Short-term memory and temporal ordering in early Parkinson's disease: effects of disease chronicity and medication

Six hours to study: temporality and ignorance in medical education

Individual scientists, clinicians, and other experts cannot have absolute knowledge of all of the theories, methods, models, and findings in their field of practice. Rather, these individuals make choices about the kind of information that will be most meaningful and impactful in their work, while choosing - or being compelled to choose - what knowledge to overlook or ignore: a process identified as sufficient knowledge. In biomedicine, medical students are socialized to deliberately decide what information matters most; so, too, do practicing physicians openly acknowledge that they make choices around knowledge in daily practice. Within this process, time is a critical factor that mediates epistemological decision-making. In other words, how does time bound or restrict what forms and depth of medical knowledge that physicians and future physicians prioritize? When would someone intentionally limit time in order to constrain the amount and types of information he, she, or they acquire? To answer these questions, this study draws upon interviews and participant observation conducted with students at a medical school in the American Midwest. This article seeks to answer the aforementioned questions and to provide a new framework for, and expand discussions of, agnotology in the anthropology of medicine.

Social factors that predict cognitive decline in older African American adults

OBJECTIVES

Projections from the United States Census Bureau suggest that the African American population may be the fastest growing race over the next 30 years and that they may be at the highest risk for developing dementia later in life. Various social factors have been shown to be associated with cognitive function and health outcomes. The present study aims to evaluate the relationship between social engagement and cognitive decline in a cohort of older African American adults.

METHODS

We utilized multilevel modeling to examine the association between cognitive decline and social engagement in a sample of 617 older African American adults.

RESULTS

Social activity was associated with global cognition, perceptual speed, perceptual orientation, and episodic memory over time. Loneliness was associated with better semantic memory performance over time. Perceived discrimination was associated with better semantic memory performance over time. Larger social network was associated with worse perceptual speed scores over time.

CONCLUSIONS

Although our findings on loneliness and perceived discrimination over time were inconsistent with prior research, our findings on social activity and social network size over time were consistent with past literature and are thought to be due to positive social interactions providing a catalyst for cognitively stimulating activities. These results suggest that interventions designed to preserve cognition in African American older adults should incorporate adequate social activity. Furthermore, to maximize effectiveness, interventions should not necessarily focus on just expanding one's social network.

A Comprehensive Meta-analysis on Short-term and Working Memory Dysfunction in Parkinson's Disease

A previous meta-analysis demonstrated short-term memory (STM) and working memory (WM) dysfunction in patients with Parkinson's disease (PD). However, considerable research on the topic that calls into question the extent of such impairments in PD has since been published. The aim of the present quantitative review was to provide the largest statistical overview on STM and WM dysfunction in Parkinson's disease (PD), while simultaneously providing novel insights on moderating factors of effect size heterogeneity in PD. The systematic literature search in PubMed, PsycINFO, PsycArticles, Scopus and Web of Science databases allowed us to estimate 350 effect sizes from 145 empirical studies that reported STM and WM scores for patients with PD against healthy controls. The outcomes indicated general dysfunction in the visuospatial domain and poor verbal WM in PD. Subgroup analyses suggested that mild cognitive impairment is associated with STM and WM difficulties in PD. Furthermore, meta-regression analyses revealed that disease duration accounted for more than 80% of the visuospatial STM effect size variance (β = 0.136, p < .001, R² = .8272), larger daily levodopa equivalent dose was associated with WM dysfunction (verbal: β = -0.001, p = .016, R² = .1812; visuospatial: β = 0.003, p = .069, R² = .2340), and years of education partially explained the verbal STM effect size variance (β = -0.027, p = .040, R² = .1171). Collectively, these findings advance our understanding of underlying factors that influence STM and WM functioning in PD, while at the same time providing novel directions for future research.

Cognitive Rehabilitation for Individuals With Parkinson's Disease: Developing and Piloting an External Aids Treatment Program

Purpose Cognitive deficits are common in Parkinson's disease (PD) and can have a detrimental effect on daily activities. To date, most cognitive treatments have had an impairment-based focus with primary outcome measures of formal neuropsychological test scores. Few, if any, studies have focused on functional improvement or patient-centered goals. Method Three individuals with idiopathic PD participated in an 8-week pilot treatment program to train for the use of compensatory external aids to achieve personalized goals. Goal attainment scaling was the primary outcome measure, which was independently judged by multiple raters at baseline, postintervention, and 1 month posttreatment and analyzed via T-score analysis. Descriptive measures, including self-report and spouse-report rating scales of cognitive functioning, were employed. Results All 3 participants improved in the majority of their laboratory and home goals posttreatment, as measured by goal attainment scaling, and maintained gains for the majority of goals 1 month posttreatment. Conclusions This is the 1st known study to implement an external aids treatment program with patient-centered goals for individuals with cognitive deficits from PD. Positive outcomes were likely influenced by 3 factors: (a) a theoretically motivated focus on external aids; (b) a well-documented, systematic approach to instruction; and (c) the personalization of goals. Supplemental Material https://doi.org/10.23641/asha.10093493.

Deficit in specific cognitive domains associated with dementia in Parkinson's disease

Impairment in different cognitive domains such as executive functions, language, memory and visuospatial skills occur frequently in Parkinson disease (PD) leading to significant disability and deterioration in quality of life. Heterogeneity of cognitive impairment enhances risk of developing dementia as disease progress. The objective is to explore the pattern of cognitive impairment with reference to the affected domains in PD with or without dementia relative to healthy controls. In this study, 110 PD patients and 26 healthy control were categorized into groups using Mini Mental State Examination and Clinical Dementia Rating scores as PD without dementia (PDND, n = 65; MMSE score >24; CDR = 0-1), PD with dementia (PDD, n = 45; MMSE score ≤24; CDR = 0.5-3) and healthy control (HC, n = 26; MMSE score >26; CDR = 0). Both Patients and controls underwent individual assessments of working memory, semantic memory, attention, language, executive functions, psychomotor and visuospatial skills and dementia using different cognitive function tests. Findings revealed lower scores of word memory, attention, psychomotor speed, visuospatial skills and executive functions in PDD compared to PDND. Interestingly, in PDD scores of picture memory, semantic memory and language functions were comparable with PDND. Compared to HC, PDND had no impairment in working memory, attention and executive functions, whereas PDD had lower scores in all the cognitive domains tested. Results indicate that the deficits in word memory, attention, psychomotor speed, visuospatial skills and executive functions distinguishes PDD from PDND. Impairment in specific cognitive domains may be a biomarker for predicting onset of dementia in Parkinson's disease.

Cognitive and Neuropsychiatric Features of Early Parkinson's Disease

The clinical definition of Parkinson's disease (PD) is based on cardinal motor features including bradykinesia as well as an additional symptom of tremor, postural instability, or rigidity. Evidence from neuropathological, imaging, and clinical research suggests a premotor, early phase of PD pathology. Further understanding of the earliest biomarkers of PD is crucial for the development of neuroprotective, disease modifying, cognitive, and psychiatric interventions. Recent research has explored early non-motor markers of PD pathology. This issue is especially timely as the International Parkinson and Movement Disorder Society has recently provided a research definition for prodromal PD which includes combinations of prodromal markers and risk factors aimed at identifying target populations for disease-prevention trials. In this review of early PD, we will outline early non-motor symptoms, early cognitive and neuropsychiatric features, neuropsychological assessment strategies, emerging evidence for early biomarkers, and treatment recommendations.

Limitations of the rat medial forebrain lesion model to study prefrontal cortex mediated cognitive tasks in Parkinson's disease

Parkinson's Disease (PD) is a progressive movement disorder characterized by the loss of dopaminergic neurons in the midbrain. Besides motor impairment, PD patients exhibit non-motor symptoms that negatively impact their quality of life and often manifest prior to motor deficits. One such symptom is mild cognitive impairment (PD-MCI), which is comprised of deficits in executive function such as working memory, attention, cognitive flexibility, and spatial memory. The 6-hydroxydopamine (6-OHDA) induced unilateral medial forebrain bundle (MFB) lesion animal model successfully recapitulates PD motor impairment but is also used to assess non-motor deficits. The present study utilizes a unilateral 6-OHDA induced MFB lesion rodent model to investigate prefrontal cortex (PFC)-mediated cognitive processes that are impaired in PD patients. In a test of attentional set shifting, PD rodents demonstrated deficits in simple discrimination, but not in rule reversal or extradimensional shifts. PD rodents also exhibited deficits in a temporal order memory task but had no deficits in novel/spatial object recognition or object-in-place tasks. These results reveal limitations of the 6-OHDA induced unilateral MFB lesion model to completely recapitulate PD-MCI symptoms suggesting a need for better lesion models to study PD-MCI.

Effects of Parkinson's disease and dopamine on digit span measures of working memory

RATIONALE

Parkinson's disease (PD) impairs working memory (WM)-the ability to maintain items in memory for short periods of time and manipulate them. There is conflicting evidence on the nature of the deficits caused by the disease, and the potential beneficial and detrimental effects of dopaminergic medication on different WM processes.

OBJECTIVES

We hypothesised that PD impairs both maintenance and manipulation of items in WM and dopaminergic medications improve this in PD patients but impair it in healthy older adults.

METHODS

We tested 68 PD patients ON and OFF their dopaminergic medication, 83 healthy age-matched controls, and 30 healthy older adults after placebo and levodopa administration. We used the digit span, a WM test with three components (forwards, backwards, and sequence recall) that differ in the amount of manipulation required. We analysed the maximum spans and the percentage of lists correctly recalled, which probe capacity of WM and the accuracy of the memory processes within this capacity, respectively.

RESULTS

PD patients had lower WM capacity across all three digit span components, but only showed reduced percentage accuracy on the components requiring manipulation (backwards and sequence spans). Dopaminergic medication did not affect performance in PD patients. In healthy older adults, levodopa did not affect capacity, but did impair accuracy on one of the manipulation components (sequence), without affecting the other (backwards).

CONCLUSIONS

This suggests that the deficit of maintenance capacity and manipulation accuracy in PD patients is not primarily a dopaminergic one and supports a potential "overdosing" of intact manipulation mechanisms in healthy older adults by levodopa.

Cognitive Dysfunction in Parkinson’s Disease: The Role of Frontostriatal Circuitry

It has been known for many years that the classic motor symptoms of Parkinson’s disease are accompanied by deficits of executive function that resemble those seen after frontal lobe damage in humans. What is less clear is how different components of frontostriatal circuitry contribute to these impairments. Recently, improved methods of clinical assessment and classification, combined with novel technical approaches, such as functional neuroimaging, have led to great advances in our understanding of the fundamental mechanisms that drive frontostriatal circuitry. As a direct result, it has been possible to redefine impairments of executive function in Parkinson’s disease more precisely in terms of the specific neuropsychological, neuroanatomical, and psychopharmacological mechanisms involved.

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.

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.

Brain volumetry in Parkinson's disease with and without dementia: where are the differences?

BACKGROUND

Cognitive dysfunction is well documented in Parkinson's disease (PD). However, association between regional brain volume change and cognitive decline of PD is uncertain.

PURPOSE

To compare regional brain volume difference between PD without dementia (PDND) and PD with dementia (PDD).

MATERIAL AND METHODS

We enrolled 16 normal controls (mean ± SD: 69.5 ± 6.31) and 32 sex-, age-matched patients with PD (16 PDND and 16 PDD patients with Hoehn & Yahr stage II or III). Cognitive function was assessed using mini-mental status examination (MMSE). Intracranial volume (ICV) and the hippocampal volumes were manually measured using magnetic resonance imaging (MRI). Regional gray/white matter volume changes were analyzed using voxel-based morphometry.

RESULTS

Age, ICV, volume of gray matter volume (GMV), white matter, and hippocampi did not differ among the three groups. The regional GMV of PDD was significantly decreased in the areas of right middle frontal gyrus, short insular gyri, superior temporal gyri; both precuneus compared to PDND (uncorrected P < 0.001). In the partial correlation analysis (controlled for age, sex, ICV), regional GMV of PD was positively correlated with MMSE score in the areas of short insular gyri, right circular insular sulcus, right calcarine sulcus, left superior temporal gyrus (planum porale), and left inferior precentral sulcus (uncorrected P < 0.001).

CONCLUSION

We suggest that the volume loss of hippocampus may not be a finding in developing of PDD while variation of the regional volume of the frontal, insular cortex, superior temporal gyri, and precuneus lobes may be a phenomenon of PDD.

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.

Dementia in Parkinson's disease

Parkinson's disease is the second most common neurodegenerative illness diagnosed in the United States. Dementia is recognized as a common component of advanced Parkinson's disease (PD). In patients with early PD, cognitive changes occur and primarily reflect impairment in executive function. It is unknown if the early cognitive changes detected on neuropsychological testing in Parkinson's disease are predictive of the subsequent development of Parkinson's disease with dementia (PDD). Many patients with PD develop dementia characterized by a wide range of cognitive deficits distinct from those seen in Alzheimer's disease (AD). Neuropsychiatric problems frequently accompany PDD. This chapter reviews the epidemiology, clinical characteristics of early and late cognitive changes, pathology, neuroimaging, diagnosis, and treatment of PDD.

Prospective memory in Parkinson disease across laboratory and self-reported everyday performance

Prospective memory is a complex cognitive construct ubiquitous in everyday life that is thought to sometimes rely on executive skills commonly affected by Parkinson's disease (PD). The present study investigated the effect of PD on prospective memory tasks with varying demand on executive control processes, namely on the amount of strategic attentional monitoring required for intention retrieval. Individuals with PD but without dementia and healthy adults performed laboratory event-based prospective memory tasks that varied in whether strategic attentional monitoring (nonfocal condition) or spontaneous processes (focal condition) were primarily involved in intention retrieval. Participants also completed a questionnaire rating their frequency of prospective memory failures in everyday life for both self-cued and environment-cued tasks. PD participants performed worse than non-PD participants in the nonfocal, but not focal, condition of the laboratory task. They also reported more everyday failures than non-PD participants for self-cued, but not environment-cued, prospective memory tasks. Thus, nondemented individuals with PD are preferentially impaired on prospective memory tasks for which higher levels of executive control are needed to support intention retrieval. This pattern is consistent across laboratory and reported real-world performance.

The role of the basal ganglia in learning and memory: neuropsychological studies

In recent years, a common approach to understanding how the basal ganglia contribute to learning and memory in humans has been to study the deficits that occur in patients with basal ganglia pathology, such as Parkinson's disease and Huntington's disease. Pharmacological manipulations in patients and in healthy volunteers have also been conducted to investigate the role of dopamine, a neurotransmitter that is crucial for normal striatal functioning. When combined with powerful functional neuroimaging methods such as positron emission tomography and functional magnetic resonance imaging, such studies can provide important new insights into striatal function and dysfunction in humans. In this review, we consider this broad literature in an attempt to define a specific role for the caudate nucleus in learning and memory, and in particular, how this role may differ from that of the putamen. We conclude that the caudate nucleus contributes to learning and memory through the excitation of correct action schemas and the selection of appropriate sub-goals based on an evaluation of action-outcomes; both processes that are fundamental to all tasks involve goal-directed action.

Clinical diagnostic criteria for dementia associated with Parkinson's disease

Dementia has been increasingly more recognized to be a common feature in patients with Parkinson's disease (PD), especially in old age. Specific criteria for the clinical diagnosis of dementia associated with PD (PD-D), however, have been lacking. A Task Force, organized by the Movement Disorder Study, was charged with the development of clinical diagnostic criteria for PD-D. The Task Force members were assigned to sub-committees and performed a systematic review of the literature, based on pre-defined selection criteria, in order to identify the epidemiological, clinical, auxillary, and pathological features of PD-D. Clinical diagnostic criteria were then developed based on these findings and group consensus. The incidence of dementia in PD is increased up to six times, point-prevelance is close to 30%, older age and akinetic-rigid form are associated with higher risk. PD-D is characterized by impairment in attention, memory, executive and visuo-spatial functions, behavioral symptoms such as affective changes, hallucinations, and apathy are frequent. There are no specific ancillary investigations for the diagnosis; the main pathological correlate is Lewy body-type degeneration in cerebral cortex and limbic structures. Based on the characteristic features associated with this condition, clinical diagnostic criteria for probable and possible PD-D are proposed.

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.

Parkinson's disease and arithmetics: the role of executive functions

Brain imaging studies as well as neuropsychological case studies suggest an important role for basal ganglia in arithmetic processing. Aim of this study was to assess possible numerical deficits in PD and functional relations between numerical and other cognitive deficits. Fifteen non-demented patients with early PD (stable responders treated by l-dopa) were compared to 28 healthy age and education matched controls. Both groups underwent a neuropsychological assessment focussing on numerical abilities (quantity processing, arithmetic fact retrieval, complex mental and written calculation, transcoding, arithmetic set-shifting, calculation span), working memory and executive functions. Patients with PD showed deficits in complex mental calculation and calculation span tasks. Results of this study suggest that impairments in working memory as well as in executive functions, such as inhibition of interference, lead to secondary deficits in numerical processing. The study contributes to better understanding the specific cognitive deficits in early PD and the neurocognitive architecture of arithmetic processing.

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.

Dopaminergic basis for deficits in working memory but not attentional set-shifting in Parkinson's disease

Although Parkinson's disease is a common neurodegenerative disorder characterised by its motoric symptoms, there is an increasing recognition of accompanying impairments in cognition that have a profound impact on the quality of life of these patients. These deficits predominantly affect executive function and impairments of working memory have been frequently reported. However, the underlying neurochemical and pathological basis for these deficits are not well understood. In this study, 20 patients were tested 'on' and 'off' levodopa (L-dopa) medication on a task that allowed different aspects of working memory function such as maintenance, retrieval and manipulation to be tested within the same general paradigm as well as on an unrelated test of attentional set-shifting, which is known to be sensitive to deficits in early Parkinson's disease. Compared to healthy volunteers, PD patients were impaired at manipulation more than maintenance or retrieval of information within working memory. The patients were also impaired at the attentional set-shifting task. However, whereas L-dopa ameliorated the working memory deficit in manipulation (improving both accuracy and cognitive response time), it had no effect on the attentional set-shifting impairment. These results confirm that working memory deficits in PD are both psychologically specific and related to dopamine depletion. It is anticipated that greater understanding of these mechanisms will lead to future therapeutic improvements.

The contribution of the study of neurodegenerative disorders to the understanding of human memory

Memory impairment is one of the most common complaints affecting patients with neurodegenerative disorders, and its investigation has provided insights into the function and properties of human memory. The study of Alzheimer's disease has indicated the importance of mesial temporal structures and the hippocampus in episodic memory. In progressive supranuclear palsy, frontotemporal dementias, Parkinson's disease and Huntington's disease fronto-striatal networks are involved in working memory and higher level cognition. The study of semantic dementia, where there is lobar atrophy of the temporal lobe, has shown that the temporal neocortex has an important function in semantic memory. The investigation of human memory in neurodegenerative disorders suggests that the interaction of networks subserving episodic memory, semantic memory, and working memory contributes to higher level cognition and results in the fundamental homeostatic processes of recall and learning.

The effects of cognitive abilities on driving in people with Parkinson's disease

OBJECTIVE

The aim was to develop a cognitive screening procedure, which could be used to identify cognitive problems in patients with Parkinson's disease, which might affect their safety to drive.

DESIGN

Two group comparison of those found safe to drive and those found unsafe.

SETTING

People living in the community who were attending an outpatient Movement Disorders clinic or who had been referred to a Regional Mobility Centre.

PARTICIPANTS

Fifty-one people with Parkinson's disease who were driving or who wished to resume driving. The 41 men and 10 women were aged 44 - 85 years (mean 64.4 SD 9.1).

MAIN MEASURES

Webster's Rating Scale, Unified Parkinson's Disease Rating Scale motor examination, Stroke Drivers Screening Assessment, Adult Memory and Information Processing Battery, Stroop, Paced Auditory Serial Addition Task and a Tapping task.

RESULTS

The unsafe drivers were significantly more disabled, as assessed on Webster's Scale, than those who were found safe to drive. There were no significant differences in the cognitive abilities of safe and unsafe drivers. The most common faults, which caused drivers to be judged unsafe, were lack of observations to the side at junctions, poor positioning on the road and poor driving on roundabouts. There were significant correlations (p < 0.05) between driving ability and performance on the SDSA Dot Cancellation task and the AMIPB Story Recall and Information Processing A.

CONCLUSIONS

Cognitive abilities were not found to be associated with fitness to drive in people with Parkinson's disease. Webster's Rating Scale differentiated between safe and unsafe drivers. This could be used to determine who to refer to a mobility centre for advice on fitness to drive.

Arrangement de scripts dans la maladie de Huntington

According to Norman and Shallice, the basal ganglia are involved in the activation and maintenance of overlearned or routine scripts in action planning. This study aimed to investigate how patients with Huntington disease manipulate scripts. Ten patients with Huntington's disease and 12 normal control subjects matched by age and education were asked to re-establish the sequential order of series of script actions which were given with or without distractor elements (i.e. with or without actions belonging to trivial scripts). Compared with normal controls, patients with Huntington disease made significantly more errors in script sequencing. However there was no significant difference in performance between patients with Huntington disease and normal control subjects in inhibiting irrelevant actions. These results suggest that early Huntington's disease patients exhibit early impairment in their ability to produce temporally coherent sequences without deficit in their ability to eliminate distractors in the action domain. These results support in part the predictions of Norman and Shallice's model. From a neuroanatomical point of view, this dissociation of performance fits with what is known about the neuropathological progression of Huntington's disease in which neuronal loss progresses in a dorsal-to-ventral direction and with what was shown in patients with circumscribed frontal lobe damage. In these patients, impairment in script sequencing is related to lesions in the lateral prefrontal regions.

Striatal contributions to working memory: a functional magnetic resonance imaging study in humans

Although the role of the frontal cortex in executive performance has been widely accepted, issues regarding the contribution of subcortical structures to these functions remain unresolved. In this study, the neural circuitry underlying selective subcomponents of working memory was investigated using event-related functional magnetic resonance imaging (fMRI). Ten healthy volunteers performed a verbal memory task, which allowed different aspects of working memory function such as maintenance, retrieval and manipulation to be tested within the same general paradigm. During performance of this task as a whole, fMRI revealed increases in signal intensity throughout the frontostriatal network. However, when signal intensity during the manipulation of information within working memory was compared to that during periods requiring only simple maintenance and retrieval, significant changes were observed only in the caudate nuclei, bilaterally. These results suggest an essential and specific role for the caudate nucleus in executive function, which may underlie the cognitive disturbances observed in frontostriatal neurodegenerative disorders such as Parkinson's disease.

Emotion recognition in patients with idiopathic Parkinson's disease

Emotion recognition (ER) was examined in 64 patients with idiopathic Parkinson's disease (PD; 56 bilateral and 8 right-sided) and 64 matched healthy volunteers. Participants were administered an ER battery, consisting of the following subscores: overall ER (OER), overall facial ER, facial emotion identification (FEI) and discrimination, overall prosodic ER, and prosodic emotion identification (PEI) and discrimination. Measures of visuospatial functions, auditory attention, and depression were also administered. After controlling for visuospatial functions, auditory attention and depression, results indicated that patients with bilateral PD had poorer performance on all ER subscores, regardless of the modality and type of experimental task involved, relative to healthy volunteers. However, patients with right-sided PD had difficulty on FEI and PEI only. Whereas none of the clinical variables examined in this study predicted any of the ER subscores, visual organization and auditory attention positively predicted OER in patients with PD. In addition, visual organization also positively predicted FEI in these patients. Implications are discussed in terms of the neural substrates underlying ER.

Rivastigmine (Exelon) for dementia in patients with Parkinson's disease

OBJECTIVES

To study the efficacy of cholinesterase inhibitors in the treatment of dementia in patients with Parkinson's disease (PD).

METHODS

We treated twenty-eight demented patients with PD openly for 26 weeks with rivastigmine (mean daily dose 7.2 +/- 3.3 mg/day). Baseline scores were compared with those at weeks 12, 26 and after 8 weeks of washout.

RESULTS

Twenty patients completed 26 weeks of treatment and eight dropped out because of side effects. The Unified Parkinson's Disease Rating Scale mental subscore improved significantly at week 26 (P < 0.01) while the motor score (part III) did not change. The mean ADAScog total score improved by 7.3 points at week 26 (P < 0.002). The subscores for recognition, word finding, remembering instructions and concentration items of the ADAScog improved significantly as well (P < 0.02, P < 0.05, P < 0.005 and P < 0.003, respectively).

CONCLUSIONS

Rivastigmine may improve the cognitive functions in PD patients with dementia with no worsening of motor function.

The relationship between executive function and verbal memory in Parkinson's disease

A growing body of evidence suggests that the various cognitive symptoms found in Parkinson's disease (PD) are secondary to executive dysfunction. Studies addressing this possibility for memory impairment specifically have not included measures of working memory nor have they ruled-out potential mediating variables such as overall level of cognitive impairment or depression. The purpose of this study was to include measures of these variables in determining the relationship between multiple aspects of executive function and delayed verbal recall in 32 idiopathic PD patients. Results were consistent with the original hypothesis and further suggest that working memory is a key factor in recall memory and may mediate the relationship between other executive measures and recall in PD.

Using executive heterogeneity to explore the nature of working memory deficits in Parkinson's disease

Idiopathic Parkinson's disease (IPD) is characterised by a triad of motor symptoms, namely bradykinesia, rigidity and resting tremor, although cognitive impairment is a common feature of the disease and has been accepted as one of the strong predictors of quality of life in such patients. Neuropsychological testing in Parkinson's disease often reveals a pattern of cognitive impairment similar to that observed in patients with frontal lobe lesions, although clear differences between the two groups have also often been reported. This apparent inconsistency in the literature may reflect heterogeneity among different groups of patients with Parkinson's disease, although to date this possibility has not been formally addressed. In this study, two groups of patients with Parkinson's disease were assessed on a novel verbal memory task, which allowed different aspects of working memory function such as maintenance, retrieval and manipulation to be tested within the same general paradigm. The two groups were selected according to either good or bad performance on a 'standard', visuospatial test of executive function (The Tower of London Task), but were well matched on all other demographic and cognitive measures tested. The sub-group of Parkinson's disease patients with Tower of London defined executive deficit were specifically impaired at manipulating information within verbal working memory, both compared to controls and to the group of patients with no predefined executive impairments. In contrast, the three groups did not differ in their ability to maintain or retrieve information within verbal working memory. Given the known preferential role of the dorsolateral frontal cortex in higher executive functions, (including both planning and the manipulation of information within working memory), these results suggest that, in a subset of Parkinson's disease patients, it is the frontostriatal circuitry involving this region which is primarily affected, while other components of this circuitry may be relatively spared. The results also suggest that performance on the Tower of London task may prove to be a useful discriminant variable in defining the nature of cognitive heterogeneity in Parkinson's disease.

Motor sequencing in Parkinson's disease: relationship to executive function and motor rigidity

Parkinson's disease (PD) is a movement disorder that also affects central cognitive processing; however, the extent to which high-order cognitive processes disrupted by PD affect complex motor function is incompletely explicated. The present analysis provides an examination of the relative contributions of simple motor versus complex cognitive functions involving sequencing, problem solving, and overall cognitive status to complex motor movements involving sequencing and temporal ordering in PD. Motor sequencing performance was videotaped for quantitative scoring. Compared with an age-matched control group, the PD group was impaired on motor agility and motor sequencing tasks in addition to cognitive sequencing and set shifting tasks. Neither current cognitive functioning, age, disease duration, nor overall intellectual abilities accounted for the relationships between motor sequencing and cognitive sequencing abilities in PD. By contrast, both sequencing and nonsequencing executive functions predicted motor sequencing performance as well as or better than motor rigidity or overall cognitive status. These relationships were strongest for the most challenging motor sequencing task, fist-edge-palm, and did not apply to the least challenging task, which required simple alternations of hand movements. Unlike PD, controls showed correlations between motor sequencing tests and executive functioning only tapping nonsequencing abilities. Thus, despite the predominant motor feature of PD, executive functions, as assessed by sequencing and set formation, predicted motor sequencing performance as well as or better than simple motor performance. The results further suggest that the more complex the motor sequencing task, the more susceptible it is to influence from generalized cognitive sequencing ability.

Neurobehavioral aspects of movement disorders

Cognitive, behavioral, affective, and psychiatric symptoms occur in almost all movement disorders. Diagnosis and management of movement disorders depends critically on an understanding of these neurobehavioral symptoms. This article reviews the neurobehavioral aspects of two representative movement disorders; Parkinson's disease and Huntington's disease.

Dopamine supports sentence comprehension in Parkinson's Disease

OBJECTIVE

To determine the role of dopamine in the executive resource component of sentence comprehension.

METHODS

We studied sentence-picture matching in 20 right-handed, non-demented, native English speakers with mild Parkinson's disease (PD) when 'on' and 'off' their levodopa, taking into account disease duration to control for endogenous dopamine metabolism. We also administered a verbal working memory measure that does not involve specific grammatical manipulations.

RESULTS

PD patients 'off' levodopa demonstrated a significant discrepancy in their comprehension of grammatically complex sentences compared to grammatically simpler sentences that was not evident when PD patients were 'on' levodopa. An error analysis demonstrated that impaired comprehension of grammatically complex sentences when 'off' levodopa was associated with poorer performance on foils requiring working memory resources. Performance on an independent measure of verbal working memory correlated only with comprehension of grammatically complex sentences during levodopa supplementation, but working memory according to this measure did not differ during 'on' and 'off' states.

CONCLUSION

Dopamine supports the executive resources contributing to sentence comprehension in PD.

Defective representation of knowledge in Parkinson's disease: evidence from a script-production task

The deficits seen in frontal-lobe patients and in the elderly show clearly that spontaneous script generation depends on good frontal-lobe function. Shallice, however, has proposed that one aspect of script generation (contention scheduling, CS) which is involved in the activation and maintenance of overlearned or routine scripts may depend more on the basal ganglia. Patients with Parkinson's disease would thus be expected to manifest deficits somewhat different from those observed in frontal-lobe patients when generating scripts. The performances of 16 nondemented and nondepressed patients with idiopathic Parkinson's disease were compared to those of 16 age-matched normal control subjects under two experimental conditions; routine, forward script generation and nonroutine, backward script generation. Parkinsonian patients generated scripts significantly deprived of contextual elements in the forward condition and made significantly more sequencing and perseverative errors in both forward and backward conditions than did normal subjects. They also produced a significantly higher number of irrelevant intrusions, in both conditions, than did controls. These results support, in a general sense, Shallice's notion that the basal ganglia are important in script generation; however, other specific predictions of Shallice's model were not supported by our findings.

Spoken language production in Huntington's and Parkinson's diseases

The purpose of this study was to investigate the presence and nature of spoken language deficits in Huntington's (HD) and Parkinson's (PD) diseases. Specifically, the study examined whether (a) the spoken language abilities of patients with HD or PD differ from those of age-matched control participants with no brain damage, (b) HD and PD are associated with similar spoken language profiles, and (c) the spoken language abilities of patients with HD or PD are related to the severity of their motor speech deficits, cognitive impairments, or both. All participants completed picture description tasks and a battery of cognitive and motor speech tests. Syntactic, quantitative, and informativeness measures of spoken language were analyzed. In terms of syntax, patients with HD produced shorter utterances, a smaller proportion of grammatical utterances, a larger proportion of simple sentences, and fewer embeddings per utterance than their non-brain-damaged peers. The HD group also produced utterances that were shorter and syntactically simpler than those of the PD group, despite similar performances on the cognitive and motor speech tests. The only syntactic difference between the PD group and their control group was that patients with PD produced a smaller proportion of grammatical sentences. Although the patient and control participants tended to produce similar amounts of verbal output, less of what the patients said was considered informative. Correlations between language measures and test battery results suggested that the spoken language abilities of patients with HD or PD are related to a variety of neuropsychological and motor speech changes. The implications of these findings for the clinical management of HD and PD are discussed.

Cognitive processes involved in delayed non-matching-to-sample performance in Parkinson's disease

Visual recognition memory was assessed in terms of delay duration, memory load and amount of interference(s) in non-demented patients with Parkinson's disease (PD) using an automated delayed non-matching-to-sample (DNMS) task with trial-unique stimuli. Special attention was focused on the different cognitive functions engaged by these patients in solving this recognition memory task. Thirteen patients with PD, carefully selected according to their stable regimen and anticholinergic medication, were compared to 12 controls matched by age and educational level. Besides the DNMS task, a neuropsychological battery that included tasks carefully selected according to processes potentially required to perform the DNMS task (e.g. attention, executive functions, visual discrimination and motor speed) was administered to the subjects. As compared with controls, patients with PD showed a deficit on most DNMS subscores, except those requiring the least cognitive load. The correlative analysis between the DNMS and other neuropsychological tasks suggests involvement of long-term memory mainly in the DNMS performance for the control group, contrasting with a major involvement of executive functions for the patients with PD. These data indicate that visual recognition memory impairment in non-demented patients with PD is largely due to an executive dysfunction, notably in working memory. Several hypotheses are proposed concerning the neuronal substrates underlying the impairment on the visual DNMS task in PD.

Sentence processing in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative condition that is associated with the depletion of dopamine (DA)-containing neurons in specific brain regions. This article reviews one consequence of this defect-sentence comprehension difficulty in nondemented patients with PD. The first section describes the pattern of cognitive deficits seen in patients with PD, focusing specifically on their difficulties with language processing. Subsequent sections relate the profile of cognitive impairments in PD to studies investigating compromised DA metabolism in fronto-striatal brain regions. The findings suggest that the sentence comprehension deficit in PD is due in large part to limitations in the strategic distribution of cognitive resources such as selective attention that contribute to the processing of complex material. The physiological basis for this deficit appears to be associated with the disruption of a fronto-striatal cerebral network that is compromised following degradation of the DA projection system.

Differential diagnosis of the major progressive dementias and depression in middle and late adulthood: a summary of the literature of the early 1990s

There is a preponderance of research on the neuropsychology of the various dementias. There are also direct comparisons between two or more dementias available in the literature. This paper sought to summarize the most recent literature, primarily from 1990 through mid-1996, including recent reviews of the literature from previous decades. The purpose was to provide, in one location, a summary of neuropsychological (i.e., cognitive, motor, and psychiatric) characteristics of major noninfectious, progressive dementias and depression of middle and late adulthood. It is hoped that this review, particularly a summary table provided, will serve as a guide in the differential diagnosis of the dementias by clinicians. In addition to Alzheimer's disease, vascular dementias, Parkinson's disease, Lewy body dementia, Huntington's disease, and frontal lobe dementia, the impact of depression on cognitive functioning is covered given the frequency with which neuropsychologists are asked to differentiate depression from primary dementia.

Decreased driving ability in people with Parkinson's disease

BACKGROUND

Driving is a complex form of activity involving especially cognitive and psychomotor functions. These functions may be impaired by Parkinson's disease. The relation between Parkinson's disease and driving ability is still obscure and clinicians have to make decisions concerning the driving ability of their patients based on insufficient information. Until now no studies have compared different methods for evaluating the driving ability of patients with Parkinson's disease.

METHODS

The driving ability of 20 patients with idiopathic Parkinson's disease and 20 age and sex matched healthy control subjects was evaluated by a neurologist, psychologist, vocational rehabilitation counsellor, and driving instructor using a standard 10 point scale. The patients and controls also evaluated their own driving ability. Cognitive and psychomotor laboratory tests and a structured on road driving test were used for evaluating the subjects' driving ability.

RESULTS

The patients with Parkinson's disease performed worse than the controls both in the laboratory tests and in the driving test. There was a high correlation between the laboratory tests and driving test both in the patient group and in the control group. Disease indices were not associated with the driving test. The neurologist overestimated the ability of patients with Parkinson's disease to drive compared with the driving ability evaluated by the structured on road driving test and with the driving related laboratory tests. Patients themselves were not capable of evaluating their own ability reliably.

CONCLUSION

Driving ability is greatly decreased in patients with even mild to moderate Parkinson's disease. The evaluation of patients' driving ability is very difficult to carry out without psychological and psychomotor tests and/or a driving test.