Changes in Verbal Fluency in Parkinson's Disease

Parkinson's disease psychosis associated with accelerated multidomain cognitive decline

BACKGROUND

Cognitive deficits are associated with poor quality of life and increased risk of development of dementia in patients with Parkinson's disease (PD) psychosis. The trajectory of cognitive decline in PD psychosis remains however unclear.

OBJECTIVE

We examined this using data from the Parkinson's Progression Markers Initiative study.

METHODS

We analysed data from patients with drug-naïve PD (n=676) and healthy controls (HC, n=187) over 5 years, and examined all cognitive measures assessed at each time point. We classified patients with PD into those who developed psychosis over the course of the study (PDP) and those without psychosis throughout (PDnP) using the Movement Disorders Society Unified Parkinson's Disease Rating Scale part I hallucinations/psychosis item. We used linear mixed-effect models with restricted maximum likelihood. Age, sex, ethnicity, education and neuropsychiatric and PD-specific symptoms were entered as covariates of interest.

FINDINGS

There were no baseline cognitive differences between PD patient groups. There were differences in cognitive performance between PD and HC across the majority of the assessments.Patients with PDP exhibited greater cognitive decline over 5 years compared with PDnP across most domains even after controlling for sociodemographics, depression, sleepiness, rapid eye movement sleep behaviour disorder and motor symptom severity (immediate recall, b=-0.288, p=0.003; delayed recall, b=-0.146, p=0.003; global cognition, Montreal Cognitive Assessment, b=-0.206, p<0.001; visuospatial, b=-0.178, p=0.012; semantic fluency, b=-0.704, p=0.002; processing speed, b=-0.337, p=0.029).

CONCLUSIONS

Patients with PD psychosis exhibited decline in semantic aspects of language, processing speed, global cognition, visuospatial abilities and memory, regardless of sociodemographic characteristics, neuropsychiatric and motor symptoms. These cognitive domains, particularly semantic aspects of language may therefore play an important role in PD psychosis and warrant further investigation.

TRIAL REGISTRATION NUMBER

NCT01141023.

Exploring the utility of process scores in elucidating the role of cognitive and affective factors that influence verbal fluency performance in Parkinson's disease

OBJECTIVES

Cognitive and affective factors have been implicated in verbal fluency (VF) performance in Parkinson's disease (PD). This exploratory study aimed to investigate the relationships between cognitive and affective variables on traditional ("core") and "process" (error and interval) scores of VF and elucidate unique information these scores may provide regarding mechanisms underlying VF.

METHODS

Sixty-two PD patients without dementia completed clinical neuropsychological examinations consisting of attention, processing speed, language, executive functioning, visuospatial, memory, and mood measures. Hierarchical regression and negative binomial regression analyses were used to evaluate relationships between outcome and predictor variables.

RESULTS

Generativity results revealed that processing speed and working memory explained up to 34% of the variance of total letter fluency responses (p = <.001) and processing speed explained 24% of the variance for total semantic fluency (p = .003). For category switching generativity, only age predicted 20% of the variance (p = .01). Two executive functioning measures were negatively associated with error production over the duration (b = -.055, p = .028; b = -.062, p = .004) and final 45-second interval (b = -.072, p = .003; b = -.044, p = .033) of the category switching task. In the initial 15-second task interval, a positive predictive relationship between error production and indifference apathy (b = .616, p = .044) was demonstrated.

CONCLUSIONS

Findings demonstrate the potential utility of "process" scores in detecting subtle cognitive impairment in Parkinson's disease patients without dementia and tentatively evidence the role of indifference apathy in task initiation.

Differential Cognitive Effects of Unilateral Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

OBJECTIVE

The aim of this study was to investigate the cognitive effects of unilateral directional versus ring subthalamic nucleus deep brain stimulation (STN DBS) in patients with advanced Parkinson's disease.

METHODS

We examined 31 participants who underwent unilateral STN DBS (left n = 17; right n = 14) as part of an National Institutes of Health (NIH)-sponsored randomized, double-blind, crossover study contrasting directional versus ring stimulation. All participants received unilateral DBS implants in the hemisphere more severely affected by motor parkinsonism. Measures of cognition included verbal fluency, auditory-verbal memory, and response inhibition. We used mixed linear models to contrast the effects of directional versus ring stimulation and implant hemisphere on longitudinal cognitive function.

RESULTS

Crossover analyses showed no evidence for group-level changes in cognitive performance related to directional versus ring stimulation. Implant hemisphere, however, impacted cognition in several ways. Left STN participants had lower baseline verbal fluency than patients with right implants (t [20.66 = -2.50, p = 0.02]). Verbal fluency declined after left (p = 0.013) but increased after right STN DBS (p < 0.001), and response inhibition was faster following right STN DBS (p = 0.031). Regardless of hemisphere, delayed recall declined modestly over time versus baseline (p = 0.001), and immediate recall was unchanged.

INTERPRETATION

Directional versus ring STN DBS did not differentially affect cognition. Similar to prior bilateral DBS studies, unilateral left stimulation worsened verbal fluency performance. In contrast, unilateral right STN surgery increased performance on verbal fluency and response inhibition tasks. Our findings raise the hypothesis that unilateral right STN DBS in selected patients with predominant right brain motor parkinsonism could mitigate declines in verbal fluency associated with the bilateral intervention. ANN NEUROL 2024;95:1205-1219.

Corpus callosum and cerebellum participate in semantic dysfunction of Parkinson's disease: a diffusion tensor imaging-based cross-sectional study

Language dysfunction is common in Parkinson's disease (PD) patients, among which, the decline of semantic fluency is usually observed. This study aims to explore the relationship between white matter (WM) alterations and semantic fluency changes in PD patients. 127 PD patients from the Parkinson's Progression Markers Initiative cohort who received diffusion tensor imaging scanning, clinical assessment and semantic fluency test (SFT) were included. Tract-based special statistics, automated fiber quantification, graph-theoretical and network-based analyses were performed to analyze the correlation between WM structural changes, brain network features and semantic fluency in PD patients. Fractional anisotropy of corpus callosum, anterior thalamic radiation, inferior front-occipital fasciculus, and uncinate fasciculus, were positively correlated with SFT scores, while a negative correlation was identified between radial diffusion of the corpus callosum, inferior longitudinal fasciculus, and SFT scores. Automatic fiber quantification identified similar alterations with more details in these WM tracts. Brain network analysis positively correlated SFT scores with nodal efficiency of cerebellar lobule VIII, and nodal local efficiency of cerebellar lobule X. WM integrity and myelin integrity in the corpus callosum and several other language-related WM tracts may influence the semantic function in PD patients. Damage to the cerebellum lobule VIII and lobule X may also be involved in semantic dysfunction in PD patients.

Caregiver Burden in Parkinson Disease: A Scoping Review of the Literature from 2017-2022

Caregiver burden is a term that refers to the adverse effect of caregiving on the physical, emotional, social, spiritual, and financial well-being of the caregiver. Caregiver burden is associated with providing care to an individual with a chronic illness or disability, and the unique symptoms of Parkinson disease (PD) can amplify a patient's needs and reliance on others, leading to adverse outcomes for patients and their caregivers. In this scoping review of the literature from January 2017 through April 2022 that included 114 studies, we provide an updated, evidence-based summary of patient and caregiver-related factors that contribute to caregiver burden in PD. We also describe the impact of caregiver stress and burden on caregivers based on qualitative research studies and review recent interventions to mitigate burden. By providing clinical updates for practitioners, this review is designed to improve recognition of caregiver burden in the post-pandemic era and foster the development of targeted interventions to reduce caregiver burden in PD.

Association of liver fibrosis with cognitive decline in Parkinson's disease

BACKGROUND

Cognitive decline is a common but variable non-motor manifestation of Parkinson's disease. Chronic liver disease contributes to dementia, but its impact on cognitive performance in Parkinson's disease is unknown. We assessed the effect of liver fibrosis on cognition in Parkinson's disease.

METHODS

We conducted a retrospective cohort study using data from the Parkinson's Progression Markers Initiative. Our exposure was liver fibrosis at baseline, based on the validated Fibrosis-4 score. Our primary outcome was the Montreal Cognitive Assessment, and additional outcome measures were the Symbol Digit Modalities Test, the Benton Judgement of Line Orientation, the Letter-Number Sequencing Test, and the Modified Semantic Fluency Test. We used linear regression models to assess the relationship between liver fibrosis and scores on cognitive assessments at baseline and linear mixed models to evaluate the association between baseline Fibrosis-4 score with changes in each cognitive test over five years. Models were adjusted for demographics, comorbidities, and alcohol use.

RESULTS

We included 409 participants (mean age 61, 40 % women). There was no significant association between liver fibrosis and baseline performance on any of the cognitive assessments in adjusted models. However, over the subsequent five year period, liver fibrosis was associated with more rapid decline in scores on the Montreal Cognitive Assessment (interaction coefficient, -0.07; 95 % CI, -0.12, -0.02), the Symbol Digit Modalities Test, the Benton Judgement of Line Orientation, and the Modified Semantic Fluency Test.

CONCLUSION

In people with Parkinson's disease, the presence of comorbid liver fibrosis was associated with more rapid decline across multiple cognitive domains.

Differential cognitive effects of unilateral left and right subthalamic nucleus deep brain stimulation for Parkinson disease

Objective

To investigate hemispheric effects of directional versus ring subthalamic nucleus (STN) deep brain stimulation (DBS) surgery on cognitive function in patients with advanced Parkinson's disease (PD).

Methods

We examined 31 PD patients (Left STN n = 17; Right STN n = 14) who underwent unilateral subthalamic nucleus (STN) DBS as part of a NIH-sponsored randomized, cross-over, double-blind (ring vs directional) clinical trial. Outcome measures were tests of verbal fluency, auditory-verbal memory, and response inhibition. First, all participants were pooled together to study the effects of directional versus ring stimulation. Then, we stratified the groups by surgery hemisphere and studied the longitudinal changes in cognition post-unilateral STN DBS.

Results

Relative to pre-DBS cognitive baseline performances, there were no group changes in cognition following unilateral DBS for either directional or ring stimulation. However, assessment of unilateral DBS by hemisphere revealed a different pattern. The left STN DBS group had lower verbal fluency than the right STN group (t(20.66 = -2.50, p = 0.02). Over a period of eight months post-DBS, verbal fluency declined in the left STN DBS group (p = 0.013) and improved in the right STN DBS group over time (p < .001). Similarly, response inhibition improved following right STN DBS (p = 0.031). Immediate recall did not significantly differ over time, nor was it affected by implant hemisphere, but delayed recall equivalently declined over time for both left and right STN DBS groups (left STN DBS p = 0.001, right STN DBS differ from left STN DBS p = 0.794).

Conclusions

Directional and ring DBS did not differentially or adversely affect cognition over time. Regarding hemisphere effects, verbal fluency decline was observed in those who received left STN DBS, along with the left and right STN DBS declines in delayed memory. The left STN DBS verbal fluency decrement is consistent with prior bilateral DBS research, likely reflecting disruption of the basal-ganglia-thalamocortical network connecting STN and inferior frontal gyrus. Interestingly, we found an improvement in verbal fluency and response inhibition following right STN DBS. It is possible that unilateral STN DBS, particularly in the right hemisphere, may mitigate cognitive decline.

Semantic fluency deficits and associated brain activity in Parkinson's disease with mild cognitive impairment

People living with Parkinson's disease (PD) with poor verbal fluency have an increased risk of developing dementia. This study examines the neural mechanisms underpinning semantic fluency deficits in patients with PD with mild cognitive impairment (PD-MCI) compared to those without MCI (PD-NC) and control participants without PD (non-PD). Thirty-seven (37) participants with PD completed a cognitive assessment battery to identify MCI (13 PD-MCI). Twenty sex- and age-matched non-PD patients also participated. Participants were scanned (3T Siemens PRISMA) while performing semantic fluency, semantic switching, and automatic speech tasks. The number of responses and fMRI data for semantic generation and semantic switching were analyzed. Participants also completed a series of verbal fluency tests outside the scanner, including letter fluency. Participants with PD-MCI performed significantly worse than PD-NC and non-PD participants during semantic fluency and semantic switching tasks. PD-MCI patients showed greater activity in the right angular gyrus than PD-NC and non-PD patients during semantic switching. Increased right angular activity correlated with worse verbal fluency performance outside the scanner. Our study showed that the PD-MCI group performed worse on semantic fluency than either the PD-NC or non-PD groups. Increased right angular gyrus activity in participants with PD-MCI during semantic switching suggests early compensatory mechanisms, predicting the risk of future dementia in PD.

Semantic fluency and processing speed are reduced in non-cognitively impaired participants with Parkinson's disease

Introduction: Parkinson's disease (PD) is associated with a range of cognitive deficits. Few studies have carefully examined the subtle impacts of PD on cognition among patients who do not meet formal criteria for MCI or dementia. The aim of the current study was thus to describe the impact of PD on cognition in those without cognitive impairment in a well-characterized cohort.Methods: Non-cognitively impaired participants (122 with PD, 122 age- and sex-matched healthy volunteers) underwent extensive cognitive testing. Linear regression analyses compared diagnostic group performance across cognitive measures. For cognitive tasks that were significantly different between groups, additional analyses examined group differences restricting the group inclusion to PD participants with mild motor symptoms or disease duration less than 10 years.Results: Processing speed and semantic verbal fluency were significantly lower in the PD group (B = -3.77, 95% CIs [-5.76 to -1.77], p < .001, and B = -2.02, 95% CIs [-3.12, -0.92], p < .001, respectively), even after excluding those with moderate to severe motor symptoms (B = -2.73, 95% CIs [-4.94 to -0.53], p = .015 and B = -2.11, 95% CIs [-3.32 to -0.91], p < .001, respectively) or longer disease duration (B = -3.89, 95% CIs [-6.14 to -1.63], p < .001 and B = -1.58, 95% CIs [-2.78 to -0.37], p = .010, respectively). Semantic verbal fluency remained significantly negatively associated with PD diagnosis after controlling for processing speed (B = -1.66, 95% CIs [-2.79 to -0.53], p = .004).Conclusions: Subtle decline in specific cognitive domains may be present among people diagnosed with PD but without evidence to support a formal cognitive diagnosis. These results suggest the importance of early awareness of the potential for diminishing aspects of cognition in PD even among those without mild cognitive impairment or dementia.

Semantic Memory and Lexical Availability in Parkinson's Disease: A Statistical Learning Study

Parkinson’s disease (PD) is a neurodegenerative disorder that causes a progressive impairment in motor and cognitive functions. Although semantic fluency deficits have been described in PD, more specific semantic memory (SM) and lexical availability (LA) domains have not been previously addressed. Here, we aimed to characterize the cognitive performance of PD patients in a set of SM and LA measures and determine the smallest set of neuropsychological (lexical, semantic, or executive) variables that most accurately classify groups. Thirty early-stage non-demented PD patients (age 35–75, 10 females) and thirty healthy controls (age 36–76, 12 females) were assessed via general cognitive, SM [three subtests of the CaGi battery including living (i.e., elephant) and non-living things (i.e., fork)], and LA (eliciting words from 10 semantic categories related to everyday life) measures. Results showed that PD patients performed lower than controls in two SM global scores (picture naming and naming in response to an oral description). This impairment was particularly pronounced in the non-living things subscale. Also, the number of words in the LA measure was inferior in PD patients than controls, in both larger and smaller semantic fields, showing a more inadequate recall strategy. Notably, the classification algorithms indicated that the SM task had high classification accuracy. In particular, the denomination of non-living things had a classification accuracy of ∼80%. These results suggest that frontostriatal deterioration in PD leads to search strategy deficits in SF and the potential disruption in semantic categorization. These findings are consistent with the embodied view of cognition.

Acute low frequency dorsal subthalamic nucleus stimulation improves verbal fluency in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder that results in movement-related dysfunction and has variable cognitive impairment. Deep brain stimulation (DBS) of the dorsal subthalamic nucleus (STN) has been shown to be effective in improving motor symptoms; however, cognitive impairment is often unchanged, and in some cases, worsened particularly on tasks of verbal fluency. Traditional DBS strategies use high frequency gamma stimulation for motor symptoms (∼130 Hz), but there is evidence that low frequency theta oscillations (5-12 Hz) are important in cognition.

METHODS

We tested the effects of stimulation frequency and location on verbal fluency among patients who underwent STN DBS implantation with externalized leads. During baseline cognitive testing, STN field potentials were recorded and the individual patients' peak theta frequency power was identified during each cognitive task. Patients repeated cognitive testing at five different stimulation settings: no stimulation, dorsal contact gamma (130 Hz), ventral contact gamma, dorsal theta (peak baseline theta) and ventral theta (peak baseline theta) frequency stimulation.

RESULTS

Acute left dorsal peak theta frequency STN stimulation improves overall verbal fluency compared to no stimulation and to either dorsal or ventral gamma stimulation. Stratifying by type of verbal fluency probes, verbal fluency in episodic categories was improved with dorsal theta stimulation compared to all other conditions, while there were no differences between stimulation conditions in non-episodic probe conditions.

CONCLUSION

Here, we provide evidence that dorsal STN theta stimulation may improve verbal fluency, suggesting a potential possibility of integrating theta stimulation into current DBS paradigms to improve cognitive outcomes.

Comparing the Clinical and Neuropsychological Characteristics of Parkinson's Disease With and Without Freezing of Gait

Introduction

Freezing of gait (FOG) is one of the most common walking problems in Parkinson’s disease (PD). Impaired cognitive function is believed to play an important role in developing and aggravating FOG in PD. But some evidence suggests that motor function discrepancy may affect testing results. Therefore, we think it is necessary for PD-FOG(+) and PD-FOG(−) patients to complete neuropsychological tests under similar motor conditions.

Methods

This study recruited 44 idiopathic PD patients [PD-FOG(+) n = 22, PD-FOG(−) n = 22] and 20 age-matched healthy controls (HC). PD-FOG(+) and PD-FOG(−) patients were matched for age, year of education, and Hoehn and Yahr score (H&Y). All participants underwent a comprehensive battery of neuropsychological assessment, and demographical and clinical information was also collected.

Results

PD patients showed poorer cognitive function, higher risks of depression and anxiety, and more neuropsychiatric symptoms compared with HC. When controlling for age, years of education, and H&Y, there were no statistical differences in cognitive function between PD-FOG(+) and PD-FOG(−) patients. But PD-FOG(+) patients had worse motor and non-motor symptoms than PD-FOG(−) patients. PD patients whose motor symptoms initiated with rigidity and initiated unilaterally were more likely to experience FOG.

Conclusion

Traditional neuropsychological testing may not be sensitive enough to detect cognitive impairment in PD. Motor symptoms initiated with rigidity and initiated unilaterally might be an important predictor of FOG.

Enhancement of Executive Functions but Not Memory by Multidomain Group Cognitive Training in Patients with Parkinson's Disease and Mild Cognitive Impairment: A Multicenter Randomized Controlled Trial

Background

Meta-analyses have demonstrated cognitive training (CT) benefits in Parkinson's disease (PD) patients. However, the patients' cognitive status has only rarely been based on established criteria. Also, prediction analyses of CT success have only sparsely been conducted.

Objective

To determine CT effects in PD patients with mild cognitive impairment (PD-MCI) on cognitive and noncognitive outcomes compared to an active control group (CG) and to analyze CT success predictors.

Methods

Sixty-four PD-MCI patients (age: 67.61 ± 7.70; UPDRS-III: 26.58 ± 13.54; MoCA: 24.47 ± 2.78) were randomized to either a CT group or a low-intensity physical activity CG for six weeks (twice weekly, 90 minutes). Outcomes were assessed before and after training. MANOVAs with follow-up ANOVAs and multiple regression analyses were computed.

Results

Both interventions were highly feasible (participation, motivation, and evaluation); the overall dropout rate was 4.7%. Time × group interaction effects favoring CT were observed for phonemic fluency as a specific executive test (p=0.018, η_p²=0.092) and a statistical trend for overall executive functions (p=0.095, η_p²=0.132). A statistical trend for a time × group interaction effect favoring CG was shown for the digit span backward as a working memory test (p=0.098, η_p²=0.043). Regression analyses revealed cognitive baseline levels, education, levodopa equivalent daily dose, motor scores, and ApoE status as significant predictors for CT success.

Conclusions

CT is a safe and feasible therapy option in PD-MCI, yielding executive functions improvement. Data indicate that vulnerable individuals may show the largest cognitive gains. Longitudinal studies are required to determine whether CT may also attenuate cognitive decline in the long term. This trial is registered with DRKS00010186.

Differential patterns of internally generated responses in parkinsonian disorders

Internally generated responses are centrally affected in parkinsonian disorders. This study investigated the cognitive components crucial for response generation as reflected in performance on verbal and non-verbal fluency tasks, which require voluntary internal generation of multiple responses. Participants with parkinsonian disorders (N = 58: 29 Parkinson's disease [PD], 22 corticobasal syndrome [CBS], 8 progressive supranuclear palsy [PSP]) and 89 age-matched controls completed baseline cognitive assessments and eight fluency tasks of four types: word, design, gesture, and ideational. We analysed the total number of correct responses generated and error rates (including repetitions and rule breaks) for PD, CBS and Control groups. The small PSP patient group's performance is reported for comparative purposes only. CBS patients were significantly reduced in the number of correct responses generated across all fluency tasks, without incurring significant errors. The only exception was that CBS patients produced a significantly higher number of repetitions on one nonverbal task (design fluency). By contrast, PD patients' generation was reduced on only three fluency tasks (phonemic word, meaningless gesture, conventional idea). However, they also produced a high error rate on four fluency tasks (rule-break errors: phonemic/semantic word; repetitions: semantic word, meaningless gestures). Overall, the pattern of fluency task performance differs between patient groups. Specifically, the quantity of responses generated is differentially and primarily affected in CBS patients, whereas the quality of responses generated is primarily affected in PD patients. This suggests potentially different patterns of performance for parkinsonian disorders and has implications for the cognitive processes crucial for internally-guided response generation.

Combining a Cognitive Concurrent Task with a Motor or Motor-Cognitive Task: Which Is Better to Differentiate Levels of Affectation in Parkinson’s Disease?

Introduction

Cognitive decline usually coexists with motor impairment in PD. Multitask settings provide appropriate measures to evaluate the complex interaction between motor and cognitive impairments. The main objective was to analyze which concurrent task, i. e., motor or hybrid motor-cognitive, in combination with a cognitive task better differentiates between PD patients with mild and moderate levels of disease.

Methods

Thirty-seven individuals (19 male and 18 female) with idiopathic PD performed dual and triple tasks combining a cognitive task (phonemic fluency) with motor (pedaling) and/or cognitive-motor hybrid (tracking) tasks. Mild and moderate disability PD groups were specified considering the Hoehn and Yahr scale. Mixed ANOVA analyses for each of the concurrent task were carried out to test differences between the single and dual or triple condition performances comparing the low and high PD disability groups. Supplementary mixed ANCOVA analysis was performed considering the cognitive status as the covariate.

Results

The only significant differences between disability PD groups were found for performances in the cognitive-motor hybrid (tracking) task, both in dual and triple conditions. Our results showed a better performance for the mild rather than for the moderate disability group in the single condition task and a significant decline of the mild disability group in the dual and triple condition when compared to the levels of those shown by the moderate disability group. The group-condition interaction remained significant when the cognitive status was statistically controlled.

Conclusion

The hybrid of motor-cognitive task combining with a cognitive task (i. e., fluency) successfully differentiated between mild and moderate PD patients in the context of dual and triple multitask sets even when the cognitive status was statistically controlled. Our results highlight the importance of jointly measuring the complex interplay between motor and cognitive skills in PD.