Cognitive change in Parkinson disease

Impacts of gait freeze on quality of life in Parkinson's disease, from the perspectives of patients and their carers

BACKGROUND

The World Health Organisation (WHO) reports that morbidity and mortality due to Parkinson's disease (PD) are increasing faster than for other neurodegenerative conditions. People with Parkinson's (PwP) present with a variety of motor symptoms, such as tremor, bradykinesia, and rigidity. Freezing of gait (FoG) is a significant motor symptom that manifests as temporary episodes of inability to move one's feet, despite the intention to walk.

AIMS

This study examined the impact of FoG on quality of life (QoL) within an Irish cohort of PwP, from the perspectives of both PwP and their carers, using validated questionnaires that had been adapted for online use.

METHODS

PwP and their carers were recruited by outreach to the Irish Parkinson's Community. Anonymous online questionnaires were distributed, which combined a demographic survey with several clinically validated surveys, including Freezing of Gait Questionnaire (FoG-Q), Parkinson's Disease Questionnaire 8 (PDQ-8), and Parkinson's Disease Carer Questionnaire (PDQ-C).

RESULTS

There was a strong correlation (p < 0.001) between severity of FoG and lower QoL among PwP. Significant correlation was also found between FoG severity and several motor symptoms, such as postural instability and difficulty with balance, and non-motor symptoms, such as cognitive changes and pain/discomfort. FoG severity correlated with disease progression. Significant correlation was also found between FoG and symptoms, as assessed from the perspective of the patients' carers.

CONCLUSIONS

This study shows that FoG is a significant detriment to the QoL of PwP, from the perspectives of patients and carers. This method of assessing FoG and QoL using online questionnaires has potential to enhance the reach and flexibility of this type of research. These findings will inform future studies on larger cohorts and highlight unmet clinical needs in PwP.

Neurocognitive Psychiatric and Neuropsychological Alterations in Parkinson's Disease: A Basic and Clinical Approach

The main histopathological hallmarks of Parkinson's disease (PD) are the degeneration of the dopaminergic neurons of the substantia nigra pars compacta and the loss of neuromelanin as a consequence of decreased dopamine synthesis. The destruction of the striatal dopaminergic pathway and blocking of striatal dopamine receptors cause motor deficits in humans and experimental animal models induced by some environmental agents. In addition, neuropsychiatric symptoms such as mood and anxiety disorders, hallucinations, psychosis, cognitive impairment, and dementia are common in PD. These alterations may precede the appearance of motor symptoms and are correlated with neurochemical and structural changes in the brain. This paper reviews the most crucial pathophysiology of neuropsychiatric alterations in PD. It is worth noting that PD patients have global task learning deficits, and cognitive functions are compromised in a way is associated with hypoactivation within the striatum, anterior cingulate cortex, and inferior frontal sulcus regions. An appropriate and extensive neuropsychological screening battery in PD must accurately assess at least five cognitive domains with some tests for each cognitive domain. This neuropsychological screening should consider the pathophysiological and clinical heterogeneity of cognitive dysfunction in PD.

Cognitive Impairments and Self-Reported Sleep in Early-Stage Parkinson's Disease with Versus without Probable REM Sleep Behavior Disorder

Parkinson’s disease (PD) is associated with cognitive and sleep impairments. The presence of rapid eye movement (REM) sleep behavior disorder (RBD) symptoms may represent a worse disease prognosis for PD individuals. We investigated cognitive functioning and self-reported sleep in early-stage PD individuals with (n = 19) or without (n = 31) probable RBD. Probable RBD was defined as >5 on the REM Sleep Behavior Disorder Screening Questionnaire. Inhibition, visuospatial cognitive abilities, working memory, sustained visual attention, verbal fluency, and episodic memory were assessed. Sleep impairments were assessed using the Pittsburgh Sleep Quality Index, Insomnia Severity Index, Epworth Sleepiness Scale, and Patient-Reported Outcomes Measurement Information System questionnaires. Chi-squared, Mann-Whitney U, and independent sample t-tests were employed to assess group differences. Participants with PD and probable RBD performed significantly worse on word reading and switching verbal fluency tasks than PD participants without probable RBD (p < 0.05). No significant differences were found in mood, PD severity, or sleep measures between PD individuals with or without probable RBD. Cognitive tasks that involve verbal or switching components may be most impaired in PD individuals with probable RBD. Larger samples are needed to determine whether other cognitive domains and sleep features are significantly associated with RBD in PD.

The Modality Effect on Delayed Free Recall in Non-demented Patients With Mild Parkinson's Disease Progression

Background: The modality effect plays the central role in learning and memory functions. Retrieval failure constitutes a common memory impairment that occurs among patients with Parkinson’s disease (PD). However, little knowledge exists about the relation between modality effect and delayed recall impairment in PD. The primary goal of this study was to compare delayed free recall performance between three different memory modalities (verbal, visual, and cross visual-verbal) in a sample of non-demented patients with mild PD progression. The secondary goal was to explore the frequency of deficient performance on the basis of normative comparisons on each of the three delayed free-recall measures.

Method: A total of 71 non-demented patients with mild PD progression were recruited for the administration of the Montreal Cognitive Assessment (MoCA), the Rey Auditory Verbal Learning Test (RAVLT), the Rey Osterrieth Complex Figure Test (ROCFT), and the Greek Version of Face-Name Associative Memory Examination (GR-FNAME12).

Results: The percentages of deficient-performances for the three delayed free recall measures were 45.1% (32/71), 39.4% (28/71) and 31% (22/71) for the GR-FNAME12, ROFCT and RAVLT, respectively. The results indicated no significant difference between performances of the GR-FNAME12 and ROCFT, both of which were significantly lower than performance on the RAVLT.

Conclusions: In conclusion, delayed free recall appears to be more severely affected in the cross visual-verbal and visual memory modalities than in verbal-memory modalities in the early phase of PD progression.

Zebrafish as an Emerging Model for Bioassay-Guided Natural Product Drug Discovery for Neurological Disorders

Most neurodegenerative diseases are currently incurable, with large social and economic impacts. Recently, there has been renewed interest in investigating natural products in the modern drug discovery paradigm as novel, bioactive small molecules. Moreover, the discovery of potential therapies for neurological disorders is challenging and involves developing optimized animal models for drug screening. In contemporary biomedicine, the growing need to develop experimental models to obtain a detailed understanding of malady conditions and to portray pioneering treatments has resulted in the application of zebrafish to close the gap between in vitro and in vivo assays. Zebrafish in pharmacogenetics and neuropharmacology are rapidly becoming a widely used organism. Brain function, dysfunction, genetic, and pharmacological modulation considerations are enhanced by both larval and adult zebrafish. Bioassay-guided identification of natural products using zebrafish presents as an attractive strategy for generating new lead compounds. Here, we see evidence that the zebrafish's central nervous system is suitable for modeling human neurological disease and we review and evaluate natural product research using zebrafish as a vertebrate model platform to systematically identify bioactive natural products. Finally, we review recently developed zebrafish models of neurological disorders that have the potential to be applied in this field of research.

The transcriptional response of skin to fluorescent light exposure in viviparous (Xiphophorus) and oviparous (Danio, Oryzias) fishes

Differences in light sources are common in animal facilities and potentially can impact experimental results. Here, the potential impact of lighting differences on skin transcriptomes has been tested in three aquatic animal models commonly utilized in biomedical research, (Xiphophorus maculatus (platyfish), Oryzias latipes (medaka) and Danio rerio (zebrafish). Analysis of replicate comparative RNA-Seq data showed the transcriptional response to commonly utilized 4100K or "cool white" fluorescent light (FL) is much greater in platyfish and medaka than in zebrafish. FL induces genes associated with inflammatory and immune responses in both medaka and zebrafish; however, the platyfish exhibit suppression of genes involved with immune/inflammation, as well as genes associated with cell cycle progression. Furthermore, comparative analyses of gene expression data from platyfish UVB exposures, with medaka and zebrafish after exposure to 4100K FL, show comparable effects on the same stress pathways. We suggest the response to light is conserved, but that long-term adaptation to species specific environmental niches has resulted in a shifting of the wavelengths required to incite similar "genetic" responses in skin. We forward the hypothesis that the "genetic perception" of light may have evolved differently than ocular perception and suggest that light type (i.e., wavelengths emitted) is an important parameter to consider in experimental design.

Onset of Mild Cognitive Impairment in Parkinson Disease

OBJECTIVE

Characterize the onset and timing of cognitive decline in Parkinson disease (PD) from the first recognizable stage of cognitively symptomatic PD-mild cognitive impairment (PD-MCI) to PD dementia (PDD). Thirty-nine participants progressed from PD to PDD and 25 remained cognitively normal.

METHODS

Bayesian-estimated disease-state models described the onset of an individual's cognitive decline across 12 subtests with a change point.

RESULTS

Subtests measuring working memory, visuospatial processing ability, and crystalized memory changed significantly 3 to 5 years before their first nonzero Clinical Dementia Rating and progressively worsened from PD to PD-MCI to PDD. Crystalized memory deficits were the hallmark feature of imminent conversion of cognitive status. Episodic memory tasks were not sensitive to onset of PD-MCI. For cognitively intact PD, all 12 subtests showed modest linear decline without evidence of a change point.

CONCLUSIONS

Longitudinal disease-state models support a prodromal dementia stage (PD-MCI) marked by early declines in working memory and visuospatial processing beginning 5 years before clinical diagnosis of PDD. Cognitive declines in PD affect motor ability (bradykinesia), working memory, and processing speed (bradyphrenia) resulting in PD-MCI where visuospatial imagery and memory retrieval deficits manifest before eventual development of overt dementia. Tests of episodic memory may not be sufficient to detect and quantify cognitive decline in PD.

Population Base Rates and Disease Course of Common Psychiatric and Neurodegenerative Disorders

Knowledge of population base rates of neurological and psychiatric disorders is fundamental for diagnostic decision making. Consideration of relevant probabilistic information can improve diagnostic efficiency and accuracy. However, such data continue to be misused or underutilized, which can lead to misdiagnoses and negative patient outcomes. The aim of the current review is to create an easily accessible and comprehensive reference of existing age of onset as well as prevalence and incidence data for common neurodegenerative and psychiatric disorders in adults. Relevant epidemiological data were compiled from well-respected and frequently-cited textbooks and scholarly studies. Reviews were collected from PubMed, and publicly-available sources were gathered from Google Scholar. Results are organized and presented in several tables and a figure, which can be used as a diagnostic guide for students and clinicians across healthcare disciplines.

Fully automated structural MRI of the brain in clinical dementia workup

Background The dementia syndrome has been regarded a clinical diagnosis but the focus on supplemental biomarkers is increasing. An automatic magnetic resonance imaging (MRI) volumetry method, NeuroQuant® (NQ), has been developed for use in clinical settings. Purpose To evaluate the clinical usefulness of NQ in distinguishing Alzheimer's disease dementia (AD) from non-dementia and non-AD dementia. Material and Methods NQ was performed in 275 patients diagnosed according to the criteria of ICD-10 for AD, vascular dementia and Parkinson's disease dementia (PDD); the Winblad criteria for mild cognitive impairment; the Lund-Manchester criteria for frontotemporal dementia; and the revised consensus criteria for Lewy body dementia (LBD). Receiver operating curve (ROC) analyses with calculation of area under the curve (AUC) and regression analyses were carried out. Results Forebrain parenchyma (AUC 0.82), hippocampus (AUC 0.80), and inferior lateral ventricles (AUC 0.78) yielded the highest AUCs for AD/non-dementia discrimination. Only hippocampus (AUC 0.62) and cerebellum (AUC 0.67) separated AD from non-AD dementia. Cerebellum separated AD from PDD-LBD (AUC 0.83). Separate multiple regression analyses adjusted for age and gender, showed that memory (CERAD 10-word delayed recall) (beta 0.502, P < 0.001) was more strongly associated to the hippocampus volume than the diagnostic distinction of AD versus non-dementia (beta -0.392, P < 0.001). Conclusion NQ measures could separate AD from non-dementia fairly well but generally poorer from non-AD dementia. Degree of memory impairment, age, and gender, but not diagnostic distinction, were associated to the hippocampus volume in adjusted analyses. Surprisingly, cerebellum was found relevant in separating AD from PDD-LBD.

The relation of anxiety and cognition in Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) has long been conceptualized as a motor disorder, but nonmotor symptoms also manifest in the disease and significantly reduce quality of life. Anxiety and cognitive dysfunction are prevalent nonmotor symptoms, even in early disease stages, but the relation between these symptoms remains poorly understood. We examined self-reported anxiety and neurocognitive function, indexed by measures of executive function (set-shifting and phonemic fluency), categorical fluency, and attention/working memory. We hypothesized that anxiety would correlate with cognitive performance.

METHOD

The Beck Anxiety Inventory and cognitive tests (Trail Making, Verbal Fluency, Digit Span) were administered to 77 nondemented adults with mild to moderate idiopathic PD (39 men, 38 women; Mage = 62.9 years).

RESULTS

Higher anxiety was associated with more advanced disease stage and severity and with poorer set-shifting when using a derived metric to account for motoric slowing. Depression correlated with greater anxiety and disease severity, but not with cognitive performance.

CONCLUSIONS

Our findings support the association of anxiety with a specific domain of executive function, set-shifting, in nondemented individuals with mild to moderate PD, raising the possibility that treatment of anxiety may alleviate aspects of executive dysfunction in this population. (PsycINFO Database Record

Relationship between Alzheimer's disease GWAS-linked top hits and risk of Parkinson's disease with or without cognitive decline: a Chinese population-based study

Alzheimer's disease (AD), Parkinson's disease (PD), and cognitive impairment in PD have overlapping clinical and pathological features. To examine whether there is a genetic link for these diseases, we performed a case-control study in Chinese population to evaluate the association of AD genome-wide association studies top hits with both PD and cognitive function in PD, investigating 13 single-nucleotide polymorphisms in 9 genes (BIN1, CLU, ABCA7, CR1, PICALM, MS4A6A, CD33, MS4A4E, and CD2AP). A total of 454 controls and 442 PD patients were genotyped, including 75 mild cognitive impairment and 99 dementia. As a result, no significant association of the AD-susceptibility loci was identified in PD cases, PD-dementia, or PD-mild cognitive impairment. Our findings imply that the 13 single-nucleotide polymorphisms from AD genome-wide association studies may not play major role in the genetic predisposition with PD and cognitive function in PD in a Chinese population.

DEVELOPMENT OF CLINICAL DEMENTIA RATING SCALE CUTOFF SCORES FOR PATIENTS WITH PARKINSON'S DISEASE

BACKGROUND

The purpose of this study was to explore validity of the Clinical Dementia Rating Scale in measuring cognitive impairment among individuals with Parkinson's disease. The scale was created for use in patients with Alzheimer's disease and, to date, there have been no published studies examining if this tool is appropriate for patients with Parkinson's disease.

METHODS

The data were obtained from the National Alzheimer's Coordinating Center database and included 490 subjects diagnosed with Parkinson's disease, further categorized as having Parkinson's disease dementia (n= 151), mild cognitive impairment (n= 186), or normal cognition (n = 153) by a treating physician. Sensitivity, specificity, positive predictive value and negative predictive values were calculated for the Clinical Dementia Rating Scale Global Score as well as the Sum of Boxes Score using existing cutoff scores. Finally, new cutoff scores were calculated using sensitivity and specificity values derived using Receiver Operating Characteristic curves.

RESULTS

Sensitivity and specificity of the published Global Score cutoff scores for patients with dementia were .34 and .10, respectively. The newly calculated cutoff scores for patients with dementia yielded a sensitivity of .79 and a specificity of .96. The area under the curve was 0.92 (95% CI = 0.90-0.95).

CONCLUSION

The CDR is a useful tool in identifying dementia in patients with Parkinson's disease when the cutoff scores are adjusted.

Changes of brain gray matter structure in Parkinson's disease patients with dementia

Voxel-based morphometry is gaining considerable interest for studies examining Parkinson's disease dementia patients. In this study, 12 patients with clinically defined Parkinson's disease and dementia and 12 non-demented patients with Parkinson's disease were examined using a T1WI three-dimensional fast spoiled gradient echo sequence. Gray matter data were analyzed using a voxel-based morphometry method and independent sample t-test based on Statistical Parametric Mapping 5 software. Differences in gray matter volume were represented with statistical parametric mapping. Compared with Parkinson's disease patients without dementia, decreased gray matter volume in Parkinson's disease dementia patients was observed in the bilateral superior temporal gyrus, bilateral posterior cingulate and left cingulate gyrus, right parahippocampal gyrus and hippocampus, right precuneus and right cuneus, left inferior frontal gyrus and left insular lobe. No increased gray matter volume was apparent. These data indicate that gray matter atrophy in the limbic system and cerebral neocortex is related to the presence of dementia.

The spectrum of cognitive impairment in Lewy body diseases

Cognitive impairment represents an important and often defining component of the clinical syndromes of Lewy body disorders: Parkinson's disease and dementia with Lewy bodies. The spectrum of cognitive deficits in these Lewy body diseases encompasses a broad range of clinical features, severity of impairment, and timing of presentation. It is now recognized that cognitive dysfunction occurs not only in more advanced Parkinson's disease but also in early, untreated patients and even in those patients with pre-motor syndromes, such as rapid eye movement behavior disorder and hyposmia. In recent years, the concept of mild cognitive impairment as a transitional or pre-dementia state in Parkinson's disease has emerged. This has led to much research regarding the diagnosis, prognosis, and underlying neurobiology of mild cognitive impairment in Parkinson's disease, but has also raised questions regarding the usefulness of this concept and its application in clinical and research settings. In addition, the conundrum of whether Parkinson's disease dementia and dementia with Lewy bodies represent the same or different entities remains unresolved. Although these disorders overlap in many aspects of their presentations and pathophysiology, they differ in other elements, such as timing of cognitive, behavioral, and motor symptoms; medication responses; and neuropathological contributions. This article examines the spectrum and evolution of cognitive impairment in Lewy body disorders and debates these controversial issues in the field using point-counterpoint approaches.

Neurotransmitter CART as a New Therapeutic Candidate for Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. To date, there is no effective treatment that halts its progression. Increasing evidence indicates that mitochondria play an important role in the development of PD. Hence mitochondria-targeted approaches or agents may have therapeutic promise for treatment of the disease. Neuropeptide CART (cocaine-amphetamine-regulated transcript), a hypothalamus and midbrain enriched neurotransmitter with an antioxidant property, can be found in mitochondria, which is the main source of reactive oxygen species. Systemic administration of CART has been found to ameliorate dopaminergic neuronal loss and improve motor functions in a mouse model of PD. In this article, we summarize recent progress in studies investigating the relationship between CART, dopamine, and the pathophysiology of PD, with a focus on mitochondria-related topics.

Spectroscopic changes associated with mild cognitive impairment and dementia in Parkinson's disease

Frontal subcortical cognitive defects are predominant in Parkinson's disease (PD). Temporal lobe dysfunction seems more relevant for progression to dementia. We aimed to study the relative importance of temporal lobe defects versus executive impairment in the progression to dementia in PD by using proton magnetic resonance spectroscopy ((1)H-MRS). The (1)H-MRS features of PD patients with intact cognition (PD-CgInt; n = 16), mild cognitive impairment (MCI; n = 15) and dementia (PDD; n = 15) were compared, to delineate the metabolic alterations correlating with cognitive status. Metabolite concentrations were acquired from voxels localized to the hippocampus and dorsolateral prefrontal cortex (DL-PFC). Cognitive status was established following the Movement Disorder Society PDD criteria, administering the Clinical Dementia Rating Scale and Mattis Dementia Rating Scale. The Parkinson's Disease Cognitive Rating Scale (PD-CRS) was used to correlate (1)H-MRS with neuropsychology. N-acetylaspartate (NAA) concentrations in the right DL-PFC were decreased in PD-MCI compared with PD-CgInt patients (p = 0.002), and correlated with frontal subcortical tasks. Decreased NAA concentrations in the left hippocampus in PDD compared to PD-MCI (p = 0.03) correlated with confrontation naming. The present findings support that executive impairment is related to dorsolateral prefrontal dysfunction from the early stages, while progression to dementia is linked to the additional impairment of temporal lobe structures. The PD-CRS was able to capture the differential impairment of prefrontal versus temporal cortical areas.

Neuropathologic substrates of Parkinson disease dementia

OBJECTIVE

A study was undertaken to examine the neuropathological substrates of cognitive dysfunction and dementia in Parkinson disease (PD).

METHODS

One hundred forty patients with a clinical diagnosis of PD and either normal cognition or onset of dementia 2 or more years after motor symptoms (PDD) were studied. Patients with a clinical diagnosis of dementia with Lewy bodies were excluded. Autopsy records of genetic data and semiquantitative scores for the burden of neurofibrillary tangles, senile plaques, Lewy bodies (LBs), and Lewy neurites (LNs) and other pathologies were used to develop a multivariate logistic regression model to determine the independent association of these variables with dementia. Correlates of comorbid Alzheimer disease (AD) were also examined.

RESULTS

Niney-two PD patients developed dementia, and 48 remained cognitively normal. Severity of cortical LB (CLB)/LN pathology was positively associated with dementia (p < 0.001), with an odds ratio (OR) of 4.06 (95% confidence interval [CI], 1.87-8.81), as was apolipoprotein E4 (APOE4) genotype (p = 0.018; OR, 4.19; 95% CI, 1.28-13.75). A total of 28.6% of all PD cases had sufficient pathology for comorbid AD, of whom 89.5% were demented. The neuropathological diagnosis of PDD+AD correlated with an older age of PD onset (p = 0.001; OR, 1.12; 95% CI, 1.04-1.21), higher CLB/LN burden (p = 0.037; OR, 2.48; 95% CI, 1.06-5.82), and cerebral amyloid angiopathy severity (p = 0.032; OR, 4.16; 95% CI, 1.13-15.30).

INTERPRETATION

CLB/LN pathology is the most significant correlate of dementia in PD. Additionally, APOE4 genotype may independently influence the risk of dementia in PD. AD pathology was abundant in a subset of patients, and may modify the clinical phenotype. Thus, therapies that target α-synuclein, tau, or amyloid β could potentially improve cognitive performance in PD.

Cognitive impairment is common in Parkinson's disease without dementia in the early and middle stages in a Han Chinese cohort

BACKGROUND

Cognitive impairments have been reported to be common in Parkinson's disease (PD) without dementia, which occur not only in the late stages of PD, but also in the early and middle stages. Until now, no reports on the profile of cognitive impairment in Chinese non-demented PD population have been published yet. Different ethnic groups should be assessed to improve evaluation of cognitive impairment in clinical practice. The aims of this study are to estimate the frequencies and profile of cognitive impairments and to explore the risk factors of cognitive impairments in Han Chinese non-demented PD patients at early and middle stages.

METHODS

Eighty non-demented PD patients in early and middle stages and 86 healthy controls were invited to participate in this study. Neuropsychological batteries testing executive function, visuospatial function, memory and attention were evaluated. Cognitive impairments were defined as impaired performance in at least one cognitive domain.

RESULTS

Neuropsychological batteries detected 30 cases with executive dysfunction, 27 cases with memory impairment, eight cases with visuospatial dysfunction and seven cases with attention impairment. As many as 48 cases (60%) of PD patients presented cognitive impairment. Logistic regression analysis indicated that education level and Hoehn & Yahr stage were associated with cognitive impairment in PD.

CONCLUSIONS

Cognitive impairment is common in the early and middle stages of PD without dementia; executive function is the most common domain impaired in a Chinese PD population. Cognitive impairment might be predicted by lower education level and higher Hoehn and Yahr stage.

Is all cognitive impairment in Parkinson's disease "mild cognitive impairment"?

Cognitive impairment can be demonstrated in Parkinson's disease (PD) from the very beginning of the disease. Clinical manifestations range from slight deficits, only demonstrable by means of neuropsychological testing, up to dementia. If a linear involution is supposed for the cognitive worsening in PD, then the relatively subtle cognitive defects should be taken as the earliest signs of dementia implying that PD-MCI concept would be thoroughly equivalent to that used for the early prediction of other dementias among healthy population. Cognitive defects in PD, however, may not follow a normal distribution. While fronto-striatal deficits, such as working memory, set-shifting and free-recall verbal memory appear altered in most patients during long periods of time, certain functions depending on more posterior-cortical regions, such as copying or naming, usually characterize patients with dementia. Fronto-striatal and posterior-cortical cognitive defects may have a different pathophysiological substrates, evolution and prognosis. While fronto-striatal defects appear more related to dopaminergic defects, posterior-cortical defects may obey multiple neurotransmitter failure. Designing criteria to accurately diagnose PD-MCI is highly relevant for clinical treatment, research, care-giving and decision-making. Besides quantitative defects, an operative definition of MCI in PD should clearly distinguish a "risky cognitive profile" among the broad cognitive defects intrinsic to PD. Thus, along with other possible biological markers, from a neuropsychological point of view, posterior-cortical defects probably represent the very syndrome of MCI in PD.

Longitudinal changes in cognition in Parkinson's disease with and without dementia

BACKGROUND

The longitudinal cognitive course in Parkinson's disease (PD) with and without dementia remains undefined. We compared cross-sectional models of cognition in PD (both with and without dementia), Alzheimer's disease (AD), and nondemented aging and followed the participants over time.

METHOD

Previously validated models of cognitive performance in AD and nondemented aging were extended to individuals with PD (with dementia, n = 71; without dementia, n = 47). Confirmatory factor analysis and piecewise regression were used to compare the longitudinal course of participants with PD with 191 cognitively healthy subjects and 115 individuals with autopsy-confirmed AD.

RESULTS

A factor analytic model with one general factor and three specific factors (verbal memory, visuospatial memory, working memory) fit demented and nondemented PD. Longitudinal change indicated that individuals with PD with dementia declined significantly more rapidly on visuospatial and verbal memory tasks than AD alone. Cognitive declines across all factors in AD and PD dementia accelerated several years prior to clinical dementia diagnosis.

CONCLUSION

Both specific and global cognitive changes are witnessed in PD and AD. Longitudinal profiles of cognitive decline in PD and AD differed. PD with or without dementia has a core feature of longitudinal decline in visuospatial abilities.

Profile of cognitive impairment in Parkinson's disease

Cognitive impairment (CI) is a common nonmotor complication of Parkinson's disease (PD), and is associated with significant disability for patients and burden for caregivers. Similar to motor symptoms, the characteristics of CI in PD can be quite variable, both in terms of what cognitive domains are impaired, and the timing of onset and rate of progression. This review will examine the profile of cognitive domain impairments observed in PD, with a focus on early CI (without dementia). We will also discuss possible relationships between specific cognitive domain impairments in PD and pathological processes such as Lewy-related pathology and Alzheimer's disease. It is our hypothesis that the specific characteristics of CI observed in individual PD patients provide clues to the underlying pathological processes, and that understanding the biological basis of this clinical phenomenon will assist in directing disease-specific treatments. Given the high lifetime risk for CI in PD, it is imperative that we improve our understanding and treatments for this common and disabling problem in PD.

Effects of cholinesterase inhibitors in Parkinson's disease dementia: a review of clinical data

AIMS

Cognitive impairment and dementia are common features of Parkinson's disease (PD). Patients with Parkinson's disease dementia (PDD) often have significant cholinergic defects, which may be treated with cholinesterase inhibitors (ChEIs). The objective of this review was to consider available efficacy, tolerability, and safety data from studies of ChEIs in PDD.

DISCUSSIONS

A literature search resulted in the identification of 20 relevant publications. Of these, the treatment of PD patients with rivastigmine, donepezil, or galantamine was the focus of six, eleven, and two studies respectively, while one study reported use of both tacrine and donepezil. The majority of studies were small (<40 patients), with the exception of two large randomized controlled trials (RCTs) that are the main focus of this review. In the smaller studies, treatment benefits were reported on a range of outcome measures, though results were extremely variable. While the full results of a large RCT of donepezil in patients with PDD are not yet available, significant treatment differences were reported on the CIBIC-plus at the highest treatment dose. A trend toward improvement was also observed in treated patients on the ADAS-cog. The second large RCT found significant improvements in rivastigmine-treated patients compared with placebo on both the ADAS-cog (P < 0.001) and the ADCS-CGIC (P < 0.007), as well as on all secondary efficacy outcomes. Consequently, rivastigmine is now widely approved for the symptomatic treatment of mild to moderate PDD.

CONCLUSIONS

Taken together, these studies suggest that ChEIs are efficacious in the treatment of PDD.

Pharmacological therapy in Parkinson's disease: focus on neuroprotection

Although the number of available therapeutic approaches in Parkinson's disease (PD) is steadily increasing the search for effective neuroprotective agent is continuing. Such research is directed at influencing the key steps in the pathomechanism: the mitochondrial dysfunction, the oxidative stress, the neuroinflammatory processes and the final common apoptotic pathway. Earlier-developed symptomatic therapies were implicated to be neuroprotective, and promising novel disease modifying approaches were brought into the focus of interest. The current review presents a survey of our current knowledge relating to the pathomechanism of PD and discusses the putative neuroprotective therapy.

Persistent short-term memory defects following sleep deprivation in a drosophila model of Parkinson disease

STUDY OBJECTIVES

Parkinson disease (PD) is the second most common neurodegenerative disorder in the United States. It is associated with motor deficits, sleep disturbances, and cognitive impairment. The pathology associated with PD and the effects of sleep deprivation impinge, in part, upon common molecular pathways suggesting that sleep loss may be particularly deleterious to the degenerating brain. Thus we investigated the long-term consequences of sleep deprivation on shortterm memory using a Drosophila model of Parkinson disease.

PARTICIPANTS

Transgenic strains of Drosophila melanogaster.

DESIGN

Using the GAL4-UAS system, human alpha-synuclein was expressed throughout the nervous system of adult flies. Alpha-synuclein expressing flies (alpha S flies) and the corresponding genetic background controls were sleep deprived for 12 h at age 16 days and allowed to recover undisturbed for at least 3 days. Short-term memory was evaluated using aversive phototaxis suppression. Dopaminergic systems were assessed using mRNA profiling and immunohistochemistry. MEASURMENTS AND RESULTS: When sleep deprived at an intermediate stage of the pathology, alpha S flies showed persistent short-term memory deficits that lasted > or = 3 days. Cognitive deficits were not observed in younger alpha S flies nor in genetic background controls. Long-term impairments were not associated with accelerated loss of dopaminergic neurons. However mRNA expression of the dopamine receptors dDA1 and DAMB were significantly increased in sleep deprived alpha S flies. Blocking D1-like receptors during sleep deprivation prevented persistent shortterm memory deficits. Importantly, feeding flies the polyphenolic compound curcumin blocked long-term learning deficits.

CONCLUSIONS

These data emphasize the importance of sleep in a degenerating/reorganizing brain and shows that pathological processes induced by sleep deprivation can be dissected at the molecular and cellular level using Drosophila genetics.

Increased vulnerability to 6-hydroxydopamine lesion and reduced development of dyskinesias in mice lacking CB1 cannabinoid receptors

Motor impairment, dopamine (DA) neuronal activity and proenkephalin (PENK) gene expression in the caudate-putamen (CPu) were measured in 6-OHDA-lesioned and treated (L-DOPA+benserazide) CB1 KO and WT mice. A lesion induced by 6-OHDA produced more severe motor deterioration in CB1 KO mice accompanied by more loss of DA neurons and increased PENK gene expression in the CPu. Oxidative/nitrosative and neuroinflammatory parameters were estimated in the CPu and cingulate cortex (Cg). CB1 KO mice exhibited higher MDA levels and iNOS protein expression in the CPu and Cg compared to WT mice. Treatment with L-DOPA+benserazide (12 weeks) resulted in less severe dyskinesias in CB1 KO than in WT mice. The results revealed that the lack of cannabinoid CB1 receptors increased the severity of motor impairment and DA lesion, and reduced L-DOPA-induced dyskinesias. These results suggest that activation of CB1 receptors offers neuroprotection against dopaminergic lesion and the development of L-DOPA-induced dyskinesias.

Executive cognitive tests for the evaluation of patients with Parkinson's disease

Parkinson's disease (PD) is characterized by changes in movement, which are later followed by cognitive, behavioral and psychological changes. The objective of the present study was to correlate different tests used to examine executive functions in PD patients followed at a specialized outpatient clinic.

METHODS

Thirty-five patients with idiopathic PD aged 63.0 years on average and with mean schooling of 5.5±4.2 years, were examined using the following tests: Mattis Dementia Rating Scale (MDRS), Scales for Outcomes of Parkinson's Disease-Cognition (SCOPA-COG), Wisconsin Card Sorting Test (WCST), Frontal Assessment Battery (FAB), Digit Span - Inverse Order (IO) (a subtest of the WAIS III) and Verbal Fluency Test (category animals).

RESULTS

Significant correlations were detected between FAB and MDRS Conceptualization (0.814), MDRS Initiation/Perseveration (I/P) and SCOPA-COG Executive Function (0.643), FAB and MDRS I/P (0.601), FAB and Verbal Fluency (0.602), MDRS I/P and MDRS Conceptualization (0.558), Verbal Fluency and MDRS I/P (0.529), MDRS Attention and SCOPA-COG Executive Function (0.495), MDRS Conceptualization and SCOPA-COG Executive Function (0.520), FAB and Digit Span (OI) (0.503), Verbal Fluency and MDRS Conceptualization (0.501), and WCST perseverative errors and FAB (-0.379), WCST perseverative errors and MDRS Conceptualization (0.445), WCST perseverative errors and MDRS I/P (-0.407) and WCST categories completed and MDRS Conceptualization (0.382).

DISCUSSION

The results demonstrated strong correlations between most of the tests applied, but no associations were detected between the WCST and the other tests, a fact that may be explained by the heterogeneity of scores obtained in the tests by the patients evaluated. A difficulty of the present study was the lack of a control groups for the establishment of adequate standards for this population.

Dementia and functional decline in patients with Parkinson's disease

Functional decline in Parkinson's disease (PD), characterized by reduced ability to carry out activities of daily living, usually results from typical motor impairment and may be aggravated by concomitant cognitive impairment.

Objective

To compare the functional decline in Parkinson's disease between patients with dementia and cognitively preserved patients.

Methods

From an original sample composed of 50 patients with a clinical diagnosis of idiopathic PD seen in a consecutive series, 33 non-depressed patients were selected comprising 13 with dementia and 20 cognitively preserved individuals. All patients enrolled in this study were drawn from a public outpatient clinic, specialized in movement disorders. The clinical stage of PD was determined by the Hoehn & Yahr scale, and the functional capacity was verified using the Unified Parkinson's Disease Rating Scale UPDRS ADL (subscale II: activities of daily living) and the Schwab & England scale. The two last scales measure the functional degree of independence in activities of daily living. The neuropsychological assessment was performed using The Cambridge Examination for Mental Disorders of the Elderly - CAMCOG, Cognitive Section and the Stroop Color Word Test.

Results

As expected, in comparison with cognitively preserved patients, the group with dementia presented significantly lower scores throughout the neuropsychological evaluation. The patients with dementia were found to have a longer period of disease, a more advanced clinical staging according to the Hoehn & Yahr, and greater functional decline according both to the UPDRS ADL and Schwab & England, with statistically significant difference between the groups.

Conclusion

Patients with dementia were at a more advanced clinical stage of Parkinson's disease and evidenced greater functional decline in comparison with patients without dementia.

Zebrafish: An in vivo model for the study of neurological diseases

As the population ages, there is a growing need for effective therapies for the treatment of neurological diseases. A limited number of therapeutics are currently available to improve cognitive function and research is limited by the need for in vivo models. Zebrafish have recently become a focus of neurobehavioral studies since larvae display neuropathological and behavioral phenotypes that are quantifiable and relate to those seen in man. Due to the small size of Zebrafish larvae, assays can be undertaken in 96 well plates and as the larvae can live in as little as 200 mul of fluid, only a few milligrams of compound are needed for screening. Thus in vivo analysis of the effects of compounds can be undertaken at much earlier stages in the drug discovery process. This review will look at the utility of the zebrafish in the study of neurological diseases and its role in improving the throughput of candidate compounds in in vivo screens.

Neuropsychological characteristics of dementia with Lewy bodies and Parkinson's disease with dementia: differentiation, early detection, and implications for "mild cognitive impairment" and biomarkers

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are neurodegenerative conditions sharing a disorder of alpha-synuclein metabolism. Temporal differences in the emergence of symptoms and clinical features warrant the continued clinical distinction between DLB and PDD. While DLB and PDD groups' neuropsychological profiles often differ from those in Alzheimer's disease (AD), the diagnostic sensitivity, specificity, and predictive values of these profiles remain largely unknown. PDD and DLB neuropsychological profiles share sufficient similarity to resist accurate and reliable differentiation. Although heterogeneous cognitive changes (predominantly in memory and executive function) may manifest earlier and more frequently than previously appreciated in Parkinson's disease (PD), and executive deficits may be harbingers of dementia, the enthusiasm to uncritically extend the concept of mild cognitive impairment (MCI) to PD should be tempered. Instead, future research might strive to identify the precise neuropsychological characteristics of the prodromal stages of PD, PDD, and DLB which, in conjunction with other potential biomarkers, facilitate early and accurate diagnosis, and the definition of neuroprotective, neurorestorative, and symptomatic treatment endpoints.