A précis of recent advances in the neuropsychology of mild cognitive impairment(s) in Parkinson's disease and a proposal of preliminary research criteria

Efficacy of non-computerized cognitive rehabilitation in Parkinson's disease: A one year follow up study

In this study, we explored the effect of non-computerized cognitive rehabilitation in patients with Parkinson's disease in comparison with an intervention with elements of music therapy after the completion of a three-month program and one year after the end of the intervention. After the initial neuropsychological examination, the respondents were divided into two intervention groups. The experimental group (n = 26) underwent a twelve-week program of cognitive rehabilitation at a frequency of 60 minutes once a week. The control group (n = 27) underwent an intervention program with elements of music therapy at the same frequency. Respondents who underwent the cognitive rehabilitation program improved in the delayed recall from visual memory in the follow-up examination after the end of the cognitive intervention. One year after the end, the effect of cognitive rehabilitation persisted in delayed recall from visual memory and in executive mental flexibility. Cognitive rehabilitation is an effective approach to compensate for cognitive deficits in P D, but other approaches to cognitive stimulation may be equally effective.

An Examination of Cognitive Heterogeneity in Parkinson Disease: The Dual-Syndrome Hypothesis

PURPOSE

Cognitive impairment is one of the most debilitating nonmotor symptoms in Parkinson disease (PD), and its presentation is heterogeneous. One proposed model to explain cognitive variability in PD is the dual-syndrome hypothesis. This hypothesis delineates two cognitive profiles, a "fronto-striatal" profile and a "posterior cortical" profile according to symptom presentation, associated motor phenotype, and risk for dementia. The current study examined the dual-syndrome hypothesis in individuals with idiopathic PD to evaluate the existence of these profiles, determine the association with the motor phenotype (tremor dominant vs. postural instability/gait disorder), and assess the relative risk for dementia.

METHOD

A retrospective examination was conducted using data from the Parkinson's Progression Markers Initiative database at baseline (within 2 years of diagnosis) and 5 years after baseline. Descriptive categorizations, cluster analyses, generalized linear mixed models, and logistic regressions were used to address the research questions.

RESULTS

There was emerging evidence of cognitive profiles; however, these were not fully supported by cluster analyses. Baseline cognitive profile was associated with later motor phenotype, and as predicted, dementia risk was greatest in persons with baseline posterior cortical impairments.

CONCLUSION

The current results provide mixed support for the dual-syndrome hypothesis, with some evidence that the posterior cortical cognitive profile is associated with postural instability and gait disorder as well as greater dementia risk.

Strategic Spatial Anchoring as Cognitive Compensation During Word Categorization in Parkinson's Disease: Evidence from Eye Movements

The association between a word and typical location (e.g., cloud-up) appears to modulate healthy individuals' response times and visual attention. This study examined whether similar effects can be observed in a clinical population characterized by difficulties in both spatial representation and lexical processing. In an eye-tracking experiment, participants categorized spoken words as either up-associated or down-associated. Parkinson's disease patients exhibited a tendency to maintain their visual attention in the upper half of the screen, however, this tendency was significantly lower when participants categorized concepts as down-associated. Instead, the control group showed no preference for either the upper or lower half of the screen. We argue that Parkinson's disease patients present an over-reliance on space during word categorization as a form of cognitive compensation. Such compensation reveals that this clinical population may use spatial anchoring when categorizing words with a spatial association, even in the absence of explicit spatial cues.

Mind the gaps: What we don't know about cognitive impairment in essential tremor

INTRODUCTION

Although the hallmark feature of essential tremor (ET) is tremor, there is growing appreciation that cognitive impairment also occurs, including increased prevalence of mild cognitive impairment (MCI) and increased prevalence and incidence of dementia. With emerging knowledge of ET-cognitive impairment, come fundamental questions regarding its course, bases, predictors and clinical outcomes. Studies in the general population and in Parkinson's disease (PD), a related movement disorder, offer a starting point from which to begin filling these clinically important knowledge gaps.

METHODS

A PubMed search (June 2018) identified articles for this review.

RESULTS

Much of our knowledge of cognitive impairment in ET is of the static condition (e.g., prevalence of cognitive impairment in ET), with nearly no information on its bases, predictors and dynamics (i.e., course, and clinical outcomes). In PD, where such data have been published, rates of cognitive decline and conversion to MCI/dementia are higher than in the general population. Predictors of cognitive change in PD and the general population have also been identified, yet they only partially overlap one another.

CONCLUSION

The predictors and dynamics of cognitive impairment have been investigated fairly extensively in the general population, to a somewhat lesser extent in PD, and are emerging only now in ET. We suggest that longitudinal studies specific to ET are needed, and we outline variables to be considered in these investigations. Increased knowledge of ET-cognitive impairment will facilitate meaningful counseling of patients and their families.

Training working memory updating in Parkinson's disease: A randomised controlled trial

Frontostriatal dysfunction in Parkinson's disease (PD) increases the risk for working memory (WM) impairment and depression, calling for counteractive measures. Computerised cognitive rehabilitation is a promising option, but targeted training protocols are lacking and lab-based training can be demanding due to the repeated visits. This study tested the feasibility and efficacy of home-based computerised training targeting mainly WM updating in PD. Fifty-two cognitively well-preserved PD patients were randomised to a WM training group and an active control group for five weeks of training (three 30-min sessions per week). WM training included three computerised adaptive WM tasks (two updating, one maintenance). The outcomes were examined pre- and post-training with trained and untrained WM tasks, tasks tapping other cognitive domains, and self-ratings of executive functioning and depression. Home-based training was feasible for the patients. The training group improved particularly on the updating training tasks, and showed posttest improvement on untrained WM tasks structurally similar to the trained ones. Moreover, their depression scores decreased compared to the controls. Our study indicates that patients with mild-to-moderate PD can self-administer home-based computerised WM training, and that they yield a similar transfer pattern to untrained WM tasks as has been observed in healthy older adults.

Strengths and challenges in conducting clinical trials in Parkinson's disease mild cognitive impairment

Treatments to slow the progression of cognitive dysfunction to dementia and improve the quality of life of persons with Parkinson's disease (PD) are desperately needed. Because PD mild cognitive impairment is considered a transitional stage before dementia, it opens a window to timely intervention. This article critically reviews the strengths and challenges of pharmacologic and nonpharmacologic clinical therapeutic trials in PD mild cognitive impairment conducted during the past 5 years, including ongoing trials. Relatively few high-quality trials have been conducted, and some important factors in designing future clinical trials are discussed. © 2018 International Parkinson and Movement Disorder Society.

Neuropsychological Profiles in Mild Cognitive Impairment due to Alzheimer's and Parkinson's Diseases

Background: Neuropsychological comparisons between patients with mild cognitive impairment due to Parkinson’s disease (MCI-PD) and Alzheimer’s disease (MCI-AD) is mostly based on indirect comparison of patients with these disorders and normal controls (NC).

Objective: The focus of this study was to make a direct comparison between patients with these diseases.

Methods: The study compared 13 patients with MCI-PD and 19 patients with MCI-AD with similar age, education and gender. The participants were recruited and assessed at the same university clinic with equal methods.

Results: The main finding was that on group level, MCI-AD scored significantly poorer on learning and memory tests than MCI-PD, whereas MCI-PD were impaired on 1 of 3 measures of executive functioning.

Conclusion: MCI-AD performed poorer learning and memory tests, whereas MCI-PD only scored below the employed cut-off on one single executive test. In general, MCI-PD was noticeably less cognitively impaired than MCI-AD.

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.

N-Propargyl Caffeamide (PACA) Ameliorates Dopaminergic Neuronal Loss and Motor Dysfunctions in MPTP Mouse Model of Parkinson's Disease and in MPP+-Induced Neurons via Promoting the Conversion of proNGF to NGF

Insufficient production of nerve growth factor (NGF) is implicated in Parkinson's disease (PD). We recently discovered that caffeic acid derivative N-propargyl caffeamide (PACA) not only potentiated NGF-induced neurite outgrowth but also attenuated 6-hydroxydopamine neurotoxicity in neuronal culture. The aim of the present study was to investigate whether PACA could increase NGF levels against 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) neurotoxicity in a mouse PD model. We induced parkinsonism in mice by intraperitoneal injection of MPTP for seven consecutive days. Animal motor functions were assessed by rotarod test and pole test. Our results showed that PACA ameliorated motor impairments in MPTP-challenged mice. Based on Western blot analysis and/or immunofluorescence staining of NGF and tyrosine hydroxylase (TH), PACA preserved TH levels in the midbrain substantia nigra pars compacta. PACA also increased NGF expression while it decreased proNGF accumulation. Interestingly, NGF was widely induced in the midbrains including astrocytes. To elucidate the mechanisms by which PACA induces NGF, we focused on the effects of PACA on two neurotrophic signaling pathways, the PI3K and MEK pathways. We found that PACA induced the phosphorylation of Akt, ERK, and CREB against MPTP-mediated alterations. Importantly, PACA increased NGF levels and subsequently induced TrkA activation in MPTP-treated mice. Consistently, PACA also increased NGF levels in dopaminergic PC12 cells and primary rat midbrain neurons against N-methyl-4-phenylpyridinium iodide (MPP⁺) toxicity. ERK and PI3K inhibitors attenuated the effects of PACA on NGF levels. Collectively, our results suggest that PACA may rescue NGF insufficiency via sequential activation of PI3K/Akt, ERK1/2, and CREB signaling pathways. Graphical Abstract ᅟ.

Functional connectivity disruptions correlate with cognitive phenotypes in Parkinson's disease

Cognitive deficits in Parkinson's disease are thought to be related to altered functional brain connectivity. To date, cognitive-related changes in Parkinson's disease have never been explored with dense-EEG with the aim of establishing a relationship between the degree of cognitive impairment, on the one hand, and alterations in the functional connectivity of brain networks, on the other hand.

This study was aimed at identifying altered brain networks associated with cognitive phenotypes in Parkinson's disease using dense-EEG data recorded during rest with eyes closed. Three groups of Parkinson's disease patients (N = 124) with different cognitive phenotypes coming from a data-driven cluster analysis, were studied: G1) cognitively intact patients (63), G2) patients with mild cognitive deficits (46) and G3) patients with severe cognitive deficits (15). Functional brain networks were identified using a dense-EEG source connectivity method. Pairwise functional connectivity was computed for 68 brain regions in different EEG frequency bands. Network statistics were assessed at both global (network topology) and local (inter-regional connections) level.

Results revealed progressive disruptions in functional connectivity between the three patient groups, typically in the alpha band. Differences between G1 and G2 (p < 0.001, corrected using permutation test) were mainly frontotemporal alterations. A statistically significant correlation (ρ = 0.49, p < 0.001) was also obtained between a proposed network-based index and the patients' cognitive score. Global properties of network topology in patients were relatively intact.

These findings indicate that functional connectivity decreases with the worsening of cognitive performance and loss of frontotemporal connectivity may be a promising neuromarker of cognitive impairment in Parkinson's disease.

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We test the use of dense-EEG to identify altered brain networks associated with cognitive phenotypes in Parkinson's disease.

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The functional connectivity decreases with the worsening of cognitive performance

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The loss of frontotemporal connectivity may be a promising neuromarker of cognitive impairment in Parkinson's disease.

Spatial and dynamical handwriting analysis in mild cognitive impairment

Background and Objectives Standard clinical procedure of Mild Cognitive Impairment (MCI) assessment employs time-consuming tests of psychological evaluation and requires the involvement of specialists. The employment of quantitative methods proves to be superior to clinical judgment, yet reliable, fast and inexpensive tests are not available. This study was conducted as a first step towards the development of a diagnostic tool based on handwriting. Methods In this paper the handwriting sample of a group of 37 patients with MCI (mean age 76.1±5.8) and 37 healthy controls (mean age 74.8±5.7) was collected using a Livescribe Echo Pen while completing three tasks: (1) regular writing, (2) all-capital-letters writing, and (3) single letter multiply repeated. Parameters differentiating both groups were selected in each task. Results Subjects with confirmed MCI needed more time to complete task one (median 119.5s, IQR - interquartile range - 38.1 vs. 95.1s, IQR 29.2 in control and MCI group, p-value <0.05) and two (median 84.2s, IQR 49.2 and 53.7s, IQR 30.5 in control and MCI group) as their writing was significantly slower. These results were associated with a longer time to complete a single stroke of written text. The written text was also noticeably larger in the MCI group in all three tasks (e.g. median height of the text block in task 2 being 22.3mm, IQR 12.9 in MCI and 20.2mm, IQR 8.7 in control group). Moreover, the MCI group showed more variation in the dynamics of writing: longer pause between strokes in task 1 and 2. The all-capital-letters task produced most of the discriminating features. Conclusion Proposed handwriting features are significant in distinguishing MCI patients. Inclusion of quantitative handwriting analysis in psychological assessment may be a step forward towards a fast MCI diagnosis.

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.

Clinical Utility of the Envelope Task in Mild Cognitive Impairment and Dementia

Objective: Prospective memory (PM) is a cognitive function defined as the ability to perform an intention at an appropriate moment in the future. In the aging population, PM is essential for maintaining independent daily living. Introduced as a simple and quick way to assess PM in clinical settings, the envelope task has to date received very limited empirical and practical interest. Methods: The present study investigated the task’s clinical utility in detecting PM impairment in a sample composed of 49 healthy older adults (OA), 41 patients with Alzheimer’s disease, and 64 individuals with amnestic and nonamnestic mild cognitive impairment (MCI) of heterogeneous etiology: 17 of idiopathic nature, 20 presenting an idiopathic rapid-eye movement sleep behaviour disorder, and 27 patients diagnosed with idiopathic Parkinson’s disease. Results: The envelope task was highly sensitive and specific in discriminating Alzheimer’s disease patients from OA. Although it was specific in distinguishing MCI individuals from OA, its sensitivity was modest, especially in patients presenting a nonamnestic MCI subtype. Conclusions: Given its high specificity and simple low-cost administration procedure, the envelope task is a promising instrument for clinicians who seek to rapidly assess PM impairment in their daily practice.

Cognitive decline in Parkinson's disease: the complex picture

Mild cognitive impairment (PD-MCI) and dementia (PDD) are among the most frequent non-motor symptoms in Parkinson's disease (PD). PD-MCI is six times more likely than age-matched controls to develop dementia and the PDD prevalence is 80% after 15-20 years of disease. Therefore, research has focused on the identification of early dementia biomarkers including specific cognitive at-risk profiles hoping to implement therapeutic interventions when they are most likely to be efficacious. However, given the heterogeneous neuropathological, neurochemical, and neuropsychological nature of cognitive deficits, definition of a comprehensive cognitive model of PDD is a challenge. Evidence from neuroimaging studies using different methods and techniques suggests that in addition to degeneration of the dopaminergic system, other mechanisms have a role including β-amyloid and tau deposition, and that specific cognitive scales could help identifying a malignant profile. Prospective studies combining neuroimaging techniques and specific cognitive tests are required to define the interplay between the various neurodegenerative processes and the contribution of structural disconnection in brain functional networks, heralding the development of dementia in PD.

The Diagnostic Accuracy of Parkinson's Disease Mild Cognitive Impairment Battery Using the Movement Disorder Society Task Force Criteria

Background

The aim of the present study was to provide empirical evidence regarding the classification accuracy of the International Parkinson and Movement Disorder Society (MDS) neuropsychological battery (NB) in the determination of Parkinson's disease mild cognitive impairment (PD-MCI).

Methods

The present cross-sectional study included 106 PD patients subjected to PD-MCI classification at Level I and 120 healthy controls (HCs). All HC and PD subjects were then assessed with MDS-NB at Level II and matched according to age and education using different thresholds (1.5 and 2.0 standard deviations [SDs] below average).

Results

We found that Level I and II resulted in different classifications of PD-MCI status. Detection thresholds of -1.5 SD and -2.0 SDs at Level II had also a significant impact on the discriminative validity of all measures in the MDS neuropsychological battery, based on area under the curve analyses. Overall, semantic fluency showed the highest potential in all comparisons not only between PD-MCI and HC, but also between PD-MCI and PD with no deficit (PD-ND).

Conclusions

Our results show that the battery at Level II is applicable and that some measures, such as semantic fluency, have high discriminative validity in the detection of PD-MCI versus PD-ND and HCs.

French consensus procedure for assessing cognitive function in Parkinson's disease

INTRODUCTION

One of the objectives of the French expert centers for Parkinson's disease (NS-Park) network was to determine a consensus procedure for assessing cognitive function in patients with Parkinson's. This article presents this procedure and briefly describes the selected tests.

METHODS

A group of 13 experts used the Delphi method for consensus building to define the overall structure and components of the assessment procedure. For inclusion in the battery, tests had to be validated in the French language, require little motor participation, have normative data and be recognized by the international community. Experimental tasks and tests requiring specific devices were excluded.

RESULTS

Two possibilities were identified, depending on whether an abbreviated or comprehensive assessment of cognitive function was necessary. For an abbreviated assessment, the experts recommended the Montreal Cognitive Assessment (MoCA) as a screening test for cognitive impairment or dementia. For a comprehensive neuropsychological assessment, the experts recommended assessing global efficiency plus the five main cognitive domains (attention and working memory, executive function, episodic memory, visuospatial function and language) that may be impaired in Parkinson's disease, using two tests for each domain.

DISCUSSION AND CONCLUSION

A common procedure for assessing cognitive function is now available across the French network dedicated to Parkinson's disease, and is recommended for both research and clinical practice. It will also help to promote standardization of the neuropsychological assessment of Parkinson's disease.

The Prague Stroop Test: Normative standards in older Czech adults and discriminative validity for mild cognitive impairment in Parkinson's disease

OBJECTIVE

The aim of this study was to provide normative data for older and very old Czech adults on the Prague Stroop Test (PST) and to test its discriminative validity in individuals with Parkinson's disease mild cognitive impairment (PD-MCI).

METHOD

The construction of the PST was modeled after the Victoria Stroop Test. We examined 539 participants aged 60-96 that met strict inclusion criteria. After, we compared the PST scores for a group of 45 PD-MCI patients with a healthy adult sample (HAS) of 45 age- and education-matched individuals.

RESULTS

I. In the non-clinical sample, robust age- and education-related influences were observed on all PST scores. No gender effect was noted. II. For clinical cases, interference condition (PST-C) was able to discriminate between PD-MCI and HAS (all scores ps < .01). Area under the curve (AUC) was 77% when a screening cut-off of ≤ 27 s was used, showing sensitivity of 82% and specificity of 53%. A more conservative diagnostic cut-off of ≤ 33 s showed sensitivity of 60% and specificity of 80%.

DISCUSSION

The present study provides PST normative data for basic, interference, and error scores stratified by age (60-96 years). PST appears to be a helpful tool for the diagnostics of PD-MCI especially in research settings at Level II (Litvan et al., 2012) and for PD-MCI attention/working memory and executive function subtyping.

Different PD-MCI criteria and risk of dementia in Parkinson's disease: 4-year longitudinal study

The Movement Disorder Society Task Force (MDS-TF) has proposed diagnostic criteria for mild cognitive impairment in Parkinson's disease (PD-MCI). We hypothesized that the risk of dementia (PDD) varies across the different cutoff schemes allowed. A longitudinal study followed 121 non-demented PD patients for up to 4.5 years. In Part One, unique groups of patients were identified as PD-MCI at baseline using the MDS-TF requirement of two impaired cognitive test scores, with both scores classified as impaired at either (i) 2 s.d., (ii) 1.5 s.d. or (iii) 1 s.d. below normative data; relative risk (RR) of PDD was assessed at each criterion. In Part Two, the whole sample was reassessed and (i) RR of PDD determined when two impairments at 1.5 s.d. existed within a single cognitive domain, followed by (ii) RR of PDD in the unique group whose two impairments at 1.5 s.d. did not exist within a single domain (i.e., only across two domains). Twenty-one percent of patients converted to PDD. Part One showed that the 1.5 s.d. criterion at baseline is optimal to maximize progression to PDD over 4 years. Part Two, however, showed that the 1.5 s.d. cutoff produced a high RR of PDD only when two impairments were identified within a single cognitive domain (7.2, 95% confidence interval (CI)=3.4-16.6, P<0.0001; 51% converted). The RR when the 1.5 s.d. impairments occurred only across two different domains, was nonsignificant (1.7, CI=0.5-7.4, P=0.13; 11% converted) and similar to using a 1 s.d. criterion (1.9, CI=0.3-4.3, P=0.13; 8% converted). If the intent of a PD-MCI diagnosis is to detect increased risk of PDD in the next 4 years, optimal criteria should identify at least two impairments at 1.5 s.d. within a single cognitive domain.

Temporal Lobe and Frontal-Subcortical Dissociations in Non-Demented Parkinson's Disease with Verbal Memory Impairment

Objective

The current investigation examined verbal memory in idiopathic non-dementia Parkinson’s disease and the significance of the left entorhinal cortex and left entorhinal-retrosplenial region connections (via temporal cingulum) on memory impairment in Parkinson’s disease.

Methods

Forty non-demented Parkinson’s disease patients and forty non-Parkinson’s disease controls completed two verbal memory tests – a wordlist measure (Philadelphia repeatable Verbal Memory Test) and a story measure (Logical Memory). All participants received T1-weighted and diffusion magnetic resonance imaging (3T; Siemens) sequences. Left entorhinal volume and left entorhinal-retrosplenial connectivity (temporal cingulum edge weight) were the primary imaging variables of interest with frontal lobe thickness and subcortical structure volumes as dissociating variables.

Results

Individuals with Parkinson’s disease showed worse verbal memory, smaller entorhinal volumes, but did not differ in entorhinal-retrosplenial connectivity. For Parkinson’s disease entorhinal-retrosplenial edge weight had the strongest associations with verbal memory. A subset of Parkinson’s disease patients (23%) had deficits (z-scores < -1.5) across both memory measures. Relative to non-impaired Parkinson’s peers, this memory-impaired group had smaller entorhinal volumes.

Discussion

Although entorhinal cortex volume was significantly reduced in Parkinson’s disease patients relative to non-Parkinson’s peers, only white matter connections associated with the entorhinal cortex were significantly associated with verbal memory performance in our sample. There was also no suggestion of contribution from frontal-subcortical gray or frontal white matter regions. These findings argue for additional investigation into medial temporal lobe gray and white matter connectivity for understanding memory in Parkinson’s disease.

Subjective Cognitive Complaints in Parkinson Disease Without Dementia: A Preliminary Study

Little is known about the subjective cognitive complaints of individuals with Parkinson disease (PD). Such complaints have become a topic of interest recently as they play a role in the diagnosis of neurocognitive disorders. The aim of this preliminary study was to determine whether a sample of nondemented individuals with PD reported significantly more difficulties with multiple elements of cognition than a control sample and to assess the relation between their ratings and demographics, motor symptom severity, neuropsychological test performance, and measures of depression and anxiety. Forty nondemented individuals with PD and 27 healthy individuals completed a questionnaire assessing everyday cognitive difficulties. Independent t tests indicated that individuals with PD reported significantly more cognitive complaints in general and in specific tasks involving complex attention, executive function, processing speed, and verbal fluency but not memory. Questionnaire ratings significantly correlated with measures assessing anxiety, verbal memory, processing speed, and verbal fluency. Results suggest that it is important to ask individuals with PD about cognitive complaints across several cognitive domains and also inquire about symptoms of anxiety, which may be related to their self-reported cognitive difficulties.

Cognitive impairment in early-stage non-demented Parkinson's disease patients

OBJECTIVES

In Parkinson's disease (PD), Parkinson's disease dementia (PDD) and Parkinson's disease-mild cognitive impairment (PD-MCI) are common. PD-MCI is a risk factor for developing PDD. Knowledge of cognition in early-stages PD is essential in understanding and predicting the dementia process.

MATERIALS AND METHODS

We describe the cognitive profile in early-stage PD patients with no prior clinical suspicion of cognitive impairment, depression or psychiatric disturbances, and investigate possible features distinguishing patients with cognitive deficits, defining a PD-MCI risk-profile. Single Photon Emission Computerized Tomography (SPECT) DaT-scan and neurological examination confirmed the diagnosis. Mini-mental state examination-, Addenbrooke's Cognitive Examination, Unified Parkinson's Disease Rating Scale scoring, Hoehn &Yahr/Activity of Daily Living staging and a neuropsychological test battery were applied. Mild cognitive impairment patients were identified according to modified criteria by Troster necessarily omitting subjective cognitive complaints. 80 patients, mean age 61.0 years (SD 6.6), mean duration of disease 3.4 years (SD 1.2) were included. 76 patients were neuropsychologically tested.

RESULTS

26 (34%) patients fulfilled modified PD-MCI criteria, 18 (69%) of these showed episodic memory deficits, 14 (54%) executive dysfunction, 13 (50%) language/praxis deficits, 12 (46%) visuospatial/constructional deficits and 9 (35%) attention/working memory deficits. Cognitive impairment was associated with higher Unified Parkinson's Disease Rating scale (UPDRS)-, bradykinesia- and rigidity scores and more symmetric distribution of symptoms, but not tremor scores. Patients with cognitive impairment were less educated. Other demographic and clinical variables were comparable.

CONCLUSIONS

34% of early-stage PD patients without prior clinical suspicion of cognitive impairment exhibit cognitive impairment, which is associated to disease severity, especially bradykinesia, rigidity, axial symptoms and less asymmetry of motor symptoms, even at early disease stages and when cognitive symptoms are mild.

Reading comprehension in Parkinson's disease

PURPOSE

Although individuals with Parkinson's disease (PD) self-report reading problems and experience difficulties in cognitive-linguistic functions that support discourse-level reading, prior research has primarily focused on sentence-level processing and auditory comprehension. Accordingly, the authors investigated the presence and nature of reading comprehension in PD, hypothesizing that (a) individuals with PD would display impaired accuracy and/or speed on reading comprehension tests and (b) reading performances would be correlated with cognitive test results.

METHOD

Eleven adults with PD and 9 age- and education-matched control participants completed tests that evaluated reading comprehension; general language and cognitive abilities; and aspects of attention, memory, and executive functioning.

RESULT

The PD group obtained significantly lower scores on several, but not all, reading comprehension, language, and cognitive measures. Memory, language, and disease severity were significantly correlated with reading comprehension for the PD group.

CONCLUSION

Individuals in the early stages of PD without dementia or broad cognitive deficits can display reading comprehension difficulties, particularly for high- versus basic-level reading tasks. These reading difficulties are most closely related to memory, high-level language, and PD symptom severity status. The findings warrant additional research to delineate further the types and nature of reading comprehension impairments experienced by individuals with PD.

Mild cognitive impairment: a concept and diagnostic entity in need of input from neuropsychology

This virtual issue consists of studies previously published in the Journal of the International Neuropsychological Society and selected on the basis of their content related to one of the most highly researched concepts in behavioral neurology and neuropsychology over the past decade: mild cognitive impairment (MCI). The reliance on cognitive screening measures, staging-based rating scales, and limited neuropsychological testing in diagnosing MCI across most research studies may miss individuals with subtle cognitive declines or mis-diagnose MCI in those who are otherwise cognitively normal on a broader neuropsychological battery of tests. The assembled articles highlight the perils of relying on these conventional criteria for MCI diagnosis and reveal how the reliability of diagnosis is improved when sound neuropsychological approaches are adopted. When these requirements are met, we illustrate with a second series of articles that neuropsychological measures associate strongly with biomarkers and often reflect pathology beyond or instead of typical AD distributions. The final set of articles reveal that people with MCI demonstrate mild but identifiable functional difficulties, and a challenge for neuropsychology is how to incorporate this information to better define MCI and distinguish it from early dementia. Neuropsychology is uniquely positioned to improve upon the state of the science in MCI research and practice by providing critically important empirical information on the specific cognitive domains affected by the predominant neurodegenerative disorders of late life as well as on the diagnostic decision-making strategies used in studies. When such efforts to more comprehensively assess neuropsychological functions are undertaken, better characterizations of spared and impaired cognitive and functional abilities result and lead to more convincing associations with other biomarkers as well as to prediction of clinical outcomes.

The 5 Objects Test: a novel, minimal-language, memory screening test

Very brief screening tests are useful in primary care, but may show reduced sensitivity in detecting Alzheimer's disease or other dementias in the early stages and may show an education or age bias. We examined the reliability, validity, sensitivity, specificity and relationship with demographic variables of a novel, very brief memory screening test that makes limited language demands. Participants were 452 neurological patients with different diagnoses and a community-dwelling sample of 119 middle-aged and older controls. The 5 Objects Test requires the recall of the locations of five everyday objects, immediately after placement and after a brief period of time. The test was unaffected by age and education and showed good reliability and discriminant validity. In receiver operating characteristic (ROC) analyses, specificity was high across a range of sensitivities in all four main comparisons (AD cases versus controls; all dementia cases versus controls; memory-impaired versus non memory-impaired patients; MCI cases versus controls), and sensitivity was lowest in differentiating MCI cases from controls. The test showed similar areas under the ROC curve to the much longer modified Mini Mental State Examination. The 5 Objects Test is a reliable and valid very brief screening test that is suitable for primary care. Because of its limited linguistic demands, the test is appropriate for persons with limited language use or from different linguistic backgrounds.

Trends and issues in characterizing early cognitive changes in Parkinson's disease

In this review, we first discuss trends and issues in measuring cognitive changes in PD, including recent efforts to define the diagnostic classification of "PD Mild Cognitive Impairment" (PD-MCI). After reviewing some limitations associated with this diagnosis, we discuss how measures derived from the neurocognitive sciences offer better precision in detecting early cognitive changes in PD. To support this idea, we highlight 2 influential lines of current investigation that are unveiling novel insights about specific cognitive processes that are vulnerable early in PD and of critical importance to clinicians involved in treating PD: action control and reward learning and decision making. We conclude by highlighting some extant issues and unresolved questions for future investigations.

Social brain dysfunctions in patients with Parkinson's disease: a review of theory of mind studies

Human social interaction is essential in daily life and crucial for a promising life, especially in people who suffer from disease. Theory of Mind (ToM) is fundamental in social interaction and is described as the ability to impute the mental states of others in social situations. Studies have proposed that a complex neuroanatomical network that includes the frontal cortex mediates ToM. The primary neuropathology of Parkinson’s disease (PD) involves the frontal-striatal system; therefore, patients with PD are expected to exhibit deficits in ToM. In this review, we summarize the current research with a particular focus on the patterns of impaired ToM, potential mediators of ToM, and the impact of ToM deficits on clinical disability in PD. Further studies to investigate the progression of ToM and its relationship with dementia in subjects in PD are needed.

Remission of cognitive deficits in Parkinson's disease: recovery from a nonamnestic mild cognitive impairment or psychiatric symptoms remission?

Mild cognitive impairment is a clinical condition more frequent in patients with Parkinson's disease than in general population. The nonamnestic presentations, usually characterized by executive dysfunction, are most prevalent. We present a case report of a Parkinson's disease patient diagnosed with nonamnestic mild cognitive impairment that showed complete remission of cognitive symptoms after one year. We discuss the possible causes for the remission, focusing on the treatment of medical conditions such as a major depressive episode and vitamin B12 deficiency, in addition to the change of pharmacological treatment. In a third assessment, cognitive performance remained normal. The case report highlights the importance of controlling clinical comorbidities on the assessment and followup of mild cognitive impairment, especially on Parkinson's disease.

Clinical differences among mild cognitive impairment subtypes in Parkinson's disease

Mild cognitive impairment is increasingly recognized as a construct in Parkinson's disease (PD) and occurs in about 25% of nondemented PD patients. Although executive dysfunction is the most frequent type of cognitive deficit in PD, the cognitive phenotype of PD mild cognitive impairment (PD-MCI) is broad. PD-MCI subtypes are represented by amnestic and nonamnestic domain impairment as well as single- and multiple-domain impairment. However, it is unclear whether patients with different PD-MCI subtypes also differ in other clinical characteristics in addition to cognitive profile. We studied 128 PD-MCI subjects at our Movement Disorders center, comparing clinical, motor, and behavioral characteristics across the PD-MCI subtypes. We found varying proportions of impairment subtypes: nonamnestic single domain, 47.7%; amnestic multiple domain, 24.2%; amnestic single domain, 18.8%; and nonamnestic multiple domain, 9.5%. Attentional/executive functioning and visuospatial abilities were the most frequently impaired domains. PD-MCI subtypes differed in their motor features, with nonamnestic multiple-domain PD-MCI subjects showing particularly pronounced problems with postural instability and gait. Differences among PD-MCI subtypes in age, PD duration, medication use, mood or behavioral disturbances, and vascular disease were not significant. Thus, in addition to differing cognitive profiles, PD-MCI subtypes differed in motor phenotype and severity but not in mood, behavioral, or vascular comorbidities. Greater postural instability and gait disturbances in the nonamnestic multiple-domain subtype emphasize shared nondopaminergic neural substrates of gait and cognition in PD. Furthermore, increased burden of cognitive dysfunction, rather than type of cognitive deficit, may be associated with greater motor impairment in PD-MCI.