Verbal Learning Impairment in Parkinson's Disease: Role of the Frontostriatal System in Working and Strategic Memory

INTRODUCTION

Learning is a long-term memory process, influenced by working memory control processes, including recognition of semantic properties of items by which subjects generate a semantic structure of engrams. The aim of the study was to investigate the verbal learning strategies of individuals with Parkinson's disease (PD).

METHODS

Thirty individuals with idiopathic PD and healthy control (HC) subjects were tested with a multi-trial word list learning, under two conditions: without cue and then with an explicit cue suggesting the categories in the list, respectively.

RESULTS

In comparison to HC subjects, individuals with PD recalled fewer words and achieved a reduced number of categorical clusters; the strategical cue did not improve their performance.

CONCLUSION

This suggests, besides a difficulty in identifying the correct learning strategy, a deficit in working memory, which undermines the strategy implementation.

Deep multimodality-disentangled association analysis network for imaging genetics in neurodegenerative diseases

Imaging genetics is a crucial tool that is applied to explore potentially disease-related biomarkers, particularly for neurodegenerative diseases (NDs). With the development of imaging technology, the association analysis between multimodal imaging data and genetic data is gradually being concerned by a wide range of imaging genetics studies. However, multimodal data are fused first and then correlated with genetic data in traditional methods, which leads to an incomplete exploration of their common and complementary information. In addition, the inaccurate formulation in the complex relationships between imaging and genetic data and information loss caused by missing multimodal data are still open problems in imaging genetics studies. Therefore, in this study, a deep multimodality-disentangled association analysis network (DMAAN) is proposed to solve the aforementioned issues and detect the disease-related biomarkers of NDs simultaneously. First, the imaging data are nonlinearly projected into a latent space and imaging representations can be achieved. The imaging representations are further disentangled into common and specific parts by using a multimodal-disentangled module. Second, the genetic data are encoded to achieve genetic representations, and then, the achieved genetic representations are nonlinearly mapped to the common and specific imaging representations to build nonlinear associations between imaging and genetic data through an association analysis module. Moreover, modality mask vectors are synchronously synthesized to integrate the genetic and imaging data, which helps the following disease diagnosis. Finally, the proposed method achieves reasonable diagnosis performance via a disease diagnosis module and utilizes the label information to detect the disease-related modality-shared and modality-specific biomarkers. Furthermore, the genetic representation can be used to impute the missing multimodal data with our learning strategy. Two publicly available datasets with different NDs are used to demonstrate the effectiveness of the proposed DMAAN. The experimental results show that the proposed DMAAN can identify the disease-related biomarkers, which suggests the proposed DMAAN may provide new insights into the pathological mechanism and early diagnosis of NDs. The codes are publicly available at https://github.com/Meiyan88/DMAAN.

Parkinson's Disease Cognitive Phenotypes Show Unique Clock Drawing Features when Measured with Digital Technology

BACKGROUND

A companion paper (Crowley et al., 2020) reports on the neuroimaging and neuropsychological profiles of statistically determined idiopathic non-dementia Parkinson's disease (PD).

OBJECTIVE

The current investigation sought to further examine subtle behavioral clock drawing differences within the same PD cohort by comparing 1) PD to non-PD peers on digitally acquired clock drawing latency and graphomotor metrics, and 2) PD memory, executive, and cognitively well phenotypes on the same variables.

METHODS

230 matched participants (115 PD, 115 non-PD) completed neuropsychological tests and dCDT. Statistically-derived PD cognitive phenotypes characterized PD participants as PD low executive (PDExe; n = 25), PD low memory (PDMem; n = 34), PD cognitively well (PDWell; n = 56). Using a Bayesian framework and based on apriori hypotheses, we compared groups on: total completion time (TCT), pre-first hand latency (PFHL), post-clock face latency (PCFL), total clock face area (TCFA), and total number of pen strokes.

RESULTS

Fewer strokes and slower performance to command were associated with higher odds of PD diagnosis, while a larger clock face in the copy condition was associated with lower odds of PD diagnosis. Within PD cognitive phenotypes, slower performance (TCT, PCFL) and smaller clock face to command were associated with higher odds of being PDExe than PDWell, whereas larger clock faces associated with higher odds of being PDMem than PDWell. Longer disease duration, more pen strokes (command) and smaller clocks (command) associated with higher odds of being PDExe than PDWell.

CONCLUSION

Digitally-acquired clock drawing profiles differ between PD and non-PD peers, and distinguish PD cognitive phenotypes.

Partial correlation coefficient for a study with repeated measurements

Repeated data are increasingly collected in studies to investigate the trajectory of change in measurements over time. Determining a link between one repeated measurement with another that is considered as the biomarker for disease progression, may provide a new target for drug development. When a third variable is associated with one of the two measurements, partial correlation after eliminating the effect of that variable is able to provide reliable estimate for association as compared to the existing raw correlation for repeated data. We propose using linear regression models to compute residuals by modeling a relationship between each measurement and a third variable. The computed residuals are then used in a linear mixed model (implemented by SAS Proc Mixed) to compute partial correlation for repeated data. Alternatively, the partial correlation may be computed as the average of partial correlations at each visit. We provide two real examples to illustrate the application of the proposed partial correlation, and conduct extensive numerical studies to compare the proposed partial correlation coefficients.

Do Patients With Parkinson's Disease Exhibit Reduced Cheating Behavior? A Neuropsychological Study

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by loss of dopamine neurons. Since a seminal report was published in the early twentieth century, a growing body of literature has suggested that patients with PD display characteristic personality traits, such as cautiousness and inflexibility. Notably, PD patients have also been described as "honest," indicating that they have a remarkable tendency to avoid behaving dishonestly. In this study, we predicted that PD patients show reduced cheating behavior in opportunities for dishonest gain due to dysfunction of the dopaminergic reward system. Thirty-two PD patients without dementia and 20 healthy controls (HC) completed an incentivized prediction task where participants were rewarded based on their self-reported accuracy, affording them the opportunity to behave dishonestly. Compared with HC, PD patients showed significantly lower accuracy in the prediction task. Furthermore, the mean accuracy of PD patients was virtually equivalent to the chance level. These results indicate that PD patients exhibit reduced cheating behavior when confronted with opportunities for dishonest gain.

Effect of striatal dopamine depletion on cognition in de novo Parkinson's disease

INTRODUCTION

To investigate the relationship between the sub-regional pattern of striatal dopamine depletion and cognitive impairment in early-stage Parkinson's disease (PD), and determine the effect of striatal dopamine density on cognitive prognosis.

METHODS

Patients with drug-naïve non-demented PD were divided into mild cognitive impairment (PD-MCI; n = 129) and cognitively normal (PD-CogN; n = 182) groups. Using quantification of the dopamine transporter (DAT) availability in each striatal sub-region with ¹⁸F-FP-CIT PET scans, we performed inter-group comparative analysis of DAT availability and multivariate linear regression analysis to assess the association between DAT availability and cognitive performance. Additionally, the effect of baseline DAT availability on the cognitive decline across time as well as on changes in the cognitive status was estimated.

RESULTS

The PD-MCI group exhibited more severely decreased DAT availability in all the striatal sub-regions compared to the PD-CogN group, although there was no significant difference in PD duration. The DAT availability in the caudate, anterior putamen, and ventral striatum was directly associated with attention/working memory, frontal/executive, and visuospatial functions, while the DAT availability of the posterior putamen was not. However, the baseline DAT availability of the striatal sub-regions did not influence the cognitive decline or cognitive status in the longitudinal cognitive assessment.

CONCLUSION

Our results suggest that striatal DAT availability may determine MCI in patients with de novo PD. Dopamine loss in the associative and limbic striatum is closely linked to cognitive deficits in early-stage PD, although it does not affect cognitive prognosis.

Preserved priming effect in individuals with schizophrenia: cues towards rehabilitation

INTRODUCTION

Individuals with schizophrenia and affective disorders show relatively intact implicit memory as compared to declarative memory. Implicit memory is usually assessed with skill learning and priming tasks. Whereas priming is thought to involve storage changes in the posterior neocortex, skill learning is thought to rely more on the corticostriatal pathway. Since frontostriatal and frontotemporal dysfunctions are, respectively, found in schizophrenia and affective disorders, we hypothesised that individuals with schizophrenia and first-episode psychosis would exhibit disturbances in skill learning, but not priming.

METHODS

Thirty-five patients (11 first-episode psychosis; 11 schizophrenia; 13 affective disorders) and 10 controls completed a procedural learning and priming task. Participants had to identify fragmented images throughout five training sessions. The improvement of the threshold at which the images could be identified between the first and last session was used as an index of procedural learning. In a final session, the identification thresholds for old and new images were compared to assess the priming effect.

RESULTS

Whereas individuals with schizophrenia and first-episode psychosis showed impaired skill learning, the priming effect was similar in all groups.

CONCLUSION

Even though some aspects of learning and memory are affected in schizophrenia, our results suggest that the posterior cortical pathway remains efficient at modulating the priming effect. This intact ability could be used to guide the elaboration of new rehabilitation programmes.

Self-awareness of memory impairment in Parkinson’s disease: a review of the literature

Purpose

– The purpose of this paper is to review and provide information on the small but growing body of literature that demonstrates that some people with Parkinson’s disease (PD) are unaware of the memory impairment, and this has clinical implications for how family members care for their loved one, and how clinical staff and others may interact with them on a day-to-day perspective.

Design/methodology/approach

– The approach takes the form of a general review.

Findings

– People with PD experience a variety of cognitive impairment including deficits in memory and higher level executive processes. Impairment in these areas can occur early in the disease course and result in adverse consequences including distractibility, trouble recalling information, and problems remembering to execute planned actions like adhering to medication regimes. The literature also suggests heterogeneity in both the memory performance of people with PD and in the definition of awareness used to investigate this phenomenon.

Practical implications

– Strategies for remembering may be of practical importance for people with PD, and/or caregivers should be introduced and educated to the nature of memory impairment in PD, as well as its likely course and natural progression in a non-threatening way before they are later instructed on “tips” for maximising daily functioning as more severe cognitive deficits begin to appear.

Originality/value

– This paper adds to the small body of literature that investigates patients’ awareness of memory impairment in PD and advocates for ongoing research within the area.

Gait in Parkinson's disease: A visuo-cognitive challenge

Vision and cognition have both been related to gait impairment in Parkinson's disease (PD) through separate strands of research. The cumulative and interactive effect of both (which we term visuo-cognition) has not been previously investigated and little is known about the influence of cognition on vision with respect to gait. Understanding the role of vision, cognition and visuo-cognition in gait in PD is critical for data interpretation and to infer and test underlying mechanisms. The purpose of this comprehensive narrative review was to examine the interdependent and interactive role of cognition and vision in gait in PD and older adults. Evidence from a broad range of research disciplines was reviewed and summarised. A key finding was that attention appears to play a pivotal role in mediating gait, cognition and vision, and should be considered emphatically in future research in this field.

Memory Similarities Between Essential Tremor and Parkinson's Disease: A Final Common Pathway?

OBJECTIVE

A growing body of literature supports the view that essential tremor (ET) involves alteration of cerebellar-thalamo-cortical networks which can result in working memory and executive deficits. In this study, we tested the hypothesis that individuals with ET would exhibit worse performance on memory tasks requiring more intrinsic organization and structuring (i.e., word lists) relative to those with fewer 'executive' demands (i.e., stories), similar to that previously observed in individuals with Parkinson's disease (PD).

METHOD

Participants included a convenience sample of 68 ET patients and 68 idiopathic PD patients, retrospectively matched based on age, education, and sex. All patients underwent routine neuropsychological evaluation assessing recent memory, auditory attention/working memory, language, and executive function. Memory measures included the Hopkins Verbal Learning Test-R and WMS-III Logical Memory.

RESULTS

Both ET and PD patients performed significantly worse on word list than story memory recall tasks. The magnitude of the difference between these two memory tasks was similar for ET and PD patients. In both patient groups, performance on measures of executive function and auditory attention/working memory was not distinctly correlated with word list vs. story recall.

CONCLUSIONS

These findings suggest that frontal-executive dysfunction in both ET and PD may negatively influence performance on memory tests that are not inherently organized. Although the pathophysiology of these two 'movement disorders' are quite distinct, both have downstream effects on thalamo-frontal circuitry which may provide a common pathway for a similar memory phenotype. Findings are discussed in terms of neuroimaging evidence, conceptual models, and best practice.

Structural MRI Correlates of Episodic Memory Processes in Parkinson's Disease Without Mild Cognitive Impairment

BACKGROUND

Changes in episodic memory are common early in Parkinson's disease (PD) and may be a risk factor for future cognitive decline. Although medial temporal lobe (MTL) memory and frontostriatal (FS) executive systems are thought to play different roles in distinct components of episodic memory impairment in PD, no study has investigated whether different aspects of memory functioning are differentially associated with MTL and FS volumes in nondemented patients without mild cognitive impairment (PD-woMCI).

OBJECTIVES

The present study investigated MRI markers of different facets of memory functioning in 48 PD-woMCI patients and 42 controls.

METHODS

Regional volumes were measured in structures comprising the MTL and FS systems and then correlated with key indices of memory from the California Verbal Learning Test.

RESULTS

In PD-woMCI patients, memory was impaired only for verbal learning, which was not associated with executive, attention/working memory, or visuospatial functioning. Despite an absence of cortical atrophy, smaller right MTL volumes in patients were associated with poorer verbal learning, long delayed free recall, long delayed cued recall, and recognition memory hits and false positives. Smaller right pars triangularis (inferior frontal) volumes were also associated with poorer long delayed cued recall and recognition memory hits. These relationships were not found in controls.

CONCLUSIONS

The findings indicate that MTL volumes are sensitive to subtle changes in almost all facets of memory in PD-woMCI, whereas FS volumes are sensitive only to memory performances in cued-testing formats.

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.

Potential biomarkers relating pathological proteins, neuroinflammatory factors and free radicals in PD patients with cognitive impairment: a cross-sectional study

BACKGROUND

Cognitive impairment strikingly reduces the quality of life of Parkinson's disease (PD) patients. Studies find that pathological proteins, neuroinflammatory factors and free radicals may involve in the pathogenesis of cognitive impairment of PD, however, results are inconclusive.

METHODS

We recruited 62 PD patients and 31 healthy controls. PD patients were identified with cognitive impairment, including PD with mild cognitive impairment (PD-MCI) and PD with dementia (PDD) according to the diagnostic criteria for PD-MCI and PDD issued by Movement Disorder Society Task Force. The levels of pathological proteins, including β-amyloid 1-42 (Aβ1-42),Total-tau (T-tau) and phosphorelated tau (P-tau), neuroinflammatory factors,including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interferon-γ (INF-γ) and prostaglandin E2 (PGE2), free radicals, including hydroxyl radical (·OH), hydrogen peroxide (H2O2) and nitric oxide (NO) in cerebrospinal fluid(CSF) were detected. The levels of above factors in CSF were compared among healthy controls and patients with and without cognitive impairment. Correlation analyses were performed between Montreal Cognitive Assessment (MoCA) score and the levels of above factors in CSF.

RESULTS

T-tau level in CSF from PD-CI patients are significantly elevated comparing with those without cognitive impairment and controls (P = 0.016 and 0.004, respectively). The levels of P-tau (S396) and · OH in PD-CI patients are significantly higher than controls (P = 0.001 and 0.014, respectively). IL-6 levels in PD-CI patients are strikingly enhanced comparing with those without cognitive impairment (P = 0.005). MoCA score is negatively correlated with the levels of T-tau (r = -0.340), P-tau (S396) (r = -0.448), IL-6 (r = -0.489) and · OH (r = -0.504) in PD-CI patients.

CONCLUSIONS

Elevated levels of T-tau, P-tau (S396), IL-6 and · OH in CSF are significantly correlated with cognitive impairment in PD patients. This investigation may suggest the potential biomarkers relating pathological proteins, neuroinflammatory factors and free radicals in PD patients with cognitive impairment.

Prospective memory in Parkinson's disease: a meta-analysis

Prospective memory (PM) refers to the ability to remember to carry out an intended action in the future and it is pervasive in our daily living. A failure to execute an intended action (e.g., take medication) at the appropriate juncture in future (e.g., after dinner) can negatively affect our daily functioning and at times, may have devastating effects (e.g., forgetting to turn off the gas stove before leaving the house). Patients with Parkinson's disease (PD) exhibit widespread cognitive deficits including deficits in PM. The present study provides a meta-analytic review of PM in PD. Results across nine studies indicated time and event-based PM to be similarly impaired in PD, with time-based PM compromised to a slightly larger extent (Hedges' g = -0.71) as compared to event-based PM (Hedges' g = -0.55). The impairment in PM is more likely due to failure in self-initiated retrieval of intention to be executed, rather than forgetting the content of the intention itself. Furthermore, factors such as intervening task complexity and the mediating role of other executive functions have also been proposed to be responsible for impaired PM in PD.

Reliability of three Benton Judgment of Line Orientation short forms in idiopathic Parkinson's disease

Individuals with Parkinson's disease (PD) often exhibit deficits in visuospatial functioning throughout the course of their disease. These deficits should be carefully assessed as they may have implications for patient safety and disease severity. One of the most commonly administered tests of visuospatial ability, the Benton Judgment of Line Orientation (JLO), consists of 30 pairs of lines requiring the patient to match the orientation of two lines to an array of 11 lines on a separate page. Reliable short forms have been constructed out of the full JLO form, but the reliability of these forms in PD has yet to be examined. Recent functional MRI studies examining the JLO demonstrate right parietal and occipital activation, as well as bilateral frontal activation and PD is known to adversely affect these pathways. We compared the reliability of the original full form to three unique short forms in a sample of 141 non-demented, idiopathic PD patients and 56 age- and education-matched controls. Results indicated that a two-thirds length short form can be used with high reliability and classification accuracy in patients with idiopathic PD. The other short forms performed in a similar, though slightly less reliable manner.

The contribution of trail making to the prediction of performance-based instrumental activities of daily living in Parkinson's disease without dementia

Performance on Part B of the Trail Making Test (TMT) contributes to the prediction of ability to complete instrumental activities of daily living (IADLs) in Parkinson's disease (PD). Although this suggests that cognitive flexibility is important in the everyday functioning of individuals with PD, this may not be the case as the TMT is multifactorial, involving motor speed, visual scanning, sequencing, and cognitive flexibility. The purpose of the current study was to determine which elements of the task contribute to the prediction of IADLs in a sample of 30 nondemented individuals with PD. Correlational analyses indicated strong relationships between a performance-based measure of IADLs and measures involving scanning, sequencing, and cognitive flexibility from the Delis-Kaplan Executive Function System (D-KEFS) TMT. Results from standard regressions indicated that measures of sequencing and level of depression but not scanning, cognitive flexibility, or demographic variables made a significant, independent contribution to the prediction of IADLs. These results suggest that the sequencing element of the TMT is paramount in the prediction of IADLs in PD.

Clock test deficits related to the global cognitive state in Alzheimer's and Parkinson's disease

BACKGROUND/AIMS

Clock drawing (CD) seems to be impaired quite early in the process of cognitive decline in Parkinson's disease (PD).

METHODS

We assessed performance on the CD test (CDT), clock setting test (CST) and clock reading test (CRT) in 32 elderly healthy controls, 41 patients with PD, 23 patients with amnestic mild cognitive impairment (aMCI) and 40 patients with Alzheimer's dementia (AD). Our focus was on comparing the performance of PD and aMCI/AD patients in relation to their global cognitive states (operationalized by the Mini Mental Status Examination). We also analyzed qualitative differences in errors of drawing, setting and reading clocks.

RESULTS

We found that performance in CDT, but not in the CST or CRT, was impaired earlier in PD than in aMCI/AD. Incorrect placement of the minute hand was the most prominent error in both patient groups. We found no specific influence of visuospatial dysfunction in PD on clock drawing.

CONCLUSION

Our findings suggest that executive function related to retrieval of semantic memory about the minute hand is compromised early in PD.

Predictors of HVOT performance in Parkinson's disease

Evidence suggests that the Hooper Visual Organization Test (HVOT) has naming and executive components that vary in size depending on neurological diagnosis. The current study used a sample of individuals with Parkinson's disease (PD) to demonstrate for the first time that an executive measure can be the best predictor of HVOT performance. Forty-eight nondemented and nondepressed individuals with idiopathic PD completed the HVOT and other measures of visuoperception, executive function, and visual confrontation naming. Despite average performance on all neuropsychological measures, an executive measure, time to complete Trail-Making Test Part B minus time to complete Part A, was clearly the best predictor of HVOT performance in a standard regression. The pattern of neurocognitive predictors is unlike that reported in healthy individuals and other patient samples. This finding suggests that the presence of a neuropathological process can alter neurocognitive correlates even when performance is intact, and supports the contention that executive function is paramount in the cognitive profile associated with PD.

Executive functions in Parkinson's disease: systematic review and meta-analysis

Impairment of executive function (EF) is commonly reported as a feature of PD. However, the exact pattern of executive impairment remains unclear. Also, there is an ongoing discussion surrounding the definition and conceptualization of EF, which might affect the clarity of research evidence on cognition in PD. The aim of this systematic review was to describe the pattern of executive impairment in early-stage PD emerging from the research literature and to identify critical issues for improving consistency in this field. The PsychInfo, MEDLINE, Science Direct, CINAHL, and Cochrane Library databases were searched using the term "Parkinson's disease" combined with each of 14 cognitive abilities defined as representing aspects of EF. The review was limited to studies that investigated EF as the central variable in early-stage, nondemented PD patients. The review identified 33 studies of EF that were operationalized in terms of 30 abilities tested by 60 measures and variously interpreted. Many measures were used only once, so only a small part of the available research evidence could be synthesized in the meta-analysis. The meta-analysis was undertaken using data from five commonly used tests of EF drawn from 18 studies. This revealed consistent evidence for cognitive difficulties across all five EF tests. Research on EF in PD is characterized by a considerable lack of clarity with regard to measure selection and interpretation. The findings support the view that EF impairments are evident in PD. However, the clinical significance of the cognitive abnormalities reported has yet to be clarified.

Reduced verbal fluency for proper names in nondemented patients with Parkinson's disease: a quantitative and qualitative analysis

There has been an increasing interest within neuropsychology in comparing verbal fluency for different grammatical classes (e.g., verb generation vs. noun generation) in neurological populations, including Parkinson's disease (PD). However, to our knowledge, few studies have compared verbal fluency for common nouns and proper names in PD. Common nouns and proper names differ in terms of their semantic characteristics, as categories of common nouns are organized hierarchically based on semantics, while categories of proper nouns lack a well-defined semantic organization. In addition, there is accumulating evidence that the retrieval of these distinct grammatical classes are subserved by somewhat distinct neural systems. Given that verbal fluency deficits are among the first impairments to emerge in PD, and that such deficits are predictors of future cognitive decline, it is important to examine all aspects of verbal fluency in this population. For the current study, we compared the performance of a group of 32 nondemented PD patients with 32 healthy participants (HP) on verbal fluency tasks for common nouns (animals) and proper names (boys' first names). A significant interaction between verbal fluency task and diagnostic status emerged, as the PD group performed significantly worse on only the proper name fluency task. This finding may reflect the absence of well-defined semantic organization that structures the verbal search for first names, thus placing a greater onus on strategic or "executive" verbal retrieval processes.

Dysfunction of executive and related processes in childhood absence epilepsy

The nature and extent of the neuropsychological difficulties associated with childhood absence epilepsy (CAE) remain unclear. Because aberrant thalamocortical rhythms have been implicated in the pathogenesis of CAE, it was hypothesized that children with CAE would show greater difficulties in neuropsychological domains that are thought to be subserved by basal ganglia-thalamocortical circuits. Multivariate analysis of variance was used to compare the neuropsychological functioning of 16 children with CAE with that of 14 children with type 1 diabetes mellitus and 15 healthy children. The CAE group did not perform differently from the other groups on measures of intellectual functioning, memory, academic achievement, fine motor speed, or processing speed. In contrast, significant differences were found in problem solving, letter fluency, complex motor control, attention/behavioral inhibition, and psychosocial functioning. These results suggest that children with CAE show difficulties in neuropsychological functions thought to be subserved by the same regions implicated in the pathogenesis of the disorder.

Parkinson's disease as a disconnection syndrome

Parkinson's disease (PD) is a major neurodegenerative disorder that is usually considered in terms of midbrain and basal ganglia dysfunction. Regarding PD instead as a disconnection syndrome may prove beneficial to understanding aspects of cognition, perception, and other neuropsychological domains in the disease. PD is usually of unilateral onset, providing evidence of intrahemispheric dissociations and an imbalance in the usual relative strengths of the right and left hemispheres. Hence, in order to appreciate the neuropsychology of PD, it is important to apply to this disease our understanding of hemispheric lateralization effects and within-hemisphere circuitry from brainstem to higher-order association cortex. The focus of this review is on the relevance of PD-related disconnections among subcortical and cortical structures to cognition, perception, emotion, and associated brainstem-based domains such as sleep and mood disturbance. Besides providing information on disease characteristics, regarding PD as a disconnection syndrome allows us to more completely understand normal brain-behavior relations in general.

Characteristics of executive function impairment in Parkinson's disease patients without dementia

Executive function impairments in Parkinson's disease (PD) are well documented. However, uncertainties remain regarding the impact of these deficits on other areas of cognitive functioning. The goal of this study was to provide a comprehensive assessment of cognitive characteristics in patients with PD without dementia and to assess how any such deficits affected other areas of cognitive functioning. Forty PD patients without dementia were compared to healthy controls using measures of attention and speed of processing and a comprehensive set of executive function tests including working memory, planning, and problem solving. Measures of memory/learning and visuospatial skills were also included to examine the relationship between aspects of executive function and other areas of cognition. Patients with PD showed deficits on measures of executive function, problem solving, and visuospatial skills. However, they were unimpaired on measures of planning, attention, and memory/learning. Deficits in problem solving were only evident for tasks with a high visuospatial content and were no longer significant when visuospatial skills were controlled for. While deficits in executive function and visuospatial skills were apparent for PD patients compared to controls, many aspects of cognition remained intact. These can provide a focus for cognitive intervention strategies that can be effective in delaying decline for PD patients.

Sharpening the boundaries of Parkinson-associated dementia: recommendation for a neuropsychological diagnostic procedure

Older adults suffering from Parkinson's disease (PD) frequently present with an additional form of severe neurodegenerative and/or vascular pathology. Findings of differential clinical manifestations of cognitive impairment, depending on presence and nature of such coexisting brain pathology, raise the question for neuropsychological procedures that are capable not only of distinguishing between non-demented PD patients and patients with Parkinson-associated dementia (PDD), but also of detecting other types of cognitive decline, most likely Alzheimer's disease (AD) or vascular dementia (VD), superimposing PD. The aim of this article is to review the literature on neuropsychological processes at risk in developing PDD, to introduce comorbid causes of cognitive decline in the presence of PD, to discuss the scope of the "cortical versus subcortical dementia"-concept in view of its capability of differentiating dementias, and to scrutinize existing diagnostic criteria concerning the toleration of comorbidity. Additionally, we derive an evidence-based neuropsychological diagnostic procedure for assessing PDD under special consideration of these comorbid aspects.

Cognitive impairment in an adult Mexican population non-occupationally exposed to manganese

We examined the association between non-occupational exposure to Mn and cognitive functions. The study was carried out in a mining district located in Hidalgo State, Mexico, with 288 adults. Air and blood Mn concentrations were determined, and neuropsychological tests were administered to explore cognitive functions and depression. Blood Mn mean was 9.5 ± 4.14 μg/L. A total of 73% of the study group were in contact with air Mn levels that surpassed the EPA recommended guideline level for non-occupational environments (0.05 μg/m(3)). Air Mn concentration was associated as a risk factor for attention impairment (OR=1.75, 95% CI: 1.01-3.06). Blood Mn levels were not associated to any of the measured outcomes. The main finding of this study is the presence of attention impairments associated to high levels of air Mn exposure. These results confirm previous studies, in which cognitive impairment is reported for exposed population.

The contribution of executive control on verbal-learning impairment in patients with Parkinson's disease with dementia and Alzheimer's disease

Deficits in learning, memory, and executive functions are common cognitive sequelae of Parkinson's disease with dementia (PDD) and Alzheimer's disease (AD); however, the pattern of deficits within these populations is distinct. Hierarchical regression was used to investigate the contribution of two measures with executive function properties (Verbal Fluency and CLOX) on list-learning performance (CVLT-II total words learned) in a sample of 25 PDD patients and 25 matched AD patients. Executive measures were predictive of list learning in the PDD group after the contribution of overall cognition and contextual verbal learning was accounted for, whereas in the AD group the addition of executive measures did not add to prediction of variance in CVLT-II learning. These findings suggest that deficits in executive functions play a vital role in learning impairments in patients with PDD; however, for AD patients, learning difficulties appear relatively independent of executive dysfunction.

Left frontal lobe contributions to concept formation: a quantitative MRI study of performance on the Delis-Kaplan Executive Function System Sorting Test

This study examined relationships between lobar volumes and performance on the Delis-Kaplan Executive Function System (D-KEFS) Sorting Test, a standardized measure of concept formation. There were 89 participants: 19 patients with probable Alzheimer's disease, 25 patients with frontotemporal dementia, 13 patients with semantic dementia, 12 patients with progressive nonfluent aphasia, 9 patients with probable progressive supranuclear palsy, 2 patients with possible progressive supranuclear palsy, and 9 healthy participants. We used BRAINS2 software to generate volumes of the right and left frontal, temporal, and parietal lobes. Multiple regression analysis indicated that, after controlling for Mini-Mental State Examination scores, intracranial volume, and demographic variables, only the left frontal lobe significantly predicted performance on the D-KEFS Sorting Test.

Source memory and frontal functioning in Parkinson's disease

The most extensively described pathological abnormality in Parkinson's disease (PD) is loss of dopaminergic neurons in the substantia nigra pars compacta and the ventral tegmental area, with degeneration of their striatal terminals. Because of the intimate connections between the striatum and the frontal lobes, individuals with PD often demonstrate impairments on those tasks relying on the prefrontal cortex (e.g., tests of executive functioning). Source memory, or memory for context, is believed to rely on the prefrontal cortex and has been previously associated with executive functioning performance, although it has received little attention in the PD literature. Executive functioning and source memory were measured in a group of nondemented PD patients and healthy control participants. Within the PD group, an anti-Parkinson's medication withdrawal manipulation was used to examine whether source memory was affected by phasic changes in dopamine levels. Compared to healthy control participants, PD patients were impaired in source memory (both on- and off-medication) and on a composite measure of executive functioning. Within the PD group, medication administration improved motor performance but did not have a significant effect on source memory.

Creativity in Parkinson's disease as a function of right versus left hemibody onset

OBJECTIVE

Creativity is heavily dependent on divergent thinking and divergent thinking appears to be strongly dependent on fontal lobe function. Since patients with Parkinson's disease (PD) often have evidence of frontal lobe dysfunction we wanted to learn if these patients have a reduction of creativity, as well as learning if the side of onset (right versus left) influences the type (verbal versus visuospatial) of decrement in creativity.

DESIGN

Participants of this study were patients with right (RHO) or left (LHO) onset PD as well as matched controls. All subjects were given the Abbreviated Torrance Test of Creative Thinking for Adults (ATTA), a widely used test to assess creativity that examines Fluency, Originality, Flexibility and Elaboration. Subjects were also assessed with the Controlled Word Association Test (COWAT).

RESULTS/CONCLUSIONS

When compared to controls the patients with RHO, but not LHO, had a decrease of verbal creative fluency. Patients with PD often have a decrease on the COWAT, but performance on the COWAT did not differ between the RHO and the LHO patients. This suggests that patients with PD who have RHO have a decrease in verbal creativity and this decrement does not appear to be related to decreased fluency.

Answering the call: the influence of neuroimaging and electrophysiological evidence on rehabilitation

Functional recovery after brain damage or disease is dependent on the neuroplastic capability of the cortex and the nonaffected brain. Following cortical injury in the motor and sensory regions, the adjacent spared neural tissues and related areas undergo modifications that are required in order to drive more normal motor control. Current rehabilitation models seek to stimulate functional recovery by capitalizing on the inherent potential of the brain for positive reorganization after neurological injury or disease. This article discusses how neuroimaging and electrophysiological data can inform clinical practice; representative data from the modalities of functional magnetic resonance imaging, diffusion tensor imaging, magnetoencephalography, electroencephalography, and positron emission tomography are cited. Data from a variety of central nervous system disease and damage models are presented to illustrate how rehabilitation practices are beginning to be shaped and informed by neuroimaging and electrophysiological data.

Memory impairment in methamphetamine dependent patients

The authors examined the verbal memory and visual memory of 19 patients with methamphetamine dependence and 18 normal controls to assess the memory impairment due to the use of methamphetamine. There was no significant difference in the verbal memory, but a significant difference was detected in the visual memory. The results that the methamphetamine selectively impairs visual memory seem to be because visual memory tasks are more sensitive to the damage of the executive function.

Memory Deficits in Parkinson’s Disease

The purpose of this study was to investigate deficits in recognition, recall, and prospective memory among Parkinson's disease (PD) patients, and to ascertain whether task difficulty and disease severity moderate these deficits. Comparisons were made between 41 nondemented PD participants, divided into early-stage and advanced-stage groups, and 41 matched controls. PD participants exhibited deficits in recognition, recall, and prospective memory. The advanced-stage PD group produced greater deficits than the early-stage PD group in all tasks, suggesting that these deficits increase in step with overall disease severity. The results of the task difficulty manipulation provide a partial explanation for the inconsistencies in the literature concerning the existence of recognition memory deficits in PD.

Metamemory experiments in neurological populations: a review

Metamemory refers to knowledge about one's memory capabilities and strategies that can aid memory, as well as the processes involved in memory self-monitoring. Although metamemory has been studied in cognitive psychology for several decades, there have been fewer studies investigating the neuropsychology of metamemory. In recent years, a growing number of studies of neurological patient groups have been conducted in order to investigate the neural correlates of metamemory. In this review, we examine the neuropsychological evidence that the frontal lobes are critically involved in monitoring and control processes, which are the central components of metamemory. The following conclusions are drawn from this literature: (1) There is a strong correlation between indices of frontal lobe function or structural integrity and metamemory accuracy (2) The combination of frontal lobe dysfunction and poor memory severely impairs metamemorial processes (3) Metamemory tasks vary in subject performance levels, and quite likely, in the underlying processes these different tasks measure, and (4) Metamemory, as measured by experimental tasks, may dissociate from basic memory retrieval processes and from global judgments of memory.

Verbal fluency in Parkinson's disease: results of a 2-min fluency test

BACKGROUND

Patients suffering from Parkinson's disease (PD) are often reported to have an impaired performance on tests measuring executive functioning, such as fluency tasks.

AIM

To investigate whether verbal fluency is impaired in PD patients (n = 25) compared with healthy controls (n = 15) using a 2-min semantic and phonemic verbal fluency test. A 2-min version of the fluency task was used to allow for more switches between clusters to study retrieval strategies more adequately.

RESULTS

No differences in performance on both semantic and phonemic fluency tasks between the PD patients and the control persons were found. Moreover, both groups appeared to use the same retrieval strategies.

CONCLUSION

Patients suffering from PD appear to use the same strategies for producing words as healthy controls do. Different pathways may be involved in switching clusters during the fluency task than in other types of switching that may be impaired in PD, such as motor switching and concept-shifting.

Assessment of visual-spatial deficits in patients with Parkinson's disease and closed head injuries using virtual environments

Cognitive spatial deficits have been reliably reported in patients with Closed Head Injury (CHI), though in patients with Parkinson's disease (PD) the phenomenon is disputed. CHI and non-demented PD patients were tested using a Judgement of Line Orientation Test, and two spatial tests using virtual environments (VEs). Performance on the Line Orientation and one VE test was worse in the CHI group than controls, but PD patients showed no apparent spatial deficits. However, performance on the second VE test (virtual tray of objects task) did reveal a deficit, both CHI and PD groups being significantly impaired. The data illustrate that particular spatial deficits can be differentiated using appropriate VE-based tasks, and that non-demented PD patients show a paradigm-specific visual-spatial impairment.

Summation of semantic priming and complex sentence comprehension in Parkinson's disease

Research has suggested that the integrity of semantic processing may be compromised in Parkinson's disease (PD), which may account for difficulties in complex sentence comprehension. In order to investigate the time course and integrity of semantic activation in PD, 20 patients with PD and 23 healthy controls performed a lexical decision task based on the multi-priming paradigm. Semantic priming effects were measured across stimulus onset asynchronies of 250 ms, 600 ms, and 1200 ms. Further, PD participants performed an auditory comprehension task. The results revealed significantly different patterns of semantic priming for the PD group at the 250-ms and 1200-ms SOAs. In addition, a delayed time course of semantic activation was evident for PD patients with poor comprehension of complex sentences. These results provide further support to suggest that both automatic and controlled aspects of semantic activation may be compromised in PD. Furthermore, the results also suggest that some sentence comprehension deficits in PD may be related to a reduction in information processing speed.

Recognition memory in Parkinson's disease with and without dementia: evidence inconsistent with the retrieval deficit hypothesis

Parkinson's disease (PD) has been associated with a pattern of performance on memory tests in which free recall is impaired but recognition and cued recall are intact, indicating problems with memory retrieval. Recent findings suggest that PD patients exhibit deficits in recognition as well as free recall, however. The current study set out to provide clear evidence that recognition and cued recall are not intact in PD. Ninety-nine idiopathic PD patients were administered the California Verbal Learning Test and their performance was compared to a well-matched normative sample. A profile analysis revealed that nondemented patients exhibited deficits on measures of cued recall and delayed recognition that were similar in magnitude to that of free recall. This was also the case for the cued recall deficits exhibited by demented patients; however, in this group recognition was worse than free recall. In both groups poor recognition appeared due to an elevated number of false positive errors. These results are inconsistent with the retrieval deficit hypothesis but support the notion that PD memory problems are secondary to prefrontal dysfunction.

Spontaneous and directed application of verbal learning strategies in bipolar disorder and obsessive-compulsive disorder

OBJECTIVES

Individuals with bipolar disorder exhibit neuropsychological impairments when they are euthymic (neither depressed nor manic). One of the most consistently reported cognitive problems in euthymic individuals with bipolar disorder is impairment in verbal episodic memory. Recent findings suggest that episodic memory difficulties in these individuals are attributable to difficulties using organizational strategies during encoding. The purpose of the present study was (i) to investigate whether difficulties using organizational strategies in bipolar disorder are due to a failure in spontaneously initiating verbal organization strategies or are due to difficulties implementing such strategies, and (ii) to compare the characteristics of verbal organizational impairment in bipolar disorder with those observed in individuals with obsessive-compulsive disorder (OCD).

METHODS

Study participants were 20 individuals with bipolar I disorder (BP-I), 20 individuals with OCD, and 20 healthy control participants matched for age, gender, and education. Participants completed a verbal encoding paradigm that involved spontaneous and directed use of verbal organization strategies during encoding of word lists.

RESULTS

Compared with control subjects, both BP-I and OCD participants showed impaired verbal organization in the spontaneous encoding condition. In the directed encoding condition, OCD patients organized the word lists as well as control participants whereas BP-I participants exhibited lower verbal organization than both control and OCD participants. OCD and BP-I participants' free recall performance did not differ from that of control participants in the spontaneous encoding condition. In the directed encoding condition, BP-I participants recalled fewer words than OCD or control participants.

CONCLUSIONS

Episodic memory difficulties in OCD are associated with difficulties spontaneously initiating verbal organization strategies during encoding whereas the ability to implement verbal organization when instructed to do so is preserved. BP-I participants, on the other hand, exhibit difficulties in both spontaneously initiating verbal organization strategies and in the ability to implement such strategies when instructed to do so.

Cognitive and SPECT characteristics predict progression of Parkinson?s disease in newly diagnosed patients

OBJECTIVE

To identify features in cognitive functioning and regional cerebral blood flow (rCBF) in newly diagnosed Parkinson's disease (PD) patients and to determine whether these factors are able to predict the progression of the disease in general and the development of cognitive decline in particular.

METHODS

50 previously treatment-naive PD patients participated in the study. Cognitive assessment and SPECT were performed twice: at the time of diagnosis and then 3 years later. Six patients died or refused to continue. The Mattis dementia rating scale, the WAIS-R digit span test, a word list learning/recall test, a word fluency task and the Stroop word-colour test were used to assess cognitive function. rCBF was measured in 10 pairs of regions of interest. Principal component analysis of the data from the final examination was used to determine which variables allowed the formation of patient subgroups. Thereafter, factorial discriminant analysis (FDA) was performed in order to obtain a predictive model of these final classes.

RESULTS

A stepwise procedure enabled the identification of 3 clusters (26, 16 and 2 patients). As the patients in the smallest cluster met the criteria for dementia at the final examination, they were discarded from further analyses. All the cognitive variables contributed to the constitution of the two other clusters. Age, educational level and all the rCBF parameters also contributed but to a lesser extent. Comparison of these groups showed reduced overall cognitive efficiency and an exacerbated subcorticofrontal syndrome in the 16-patient cluster. FDA showed that the best predictive model for the final classes was based on 7 variables: educational level, semantic and alternating word fluency, Stroop interference index and the right medial frontal, left parietal and left lenticular nucleus rCBF findings.

CONCLUSION

Even though both cognitive and rCBF parameters help predict the progression of newly diagnosed PD patients and bearing in mind the limitations of the SPECT method used here, it appears that the contribution of cognitive assessment is greater than that of rCBF measurement.