions, screening for impaired executive function and depression could be helpful to identify patients who are at risk to develop delirium symptoms.

Changes in efficiencies and interactions of attentional networks in Parkinson's disease with sleep disturbance

Attention is composed of three distinct attentional networks: alerting, orienting, and executive control. Previous studies have confirmed that Parkinson's disease (PD) is associated with executive control deficits; however, the interactions among the three attentional networks and the influence of sleep disturbance in PD patients have not been investigated. Herein, the efficiencies for the three attentional networks and their interactions were evaluated using the revised attention network test. The results showed a significantly slower response and lower accuracy in the PD group than in the normal control group and a significantly slower response and lower accuracy in PD patients with sleep disturbance (PDS) than in PD patients without sleep disturbance (PDnS), which indicates a response deficit in PD and worsening in PDS. Additionally, the executive control efficiency was reduced in both PDS and PDnS, and significantly higher alerting efficiency and lower orienting efficiency were found in PDS. Furthermore, largely changed interactions and correlation patterns of attentional networks were found in PDS but not in PDnS. These results suggested that attentional networks were impaired in PD patients, particularly in those affected by sleep disturbances, and that PDS might establish special connections between attentional networks to compensate for cognitive dysfunction.

Informant-Reported Cognitive Decline is Associated with Objective Cognitive Performance in Parkinson's Disease

OBJECTIVE

The utility of informant-based measures of cognitive decline to accurately describe objective cognitive performance in Parkinson's disease (PD) without dementia is uncertain. Due to the clinical relevance of this information, the purpose of this study was to examine the relationship between informant-based reports of patient cognitive decline via the Informant Questionnaire of Cognitive Decline in the Elderly (IQCODE) and objective cognition in non-demented PD controlling for cognitive status (i.e., mild cognitive impairment; PD-MCI and normal cognition; PD-NC).

METHOD

One-hundred and thirty-nine non-demented PD participants (PD-MCI n = 38; PD-NC n = 101) were administered measures of language, executive function, attention, learning, delayed recall, visuospatial function, mood, and motor function. Each participant identified an informant to complete the IQCODE and a mood questionnaire.

RESULTS

Greater levels of informant-based responses of patient cognitive decline on the IQCODE were significantly associated with worse objective performance on measures of global cognition, attention, learning, delayed recall, and executive function in the overall sample, above and beyond covariates and cognitive status. However, the IQCODE was not significantly associated with language or visuospatial function.

CONCLUSIONS

Results indicate that informant responses, as measured by the IQCODE, may provide adequate information on a wide range of cognitive abilities in non-demented PD, including those with MCI and normal cognition. Findings have important clinical implications for the utility of the IQCODE in the identification of PD patients in need of further evaluation, monitoring, and treatment.

Altered Inhibitory Mechanisms in Parkinson's Disease: Evidence From Lexical Decision and Simple Reaction Time Tasks

INTRODUCTION

Although the motor signs of Parkinson's disease (PD) are well defined, nonmotor symptoms, including higher-level language deficits, have also been shown to be frequent in patients with PD. In the present study, we used a lexical decision task (LDT) to find out whether access to the mental lexicon is impaired in patients with PD, and whether task performance is affected by bradykinesia.

MATERIALS AND METHODS

Participants were 34 nondemented patients with PD, either without (off) medication (n = 16) or under optimum (on) medication (n = 18). A total of 19 age-matched control volunteers were also recruited. We recorded reaction times (RTs) to the LDT and a simple RT (control) task. In each task, stimuli were either visual or auditory. Statistical analyses consisted of repeated-measures analyses of variance and Tukey's HSD post hoc tests.

RESULTS

In the LDT, participants with PD both off and on medication exhibited intact access to the mental lexicon in both modalities. In the visual modality, patients off medication were just as fast as controls when identifying real words, but slower when identifying pseudowords. In the visual modality of the control task, RTs for pseudowords were significantly longer for PD patients off medication than for controls, revealing an unexpected but significant lexicality effect in patients that was not observed in the auditory modality. Performances of patients on medication did not differ from those of age-matched controls.

DISCUSSION

Motor execution was not slowed in patients with PD either off or on medication, in comparison with controls. Regarding lexical access, patients off medication seemed to (1) have difficulty inhibiting a cognitive-linguistic process (i.e., reading) when it was not required (simple reaction time task), and (2) exhibit a specific pseudoword processing deficit in the LDT, which may have been related to impaired lateral word inhibition within the mental lexicon. These deficits seemed to be compensated by medication.

What about the caregiver? A journey into Parkinson's disease following the burden tracks

OBJECTIVES

To investigate caregivers and patients characteristics related to different dimensions of burden in Parkinson's disease (PD).

METHODS

55 pairs of PD patients and caregivers were recruited. The burden was evaluated with the Caregiver Burden Inventory (CBI). Multivariate analysis was applied to evaluate the impact of caregivers' and patients' characteristics on the varying aspects of burden.

RESULTS

ADL score was the dominant predictor for the total score and all dimensions of CBI, except for the social burden, which is strongly predicted by the motor severity of PD. As one can easily imagine, the Total CBI decreases as the ADL score increases.

DISCUSSION

An increased appreciation for characteristics of caregiver burden is a fundamental aspect of the patient's global evaluation. Clinicians may need to directly probe for these factors in the caregiver as they may not be elicited routinely.

How Human Single-Neuron Recordings Can Help Us Understand Cognition: Insights from Memory Studies

Understanding human cognition is a key goal of contemporary neuroscience. Due to the complexity of the human brain, animal studies and noninvasive techniques, however valuable, are incapable of providing us with a full understanding of human cognition. In the light of existing cognitive theories, we describe findings obtained thanks to human single-neuron recordings, including the discovery of concept cells and novelty-dependent cells, or activity patterns behind working memory, such as persistent activity. We propose future directions for studies using human single-neuron recordings and we discuss possible opportunities of investigating pathological brain.

DailyCog: A Real-World Functional Cognitive Mobile Application for Evaluating Mild Cognitive Impairment (MCI) in Parkinson's Disease

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder affecting patient functioning and quality of life. Aside from the motor symptoms of PD, cognitive impairment may occur at early stages of PD and has a substantial impact on patient emotional and physical health. Detecting these early signs through actual daily functioning while the patient is still functionally independent is challenging. We developed DailyCog-a smartphone application for the detection of mild cognitive impairment. DailyCog includes an environment that simulates daily tasks, such as making a drink and shopping, as well as a self-report questionnaire related to daily events performed at home requiring executive functions and visual-spatial abilities, and psychomotor speed. We present the detailed design of DailyCog and discuss various considerations that influenced the design. We tested DailyCog on patients with mild cognitive impairment in PD. Our case study demonstrates how the markers we used coincide with the cognitive levels of the users. We present the outcome of our usability study that found that most users were able to use our app with ease, and provide details on how various features were used, along with some of the difficulties that were identified.

The Effects of Working Memory Updating Training in Parkinson's Disease: A Feasibility and Single-Subject Study on Cognition, Movement and Functional Brain Response

In Parkinson’s disease (PD), the fronto-striatal network is involved in motor and cognitive symptoms. Working memory (WM) updating training engages this network in healthy populations, as observed by improved cognitive performance and increased striatal BOLD signal. This two-part study aimed to assess the feasibility of WM updating training in PD and measure change in cognition, movement and functional brain response in one individual with PD after WM updating training. A feasibility and single-subject (FL) study were performed in which patients with PD completed computerized WM updating training. The outcome measures were the pre-post changes in criterion and transfer cognitive tests; cognitive complaints; psychological health; movement kinematics; and task-related BOLD signal. Participants in the feasibility study showed improvements on the criterion tests at post-test. FL displayed the largest improvements on the criterion tests and smaller improvements on transfer tests. Furthermore, FL reported improved cognitive performance in everyday life. A shorter onset latency and smoother upper-limb goal-directed movements were measured at post-test, as well as increased activation within the striatum and decreased activation throughout the fronto-parietal WM network. This two-part study demonstrated that WM updating training is feasible to complete for PD patients and that change occurred in FL at post-test in the domains of cognition, movement and functional brain response.

The Montreal Cognitive Assessment: Is It Suitable for Identifying Mild Cognitive Impairment in Parkinson's Disease?

BACKGROUND

Administering an abbreviated global cognitive test, such as the Montreal Cognitive Assessment (MoCA), is necessary for the recommended first-level diagnostic criteria for mild cognitive impairment (MCI) in Parkinson's disease (PD). Level II requires administering cognitive functioning neuropsychological tests. The MoCA's suitability for identifying PD-MCI is questionable and, despite the importance of cognitive deficits reflected through daily functioning in identifying PD-MCI, knowledge about it is scarce.

OBJECTIVES

To explore neuropsychological test scores of patients with PD who were categorized based on their MoCA scores and to analyze correlations between this categorization and patients' self-reports about daily functional-related cognitive abilities.

METHODS

A total of 78 patients aged 42 to 78 years participated: 46 with low MoCA scores (22-25) and 32 with high MoCA scores (26-30). Medical assessments and level II neuropsychological assessment tools were administered along with standardized self-report questionnaires about daily functioning that reflects patients' cognitive abilities.

RESULTS

A high percentage of the low MoCA group obtained neuropsychological test scores within the normal range; a notable number in the high MoCA group were identified with MCI-level scores on various neuropsychological tests. Suspected PD-MCI according to the level I criteria did not correspond well with the level II criteria. Positive correlations were found among the 3 self-report questionnaires.

CONCLUSIONS

These results support the ongoing discussion of the complexity of capturing PD-MCI. Considering the neuropsychological tests results, assessments that reflect cognitive encounters in real life daily confrontations are warranted among people diagnosed with PD who are at risk for cognitive decline.

Impact of 3-Day Combined Anodal Transcranial Direct Current Stimulation-Visuospatial Training on Object-Location Memory in Healthy Older Adults and Patients with Mild Cognitive Impairment

BACKGROUND

Associative object-location memory (OLM) is known to decline even in normal aging, and this process is accelerated in patients with mild cognitive impairment (MCI). Given the lack of curative treatment for Alzheimer's disease, activating cognitive resources during its preclinical phase might prevent progression to dementia.

OBJECTIVE

To evaluate the effects of anodal transcranial direct current stimulation (atDCS) combined with an associative episodic memory training on OLM in MCI patients and in healthy elderly (HE).

METHODS

In a single-blind cross-over design, 16 MCI patients and 32 HE underwent a 3-day visuospatial OLM training paired with either 20 min or 30 s (sham) atDCS (1 mA, right temporoparietal cortex). Effects on immediate (training success) and long-term memory (1-month) were investigated by conducting Mixed Model analyses. In addition, the impact of combined intervention on within-session (online) and on between-session (offline) performance were explored.

RESULTS

OLM training+atDCS enhanced training success only in MCI patients, but not HE (difference n.s.). Relative performance gain was similar in MCI patients compared to HE under atDCS. No beneficial effect was found after 1-month. Exploratory analyses suggested a positive impact on online, but a negative effect on offline performance in MCI patients. In both groups, exploratory post-hoc analyses indicated an association between initially low-performers and greater benefit from atDCS.

CONCLUSION

Cognitive training in MCI may be enhanced by atDCS, but further delineation of the impact of current brain state, as well as temporal characteristics of multi-session atDCS-training application, may be needed to induce longer-lasting effects.

Recall and Recognition Discriminability in Parkinson's Disease and Huntington's Disease

BACKGROUND

Parkinson's disease (PD) and Huntington's disease (HD) are two neurodegenerative diseases affecting frontal-striatal function and memory ability. Studies using the original California Verbal Learning Test (CVLT) to examine recall and recognition abilities between these groups have produced mixed findings. Some found that individuals with HD demonstrate worse recall and recognition than those with PD, whereas others reported comparable performance.

OBJECTIVE

We utilized multiple indices of recall and recognition discriminability, provided by the second and third editions of the CVLT (CVLT-II and CVLT-3, respectively), that allow for a more thorough assessment of more nuanced aspects of verbal memory function.

METHODS

We examined differences between individuals with PD (n = 72) and those with HD (n = 77) on CVLT-II indices of recall discriminability (immediate, short delay free and cued, long delay free and cued) and recognition discriminability (total, source, semantic, and novel) using standardized scores while controlling for education and Dementia Rating Scale-2 scores.

RESULTS

The HD group performed significantly worse than the PD group on all measures of recall and recognition discriminability (ps < 0.05), and group differences were associated with large Cohen's d effect sizes.

CONCLUSIONS

Our findings suggest that individuals with HD are more impaired than individuals with PD in more nuanced aspects of recall and recognition memory function. These CVLT indices yield more thorough assessments of recall and recognition memory function and have the potential to improve efforts to characterize and distinguish profiles of memory loss in different neurodegenerative populations, including PD and HD.

Mild cognitive impairment in Parkinson's disease

Understanding on the clinical features and neural mechanisms leading to cognitive impairment and dementia in Parkinson's disease (PD) has notably increased. At time of diagnosis, nearly all PD patients present some degree of cognitive impairment not enough severe as to significantly affect functional independence. However, even mild cognitive changes have a measurable impact to functional capacity in PD. A clinically practical differentiation is based on the importance of executive deficits in the early phases of cognitive impairment in PD and on the evidence stressing the transitional role of posterior-cortical impairment on the progression of PD-MCI to dementia. However, the pattern of cognitive impairment in PD is variable not just to the extents on which are the affected cognitive domains, but also on which are those domains that became affected first. Specific diagnostic criteria for mild cognitive impairment associated with PD (PD-MCI) and dementia (PDD) and operative guidelines for the cognitive assessment have been developed. In the present review, we will describe general notions regarding the mechanisms and the profile of cognitive deterioration in PD, the diagnostic criteria for PD-MCI, and some of the currently recommended assessment approaches.

Development of a Strategy to Predict and Detect Falls Using Wearable Sensors

Falls are a prevalent problem in actual society. Some falls result in injuries and the cost associated with their treatment is high. This is a complex problem that requires several steps in order to be tackled. Firstly, it is crucial to develop strategies that recognize the locomotion mode, indicating the state of the subject in various situations. This article aims to develop a strategy capable of identifying normal gait, the pre-fall condition, and the fall situation, based on a wearable system (IMUs-based). This system was used to collect data from healthy subjects that mimicked falls. The strategy consists, essentially, in the construction and use of classifiers as tools for recognizing the locomotion modes. Two approaches were explored. Associative Skill Memories (ASMs) based classifier and a Convolutional Neural Network (CNN) classifier based on deep learning. Finally, these classifiers were compared, providing for a tool with a good accuracy in recognizing the locomotion modes. Results have shown that the accuracy of the classifiers was quite acceptable. The CNN presented the best results with 92.71% of accuracy considering the pre-fall step different from normal steps, and 100% when not considering.

Resting-state network connectivity in cognitively unimpaired drug-naïve patients with rigidity-dominant Parkinson's disease

BACKGROUND

Parkinson's disease (PD) could be classified into akinetic-rigidity (PD_AR), tremor-dominant (PD_TD) and mixed subtypes. PD_AR patients are more prone to develop cognitive deficits. The default mode network (DMN), fronto-parietal network (FPN) and dorsal attention network (DAN) play important roles in cognitive processing. Our aim was to evaluate changes in connectivity patterns of the DMN, and its interrelation with the FPN and DAN in cognitively unimpaired drug-naïve PD_AR patients.

METHOD

Resting-state functional MRI (rs-fMRI) data was collected in 20 cognitively unimpaired early-stage drug-naïve PD_AR patients and 20 age-, gender- and cognition- matched healthy controls (HCs). Group-level independent component analysis (ICA) was used to investigate changes in functional connectivity (FC) within the DMN between PD_AR and HCs groups, and relationships between the DMN and FPN/DAN were evaluated by seed-based approach.

RESULTS

In PD_AR patients, a significantly decreased FC, as compared with HCs, was observed in the left inferior parietal lobule (IPL) within the DMN. And the left IPL had a reduced FC with the left anterior cingulate cortex (ACC), left superior frontal gyrus (SFG), and left precuneus. However, no differences were detected in the FC between the left IPL and FPN/DAN. In addition, cognitive scores on the brief visuospatial memory test revised (BVMT-R), representing for cognitive memory domain, were positively correlated with the FC of the left IPL with bilateral SFG.

CONCLUSIONS

Our study mainly revealed altered within-DMN connectivity in cognitively unimpaired PD_AR patients, which could provide further insights into the mechanism underlying cognitive decline evolution in the PD subtype.

Step length predicts executive dysfunction in Parkinson's disease: a 3-year prospective study

Cognition and gait appear to be closely related. The chronological interplay between cognitive decline and gait dysfunction is not fully understood. The aim of the present prospective study is investigating whether the dysfunction of specific gait parameters, during specific task and medication conditions, may predict subsequent cognitive impairment in Parkinson's disease (PD). We evaluated cognition and gait in 39 Parkinsonian patients at an initial assessment and after 3 years. Cognitive performance was evaluated with a neuropsychological battery designed to assess memory, executive/attention, and visuospatial domains. Gait was investigated using a gait analysis system during both the off and on states in the following conditions: (1) normal gait; (2) motor dual task; and (3) cognitive dual task. We used regression models to determine whether gait predicts subsequent cognitive dysfunction. Overall, the cognitive test scores were stable over time with the exception of the executive/attention scores, whereas all gait parameters declined. The step length during the cognitive dual task during the on state at the initial evaluation was the only significant predictor of executive/attention domain dysfunction at follow up. The results were confirmed when executive/attention dysfunction at the initial assessment evaluation was included in the regression model as a covariate. Our longitudinal study offers additional insight into the progression of gait dysfunction, and its chronological relationship with cognitive dysfunction in PD patients. In particular, the present study indicates that step length during a cognitive task when on medication is an independent predictor of future executive/attention decline.

Office-Based Screening for Dementia in Parkinson Disease: The Montreal Parkinson Risk of Dementia Scale in 4 Longitudinal Cohorts

Importance

Parkinson disease dementia dramatically increases mortality rates, patient expenditures, hospitalization risk, and caregiver burden. Currently, predicting Parkinson disease dementia risk is difficult, particularly in an office-based setting, without extensive biomarker testing.

Objective

To appraise the predictive validity of the Montreal Parkinson Risk of Dementia Scale, an office-based screening tool consisting of 8 items that are simply assessed.

Design, Setting, and Participants

This multicenter study (Montreal, Canada; Tottori, Japan; and Parkinson Progression Markers Initiative sites) used 4 diverse Parkinson disease cohorts with a prospective 4.4-year follow-up. A total of 717 patients with Parkinson disease were recruited between May 2005 and June 2016. Of these, 607 were dementia-free at baseline and followed-up for 1 year or more and so were included. The association of individual baseline scale variables with eventual dementia risk was calculated. Participants were then randomly split into cohorts to investigate weighting and determine the scale's optimal cutoff point. Receiver operating characteristic curves were calculated and correlations with selected biomarkers were investigated.

Main Outcomes and Measures

Dementia, as defined by Movement Disorder Society level I criteria.

Results

Of the 607 patients (mean [SD] age, 63.4 [10.1]; 376 men [62%]), 70 (11.5%) converted to dementia. All 8 items of the Montreal Parkinson Risk of Dementia Scale independently predicted dementia development at the 5% significance level. The annual conversion rate to dementia in the high-risk group (score, >5) was 14.9% compared with 5.8% in the intermediate group (score, 4-5) and 0.6% in the low-risk group (score, 0-3). The weighting procedure conferred no significant advantage. Overall predictive validity by the area under the receiver operating characteristic curve was 0.877 (95% CI, 0.829-0.924) across all cohorts. A cutoff of 4 or greater yielded a sensitivity of 77.1% (95% CI, 65.6-86.3) and a specificity of 87.2% (95% CI, 84.1-89.9), with a positive predictive value (as of 4.4 years) of 43.90% (95% CI, 37.76-50.24) and a negative predictive value of 96.70% (95% CI, 95.01-97.85). Positive and negative likelihood ratios were 5.94 (95% CI, 4.08-8.65) and 0.26 (95% CI, 0.17-0.40), respectively. Scale results correlated with markers of Alzheimer pathology and neuropsychological test results.

Conclusions and Relevance

Despite its simplicity, the Montreal Parkinson Risk of Dementia Scale demonstrated predictive validity equal or greater to previously described algorithms using biomarker assessments. Future studies using head-to-head comparisons or refinement of weighting would be of interest.

Slower saccadic reading in Parkinson's disease

Idiopathic Parkinson's Disease (PD) is characterized by degeneration of dopaminergic and other neurons, leading to motor and non-motor deficits. Abnormal eye movements in PD, including fixations, saccades, and convergence, are well described. However, saccadic reading, which requires serial and alternating saccades and fixations, is not well studied, despite its obvious impact on the quality of life. In this study, we assessed saccadic reading using variations of the King-Devick (KD) test, a rapid single digit number naming test, as a way to assess the ability to make serial left-to-right ocular motor movements necessary for reading. We recruited 42 treated PD patients and 80 age-matched controls and compared their reading times with a variety of measures, including age, duration of disease, Unified Parkinson's Disease Rating Scale (UPDRS), the National Eye Institute 25-Item Visual Functioning Questionnaire 25 (VFQ-25), and Montreal Cognitive assessment (MoCA) test. The subjects performed 4 trials of reading 120 single digit numbers aloud as fast as possible without making errors. In each trial, they read 3 pages (KD1, KD2, and KD3), and each page contained 40 numbers per page in 8 lines with 5 numbers/line. We found that PD patients read about 20% slower than controls on all tests (KD1, 2, and 3 tests) (p < 0.02), and both groups read irregularly spaced numbers slower than regularly spaced numbers. Having lines between numbers to guide reading (KD1 tests) did not impact reading time in both PD and controls, but increased visual crowding as a result of decreased spacing between numbers (KD3 tests) was associated with significantly slower reading times in both PD and control groups. Our study revealed that saccadic reading is slower in PD, but controls and PD patients are both impacted by visuospatial planning challenges posed by increased visual crowding and irregularity of number spacing. Reading time did not correlate with UPDRS or MoCA scores in PD patients but significantly correlated with age, duration of disease, and VFQ-25 scores. The presence of convergence insufficiency did not significantly correlate with reading time in PD patients, although on average there was slower reading time in those with convergence insufficiency by 8 s (p = 0.2613). We propose that a simple reading task using 120 single-digit numbers can be used as a screening tool in the clinical setting to assess functional ocular motor difficulties in Parkinson's disease that can have a profound impact on quality of life.

Can there be learning potential in Parkinson's disease? A comparison with healthy older adults

Patients with Parkinson's disease may show certain cognitive impairments, although it is unclear how these deficits can affect their learning potential. The study aims to use the testing-the-limits technique to compare the potential for cognitive plasticity in a group of Patients with Parkinson's disease (N = 33) and a group of healthy older adults (N = 33). Sixty-six participants performed verbal learning test to analyze the learning potential. Repeated-measures analysis of variance showed significant main effects of time, group, and the interaction. There is a lower learning potential in subjects with Parkinson's disease; however, those still maintain a certain capacity for learning and, therefore, for cognitive plasticity.

Serum IGF-1 is associated with cognitive functions in early, drug-naïve Parkinson's disease

OBJECTIVE

Cognitive deficits are common in Parkinson's disease (PD) since the early stages and many patients eventually develop dementia. Yet, occurrence of dementia in PD is unpredictable. Evidence supports the hypothesis that insulin-like growth factor-1 (IGF-1) is involved in cognitive deficits. Our aim was to evaluate the relationship between serum IGF-1 levels and neuropsychological scores in a large cohort of drug-naïve PD patients during the earliest stages of the disease.

METHODS

Serum IGF-1 levels were determined in 405 early, drug-naïve PD patients and 191 healthy controls (HC) enrolled in the Parkinson's Progression Markers Initiative (PPMI). The association between serum IGF-1 levels and neuropsychological scores was evaluated with linear regression analysis.

RESULTS

IGF-1 levels were similar in PD and HC. In PD patients the lowest IGF-1 quartile was a predictor of lower performances at the Semantic Fluency task (β = -3.46, 95%CI: -5.87 to -1.01, p = 0.005), the Symbol Digit Modalities Score (β = -2.09, 95%CI: -4.02 to -0.15, p = 0.034), and Hopkins Verbal Learning Test Retention (β = -0.05, 95%CI: -0.09 to -0.009, p = 0.019).

CONCLUSIONS

Lower serum IGF-1 levels are associated to poor performances in cognitive tasks assessing executive function, attention and verbal memory in a large cohort of early PD patients. Follow-up studies are warranted to assess if IGF-1 is related to the development of dementia in PD.

Latent Cognitive Phenotypes in De Novo Parkinson's Disease: A Person-Centered Approach

OBJECTIVES

Cognitive impairment is an important aspect of Parkinson's disease (PD), but there is considerable heterogeneity in its presentation. This investigation aims to identify and characterize latent cognitive phenotypes in early PD.

METHODS

Latent class analysis, a data-driven, person-centered, cluster analysis was performed on cognitive data from the Parkinson's Progressive Markers Initiative baseline visit. This analytic method facilitates identification of naturally occurring endophenotypes. Resulting classes were compared across biomarker, symptom, and demographic data.

RESULTS

Six cognitive phenotypes were identified. Three demonstrated consistent performance across indicators, representing poor ("Weak-Overall"), average ("Typical-Overall"), and strong ("Strong-Overall") cognition. The remaining classes demonstrated unique patterns of cognition, characterized by "Strong-Memory," "Weak-Visuospatial," and "Amnestic" profiles. The Amnestic class evidenced greater tremor severity and anosmia, but was unassociated with biomarkers linked with Alzheimer's disease. The Weak-Overall class was older and reported more non-motor features associated with cognitive decline, including anxiety, depression, autonomic dysfunction, anosmia, and REM sleep behaviors. The Strong-Overall class was younger, more female, and reported less dysautonomia and anosmia. Classes were unrelated to disease duration, functional independence, or available biomarkers.

CONCLUSIONS

Latent cognitive phenotypes with focal patterns of impairment were observed in recently diagnosed individuals with PD. Cognitive profiles were found to be independent of traditional biomarkers and motoric indices of disease progression. Only globally impaired class was associated with previously reported indicators of cognitive decline, suggesting this group may drive the effects reported in studies using variable-based analysis. Longitudinal and neuroanatomical characterization of classes will yield further insight into the evolution of cognitive change in the disease. (JINS, 2017, 23, 551-563).

Nonmotor Symptoms and Natural History of Parkinson's Disease: Evidence From Cognitive Dysfunction and Role of Noninvasive Interventions

Parkinson's disease (PD) is a common neurodegenerative disorder, characterized by motor and nonmotor symptoms (NMS). Several subsequent studies substantiate the great functional burden related to NMS, their progression, and negative effect on quality of life in PD. Additional evidence indicates interesting relationships between striatal dopaminergic function and NMS. The basal ganglia are implicated in the modulation and integration of sensory information and pain, bladder function is under control of both inhibitory (D1) and facilitatory (D2) dopaminergic inputs, finally reduced dopaminergic activity in the mesocortical and mesolimbic pathways is involved in the development of several NMS including mood, motivational, and cognitive alterations. Some NMS fluctuate in response to dopaminergic treatment and are relieved by dopamine replacement therapy, other are insensitive to current therapeutic strategies. The relation among the overall disease complications, perhaps the most important for PD patients and family members' well-being and functionality is dementia that affects most PD patients over the course of disease. Specific pharmacological treatment is lacking, and alternative approaches have been implemented to improve everyday functionality and quality of life. The state of the art suggests that cognitive rehabilitation in PD is possible and may either increase performance or preserve cognitive level over the time. However, it is also evident that cognitive abnormalities in PD are heterogeneous and we still do not have biomarkers to detect early patients at risk for dementia. Cognitive dysfunction is one the most prevalent NMS and is a clinically and functionally important disease milestone. Given the available clinical and imaging evidence it is possible to use cognition to model NMS progression and design nonpharmacological interventions. In this chapter we will address the use of cognitive rehabilitation and noninvasive brain stimulation techniques to modulate cognitive performance and rescue connectivity in affected brain circuitry.

Mild Cognitive Impairment in Parkinson's Disease: Clustering and Switching Analyses in Verbal Fluency Test

OBJECTIVES

Mild cognitive impairment is common in non-demented Parkinson disease patients (PD-MCI) and is considered as a risk factor for dementia. Executive dysfunction has been widely described in PD and the Verbal Fluency Tests (VFT) are often used for executive function assessment in this pathology. The Movement Disorder Society (MDS) published guidelines for PD-MCI diagnosis in 2012. However, no investigation has focused on the qualitative analysis of VFT in PD-MCI. The aim of this work was to study the clustering and switching strategies in VFT in PD-MCI patients. Moreover, these variables are considered as predictors for PD-MCI diagnosis.

METHODS

Forty-three PD patients and twenty normal controls were evaluated with a neuropsychological protocol and the MDS criteria for PD-MCI were applied. Clustering and switching analysis were conducted for VFT.

RESULTS

The percentage of patients diagnosed with PD-MCI was 37.2%. The Mann-Whitney U test analysis showed that PD-MCI performed poorly in different cognitive measures (digit span, Wisconsin Card Sorting Test, judgment of line orientation, and comprehension test), compared to PD patients without mild cognitive impairment (PD-nMCI). Phonemic fluency analyses showed that PD-MCI patients produced fewer words and switched significantly less, compared to controls and PD-nMCI. Concerning semantic fluency, the PD-MCI group differed significantly, compared to controls and PD-nMCI, in switches. Discriminant function analyses and logistic regression analyses revealed that switches predicted PD-MCI.

CONCLUSIONS

PD-MCI patients showed poor performance in VFT related to the deficient use of production strategies. The number of switches is a useful predictor for incident PD-MCI. (JINS, 2017, 23, 511-520).

Drosophila PINK1 and parkin loss-of-function mutants display a range of non-motor Parkinson's disease phenotypes

Parkinson's disease (PD) is more commonly associated with its motor symptoms and the related degeneration of dopamine (DA) neurons. However, it is becoming increasingly clear that PD patients also display a wide range of non-motor symptoms, including memory deficits and disruptions of their sleep-wake cycles. These have a large impact on their quality of life, and often precede the onset of motor symptoms, but their etiology is poorly understood. The fruit fly Drosophila has already been successfully used to model PD, and has been used extensively to study relevant non-motor behaviours in other contexts, but little attention has yet been paid to modelling non-motor symptoms of PD in this genetically tractable organism. We examined memory performance and circadian rhythms in flies with loss-of-function mutations in two PD genes: PINK1 and parkin. We found learning and memory abnormalities in both mutant genotypes, as well as a weakening of circadian rhythms that is underpinned by electrophysiological changes in clock neurons. Our study paves the way for further work that may help us understand the mechanisms underlying these neglected aspects of PD, thus identifying new targets for treatments to address these non-motor problems specifically and perhaps even to halt disease progression in its prodromal phase.

Smoking history is associated to cognitive impairment in Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) are more likely to suffer from cognitive impairment and dementia than healthy older adults. The aim of this study was to investigate smoking history as a risk factor for cognitive decline in PD.

METHOD

One hundred thirty-nine PD patients aged 50 years and older (Hoehn and Yahr = 1-3) were recruited from a clinical database. Global cognitive function was assessed with the Mini-Mental State Examination (MMSE) and smoking history was investigated as part of a standard clinical interview. A multiple linear regression analysis was used to develop a model for predicting participants' MMSE scores from age, education, Hoehn and Yahr stage, disease duration, the number of vascular risk factors and the number of smoking pack-years.

RESULTS

The regression model significantly accounted for 22.9% of the variance in MMSE scores. Significant predictors were education (β = .312, p < .001), age (β = -.215, p = .013) and total smoking pack-years (β = -.180, p = .029). In former smokers, the number of years since quitting had no effect on global cognition and there were no significant difference between patients who had quit smoking more than 10 years ago and those who had quit less than 10 years ago, F(1, 63) = 1.72, p = .195.

CONCLUSION

Smoking history was associated to global cognitive impairment in PD even in patients who had quit smoking. These results are in line with findings in healthy older adults that have linked smoking to cognitive impairment, global brain atrophy and functional changes. Future studies should consider a broader assessment of cognitive functions.

Cognitive phenotypes in parkinson's disease differ in terms of brain-network organization and connectivity

Cognitive deficits are common in Parkinson's disease and we suspect that dysfunctions of connected brain regions can be the source of these deficits. The aim of the present study was to investigate changes in whole-brain intrinsic functional connectivity according to differences in cognitive profiles in Parkinson's disease. 119 participants were enrolled and divided into four groups according to their cognitive phenotypes (determined by a cluster analysis): (i) 31 cognitively intact patients (G1), (ii) 31 patients with only slight mental slowing (G2), (iii) 43 patients with mild to moderate deficits mainly in executive functions (G3), (iv) 14 patients with severe deficits in all cognitive domains (G4-5). Rs-fMRI whole-brain connectivity was examined by two complementary approaches: graph theory for studying network functional organization and network-based statistics (NBS) for exploring functional connectivity amongst brain regions. After adjustment for age, duration of formal education and center of acquisition, there were significant group differences for all functional organization indexes: functional organization decreased (G1 > G2 > G3 > G4-5) as cognitive impairment worsened. Between-group differences in functional connectivity (NBS corrected, P < 0.01) mainly concerned the ventral prefrontal, parietal, temporal and occipital cortices as well as the basal ganglia. In Parkinson's disease, brain network organization is progressively disrupted as cognitive impairment worsens, with an increasing number of altered connections between brain regions. We observed reduced connectivity in highly associative areas, even in patients with only slight mental slowing. The association of slowed mental processing with loss of connectivity between highly associative areas could be an early marker of cognitive impairment in Parkinson's disease and may contribute to the detection of prodromal forms of Parkinson's disease dementia. Hum Brain Mapp 38:1604-1621, 2017. © 2016 Wiley Periodicals, Inc.