Progression of motor and cognitive impairment in Parkinson's disease

We performed a longitudinal study (mean follow-up 86.7 months) to evaluate motor and mental deterioration in patients with Parkinson's disease. Of the original 91 patients, only 61 could be re-examined 7 years later and 11 of these had become demented (PD-Dems). PD-Dems were older with worse motor and, obviously, cognitive performance than non-demented parkinsonian patients (PDs). A global cognitive decay index (DI) was calculated for each patient. Based on this, non-demented PDs were further split into 38 stable parkinsonian patients (S-PDs) with DI-30% to +30%, and 10 deteriorated but non-demented parkinsonian patients (D-PDs) with a DI worse than -30% (as had PD-Dems). D-PDs were older and had greater motor impairment than S-PDs but did not differ from PD-Dems on these measures. D-PDs and PD-Dems deteriorated especially in attention, visuospatial and executive ability tests. Ageing seems to be the main predictive factor for mental deterioration.     

The independent influence of apathy and depression on cognitive functioning in Parkinson's disease.

Objective: The purpose of the present study was to examine the independent influence of symptoms of depression and apathy, two of the most common neuropsychiatric symptoms in Parkinson's disease (PD), on executive functioning and memory in PD patients using measures designed to discriminate between these symptoms. Method: Participants included 68 nondemented, idiopathic PD patients, ages 56–82 years. The Apathy Evaluation Scale—Self-Rating and select items of the Beck Depression Inventory II were used to assess symptoms of apathy and depression, respectively. Cognitive function was assessed using the Wisconsin Card Sorting Test and Hopkins Verbal Learning Test—Revised. Correlations and hierarchical regressions were conducted to investigate the relationships between apathy, depression, and cognitive function. Hierarchical regression analyses were conducted to evaluate the degree of influence of depression and apathy on cognitive function. Results: Results revealed that symptoms of apathy, but not depression, were significantly and negatively associated with executive functioning. Immediate memory was significantly and negatively associated with both apathy and depression. However, apathy accounted for additional variance in memory performance after controlling for depression at a level approaching significance. Conclusions: Apathy is not only associated with cognitive impairment, but also with impaired daily functioning, caregiver burden and distress, medication noncompliance, and increased mortality. Differentiating apathy and depression, understanding their unique effects, and appropriately identifying apathy symptoms in patients have robust implications for the development of neuropsychological models of these effects in PD as well as practical implications in guiding improvements to patient care and enhancing quality of life in patients and caregivers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The cerebellum and cognitive functions in humans.

Recent neuropsychological studies have given rise to the hypothesis that the cerebellum is involved in nonmotor cognitive functions. The interpretation of these findings is, however, restricted by methodological problems, such as heterogenous patient samples. The present study compared patients with pathology confined to the cerebellum and patients with combined cerebellar and brainstem lesions to matched normal controls on a range of memory and learning tasks. Two procedural learning tasks were also conducted, involving perceptual (mirror reading) and conceptual (the Tower of Hanoi task) skill acquisition. Patients with damage to both cerebellum and brainstem, but not patients with cerebellar pathology alone, showed impairments on memory and visuoconstructive tasks and evidence of frontal lobe dysfunction. Cerebellar damage had no effect on skill acquisition. These results do not support the hypothesis of cerebellar involvement in procedural learning per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit category learning performance predicts rate of cognitive decline in nondemented patients with Parkinson's disease.

Nondemented patients with Parkinson's disease (PD) are impaired in learning to categorize simple perceptual stimuli when category membership is defined by a nonlinear relationship between stimulus dimensions but not when the relationship is linear (J. V. Filoteo, W. T. Maddox, D. P. Salmon, & D. D. Song, 2005). In the present study, the authors examined whether performance in either of these 2 category learning conditions was predictive of global cognitive decline following a mean of 1.6 years since the time patients were 1st seen. Results indicated that final block accuracy in the nonlinear condition, but not the linear condition, predicted global cognitive decline. Performance on the Wisconsin Card Sorting Test (WCST) did not significantly predict global cognitive decline, although there was a trend for this to be the case. In addition, the association between nonlinear category learning and global cognitive decline was not impacted by patients' performance on the WCST. Results suggest that nonlinear category learning predicts cognitive decline in nondemented patients with PD and that nonlinear category learning and WCST performances may provide independent measures of integrity of the posterior and anterior caudate, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired simultaneous cognitive task performance in Parkinson's disease: a dopamine-related dysfunction

Patients with Parkinson's disease (PD) have trouble programming two separate motor acts concurrently. We tested the hypotheses that (1) PD patients may also have difficulty processing two cognitive tasks simultaneously, and (2) the expected deficit may be related to the striatal dopaminergic depletion. We used auditory and visual choice reaction time (CRT) tasks, presented either separately or concurrently, and compared the performance of three groups of PD patients: a group of patients under their usual dose of levodopa ("standard"); a group assessed both at the time of maximal clinical benefit ("on" state) and at the time of minimal clinical benefit (treatment withdrawn for about 18 hours; "off" state); and a group of recently diagnosed untreated patients ("de novo"). Compared with controls, standard and "on" state patients had a normal performance for both separate and concurrent CRT tasks. In contrast, "off" state and de novo patients had a normal performance in the separate CRT tasks but significant deficits in the concurrent CRT tasks. These results suggest that adequate dopaminergic transmission is necessary for concurrent processing of cognitive information and that the striatum integrates the sensorimotor information required to program cognitive acts.     

Verb learning in Parkinson's disease.

The relative roles of grammatical processing and memory in the language comprehension difficulties of patients with Parkinson's disease (PD) were evaluated. 20 PD patients who did not have dementia were exposed to a new verb in a naturalistic setting. After 10 min, the semantic and grammatical information that they learned about the new verb was probed. Significant impairments in recalling some aspect of the new verb were seen in 55% of PD patients. Most of these patients demonstrated a language-sensitive deficit in appreciating grammatical information represented in the new verb. A small number of PD patients responded randomly to probes of all information about the new word, which suggests a memory impairment. It is concluded that difficulty in appreciating grammatical information contributes to the language impairments of PD patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metamemory and prospective memory in Parkinson's disease.

Objective: Metamemory is integral for strategizing about memory intentions. This study investigated the prospective memory (PM) deficit in Parkinson's disease (PD) from a metamemory viewpoint, with the aim of examining whether metamemory deficits might contribute to PM deficits in PD. Method: Sixteen patients with PD and 16 healthy older adult controls completed a time-based PM task (initiating a key press at two specified times during an ongoing task), and an event-based PM task (initiating a key press in response to animal words during an ongoing task). To measure metamemory participants were asked to predict and postdict their memory performance before and after completing the tasks, as well as complete a self-report questionnaire regarding their everyday memory function. Results: The PD group had no impairment, relative to controls, on the event-based task, but had prospective (initiating the key press) and retrospective (recalling the instructions) impairments on the time-based task. The PD group also had metamemory impairments on the time-based task; they were inaccurate at predicting their performance before doing the task but, became accurate when making postdictions. This suggests impaired metamemory knowledge but preserved metamemory monitoring. There were no group differences regarding PD patients' self-reported PM performance on the questionnaire. Conclusions: These results reinforce previous findings that PM impairments in PD are dependent on task type. Several accounts of PM failures in time-based tasks are presented, in particular, ways in which mnemonic and metacognitive deficits may contribute to the difficulties observed on the time-based task. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Verbal learning strategies in Parkinson's disease.

Word-list learning was studied in patients with Parkinson's disease (PD) and normal control (NC) participants by means of the selective-reminding procedure of H. Buschke and P. A. Fuld (1974) in 3 learning conditions using semantically unrelated items; semantically related items, whose implicit categorical structure had to be spontaneously guessed; and semantically related items, whose explicit categorical structure was known in advance. The PD patients displayed poor learning in all 3 conditions. To identify the functional locus of the PD patients' deficits, the authors performed a stochastic Markov chain analysis, which allowed individual measurements of encoding, retrieval, and category clustering abilities. PD patients were never significantly impaired in encoding word engrams; their impairment was confined to automatic and intentional retrieval and to the ability to benefit from explicit semantic clues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal fluency deficits in Parkinson's disease.

Administered verbal (category naming, letter fluency) and nonverbal (category drawing, design fluency) tasks to patients with Parkinson's disease (PD). PD patients were significantly impaired only in their category naming for a semantic target like fruit. The hypothesis that compromised lexical retrieval contributed to PD patients' impaired category naming by examining free recall and recognition on a supraspan learning task was tested. PD patients were significantly impaired in free recall but not recognition. Category naming fluency correlated with free recall but not recognition on the supraspan learning task. It is argued that the verbal fluency deficit in PD is due to a lexical retrieval impairment and that the difference between category naming and letter fluency is due to the nature of the prompts for lexical retrieval that patients can derive from these tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in mild Alzheimer's disease and early Parkinson's disease.

Alzheimer's disease (AD) and Parkinson's disease (PD) impair working memory (WM). It is unclear, however, whether the deficits seen early in the course of these diseases are similar. To address this issue, the authors compared the performance of 22 patients with mild AD, 20 patients with early PD and without dementia, and 112 control participants on tests of inhibition, short-term memory, and 2 commonly administered tests of WM. The results suggest that although mild AD and early PD both impair WM, the deficits may be related to the interruption of different processes that contribute to WM performance. Early PD disrupted inhibitory processes, whereas mild AD did not. The WM deficits seen in patients with AD may be secondary to deficits in other cognitive capacities, including semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced negative priming in Parkinson's disease.

In the ignored repetition paradigm, negative priming (NP) is defined as the increase in response time that occurs when the current target stimulus served as a distractor stimulus in the previous trial. In this study, 25 Parkinson's disease (PD) participants and 17 age-matched healthy controls (HCs) were tested using a touchscreen version of the ignored repetition task that allowed response time to be partitioned into response initiation and response execution segments. In both groups, NP effects were stronger in the response execution than in the response initiation segments. The most striking result was that the PD group showed larger NP effects overall than the HC group. In PD, clinical ratings of bradykinesia, but not tremor, were related to larger NP effects. Results indicate that in PD, disruption of dopamine neuromodulation diminishes response efficiency when action must be directed toward previously ignored information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual construction impairments in Parkinson's disease.

24 nondemented Parkinson's disease (PD) patients were asked to copy and then recall the Rey-Osterrieth Complex Figure, dividing the units of the figure into "main structural" and "detail" components. PD patients consistently omitted some main structural units from recall of the figure. When main structures were produced, PD patients were impaired at drawing these features in an organized fashion, and they produced these main units late in the course of their drawings. PD patients differed from control Ss in their recall of the figure's details, but there were no qualitatively unique features in their omission of details. Correlation and regression analyses suggest that compromised executive functioning contributed to the PD patients' constructional difficulties and that visual perception and motor functioning also played a modest role. It is concluded that visual construction impairments in PD are multifactorial in nature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visuospatial dysfunction and problem solving in Parkinson's disease.

Individuals with Parkinson's disease (PD) perform deficiently on Raven's Coloured Progressive Matrices (RCPM), in contrast to their relatively good performance on many other problem-solving tasks. The question is raised as to whether a visuospatial deficit may account for poor RCPM performance in PD. The authors analyzed RCPM results in 50 nondemented participants with PD and 39 age-matched healthy control participants. The PD group made significantly more errors than the control group on all RCPM subtests, including the subtest that mainly assessed visuospatial function (RCPM-A). For the PD group, the composite score of other visuospatial tests, but not the composite scores of tests of executive function or verbal memory, significantly predicted performance on the RCPM-A. Visuospatial impairment in PD may arise from dysfunction of the basal ganglia-thalamocortical circuit that also includes the dorsolateral prefrontal cortex and, importantly, the posterior parietal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between specific cognitive functions and falls in aging.

The current study examined the relationship between cognitive function and falls in older people who did not meet criteria for dementia or mild cognitive impairment (N = 172). To address limitations of previous research, the authors controlled for the confounding effects of gait measures and other risk factors by means of associations between cognitive function and falls. A neuropsychological test battery was submitted to factor analysis, yielding 3 orthogonal factors (Verbal IQ, Speed/Executive Attention, Memory). Single and recurrent falls within the last 12 months were evaluated. The authors hypothesized that Speed/Executive Attention would be associated with falls. Additionally, the authors assessed whether associations between different cognitive functions and falls varied depending on whether single or recurrent falls were examined. Multivariate logistic regressions showed that lower scores on Speed/Executive Attention were associated with increased risk of single and recurrent falls. Lower scores on Verbal IQ were related only to increased risk of recurrent falls. Memory was not associated with either single or recurrent falls. These findings are relevant to risk assessment and prevention of falls and point to possible shared neural substrates of cognitive and motor function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adjustments of conflict monitoring in Parkinson's disease.

Objective: In Stroop-like tasks, the detection of conflict triggers adjustments of cognitive control to reduce conflict in subsequent trials. The present study tested the hypothesis of an impaired modulation of conflict monitoring in Parkinson's disease (PD). Method: 18 PD patients and 18 healthy control (HC) participants performed a Stroop-like task in 2 conditions differing in terms of incongruent/congruent stimuli ratio. Results: HC participants demonstrated a sustained modulation of interference effect, the interference effect being decreased when the proportion of incongruent stimuli was high. A trial-by-trial analysis also showed that in the HC group, processing an incongruent stimulus reduced interference in the subsequent trial. Unlike controls, PD patients did not demonstrate any transient or sustained reduction of the interference effect. Conclusion: Within the framework of recent models, these results can be interpreted as an impairment of a proactive mode of cognitive control in patients with PD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive–motor learning in Parkinson's disease.

Procedural learning deficits are common in Parkinson's disease (PD), but contradictory results have been reported in rotary pursuit learning. This article compared rotary pursuit learning in 2 nondemented PD groups and 2 normal control (NC) groups, using a between-subjects group design in which 3 rotation speeds were presented either randomly or in blocks. The pattern of learning differed between the randomized and the blocked conditions in the NC, but not in the PD groups. Learning was impaired in the PD group in the random condition only. Memory, visuospatial, or executive skills were not associated with the PD group's poorer learning in the randomized context. Results show that procedural learning deficits are not universal with basal ganglia abnormalities but rather depend on the specific cognitive requirements of the learning context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)