Cerebellar Volume and Disease Staging in Parkinson's Disease: An ENIGMA-PD Study

BACKGROUND

Increasing evidence points to a pathophysiological role for the cerebellum in Parkinson's disease (PD). However, regional cerebellar changes associated with motor and non-motor functioning remain to be elucidated.

OBJECTIVE

To quantify cross-sectional regional cerebellar lobule volumes using three dimensional T1-weighted anatomical brain magnetic resonance imaging from the global ENIGMA-PD working group.

METHODS

Cerebellar parcellation was performed using a deep learning-based approach from 2487 people with PD and 1212 age and sex-matched controls across 22 sites. Linear mixed effects models compared total and regional cerebellar volume in people with PD at each Hoehn and Yahr (HY) disease stage, to an age- and sex- matched control group. Associations with motor symptom severity and Montreal Cognitive Assessment scores were investigated.

RESULTS

Overall, people with PD had a regionally smaller posterior lobe (dmax  = -0.15). HY stage-specific analyses revealed a larger anterior lobule V bilaterally (dmax  = 0.28) in people with PD in HY stage 1 compared to controls. In contrast, smaller bilateral lobule VII volume in the posterior lobe was observed in HY stages 3, 4, and 5 (dmax  = -0.76), which was incrementally lower with higher disease stage. Within PD, cognitively impaired individuals had lower total cerebellar volume compared to cognitively normal individuals (d = -0.17).

CONCLUSIONS

We provide evidence of a dissociation between anterior "motor" lobe and posterior "non-motor" lobe cerebellar regions in PD. Whereas less severe stages of the disease are associated with larger motor lobe regions, more severe stages of the disease are marked by smaller non-motor regions. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment

The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9  GeV/c^{2}. The most stringent limit is set for spin-independent scattering at 36  GeV/c^{2}, rejecting cross sections above 9.2×10^{-48}  cm at the 90% confidence level.

Acquired Stuttering in Parkinson's Disease

Background

Parkinson's disease frequently causes communication impairments, but knowledge about the occurrence of new-onset stuttering is limited.

Objectives

To determine the presence of acquired neurogenic stuttering and its relationship with cognitive and motor functioning in individuals with Parkinson's disease.

Method

Conversation, picture description, and reading samples were collected from 100 people with Parkinson's disease and 25 controls to identify the presence of stuttered disfluencies (SD) and their association with neuropsychological test performance and motor function.

Results

Participants with Parkinson's disease presented with twice as many stuttered disfluencies during conversation (2.2% ± 1.8%SD) compared to control participants (1.2% ± 1.2%SD; P < 0.01). 21% of people with Parkinson's disease (n = 20/94) met the diagnostic criterion for stuttering, compared with 1/25 controls. Stuttered disfluencies also differed significantly across speech tasks, with more disfluencies during conversation compared to reading (P < 0.01). Stuttered disfluencies in those with Parkinson's disease were associated with longer time since disease onset (P < 0.01), higher levodopa equivalent dosage (P < 0.01), and lower cognitive (P < 0.01) and motor scores (P < 0.01).

Conclusion

One in five participants with Parkinson's disease presented with acquired neurogenic stuttering, suggesting that speech disfluency assessment, monitoring and intervention should be part of standard care. Conversation was the most informative task for identifying stuttered disfluencies. The frequency of stuttered disfluencies was higher in participants with worse motor functioning, and lower cognitive functioning. This challenges previous suggestions that the development of stuttered disfluencies in Parkinson's disease has purely a motoric basis.

Bridging Big Data: Procedures for Combining Non-equivalent Cognitive Measures from the ENIGMA Consortium

Investigators in neuroscience have turned to Big Data to address replication and reliability issues by increasing sample sizes, statistical power, and representativeness of data. These efforts unveil new questions about integrating data arising from distinct sources and instruments. We focus on the most frequently assessed cognitive domain - memory testing - and demonstrate a process for reliable data harmonization across three common measures. We aggregated global raw data from 53 studies totaling N = 10,505 individuals. A mega-analysis was conducted using empirical bayes harmonization to remove site effects, followed by linear models adjusting for common covariates. A continuous item response theory (IRT) model estimated each individual's latent verbal learning ability while accounting for item difficulties. Harmonization significantly reduced inter-site variance while preserving covariate effects, and our conversion tool is freely available online. This demonstrates that large-scale data sharing and harmonization initiatives can address reproducibility and integration challenges across the behavioral sciences.

Altered nucleus accumbens functional connectivity precedes apathy in Parkinson's disease

Work in animal and human neuroscience has identified neural regions forming a network involved in the production of motivated, goal-directed behaviour. In particular, the nucleus accumbens and anterior cingulate cortex are recognized as key network nodes underlying decisions of whether to exert effort for reward, to drive behaviour. Previous work has convincingly shown that this cognitive mechanism, known as effort-based decision making, is altered in people with Parkinson's disease with a syndrome of reduced goal-directed behaviour - apathy. Building on this work, we investigated whether the neural regions implementing effort-based decision-making were associated with apathy in Parkinson's disease, and more importantly, whether changes to these regions were evident prior to apathy development. We performed a large, multimodal neuroimaging analysis in a cohort of people with Parkinson's disease (n = 199) with and without apathy at baseline. All participants had ∼ 2 year follow-up apathy scores, enabling examination of brain structure and function specifically in those with normal motivation who converted to apathy by ∼ 2 year follow-up. In addition, of the people with normal motivation, a subset (n = 56) had follow-up neuroimaging data, allowing for examination of the rate of change in key nodes over time in those who did, and did not, convert to apathy. Healthy control (n = 54) data was also included to aid interpretation of findings. Functional connectivity between the nucleus accumbens and dorsal anterior cingulate cortex was higher in people with normal motivation who later converted to apathy compared to those who did not, whereas no structural differences were evident between these groups. In contrast, grey matter volume in these regions was reduced in the group with existing apathy. Furthermore, of those with normal motivation who had undergone longitudinal neuroimaging, converters to apathy showed a higher rate of change in grey matter volume within the nucleus accumbens. Overall, we show that changes in functional connectivity between nucleus accumbens and anterior cingulate cortex precedes apathy in people with Parkinson's disease, with conversion to apathy associated with higher rate of grey matter volume loss in nucleus accumbens, despite no baseline differences. These findings significantly add to an accumulating body of transdiagnostic evidence that apathy arises from disruption to key nodes within a network in which normal goal-directed behaviour is instantiated, and raise the possibility of identifying those at risk for developing apathy before overt motivational deficits have arisen.

Non-Contact Hand Movement Analysis for Optimal Configuration of Smart Sensors to Capture Parkinson's Disease Hand Tremor

Parkinson’s disease affects millions worldwide with a large rise in expected burden over the coming decades. More easily accessible tools and techniques to diagnose and monitor Parkinson’s disease can improve the quality of life of patients. With the advent of new wearable technologies such as smart rings and watches, this is within reach. However, it is unclear what method for these new technologies may provide the best opportunity to capture the patient-specific severity. This study investigates which locations on the hand can be used to capture and monitor maximal movement/tremor severity. Using a Leap Motion device and custom-made software the volume, velocity, acceleration, and frequency of Parkinson’s (n = 55, all right-handed, majority right-sided onset) patients’ hand locations (25 joints inclusive of all fingers/thumb and the wrist) were captured simultaneously. Distal locations of the right hand, i.e., the ends of fingers and the wrist showed significant trends (p < 0.05) towards having the largest movement velocities and accelerations. The right hand, compared with the left hand, showed significantly greater volumes, velocities, and accelerations (p < 0.01). Supplementary analysis showed that the volumes, acceleration, and velocities had significant correlations (p < 0.001) with clinical MDS-UPDRS scores, indicating the potential suitability of using these metrics for monitoring disease progression. Maximal movements at the distal hand and wrist area indicate that these locations are best suited to capture hand tremor movements and monitor Parkinson’s disease.

Level I PD‐MCI using global cognitive tests and the risk for Parkinson's disease dementia

Background

The criteria for PD‐MCI allow the use of global cognitive tests. Their predictive value for conversion from PD‐MCI to PDD, especially compared to comprehensive neuropsychological assessment, is unknown.

Methods

The MDS PD‐MCI Study Group combined four datasets containing global cognitive tests as well as a comprehensive neuropsychological assessment to define PD‐MCI (n = 467). Risk for developing PDD was examined using a Cox model. Global cognitive tests were compared to neuropsychological test batteries (Level I&II) in determining risk for PDD.

Results

PD‐MCI based on a global cognitive test (MMSE or MoCA) increases the hazard for developing PDD (respectively HR = 2.57, P = 0.001; HR = 4.14, P = <0.001). The C‐statistics for MMSE (0.72) and MoCA (0.70) were lower than those based on neuropsychological tests (Level I = 0.82; Level II = 0.81). Sensitivity, specificity and diagnostic accuracy balance was best in Level II.

Conclusion

MMSE and MoCA predict conversion to PDD. However, Level II neuropsychological assessment seems the preferred assessment for PD‐MCI.

International Multicenter Analysis of Brain Structure Across Clinical Stages of Parkinson's Disease

BACKGROUND

Brain structure abnormalities throughout the course of Parkinson's disease have yet to be fully elucidated.

OBJECTIVE

Using a multicenter approach and harmonized analysis methods, we aimed to shed light on Parkinson's disease stage-specific profiles of pathology, as suggested by in vivo neuroimaging.

METHODS

Individual brain MRI and clinical data from 2357 Parkinson's disease patients and 1182 healthy controls were collected from 19 sources. We analyzed regional cortical thickness, cortical surface area, and subcortical volume using mixed-effects models. Patients grouped according to Hoehn and Yahr stage were compared with age- and sex-matched controls. Within the patient sample, we investigated associations with Montreal Cognitive Assessment score.

RESULTS

Overall, patients showed a thinner cortex in 38 of 68 regions compared with controls (d_max  = -0.20, d_min  = -0.09). The bilateral putamen (d_left  = -0.14, d_right  = -0.14) and left amygdala (d = -0.13) were smaller in patients, whereas the left thalamus was larger (d = 0.13). Analysis of staging demonstrated an initial presentation of thinner occipital, parietal, and temporal cortices, extending toward rostrally located cortical regions with increased disease severity. From stage 2 and onward, the bilateral putamen and amygdala were consistently smaller with larger differences denoting each increment. Poorer cognition was associated with widespread cortical thinning and lower volumes of core limbic structures.

CONCLUSIONS

Our findings offer robust and novel imaging signatures that are generally incremental across but in certain regions specific to disease stages. Our findings highlight the importance of adequately powered multicenter collaborations.

Higher perceived stress and exacerbated motor symptoms in Parkinson's disease during the COVID-19 lockdown in New Zealand

AIMS

Stress plays a key role in Parkinson's disease (PD) by acting on the dopaminergic system and worsening patients' motor function. The impact of New Zealand's strict lockdown measures to contain COVID-19 on perceived stress and PD motor symptoms remains unknown. Here we examined the relationship between perceived levels of stress, changes in physical activity levels and PD motor symptoms during lockdown.

METHODS

During lockdown, 134 participants with PD and 49 controls completed a survey assessing perceived stress, self-reported changes in PD motor symptoms and physical activity duration and intensity prior to and during lockdown.

RESULTS

Perceived stress was higher in PD than controls, and in those reporting a worsening of tremor, balance/gait, dyskinesia and bradykinesia compared to those indicating no change during the COVID-19 lockdown. These effects were not modulated by physical activity.

CONCLUSIONS

Reducing stressors may be an important adjunct treatment strategy to improve motor function in PD.

Childbirth and Delayed Parkinson's Onset: A Reproducible Nonbiological Artifact of Societal Change

BACKGROUND

Uncontrolled studies have reported associations between later Parkinson's disease onset in women and a history of giving birth, with age at onset delayed by nearly 3 years per child. We tested this association in two independent data sets, but, as a control to test for nonbiological explanations, also included men with PD.

METHODS

We analyzed valid cases from the Parkinson's Progressive Markers Initiative incident sample (145 women, 276 men) and a prevalent sample surveyed by the New Zealand Brain Research Institute (210 women, 394 men).

RESULTS

The association was present in both women and men in the Parkinson's Progressive Markers Initiative study, and absent in both in the New Zealand Brain Research Institute study. This is consistent with generational differences common to men and women, which confound with age at onset in incident-dominant samples.

CONCLUSIONS

Despite being replicable in certain circumstances, associations between childbirth and later PD onset are an artifact of generational cohort differences. © 2020 International Parkinson and Movement Disorder Society.

Meta-analysis of genome-wide DNA methylation identifies shared associations across neurodegenerative disorders

BACKGROUND

People with neurodegenerative disorders show diverse clinical syndromes, genetic heterogeneity, and distinct brain pathological changes, but studies report overlap between these features. DNA methylation (DNAm) provides a way to explore this overlap and heterogeneity as it is determined by the combined effects of genetic variation and the environment. In this study, we aim to identify shared blood DNAm differences between controls and people with Alzheimer's disease, amyotrophic lateral sclerosis, and Parkinson's disease.

RESULTS

We use a mixed-linear model method (MOMENT) that accounts for the effect of (un)known confounders, to test for the association of each DNAm site with each disorder. While only three probes are found to be genome-wide significant in each MOMENT association analysis of amyotrophic lateral sclerosis and Parkinson's disease (and none with Alzheimer's disease), a fixed-effects meta-analysis of the three disorders results in 12 genome-wide significant differentially methylated positions. Predicted immune cell-type proportions are disrupted across all neurodegenerative disorders. Protein inflammatory markers are correlated with profile sum-scores derived from disease-associated immune cell-type proportions in a healthy aging cohort. In contrast, they are not correlated with MOMENT DNAm-derived profile sum-scores, calculated using effect sizes of the 12 differentially methylated positions as weights.

CONCLUSIONS

We identify shared differentially methylated positions in whole blood between neurodegenerative disorders that point to shared pathogenic mechanisms. These shared differentially methylated positions may reflect causes or consequences of disease, but they are unlikely to reflect cell-type proportion differences.

Variations in the patterns of prevalence and therapy in Australasian Parkinson's disease patients of different ethnicities

Parkinson's disease (PD) is the second most common neurodegenerative disease in the elderly after Alzheimer's disease. It is expected that PD cumulative incidence will increase in the future, as there are far more people surviving into late age than there ever used to be. While most commonly idiopathic, rare forms of PD can be familial/genetic. In addition, socioeconomic, cultural and genetic factors may influence the way in which anti-parkinsonian medications are prescribed, and how patients respond to them. This review aims to highlight the potential impact of genetic variation on the epidemiology and therapeutics of PD, focusing on data from New Zealand and Australia.

Neuropsychiatric Symptoms Are Associated with Dementia in Parkinson's Disease but Not Predictive of it

Background

Neuropsychiatric symptoms in Parkinson's disease (PD) may increase dementia (PDD) risk. The predictive value of these symptoms, however, has not been compared to clinical and demographic predictors of future PDD.

Objectives

Determine if neuropsychiatric symptoms are useful markers of PDD risk.

Methods

328 PD participants completed baseline neuropsychiatric and MDS-Task Force-Level II assessments. Of these, 202 non-demented individuals were followed-up over a four-years period to detect conversion to PDD; 51 developed PDD. ROC analysis tested associations between baseline neuropsychiatric symptoms and future PDD. The probability of developing PDD was also modeled as a function of neuropsychiatric inventory (NPI)-total score, PD Questionnaire (PDQ)-hallucinations, PDQ-anxiety, and contrasted to cognitive ability, age, and motor function. Leave-one-out information criterion was used to evaluate which models provided useful information when predicting future PDD.

Results

The PDD group experienced greater levels of neuropsychiatric symptoms compared to the non-PDD groups at baseline. Few differences were found between the PD-MCI and PD-N groups. Six neuropsychiatric measures were significantly, but weakly, associated with future PDD. The strongest was NPI-total score: AUC = 0.66 [0.57-0.75]. There was, however, no evidence it contained useful out-of-sample predictive information of future PDD (delta ELPD = 1.8 (SD 2.5)); Similar results held for PDQ-hallucinations and PDQ-anxiety. In contrast, cognitive ability (delta ELPD = 36 (SD 8)) and age (delta ELPD = 11 (SD 5)) provided useful predictive information of future PDD.

Conclusions

Cognitive ability and age strongly out-performed neuropsychiatric measures as markers of developing PDD within 4 years. Therefore, neuropsychiatric symptoms do not appear to be useful markers of PDD risk.

Common Variants Coregulate Expression of GBA and Modifier Genes to Delay Parkinson's Disease Onset

Background

GBA mutations are numerically the most significant genetic risk factor for Parkinson's disease (PD), yet these mutations have low penetrance, suggesting additional mechanisms.

Objectives

The objective of this study was to determine if the penetrance of GBA in PD can be explained by regulatory effects on GBA and modifier genes.

Methods

Genetic variants associated with the regulation of GBA were identified by screening 128 common single nucleotide polymorphisms (SNPs) in the GBA locus for spatial cis‐expression quantitative trail locus (supported by chromatin interactions).

Results

We identified common noncoding SNPs within GBA that (1) regulate GBA expression in peripheral tissues, some of which display α‐synuclein pathology and (2) coregulate potential modifier genes in the central nervous system and/or peripheral tissues. Haplotypes based on 3 of these SNPs delay disease onset by 5 years. In addition, SNPs on 6 separate chromosomes coregulate GBA expression specifically in either the substantia nigra or cortex, and their combined effect potentially modulates motor and cognitive symptoms, respectively.

Conclusions

This work provides a new perspective on the haplotype‐specific effects of GBA and the genetic etiology of PD, expanding the role of GBA from the gene encoding the β‐glucocerebrosidase (GCase) to that of a central regulator and modifier of PD onset, with GBA expression itself subject to distant regulation. Some idiopathic patients might possess insufficient GBA‐encoded GCase activity in the substantia nigra as the result of distant regulatory variants and therefore might benefit from GBA‐targeting therapeutics. The SNPs’ regulatory impacts provide a plausible explanation for the variable phenotypes also observed in GBA‐centric Gaucher's disease and dementia with Lewy bodies. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, LLC on behalf of International Parkinson and Movement Disorder Society.

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder.

Nanopore sequencing of the glucocerebrosidase (GBA) gene in a New Zealand Parkinson's disease cohort

INTRODUCTION

Bi-allelic mutations in the gene for glucocerebrosidase (GBA) cause Gaucher disease, an autosomal recessive lysosomal storage disorder. Gaucher disease causing GBA mutations in the heterozygous state are also high risk factors for Parkinson's disease (PD). GBA analysis is challenging due to a related pseudogene and structural variations (SVs) that can occur at this locus. We have applied and refined a recently developed nanopore DNA sequencing method to analyze GBA variants in a clinically assessed New Zealand longitudinal cohort of PD.

METHOD

We examined amplicons encompassing the coding region of GBA (8.9 kb) from 229 PD cases and 50 healthy controls using the GridION nanopore sequencing platform, and Sanger validation.

RESULTS

We detected 23 variants in 21 PD cases (9.2% of patients). We detected modest PD risk variant p.N409S (rs76763715) in one case, p.E365K (rs2230288) in 12 cases, and p.T408 M (rs75548401) in seven cases, one of whom also had p.E365K. We additionally detected the possible risk variants p.R78C (rs146774384) in one case, p.D179H (rs147138516) in one case which occurred on the same haplotype as p.E365K, and one novel variant c.335C > T or p.(L335 = ), that potentially impacts splicing of GBA transcripts. Additionally, we found a higher prevalence of dementia among patients with GBA variants.

CONCLUSION

This work confirmed the utility of nanopore sequencing as a high-throughput method to identify known and novel GBA variants, and to assign precise haplotypes. Our observations may contribute to improved understanding of the effects of variants on disease pathogenesis, and to the development of more targeted treatments.

P822Statin treatment in symptomatic patients with non-obstructive coronary artery disease reduces the risk of all-cause mortality

Introduction

Symptomatic patients with non-obstructive coronary artery disease (NOCAD; stenosis >0% <50%) have a worse prognosis and an increased risk for all-cause mortality compared with age-matched controls. Currently, treatment of these patients is empiric, and secondary preventive measures are less often implemented. The goal of the study was to examine whether statin prescription has an impact on all-cause mortality in symptomatic NOCAD patients, and which factors influence statin prescription in patients with NOCAD.

Methods

We examined 4039 symptomatic patients who presented either with stable angina (SA) or an acute coronary syndrome (ACS) who underwent coronary angiography; 1582 had angiographically normal coronary arteries, 2457 had minimal disease (NOCAD). The comparison group consisted of 2998 patients with stable obstructive CAD (stenosis ≥50%). Patients had at least one lipid panel tested between April 1, 2010 to March 31, 2014. We examined the rate of statin prescription amongst the groups, as well as predictors of all-cause mortality and statin treatment.

Results

Symptomatic patients with NOCAD are less likely to receive statin therapy (60.4%) compared to patients with obstructive CAD (87.3%). After one, three and five year(s), LDL levels in NOCAD patients are higher than in CAD patients (2.21±0.88mmol/l vs. 1.84mmol/l±0.77mmol/l after 1 year). Statin treatment was associated with a significantly lower risk of all-cause mortality in NOCAD (HR 0.64 (0.44–0.95)), as well as in CAD (HR 0.44 (0.31–0.62)), but not in patients with normal coronaries HR 0.55 (0.27–1.15)). Sex, age and the presence of other cardiovascular risk factors influenced the prescription of statin therapy in the first 5 years after initial diagnosis of NOCAD- older patients with diabetes and hypertension were more likely to receive statin therapy. Women received statin therapy to a lower percentage than men in the NOCAD group (year 1: men 62.9% vs, women 56.9%; p=0.003). No effect of cardiovascular risk factors, age or sex on statin prescription was seen in the CAD group or patients with normal coronaries.

Conclusion

Statin therapy reduces the risk of all-cause mortality in symptomatic patients with NOCAD. In spite of this benefit, patients with NOCAD, and especially women, are less likely to receive secondary-preventive statin therapy.

Volitional Suppression of Parkinsonian Resting Tremor

BACKGROUND

We have observed in the clinic that a number of patients with Parkinson's disease (PD) can suppress their tremor at will for brief periods, by conscious mental processes. To our knowledge, the ability to consciously diminish one's resting tremor has not yet been reported nor assessed quantitatively.

OBJECTIVE

To provide the first detailed systematic investigation of the phenomenon of voluntary tremor suppression in PD.

METHODS

We examined changes in tremor characteristics during voluntary tremor suppression in 37 PD patients (on medication) presenting with rest tremor in their upper limb. We measured tremor oscillations with a triaxis accelerometer on the index finger of the most-affected hand (n = 27). With surface electromyography (EMG), we measured changes in neuromuscular activity of the forearm flexor digitorum superficialis and extensor digitorum muscles (n = 15). Participants completed four 1-minute trials, consisting of alternating consecutive 30-second periods of resting tremor and 30-second periods of attempted tremor suppression.

RESULTS

Bayesian multilevel modeling revealed that attempted voluntary tremor suppression did indeed reduce tremor amplitude (peak power) of the acceleration signal and increased tremor frequency of the acceleration and EMG signals. Relative EMG power in the 3- to 8-Hz tremor band was also smaller. Tremor suppression was not by enhanced voluntary contraction of the relevant muscle pairs.

CONCLUSIONS

We present novel empirical evidence that PD resting tremor can be suppressed by an act of will, as evidenced by significant modulation of key neurophysiological tremor characteristics. These data highlight that it is possible to exert significant conscious control over parkinsonian resting tremor.

Beta Amyloid Deposition Is Not Associated With Cognitive Impairment in Parkinson's Disease

The extent to which Alzheimer neuropathology, particularly the accumulation of misfolded beta-amyloid, contributes to cognitive decline and dementia in Parkinson's disease (PD) is unresolved. Here, we used Florbetaben PET imaging to test for any association between cerebral amyloid deposition and cognitive impairment in PD, in a sample enriched for cases with mild cognitive impairment. This cross-sectional study used Movement Disorders Society level II criteria to classify 115 participants with PD as having normal cognition (PDN, n = 23), mild cognitive impairment (PD-MCI, n = 76), or dementia (PDD, n = 16). We acquired 18F-Florbetaben (FBB) amyloid PET and structural MRI. Amyloid deposition was assessed between the three cognitive groups, and also across the whole sample using continuous measures of both global cognitive status and average performance in memory domain tests. Outcomes were cortical FBB uptake, expressed in centiloids and as standardized uptake value ratios (SUVR) using the Centiloid Project whole cerebellum region as a reference, and regional SUVR measurements. FBB binding was higher in PDD, but this difference did not survive adjustment for the older age of the PDD group. We established a suitable centiloid cut-off for amyloid positivity in Parkinson's disease (31.3), but there was no association of FBB binding with global cognitive or memory scores. The failure to find an association between PET amyloid deposition and cognitive impairment in a moderately large sample, particularly given that it was enriched with PD-MCI patients at risk of dementia, suggests that amyloid pathology is not the primary driver of cognitive impairment and dementia in most patients with PD.

Wrestling with uncertainty after mild traumatic brain injury: a mixed methods study

Purpose: Our objective was to explore the intersection between mild traumatic brain injury (MTBI) recovery experiences and injury understandings, using both quantitative and qualitative methods.Materials and Methods: The quantitative component was a descriptive case-control study comparing participants (n = 76) who had recovered or not recovered after an MTBI, across demographic and psychological variables. A subset of participants (n = 10) participated in a semi-structured interview to explore experiences of recovery in more detail. We followed threads across the datasets to integrate findings from component methods.Results: The quantitative analyses revealed differences between the two groups in terms of injury recovery understandings and expectations. The qualitative analyses suggested that achieving consistency across information sources was important. By tracing threads back and forth between the component datasets, we identified a super-ordinate meta-theme that captured participants' experiences of wrestling with uncertainty about their recovery and the impacts in terms of heightened anxiety, confusion, and feelings of invalidation.Conclusion: The effectiveness of psychoeducation and reassurance after MTBI may be optimized when content is tailored to the individual. Clinicians are urged to attend both to the subjective interpretations patients make of information gained from formal and informal, internal and external sources, and where information across these sources conflicts and creates uncertainty.Implications for rehabilitationEffectiveness of psychoeducation and reassurance after injury may be optimized when content is tailored to the individual rather than being generic.Effectiveness of such interventions may also be optimized by understanding the subjective interpretations individuals make of injury knowledge gleaned from formal and informal, internal and external sources.Conflicting information from such multiple sources may create uncertainty with associated increased distress as an individual negotiates their recovery from injury. Attending to this uncertainty may be a helpful target for treatment.

Declining Transmission and Immunity to Malaria and Emerging Artemisinin Resistance in Thailand: A Longitudinal Study

Background

Reductions in malaria transmission decrease naturally acquired immunity, which may influence the emergence of Plasmodium falciparum artemisinin-resistant phenotypes and genotypes over time.

Methods

Antibodies specific for P. falciparum antigens were determined in uncomplicated hyperparasitemic malaria patients over a 10-year period of declining malaria transmission and emerging artemisinin resistance in northwestern Thailand. We investigated the association between antibody levels and both parasite clearance time (PCt_½) and artemisinin resistance–associated kelch13 genotypes over time.

Results

Immunity to P. falciparum declined prior to 2004, preceding the emergence of artemisinin resistance-associated genotypes and phenotypes (maximum mean change in antibody level per year: anti-MSP1₄₂ = −0.17; 95% confidence interval [CI] = −.31 to −.04; P = .01). In this period of declining immunity, and in the absence of kelch13 mutations, PCt_½ increased. Between 2007 and 2011, levels of antibodies fluctuated, and higher antibody levels were associated with faster PCt_½ (maximum yearly change in PCt_½, in hours: EBA140_rII = −0.39; 95% CI = −.61 to −.17; P < .001).

Conclusions

Understanding the impact of changing transmission and immunity on the emergence of artemisinin resistance is important particularly as increased malaria control and elimination activities may enhance immunological conditions for the expansion of artemisinin-resistant P. falciparum.

Parkinson's in the oldest old: Impact on estimates of future disease burden

BACKGROUND

Traditionally the risk of Parkinson's has been considered to increase monotonically with age, although there is evidence that prevalence and incidence may decrease in the oldest old. To examine this further we estimated the national prevalence and incidence of Parkinson's in New Zealand, using drug-tracing methods, to examine the relationship of Parkinson's with sex and age up to 100+.

METHODS

Information on Parkinson's-related medications was extracted from the national pharmaceutical database of community-dispensed medications from 2005 to 2014. Diagnoses for a large subset of individuals were independently determined through national mortality and hospital admissions datasets. We used a Bayesian model, accommodating diagnostic uncertainty and bias, to estimate the number of people with Parkinson's.

RESULTS

The 2013 prevalence of Parkinson's in New Zealand was 210 per 100 000 population (95% uncertainty interval 208-212) with age-standardized prevalence rates higher for males (ratio 1.6:1). Incidence was 31 per 100 000 person-years (95% uncertainty interval 30-32), also higher in males (ratio 1.8:1). Incidence and prevalence by age increased exponentially until 75 years, peaked at 85 years, and then dropped sharply.

CONCLUSIONS

The prevalence of Parkinson's in New Zealand is expected to double over a 25-year period but then increase at a slower rate due to the drop-off in prevalence and incidence in the oldest old. The findings suggest that Parkinson's disease is not an aging-dependent but an age-dependent disorder.

Caregiver burden is increased in Parkinson's disease with mild cognitive impairment (PD-MCI)

BACKGROUND

There is limited evidence on caregiver outcomes associated with mild cognitive impairment in patients with Parkinson's disease (PD-MCI) and the coping strategies used by these caregivers.

METHODS

To investigate this relationship, we examined levels of burden, depression, anxiety, coping strategies and positive aspects of caregiving in the informal caregivers of 96 PD patients. The PD patients were classified using MDS-Task Force Level II criteria as showing either normal cognition (PD-N; n = 51), PD-MCI (n = 30) or with dementia (PDD; n = 15).

RESULTS

Mean Zarit Burden Interview (ZBI) score increased significantly between carers of PD-N (M = 13.39, SD = 12.22) compared to those of PD-MCI patients (M = 22.00, SD = 10.8), and between carers of PD-MCI and PDD patients (M = 29.33, SD = 9.59). Moreover, the proportion of carers showing clinically significant levels of burden (ZBI score ≥ 21) also increased as the patients' cognitive status declined (18% for PD-N; 60% for PD-MCI; and 80% for PDD) and was mirrored by an increasing amount of time spent providing care by the caregivers. Caregiver ZBI score was independent of patient neuropsychiatric symptoms, motor function, disease duration and time that caregivers spent caregiving. Caregiver use of different coping strategies increased with worsening cognition. However, we found only equivocal evidence that the use of problem-focused, emotion-focused and dysfunctional coping mediated the association between patient cognitive status and caregiver burden, because the inverse models that used caregiver burden as the mediator were also significant.

CONCLUSIONS

The study highlights the impact of Parkinson's disease on those providing care when the patient's cognition is poor, including those with MCI. Caregiver well-being has important implications for caregiver support, nursing home placement and disease course.

Eye movements in neurodegenerative diseases

PURPOSE OF REVIEW

Abnormalities of oculomotor control accompany the pathological changes underlying many neurodegenerative diseases. Clinical examination of eye movements can contribute to differential diagnosis, whereas quantitative laboratory measures can provide detailed insight into the disease process. In this review of eye movements in neurodegenerative disease, we summarise recent empirical findings and conceptual advances.

RECENT FINDINGS

Oculomotor researchers continue to be particularly prolific in studying Parkinson's disease but there is also substantial activity in Alzheimer's disease and spinocerebellar ataxia. Interesting findings have been reported in Huntington's, motor neuron disease, and glaucoma. Most studies report laboratory-based investigations but useful progress in clinical description continues to be made.

SUMMARY

Eye movements remain an active field of investigation across a variety of neurodegenerative conditions. Progress continues to be made at the clinical level as well by using laboratory techniques.

Quality-of-life aspects in idiopathic epilepsy in dogs

Quality of life (QoL) plays a significant role in the treatment of dogs with idiopathic epilepsy (IE), yet is so far understudied. This study describes the outcome evaluation of an online questionnaire based on the carer's perception focusing on 62 QoL questions in 159 dogs with IE. Results showed that seizure frequency, but not seizure severity or presence of cluster seizures, was significantly associated with carer-perceived dog's QoL. Dogs receiving third-line antiepileptic drugs had a significantly lower perceived QoL than those that did not. Generalised linear mixed model analysis demonstrated that severity of the side effects sleeping more and ataxia were significantly associated with carer-perceived dog's QoL, with higher severities predicting lower QoL scores. The degree of carer acceptability of seizure frequency and severity was significantly associated with the dog's reported seizure frequency and severity. Moreover, there was a significant association between IE-related QoL changes of the dog and the carer, with reductions in perceived canine QoL scores associated with reductions in carer QoL, and vice versa. In conclusion, aspects of canine IE can affect both the carer and their dog's QoL. This has implications for the management and requires consideration when treatment options and outcomes are discussed.

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

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

Tracking Parkinson's Disease over One Year with Multimodal Magnetic Resonance Imaging in a Group of Older Patients with Moderate Disease

Background & Objectives

Cross-sectional magnetic resonance imaging (MRI) suggests that Parkinson’s disease (PD) is associated with changes in cerebral tissue volume, diffusion tensor imaging metrics, and perfusion values. Here, we performed a longitudinal multimodal MRI study—including structural, diffusion tensor imaging (DTI), and perfusion MRI—to investigate progressive brain changes over one year in a group of older PD patients at a moderate stage of disease.

Methods

Twenty-three non-demented PD (mean age (SD) = 69.5 (6.4) years, disease duration (SD) = 5.6 (4.3) years) and 23 matched control participants (mean age: 70.6 (6.8)) completed extensive neuropsychological and clinical assessment, and multimodal 3T MRI scanning at baseline and one year later. We used a voxel-based approach to assess change over time and group-by-time interactions for cerebral structural and perfusion metrics.

Results

Compared to controls, in PD participants there was localized grey matter atrophy over time in bilateral inferior and right middle temporal, and left orbito-frontal cortices. Using a voxel-based approach that focused on the centers of principal white matter tracts, the PD and control cohorts exhibited similar levels of change in DTI metrics. There was no significant change in perfusion, cognitive, or motor severity measures.

Conclusions

In a cohort of older, non-demented PD participants, macrostructural MRI detected atrophy in the PD group compared with the control group in temporal and orbito-frontal cortices. Changes in diffusion MRI along principal white matter tracts over one year were found, but this was not differentially affected by PD.

Comparison of cognitive and UHDRS measures in monitoring disease progression in Huntington's disease: a 12-month longitudinal study

Progressive cognitive decline is a feature of Huntington’s disease (HD), an inherited neurodegenerative movement disorder. Comprehensive neuropsychological testing is the ‘gold standard’ to establish cognitive status but is often impractical in time-constrained clinics. The study evaluated the utility of brief cognitive tests (MMSE and MoCA), UHDRS measures and a comprehensive neuropsychological tests battery in monitoring short-term disease progression in HD. Twenty-two manifest HD patients and 22 matched controls were assessed at baseline and 12-month. A linear mixed-effect model showed that although the HD group had minimal change in overall global cognition after 12 months, they did show a significant decline relative to the control group. The controls exhibited a practice effect in most of the cognitive domain scores over time. Cognitive decline at 12-month in HD was found in the executive function domain but the effect of this on global cognitive score was masked by the improvement in their language domain score. The varying practice effects by cognitive domain with repeated testing indicates the importance of comparing HD patients to control group in research trials and that cognitive progression over 12 months in HD should not be judged by changes in global cognitive score. The three brief cognitive tests effectively described cognition of HD patients on cross-sectional analysis. The UHDRS cognitive component, which focuses on testing executive function and had low variance over time, is a more reliable brief substitute for comprehensive neuropsychological testing than MMSE and MoCA in monitoring cognitive changes in HD patients after 12 months.

Comparing cerebral perfusion in Alzheimer's disease and Parkinson's disease dementia: an ASL-MRI study

Emerging evidence suggests that Alzheimer's disease (AD) and Parkinson's disease dementia (PDD) share neurodegenerative mechanisms. We sought to directly compare cerebral perfusion in these two conditions using arterial spin labeling magnetic resonance imaging (ASL-MRI). In total, 17 AD, 20 PDD, and 37 matched healthy controls completed ASL and structural MRI, and comprehensive neuropsychological testing. Alzheimer's disease and PDD perfusion was analyzed by whole-brain voxel-based analysis (to assess absolute blood flow), a priori specified region of interest analysis, and principal component analysis (to generate a network differentiating the two groups). Corrections were made for cerebral atrophy, age, sex, education, and MRI scanner software version. Analysis of absolute blood flow showed no significant differences between AD and PDD. Comparing each group with controls revealed an overlapping, posterior pattern of hypoperfusion, including posterior cingulate gyrus, precuneus, and occipital regions. The perfusion network that differentiated AD and PDD groups identified relative differences in medial temporal lobes (AD Collapse

Key Words

• alzheimer's disease
• arterial spin labeling
• dementia
• mri
• parkinson's disease

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MESH Headings

• Aged
• Aged, 80 and over
• Alzheimer Disease/diagnostic imaging
• Alzheimer Disease/physiopathology
• Blood Flow Velocity
• Cerebrovascular Circulation
• Female
• Humans
• Limbic System/blood supply
• Limbic System/diagnostic imaging
• Limbic System/physiopathology
• Magnetic Resonance Angiography
• Male
• Parkinson Disease/diagnostic imaging
• Parkinson Disease/physiopathology
• Radiography

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Grants Collapse

Affiliation(s)

Campbell J Le Heron New Zealand Brain Research Institute, Christchurch, New Zealand
Sarah L Wright New Zealand Brain Research Institute, Christchurch, New Zealand
Tracy R Melzer New Zealand Brain Research Institute, Christchurch, New Zealand Department of Medicine, University of Otago, Christchurch, New Zealand
Daniel J Myall New Zealand Brain Research Institute, Christchurch, New Zealand
Michael R MacAskill New Zealand Brain Research Institute, Christchurch, New Zealand Department of Medicine, University of Otago, Christchurch, New Zealand
Leslie Livingston New Zealand Brain Research Institute, Christchurch, New Zealand Department of Medicine, University of Otago, Christchurch, New Zealand
Ross J Keenan New Zealand Brain Research Institute, Christchurch, New Zealand Christchurch Radiology Group, Christchurch, New Zealand
Richard Watts College of Medicine, University of Vermont, Burlington, Vermont, USA
John C Dalrymple-Alford New Zealand Brain Research Institute, Christchurch, New Zealand Department of Medicine, University of Otago, Christchurch, New Zealand Department of Psychology, University of Canterbury, Christchurch, New Zealand
Tim J Anderson New Zealand Brain Research Institute, Christchurch, New Zealand Department of Medicine, University of Otago, Christchurch, New Zealand Department of Neurology, Christchurch Hospital, Christchurch, New Zealand

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Evaluation of quality of life in dogs with idiopathic epilepsy

Background

The impact of epilepsy and its treatment on the quality of life (QoL) is considered an important part of treatment supervision in human epilepsy.

Objectives

To develop a list of key questions evaluating QoL in dogs with idiopathic epilepsy (IE) and their carers.

Animals

One hundred fifty‐nine dogs with IE.

Methods

Cross‐sectional study. An online project questionnaire was developed containing 90 QoL‐associated questions that were initially allocated to 14 themes representing specific areas associated with the treatment and care of an epileptic dog. Principal component analysis was applied with the aim of refining the questionnaire to the least number of questions representing useful themes without loss of descriptive value. Carers were recruited by paper mail, primary practices, and canine epilepsy websites. Data were acquired from January to November 2011.

Results

Principal component analysis removed 54 questions, leaving 7 themes with 36 questions with a minimum Cronbach's alpha value of 0.7 indicating a good internal consistency: “Seizure severity and frequency”, “Adverse effects of antiepileptic drug (AED)”, “Restrictions on the carer's life”, “Frustrations over caring for a dog with IE”, “Carer distaste of AED adverse effects”, “Carer anxiety around the seizure event”, “Perceptions on rectal diazepam use”.

Conclusions and Clinical Importance

Principal component analysis successfully reduced the number of questions without loss in descriptive value. The remaining questions correlate well with each other in capturing valuable details about aspects of QoL and represent valuable key questions (EpiQoL) in the assessment of QoL for the carers of dogs with IE.

Common carotid intima-media thickness does not add to Framingham risk score in individuals with diabetes mellitus: the USE-IMT initiative

AIMS/HYPOTHESIS

The aim of this work was to investigate whether measurement of the mean common carotid intima-media thickness (CIMT) improves cardiovascular risk prediction in individuals with diabetes.

METHODS

We performed a subanalysis among 4,220 individuals with diabetes in a large ongoing individual participant data meta-analysis involving 56,194 subjects from 17 population-based cohorts worldwide. We first refitted the risk factors of the Framingham heart risk score on the individuals without previous cardiovascular disease (baseline model) and then expanded this model with the mean common CIMT (CIMT model). The absolute 10 year risk for developing a myocardial infarction or stroke was estimated from both models. In individuals with diabetes we compared discrimination and calibration of the two models. Reclassification of individuals with diabetes was based on allocation to another cardiovascular risk category when mean common CIMT was added.

RESULTS

During a median follow-up of 8.7 years, 684 first-time cardiovascular events occurred among the population with diabetes. The C statistic was 0.67 for the Framingham model and 0.68 for the CIMT model. The absolute 10 year risk for developing a myocardial infarction or stroke was 16% in both models. There was no net reclassification improvement with the addition of mean common CIMT (1.7%; 95% CI -1.8, 3.8). There were no differences in the results between men and women.

CONCLUSIONS/INTERPRETATION

There is no improvement in risk prediction in individuals with diabetes when measurement of the mean common CIMT is added to the Framingham risk score. Therefore, this measurement is not recommended for improving individual cardiovascular risk stratification in individuals with diabetes.

White matter microstructure deteriorates across cognitive stages in Parkinson disease

OBJECTIVES

To characterize different stages of Parkinson disease (PD)-related cognitive decline using diffusion tensor imaging (DTI) and investigate potential relationships between cognition and microstructural integrity of primary white matter tracts.

METHODS

Movement Disorder Society criteria were used to classify 109 patients with PD as having normal cognition (PD-N, n = 63), mild cognitive impairment (PD-MCI, n = 28), or dementia (PD-D, n = 18), and were compared with 32 matched controls. DTI indices were assessed across groups using tract-based spatial statistics, and multiple regression was used to assess association with cognitive and clinical measures.

RESULTS

Relative to controls, PD-N showed some increased mean diffusivity (MD) in corpus callosum, but no significantly decreased fractional anisotropy (FA). Decreased FA and increased MD were identified in PD-MCI and PD-D relative to controls. Only small areas of difference were observed in PD-MCI and PD-D compared with PD-N, while DTI metrics did not differ significantly between PD-MCI and PD-D. Executive function, attention, memory, and a composite measure of global cognition were associated with MD, primarily in anterior white matter tracts; only attention was associated with FA. These differences were independent of white matter hyperintensity load, which was also associated with cognition in PD.

CONCLUSIONS

PD is associated with spatially restricted loss of microstructural white matter integrity in patients with relatively normal cognition, and these alterations increase with cognitive dysfunction. Functional impairment in executive function, attention, and learning and memory appears associated with microstructural changes, suggesting that tract-based spatial statistics provides an early marker for clinically relevant cognitive impairment in PD.

Whose name is it anyway? Varying patterns of possessive usage in eponymous neurodegenerative diseases

There has been long-standing debate over whether use of the possessive form of the names of eponymous neurological disorders should be abandoned. Which view has actually predominated in practice? We empirically assessed current and historical usage in the scientific literature. The PubMed database was queried for the percentage of titles published each year from 1960–2012 which contained the possessive form of Parkinson’s (PD), Alzheimer’s (AD), Huntington’s (HD), Wilson’s (WD), and Gaucher’s (GD) diseases (e.g. Huntington’s disease or chorea vs Huntington disease or chorea). Down syndrome (DS), well known for its changes in terminology, was used as a reference. The possessive form was nearly universal in all conditions from 1960 until the early 1970s. In both DS and GD it then declined at an approximately constant rate of 2 percentage points per year to drop below 15%. The possessive forms of both PD and AD began to decline at the same time but stabilised and have since remained above 80%, with a similar but more volatile pattern in HD. WD, meanwhile, is intermediate between the DS/GD and PD/AD/HD patterns, with a slower decline to its current value of approximately 60%. Declining possessive form usage in GD and DS papers has been remarkably uniform over time and has nearly reached completion. PD and AD appear stable in remaining predominantly possessive. The larger volume of papers published in those fields and their possibly greater public recognition and involvement may make that unlikely to change in the short-term. In a secondary analysis restricted to PD, we found that practices have switched dramatically several times in each of three US-published general neurology journals. Meanwhile, in two UK-published journals, and in the specialist title “Movement Disorders”, the possessive form has been maintained consistently. The use of eponyms in neurology shows systematic variation across time, disorders, and journals.

The role of linguistic and indexical information in improved recognition of dysarthric speech

This investigation examined perceptual learning of dysarthric speech. Forty listeners were randomly assigned to one of two identification training tasks, aimed at highlighting either the linguistic (word identification task) or indexical (speaker identification task) properties of the neurologically degraded signal. Twenty additional listeners served as a control group, passively exposed to the training stimuli. Immediately following exposure to dysarthric speech, all three listener groups completed an identical phrase transcription task. Analysis of listener transcripts revealed remarkably similar intelligibility improvements for listeners trained to attend to either the linguistic or the indexical properties of the signal. Perceptual learning effects were also evaluated with regards to underlying error patterns indicative of segmental and suprasegmental processing. The findings of this study suggest that elements within both the linguistic and indexical properties of the dysarthric signal are learnable and interact to promote improved processing of this type and severity of speech degradation. Thus, the current study extends support for the development of a model of perceptual processing in which the learning of indexical properties is encoded and retained in conjunction with linguistic properties of the signal.

The influence of motor and cognitive impairment upon visually-guided saccades in Parkinson's disease

Studies of saccades in Parkinson's disease (PD) have seldom examined the influence of cognitive status, ranging from normal cognition, through mild cognitive impairment, to dementia. In a large and heterogeneous sample, we examined how motor and cognitive impairment was reflected in the performance of reflexive, visually-guided saccades. We examined 163 people with PD and 47 similar-aged controls. Ninety three of the PD group had normal cognition (PDN), 48 had mild cognitive impairment (PD-MCI), and 22 had dementia (PDD). Pseudo-random targets (amplitudes of 5, 10, 15 and 20 deg and inter-stimulus-intervals ranging from 550 to 1800 ms) were shown in 108 mixed randomised trials, incorporating gap, step, and overlap onset conditions. Analyses were conducted using multi-level regression modeling. Participants were first assessed by continuous measures (Unified PD Rating Scale motor score and the Montreal Cognitive Assessment). Prolonged latency was significantly related to both motor and cognitive impairment, with the cognitive effect being compounded by increasing age. Decreased saccade amplitude, meanwhile, was primarily related to motor impairment. When assessed by discrete cognitive categories, all of the PD groups showed reduced saccadic amplitude relative to controls. Saccadic latencies, meanwhile, were abnormally prolonged only in the PD-MCI and PDD groups (the control and PDN groups were similar to each other). Latency in the overlap task was particularly sensitive to increasing motor and cognitive impairment. We conclude that reflexive saccades in PD are subtly decreased in amplitude even early in the disease process. Prolonged saccade latency, meanwhile, tends to occur later in the disease process, in the presence of more substantial motor and cognitive impairment, and greater age. The progressive impairment of reflexive saccades, and the differential onset of amplitude and latency impairments, may make them a useful objective tool for assessing disease status.

Reduced striatal volumes in Parkinson's disease: a magnetic resonance imaging study

Background

The presence and extent of structural changes in the brain as a consequence of Parkinson’s disease (PD) is still poorly understood.

Methods

High-resolution 3-tesla T1-weighted structural magnetic resonance images in sixty-five PD and 27 age-matched healthy control participants were examined. Putamen, caudate, and intracranial volumes were manually traced in the axial plane of 3D reconstructed images. Striatal nuclei volumes were normalized to intracranial volume for statistical comparison. Disease status was assessed using the Unified Parkinson’s Disease Rating Scale and Hoehn and Yahr scale. Cognitive status was assessed using global status tests and detailed neuropsychological testing.

Results

Both caudate and putamen volumes were smaller in PD brains compared to controls after adjusting for age and gender. Caudate volumes were reduced by 11% (p = 0.001) and putamen volumes by 8.1% (p = 0.025). PD striatal volumes were not found to be significantly correlated with cognitive or motor decline.

Conclusion

Small, but significant reductions in the volume of both the caudate and putamen occur in PD brains. These reductions are independent of the effects of age and gender, however the relation of these reductions to the functional loss of dopamine, which is characteristic of PD, remains unclear.

A follow-up investigation into the mechanisms that underlie improved recognition of dysarthric speech

Differences in perceptual strategies for lexical segmentation of moderate hypokinetic dysarthric speech, apparently related to the conditions of the familiarization procedure, have been previously reported [Borrie et al., Language and Cognitive Processes (2012)]. The current follow-up investigation examined whether this difference was also observed when familiarization stimuli highlighted syllabic strength contrast cues. Forty listeners completed an identical transcription task following familiarization with dysarthric phrases presented under either passive or explicit learning conditions. Lexical boundary error patterns revealed that syllabic strength cues were exploited in both familiarization conditions. Comparisons with data previously reported afford further insight into perceptual learning of dysarthric speech.

Clinical evaluation of cochlear hearing status in dogs using evoked otoacoustic emissions

OBJECTIVES

Evoked otoacoustic emission testing is the preferred test in human patients for sensorineural deafness screening in neonates and cochlear outer hair cell function monitoring in adults. This study evaluated evoked otoacoustic emission testing for cochlear function assessment in dogs within a clinical setting.

METHODS

Two populations of anaesthetised dogs were included. In group 1 the evoked otoacoustic emission response was compared to the brainstem auditory evoked response in 10 dogs having hearing assessment. Group 2 comprised 43 presumed normal dogs, in which the suitability of two types of evoked otoacoustic emissions, transient-evoked and distortion product otoacoustic emissions, were evaluated (brainstem auditory evoked response was not performed in this group).

RESULTS

Valid transient-evoked otoacoustic emission and distortion-product otoacoustic emission responses were successfully recorded within the clinical setting and correctly identified deaf and hearing ears. Within presumed healthy dogs, normal otoacoustic emission response was demonstrated in more than 80% of dogs using a single, short distortion-product otoacoustic emission run and in 78% of dogs with valid transient-evoked otoacoustic emission responses using a series of three repeated transient-evoked otoacoustic emission short runs.

CLINICAL SIGNIFICANCE

Transient-evoked otoacoustic emission and distortion-product otoacoustic emission testing provided a rapid, non-invasive frequency-specific assessment of cochlear function. Transient-evoked otoacoustic emission and distortion product otoacoustic emission testing is suitable as a screening procedure to detect loss of cochlear function in dogs, although further investigation is needed.

Grey matter atrophy in cognitively impaired Parkinson's disease

OBJECTIVE

Mild cognitive impairment and dementia are common non-motor features of Parkinson's disease (PD). The aim of this study was to characterise grey matter changes associated with clearly defined stages of cognitive impairment in PD using structural MRI.

METHODS

96 PD subjects were classified using detailed cognitive testing as PD with normal cognition (PD-N, n=57), PD with mild cognitive impairment (PD-MCI, n=23) or PD with dementia (PD-D, n=16); 34 controls matched for mean age and sex ratio also participated. Grey matter volume differences were evaluated using voxel based morphometry of grey matter segments derived from T1 weighted 3 T MRI, and multiple linear regression assessed the relationship between cognitive and motor impairments and grey matter concentration.

RESULTS

Compared with controls, no grey matter differences were found in PD-N. PD-MCI showed limited grey matter atrophy in the temporal, parietal and frontal cortex as well as the bilateral caudal hippocampus, amygdala and right putamen. PD-D subjects exhibited far more extensive atrophy in regions involved in PD-MCI but also had reduced grey matter volume in other large areas of the temporal lobe (including the parahippocampi), the intracalcarine and lingual gyri, posterior cingulate gyrus, frontal regions and bilateral caudate. Grey matter loss in PD correlated with global cognitive score but not motor impairment in most of these regions.

INTERPRETATION

Marked grey matter atrophy occurs in PD with dementia but far less extensive changes are evident in PD-MCI. Some grey matter atrophy precedes the development of dementia but may be accelerated once frank dementia begins.

The effects of acute tryptophan depletion on neuropsychological function, mood and movement in the healthy elderly

Few studies have investigated the function of the serotonin (5-HT) system in the elderly. Previous studies have shown effects of reducing serotonin function, by acute tryptophan depletion (ATD), on neuropsychological function in healthy subjects but this technique has not previously been employed over a wide age range in the elderly. This study compared the effects of ATD on mood, cognitive function and motor function in two groups of healthy volunteers, one group aged 50-69 and the other aged 70-89. The effects of ATD were investigated in a double-blind, placebo-controlled, counterbalanced, crossover, randomized design. The effects of ATD were not significantly different between age groups, suggesting that there is relatively little functional change across these age ranges. Compared with studies in much younger age groups there was, however, more evidence of an adverse effect of ATD on psychomotor function and working memory. There was no effect of ATD on mood despite inclusion of subjects with a family history of depression.