Cerebellar Contribution to Motor and Non-motor Functions in Parkinson's Disease: A Meta-Analysis of fMRI Findings

MRI-based differentiation of Parkinson's disease by cerebellar gray matter volume

BACKGROUND

The underlying mechanism of Parkinson's disease (PD) is associated with the neurodegeneration of the dopaminergic neurons, and the cerebellum plays a significant role together in non-motor and motor functions in PD progression. Morphological changes in the cerebellum can greatly impact patients' clinical symptoms, especially motor control symptoms, and may also help distinguish patients from healthy subjects. This study aimed to explore the potential of cerebellar gray matter volume, related to motor control function, as a neuroimaging biomarker to classify patients with PD and healthy controls (HC) by using voxel-based morphometric (VBM) measurements and support vector machine (SVM) methods based on independent component analysis (ICA).

METHODS

Cerebellar gray matter volume was measured using VBM in patients with PD (n = 27) and HC (n = 16) from the Neurocon dataset. ICA analysis was performed on the gray matter volume of all subregions, resulting in 7 independent components. These independent components were then utilized for correlation analysis with clinical scales and trained as input features for the SVM model. PD patients (n = 20) and HC (n = 20) from the TaoWu dataset were used as test data to validate our SVM model.

RESULTS

Among patients with PD, 3 out of the 7 independent components showed a significant correlation with clinical scales. The SVM model achieved an accuracy of 86 % in classifying PD patients and HC, with a sensitivity of 72.2 %, specificity of 88 %, and F1 Score of 76.5 %. The accuracy of the SVM model verification analysis using the TaoWu dataset was 70 %, with a sensitivity of 62.5 %, a specificity of 100 %, and the F1 Score was 76.9 %.

CONCLUSIONS

The results suggest that abnormal cerebellar gray matter volume, which is highly correlated with motor control function in Parkinson's patients, may serve as a valuable neuroimaging biomarker capable of distinguishing Parkinson's patients from healthy individuals. We observed that the combination of the ICA method and the SVM method produced an improved classification model. This model may function as an early warning tool that enables clinicians to conduct preliminary identification and intervention for patients with PD.

Neuroimaging and cognitive correlates of postural control in Parkinson's disease: a systematic review

Parkinson's disease (PD) can cause postural instability, which may result in falls. These issues have been associated with motor and non-motor symptoms (NMS), including cognitive dysfunction. Several techniques have been employed to investigate the underlying neural mechanisms involved in postural control in PD. These include behavioural studies assessing associations between cognition and postural control, functional neuroimaging studies, and resting-state neural correlates. This review provides an overview of these emerging bodies of research. Scopus, PubMed, and ProQuest were searched and detailed the brain-imaging technique, cohort, and postural control measures. A total of 79 studies were identified. Findings supported the notion of cortical involvement in postural control function to compensate for subcortical damage resulting from PD. Future studies should standardise their outcome measures and data analysis to allow comparisons of results across studies and ensure more comprehensive and robust data collection to enhance the reliability and validity of these findings.

Ferulic acid mitigated rotenone toxicity -Evoked Parkinson in rat model by featuring apoptosis, oxidative stress, and neuroinflammation signaling

Over time, Parkinson disease (PD) develops as a neurological illness. The goal of this study was to see whether ferulic acid has any neuroprotective benefits on the cerebellum of rats that have Parkinson's disease brought on by rotenone poisoning. A total of twenty-four male albino rats, in good condition, weighed between 200 and 250 g and nine to ten weeks old, were employed in the investigation. The control group received 1 ml of sunflower oil intraperitoneally (i.p.) each day. Rats' motor performance was considerably worse when given rotenone than it was in the control group. Rats given Ferulic Acid (FA) showed a substantial drop in the amount of glutathione (GSH) in the cerebellum. Moreover, the injection of FA resulted in a significant reduction in the optical density (OD) of the immune-positive reaction for α-synuclein, and the area percentage of BCL-2 and NF-kB immunological positive response. FA therapy, surprisingly, enhanced the OD of TH immunopositive response and apoptotic regulators (BCL2) in the cerebellum. Furthermore, FA boosted BCL2 expression, confirming the antiapoptotic effects of FA. Based on these results, FA is probably a good candidate to treat neurodegenerative diseases brought on by long-term exposure to rotenone.

Hippocampus and olfactory impairment in Parkinson disease: a comparative exploratory combined volumetric/functional MRI study

INTRODUCTION

Patients with Parkinson's Disease (PD) commonly experience Olfactory Dysfunction (OD). Our exploratory study examined hippocampal volumetric and resting-state functional magnetic resonance imaging (rs-fMRI) variations in a Healthy Control (HC) group versus a cognitively normal PD group, further categorized into PD with No/Mild Hyposmia (PD-N/MH) and PD with Severe Hyposmia (PD-SH).

METHODS

We calculated participants' relative Total Hippocampal Volume (rTHV) and performed Spearman's partial correlations, controlled for age and gender, to examine the correlation between rTHV and olfactory performance assessed by the Odor Stick Identification Test for the Japanese (OSIT-J) score. Mann-Whitney U tests assessed rTHV differences across groups and subgroups, rejecting the null hypothesis for p < 0.05. Furthermore, a seed-based rs-fMRI analysis compared hippocampal connectivity differences using a one-way ANCOVA covariate model with controls for age and gender.

RESULTS

Spearman's partial correlations indicated a moderate positive correlation between rTHV and OSIT-J in the whole study population (ρ = 0.406; p = 0.007), PD group (ρ = 0.493; p = 0.008), and PD-N/MH subgroup (ρ = 0.617; p = 0.025). Mann-Whitney U tests demonstrated lower rTHV in PD-SH subgroup compared to both HC group (p = 0.013) and PD-N/MH subgroup (p = 0.029). Seed-to-voxel rsfMRI analysis revealed reduced hippocampal connectivity in PD-SH subjects compared to HC subjects with a single cluster of voxels.

CONCLUSIONS

Although the design of the study do not allow to make firm conclusions, it is reasonable to speculate that the progressive involvement of the hippocampus in PD patients is associated with the progression of OD.

Dynamic cerebellar and sensorimotor network compensation in tremor-dominated Parkinson's disease

AIM

Parkinson's disease (PD) tremor is associated with dysfunction in the basal ganglia (BG), cerebellum (CB), and sensorimotor networks (SMN). We investigated tremor-related static functional network connectivity (SFNC) and dynamic functional network connectivity (DFNC) in PD patients.

METHODS

We analyzed the resting-state functional MRI data of 21 tremor-dominant Parkinson's disease (TDPD) patients and 29 healthy controls. We compared DFNC and SFNC between the three networks and assessed their associations with tremor severity.

RESULTS

TDPD patients exhibited increased SFNC between the SMN and BG networks. In addition, they spent more mean dwell time (MDT) in state 2, characterized by sparse connections, and less MDT in state 4, indicating stronger connections. Furthermore, enhanced DFNC between the CB and SMN was observed in state 2. Notably, the MDT of state 2 was positively associated with tremor scores.

CONCLUSION

The enhanced dynamic connectivity between the CB and SMN in TDPD patients suggests a potential compensatory mechanism. However, the tendency to remain in a state of sparse connectivity may contribute to the severity of tremor symptoms.

Neural correlates of bradykinesia in Parkinson's disease: a kinematic and functional MRI study

Bradykinesia is defined as a "complex" of motor alterations including decreased movement amplitude and/or speed and tendency to reduce them with movement repetition (sequence effect). This study aimed at investigating the neural and kinematic correlates of bradykinesia during hand-tapping in people with Parkinson's disease (pwPD) relative to healthy controls. Twenty-five pwPD and 25 age- and sex-matched healthy controls underwent brain functional MRI (fMRI) during a hand-tapping task: subjects alternatively opened and closed their right hand as fully and quickly as possible. Hand-tapping kinematic parameters were objectively measured during the fMRI task using an optical fibre glove. During the fMRI task, pwPD showed reduced hand-tapping amplitude (hypokinesia) and a greater sequence effect. PwPD relative to healthy controls showed a reduced activity of fronto-parietal areas, middle cingulum/supplementary motor area (SMA), parahippocampus, pallidum/thalamus and motor cerebellar areas. Moreover, pwPD showed an increased activity of brain cognitive areas such as superior temporal gyrus, posterior cingulum, and cerebellum crus I. The decreased activity of cerebellum IV-V-VI, vermis IV-V, inferior frontal gyrus, and cingulum/SMA correlated with hypokinesia and with the sequence effect. Interestingly, a reduced activity of areas involved in motor planning and timing correlated both with hypokinesia and with the sequence effect in pwPD. This study has the major strength of collecting objective motor parameters and brain activity simultaneously, providing a unique opportunity to investigate the neural correlates of the "bradykinesia complex".

A Model with Dopamine Depletion in Basal Ganglia and Cerebellum Predicts Changes in Thalamocortical Beta Oscillations

Parkinsonism is presented as a motor syndrome characterized by rigidity, tremors, and bradykinesia, with Parkinson's disease (PD) being the predominant cause. The discovery that those motor symptoms result from the death of dopaminergic cells in the substantia nigra led to focus most of parkinsonism research on the basal ganglia (BG). However, recent findings point to an active involvement of the cerebellum in this motor syndrome. Here, we have developed a multiscale computational model of the rodent brain's BG-cerebellar network. Simulations showed that a direct effect of dopamine depletion on the cerebellum must be taken into account to reproduce the alterations of neural activity in parkinsonism, particularly the increased beta oscillations widely reported in PD patients. Moreover, dopamine depletion indirectly impacted spike-time-dependent plasticity at the parallel fiber-Purkinje cell synapses, degrading associative motor learning as observed in parkinsonism. Overall, these results suggest a relevant involvement of cerebellum in parkinsonism associative motor symptoms.

Investigation of total cerebellar and flocculonodular lobe volume in Parkinson's disease and healthy individuals: a brain segmentation study

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder with an unexplored link to the cerebellum. In the pathophysiology of balance disorders in PD, the role of the flocculonodular lobe (FL) is linked to the impairment of the dopaminergic system. Dopamine deficiency can also lead to changes in cerebellum functions, disrupting balance control. This study compares cerebellar and FL volumes between healthy controls (HC) and PD patients, analyzing their correlation with clinical outcomes.

METHODS

We used magnetic resonance images of 23 PD patients (14 male, 9 female) and 24 HC (9 male, 15 female). Intracranial (ICV), total cerebellar, FL, and cerebellar gray matter volumes were measured using VolBrain. Clinical outcomes in PD patients were assessed using the Unified Parkinson's Disease Rating Scale (UPDRS-III) to evaluate motor function, with scores correlated to volumetric data.

RESULTS

The cerebellar and gray matter volumes in HC were 115.53 ± 10.44 cm3 and 84.83 ± 7.76 cm3, respectively, compared to 126.83 ± 13.47 cm3 and 92.37 ± 9.45 cm3 in PD patients, indicating significantly larger volumes in PD patients (p < 0.05). The flocculonodular lobe gray matter volume was 1.14 ± 0.19 cm3 in PD patients and 1.02 ± 0.13 cm3 in HC, but there was a significant increase in gray matter volume in PD patients between the groups (p < 0.05). In PD patients, significant negative correlations were observed between FL volume and the UPDRS-III scores (r =  - 0.467, p = 0.033) and between UPDRS-III scores and both total (r =  - 0.453, p = 0.039) and normalized (r =  - 0.468, p = 0.032) gray matter volumes of the FL.

CONCLUSION

Although total gray matter volumes were larger in PD patients, the volumes of FL did not differ between groups. In Parkinson's disease, increased cerebellar volume may regulate fine motor movements rather than balance.

Gray Matter Atrophy in a 6-OHDA-induced Model of Parkinson's Disease

INTRODUCTION

Magnetic resonance imaging (MRI) based brain morphometric changes in unilateral 6-hydroxydopamine (6-OHDA) induced Parkinson's disease (PD) model can be elucidated using voxel-based morphometry (VBM), study of alterations in gray matter volume and Machine Learning (ML) based analyses.

METHODS

We investigated gray matter atrophy in 6-OHDA induced PD model as compared to sham control using statistical and ML based analysis. VBM and atlas-based volumetric analysis was carried out at regional level. Support vector machine (SVM)-based algorithms wherein features (volume) extracted from (a) each of the 150 brain regions (b) statistically significant features (only) and (c) volumes of each cluster identified after application of VBM (VBM_Vol) were used for training the decision model. The lesion of the 6-OHDA model was validated by estimating the net contralateral rotational behaviour by the injection of apomorphine drug and motor impairment was assessed by rotarod and open field test.

RESULTS AND DISCUSSION

In PD, gray matter volume (GMV) atrophy was noted in bilateral cortical and subcortical brain regions, especially in the internal capsule, substantia nigra, midbrain, primary motor cortex and basal ganglia-thalamocortical circuits in comparison with sham control. Behavioural results revealed an impairment in motor performance. SVM analysis showed 100% classification accuracy, sensitivity and specificity at both 3 and 7 weeks using VBM_Vol.

CONCLUSION

Unilateral 6-OHDA induced GMV changes in both hemispheres at 7th week may be associated with progression of the disease in the PD model. SVM based approaches provide an increased classification accuracy to elucidate GMV atrophy.

Understanding the role of cerebellum in early Parkinson's disease: a structural and functional MRI study

Increasing evidence suggests that the cerebellum may have a role in the pathophysiology of Parkinson's disease (PD). Hence, the scope of this study was to investigate whether there are structural and functional alterations of the cerebellum and whether they correlate with motor and non-motor symptoms in early PD patients. Seventy-six patients with early PD and thirty-one age and sex-matched healthy subjects (HS) were enrolled and underwent a 3 T magnetic resonance imaging (MRI) protocol. The following MRI analyses were performed: (1) volumes of 5 cerebellar regions of interest (sensorimotor and cognitive cerebellum, dentate, interposed, and fastigial nuclei); (2) microstructural integrity of the cerebellar white matter connections (inferior, middle, and superior cerebellar peduncles); (3) functional connectivity at rest of the 5 regions of interest already described in point 1 with the rest of brain. Compared to controls, early PD patients showed a significant decrease in gray matter volume of the dentate, interposed and fastigial nuclei, bilaterally. They also showed abnormal, bilateral white matter microstructural integrity in all 3 cerebellar peduncles. Functional connectivity of the 5 cerebellar regions of interest with several areas in the midbrain, basal ganglia and cerebral cortex was altered. Finally, there was a positive correlation between abnormal functional connectivity of the fastigial nucleus with the volume of the nucleus itself and a negative correlation with axial symptoms severity. Our results showed that structural and functional alterations of the cerebellum are present in PD patients and these changes contribute to the pathophysiology of PD in the early phase.

Connectome-based predictive modelling estimates individual cognitive status in Parkinson's disease

INTRODUCTION

The progressive nature of Parkinson's disease (PD) affords emphasis on accurate early-stage individual-level assessment of risk and intervention appropriateness. In PD, cognitive impairment (CI) may follow or precede motor symptoms but are generally underdetected. In addition to impeding daily functioning and quality of life, CIs increase the risk for later conversion to dementia, providing a pressing need to develop novel tools to detect and interpret them. Connectome-based predictive modelling (CPM) is an emerging machine-learning approach to individual prediction that holds translational promise due to its noninvasiveness and simple implementation. The aim of this study was to investigate CPM's potential to predict and understand CIs in PD.

METHODS

Resting-state functional connectivity from 58 patients with PD of varying cognitive status was used to train a CPM-model to predict a global cognitive composite (GCC) score. The model was validated using cross-validation, permutation testing, and internal stability analyses. The combined predictive strength of two brain connectivity networks, positive and negative, directly and inversely correlated with GCC, respectively, was assessed.

RESULTS

The model significantly predicted individual GCC scores, r = 0.63, pperm < .05. Separately, the positive and negative networks were similar in performance, rs ≥ .58, ps < .05, but varied in anatomical distribution.

CONCLUSIONS

This study identified a connectome predictive of cognitive scores in PD, with features overlapping with established and emerging evidence on aberrant connectivity in PD-related CIs. Overall, CPM appears promising for clinical translation in this population, but longitudinal studies with out-of-sample validation are needed.

Structural and microstructural predictors of cognitive decline in deep brain stimulation of subthalamic nucleus in Parkinson's disease

BACKGROUND AND OBJECTIVES

The intricate relationship between deep brain stimulation (DBS) in Parkinson's disease (PD) and cognitive impairment has lately garnered substantial attention. The presented study evaluated pre-DBS structural and microstructural cerebral patterns as possible predictors of future cognitive decline in PD DBS patients.

METHODS

Pre-DBS MRI data in 72 PD patients were combined with neuropsychological examinations and follow-up for an average of 2.3 years after DBS implantation procedure using a screening cognitive test validated for diagnosis of mild cognitive impairment in PD in a Czech population - Dementia Rating Scale 2.

RESULTS

PD patients who would exhibit post-DBS cognitive decline were found to have, already at the pre-DBS stage, significantly lower cortical thickness and lower microstructural complexity than cognitively stable PD patients. Differences in the regions directly related to cognition as bilateral parietal, insular and cingulate cortices, but also occipital and sensorimotor cortex were detected. Furthermore, hippocampi, putamina, cerebellum and upper brainstem were implicated as well, all despite the absence of pre-DBS differences in cognitive performance and in the position of DBS leads or stimulation parameters between the two groups.

CONCLUSIONS

Our findings indicate that the cognitive decline in the presented PD cohort was not attributable primarily to DBS of the subthalamic nucleus but was associated with a clinically silent structural and microstructural predisposition to future cognitive deterioration present already before the DBS system implantation.

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.

Free water imaging unravels unique patterns of longitudinal structural brain changes in Parkinson's disease subtypes

Background

Research shows that individuals with Parkinson's disease (PD) who have a postural instability and gait difficulties (PIGD) subtype have a faster disease progression compared to those with a tremor dominant (TD) subtype. Nevertheless, our understanding of the structural brain changes contributing to these clinical differences remains limited, primarily because many brain imaging techniques are only capable of detecting changes in the later stages of the disease.

Objective

Free water (FW) has emerged as a robust progression marker in several studies, showing increased values in the posterior substantia nigra that predict symptom worsening. Here, we examined longitudinal FW changes in TD and PIGD across multiple brain regions.

Methods

Participants were TD and PIGD enrolled in the Parkinson's Progression Marker Initiative (PPMI) study who underwent diffusion MRI at baseline and 2 years later. FW changes were quantified for regions of interest (ROI) within the basal ganglia, thalamus, brainstem, and cerebellum.

Results

Baseline FW in all ROIs did not differ between groups. Over 2 years, PIGD had a greater percentage increase in FW in the putamen, globus pallidus, and cerebellar lobule V. A logistic regression model incorporating percent change in motor scores and FW in these brain regions achieved 91.4% accuracy in discriminating TD and PIGD, surpassing models based solely on clinical measures (74.3%) or imaging (76.1%).

Conclusion

The results further suggest the use of FW to study disease progression in PD and provide insight into the differential course of brain changes in early-stage PD subtypes.

Slower rates of prism adaptation but intact aftereffects in patients with early to mid-stage Parkinson's disease

There is currently mixed evidence on the effect of Parkinson's disease on motor adaptation. Some studies report that patients display adaptation comparable to age-matched controls, while others report a complete inability to adapt to novel sensory perturbations. Here, early to mid-stage Parkinson's patients were recruited to perform a prism adaptation task. When compared to controls, patients showed slower rates of initial adaptation but intact aftereffects. These results support the suggestion that patients with early to mid-stage Parkinson's disease display intact adaptation driven by sensory prediction errors, as shown by the intact aftereffect. But impaired facilitation of performance through cognitive strategies informed by task error, as shown by the impaired initial adaptation. These results support recent studies that suggest that patients with Parkinson's disease retain the ability to perform visuomotor adaptation, but display altered use of cognitive strategies to aid performance and generalises these previous findings to the classical prism adaptation task.

Integrated PET/MRI With 11C-CFT and 18F-FDG for levodopa response difference in Parkinson's disease

AIM

Parkinson's disease is one of the most common neurodegenerative diseases. Excellent levodopa responsiveness has been proposed as a characteristic supporting feature in substantiating the PD diagnosis. However, a small portion of clinically established PD patients shows poor levodopa response. This study aims to investigate brain function alterations of PD patients with poor levodopa responsiveness by PET/MRI.

METHOD

A total of 46 PD patients were recruited. They all completed 11C-CFT PET/MRI scans and the acute levodopa challenge test. Among these 46 PD patients, 42 participants further underwent 18F-FDG PET/MRI scans. Clinical variables regarding demographic data, disease features and cognition scales were also collected. Based on the improvement rate of UPDRS-III, PD patients were divided into non-responders (improvement rate < 33 %) and responders (improvement rate ≥ 33 %). Statistical parametric zapping was performed to analyze molecular imaging. Dopaminergic uptake and metabolism of 70 brain regions were converted to quantitative values and expressed as standard uptake value (SUV). SUV was further normalized by the cerebellum. The resulting SUV ratios and clinical variables were then compared by SPSS.

RESULTS

The difference between levodopa non-responders (n = 17) and responders (n = 29) in the UPDRS III baseline was statistically significant and the former had a lower UPDRS III baseline (19 (10, 32), p＜0.05). In contrast, no statistical difference between these two groups was found in age, gender, disease duration, cognition, motor subtype and Hoehn-Yahr stage. Dopaminergic uptake differences between levodopa non-responders (n = 17) and responders (n = 29) were shown in the left inferior frontal cortex (1.00 ± 0.09 vs 1.07 ± 0.08, p < 0.05 and FDR < 0.2), the right posterior cingulum (1.10 ± 0.10 vs 1.20 ± 0.13, p < 0.05 and FDR < 0.2) and the right insula (1.21 ± 0.12 vs 1.30 ± 0.10, p < 0.05 and FDR < 0.2). The metabolic alterations between levodopa non-responders (n = 16) and responders (n = 26) were shown in the right supplementary motor area (1.30 (1.18, 1.39) vs 1.41 (1.31, 1.53), p < 0.05 and FDR < 0.2), right precuneus (1.37 ± 0.10 vs 1.47 ± 0.18, p < 0.05 and FDR < 0.2), right parietal cortex (1.14 ± 0.15 vs 1.27 ± 0.21, p < 0.05 and FDR < 0.2), right supramarginal gyrus (1.16 (1.12, 1.26) vs 1.25 (1.14, 1.46), p < 0.05 and FDR < 0.2), right postcentral gyrus (1.15 (1.08, 1.32) vs 1.24 (1.17, 1.39), p < 0.05 and FDR < 0.2), medulla (0.75 ± 0.07 vs 0.80 ± 0.07, p < 0.05 and FDR < 0.2), right rolandic operculum (1.25 (1.18, 1.32) vs 1.33 (1.25, 1.50), p < 0.05 and FDR < 0.2), right olfactory (0.95 (0.91, 1.01) vs 1.01 (0.95, 1.15), p < 0.05 and FDR < 0.2), the right insula (1.15 (1.06, 1.22) vs 1.21 (1.12, 1.35), p < 0.05 and FDR < 0.2) and the left cerebellum crus (0.96 (0.91, 1.01) vs 0.92 (0.86, 0.96), p < 0.05 and FDR < 0.2).

CONCLUSIONS

PD patients with poor response to levodopa showed less severe impairment of baseline motor symptoms, more severe dopaminergic deficits in the left inferior frontal, right posterior cingulate cortex and the right insula, and lower metabolism in the right supplementary motor area, right precuneus, right parietal cortex, right supramarginal gyrus, right postcentral gyrus, medulla, right rolandic operculum, right olfactory, the right insula and higher metabolism in the left cerebellum crus.

Cerebellar functional connectivity change is associated with motor and neuropsychological function in early stage drug-naïve patients with Parkinson's disease

Introduction

Parkinson's Disease (PD) is a progressive neurodegenerative disorder affecting both motor and cognitive function. Previous neuroimaging studies have reported altered functional connectivity (FC) in distributed functional networks. However, most neuroimaging studies focused on patients at an advanced stage and with antiparkinsonian medication. This study aims to conduct a cross-sectional study on cerebellar FC changes in early-stage drug-naïve PD patients and its association with motor and cognitive function.

Methods

Twenty-nine early-stage drug-naïve PD patients and 20 healthy controls (HCs) with resting-state fMRI data and motor UPDRS and neuropsychological cognitive data were extracted from the Parkinson's Progression Markers Initiative (PPMI) archives. We used seed-based resting-state fMRI (rs-fMRI) FC analysis and the cerebellar seeds were defined based on the hierarchical parcellation of the cerebellum (AAL atlas) and its topological function mapping (motor cerebellum and non-motor cerebellum).

Results

The early stage drug-naïve PD patients had significant differences in cerebellar FC when compared with HCs. Our findings include: (1) Increased intra-cerebellar FC within motor cerebellum, (2) increase motor cerebellar FC in inferior temporal gyrus and lateral occipital gyrus within ventral visual pathway and decreased motor-cerebellar FC in cuneus and dorsal posterior precuneus within dorsal visual pathway, (3) increased non-motor cerebellar FC in attention, language, and visual cortical networks, (4) increased vermal FC in somatomotor cortical network, and (5) decreased non-motor and vermal FC within brainstem, thalamus and hippocampus. Enhanced FC within motor cerebellum is positively associated with the MDS-UPDRS motor score and enhanced non-motor FC and vermal FC is negatively associated with cognitive function test scores of SDM and SFT.

Conclusion

These findings provide support for the involvement of cerebellum at an early stage and prior to clinical presentation of non-motor features of the disease in PD patients.

Variations on the theme: focus on cerebellum and emotional processing

The cerebellum operates exploiting a complex modular organization and a unified computational algorithm adapted to different behavioral contexts. Recent observations suggest that the cerebellum is involved not just in motor but also in emotional and cognitive processing. It is therefore critical to identify the specific regional connectivity and microcircuit properties of the emotional cerebellum. Recent studies are highlighting the differential regional localization of genes, molecules, and synaptic mechanisms and microcircuit wiring. However, the impact of these regional differences is not fully understood and will require experimental investigation and computational modeling. This review focuses on the cellular and circuit underpinnings of the cerebellar role in emotion. And since emotion involves an integration of cognitive, somatomotor, and autonomic activity, we elaborate on the tradeoff between segregation and distribution of these three main functions in the cerebellum.

Imaging the lower limb network in Parkinson's disease

BACKGROUND

Despite the significant impact of lower limb symptoms on everyday life activities in Parkinson's disease (PD), knowledge of the neural correlates of lower limb deficits is limited.

OBJECTIVE

We ran an fMRI study to investigate the neural correlates of lower limb movements in individuals with and without PD.

METHODS

Participants included 24 PD and 21 older adults who were scanned while performing a precisely controlled isometric force generation task by dorsiflexing their ankle. A novel MRI-compatible ankle dorsiflexion device that limits head motion during motor tasks was used. The PD were tested on their more affected side, whereas the side in controls was randomized. Importantly, PD were tested in the off-state, following overnight withdrawal from antiparkinsonian medication.

RESULTS

The foot task revealed extensive functional brain changes in PD compared to controls, with reduced fMRI signal during ankle dorsiflexion within the contralateral putamen and M1 foot area, and ipsilateral cerebellum. The activity of M1 foot area was negatively correlated with the severity of foot symptoms based on the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS-III).

CONCLUSION

Overall, current findings provide new evidence of brain changes underlying motor symptoms in PD. Our results suggest that pathophysiology of lower limb symptoms in PD appears to involve both the cortico-basal ganglia and cortico-cerebellar motor circuits.

Cerebellar alterations in Parkinson's disease with postural instability and gait disorders

BACKGROUND

Few studies interrogated the involvement of cerebellum in modulating gait in Parkinson's disease (PD) patients with postural instability and gait disorders (PD-PIGD). This study aimed at assessing cerebellar atrophy and activity alterations during functional MRI (fMRI) gait-simulating motor- and dual-tasks in PD-PIGD.

METHODS

Twenty-one PD-PIGD and 23 healthy controls underwent clinical assessment, structural MRI, and fMRI including a motor-task (foot anti-phase movements) and a dual-task (foot anti-phase movements while counting backwards by threes). Grey matter cerebellar volumes were assessed using SUIT atlas. FMRI activations were extracted from each cerebellar lobule, and we correlated cerebellar and basal ganglia activity.

RESULTS

PD-PIGD patients had reduced volumes of cerebellar motor and non-motor areas relative to controls. During fMRI motor-task, patients showed greater activation of cognitive cerebellar areas (VI and Crus I-II) vs controls. During fMRI dual-task, PD-PIGD patients showed increased activity of cognitive areas (Crus II) and reduced activity of motor areas (I-IV). Cerebellar structural alterations correlated with increased fMRI activity of cerebellar cognitive areas and with lower executive-attentive performance. The increased activity of Crus I during the motor-task correlated with a better motor performance in PD-PIGD. Moreover, the increased activity of cerebellum correlated with a reduced activity of putamen.

CONCLUSIONS

In PD-PIGD, the increased activity of non-motor cerebellar areas during gait-simulating tasks may be a consequence of grey matter atrophy or an attempt to compensate the functional failure of cerebellar motor areas and basal ganglia. Cerebellar MRI metrics are useful to characterize brain correlates of motor and dual-task abilities in PD-PIGD patients.

White and gray matter alterations in de novo PD patients: which matter most?

OBJECTIVES

This paper aimed to identify white matter (WM) and gray matter (GM) abnormalities in a sample of early PD patients, and their correlations with motor and non-motor symptom severity.

METHODS

We enrolled 62 de novo PD patients and 31 healthy subjects. Disease severity and non-motor symptom burden were assessed by the Unified Parkinson's Disease Rating Scale part III and the Non-Motor Symptoms Scale, respectively. Cognitive performance was assessed using Montreal Cognitive Assessment and Frontal Assessment Battery. All subjects underwent a 3-Tesla MRI protocol. MRI analyses included tract-based spatial statistics, cortical thickness, and subcortical and cerebellar volumetry.

RESULTS

In comparison to control subjects, PD patients exhibited lower fractional anisotropy and higher mean, axial, and radial diffusivity in most WM bundles, including corticospinal tracts, the internal and external capsule, the anterior and posterior thalamic radiations, the genu and body of the corpus callosum, cerebellar peduncles, and superior and inferior longitudinal and fronto-occipital fasciculi. Correlations between Montreal Cognitive Assessment scores and fractional anisotropy values in the right posterior thalamic radiation, left superior corona radiata, right inferior-fronto-occipital fasciculus, left inferior longitudinal fasciculus, bilateral anterior thalamic radiations, and bilateral superior longitudinal fasciculi were found. Smaller cerebellar volumes in early PD patients in the left and right crus I were also found. No GM changes were present in subcortical or cortical regions.

CONCLUSION

The combined evaluation of WM and GM in the same patient sample demonstrates that WM microstructural abnormalities precede GM structural changes in early PD patients.

Proteomic alterations in the cerebellum and hippocampus in an Alzheimer's disease mouse model: Alleviating effect of palmatine

Alzheimer's disease (AD) is one of the most prevalent diseases that lead to memory deficiencies, severe behavioral abnormalities, and ultimately death. The need for more appropriate treatment of AD continues, and remains a sought-after goal. Previous studies showed palmatine (PAL), an isoquinoline alkaloid, might have the potential for combating AD because of its in vitro and in vivo activities. In this study, we aimed to assess PAL's therapeutic potential and gain insights into the working mechanism on protein level in the AD mouse model brain, for the first time. To this end, PAL was administered to 12-month-old 5xFAD mice at two doses after its successful isolation from the Siberian barberry shrub. PAL (10 mg/kg) showed statistically significant improvement in the memory and learning phase on the Morris water maze test. The PAL's ability to pass through the blood-brain barrier was verified via Multiple Reaction Monitoring (MRM). Label-free proteomics analysis revealed PAL administration led to changes most prominently in the cerebellum, followed by the hippocampus, but none in the cortex. Most of the differentially expressed proteins in PAL compared to the 5xFAD control group (ALZ) were the opposite of those in ALZ in comparison to healthy Alzheimer's littermates (ALM) group. HS105, HS12A, and RL12 were detected as hub proteins in the cerebellum. Collectively, here we present PAL as a potential therapeutic candidate owing to its alleviating effect in 5xFAD mice on not only cognitive impairment but also proteomes in the cerebellum and hippocampus.

Cerebellar impulsivity-compulsivity assessment scale

OBJECTIVE

The cerebellum has been identified as the key brain region that modulates reward processing in animal models. Consistently, we recently found that people with cerebellar ataxia have impulsive and compulsive behaviors (ICBs), the main symptoms related to abnormal reward processing. Due to the lack of a validated scale to quantitatively measure ICBs in cerebellar disorders, we aim to develop and validate a new scale, Cerebellar Impulsivity-Compulsivity Assessment (CIA).

METHODS

We recruited 62 cerebellar ataxia cases, categorized into those with ICBs and those without. We developed a preliminary version of CIA, containing 17 questions. We studied the internal consistency, test-retest reliability, and inter-rater reliability to formulate the final version of CIA, which constitutes only 10 questions. The receiver operating characteristic curve (ROC) was generated to assess the sensitivity and specificity of CIA.

RESULTS

Cerebellar ataxia cases with ICBs have threefold higher total preliminary CIA scores than those without ICBs (12.06 ± 5.96 vs. 4.68 ± 3.50, p = 0.038). Cronbach's alpha revealed good internal consistency across all items (α > 0.70). By performing the test-retest reliability and inter-rater reliability on the preliminary version of CIA, we excluded seven questions (r < 0.70) and generated the final version of CIA. Based on the ROC, a score of 8.0 in CIA was chosen as the cut-off for ICBs in individuals with cerebellar ataxia with 81% sensitivity and 81% specificity.

INTERPRETATION

CIA is a novel tool to assess ICBs in cerebellar ataxia and broaden our understanding of the cerebellum-related cognitive and behavioral symptoms.

Treadmill training in Parkinson's disease is underpinned by the interregional connectivity in cortical-subcortical network

Treadmill training (TT) has been extensively used as an intervention to improve gait and mobility in patients with Parkinson's disease (PD). Regional and global effects on brain activity could be induced through TT. Training effects can lead to a beneficial shift of interregional connectivity towards a physiological range. The current work investigates the effects of TT on brain activity and connectivity during walking and at rest by using both functional near-infrared spectroscopy and functional magnetic resonance imaging. Nineteen PD patients (74.0 ± 6.59 years, 13 males, disease duration 10.45 ± 6.83 years) before and after 6 weeks of TT, along with 19 age-matched healthy controls were assessed. Interregional effective connectivity (EC) between cortical and subcortical regions were assessed and its interrelation to prefrontal cortex (PFC) activity. Support vector regression (SVR) on the resting-state ECs was used to predict prefrontal connectivity. In response to TT, EC analysis indicated modifications in the patients with PD towards the level of healthy controls during walking and at rest. SVR revealed cerebellum related connectivity patterns that were associated with the training effect on PFC. These findings suggest that the potential therapeutic effect of training on brain activity may be facilitated via changes in compensatory modulation of the cerebellar interregional connectivity.

Potential Interactions Between Cerebellar Dysfunction and Sleep Disturbances in Dystonia

Dystonia is the third most common movement disorder. It causes debilitating twisting postures that are accompanied by repetitive and sometimes intermittent co- or over-contractions of agonist and antagonist muscles. Historically diagnosed as a basal ganglia disorder, dystonia is increasingly considered a network disorder involving various brain regions including the cerebellum. In certain etiologies of dystonia, aberrant motor activity is generated in the cerebellum and the abnormal signals then propagate through a “dystonia circuit” that includes the thalamus, basal ganglia, and cerebral cortex. Importantly, it has been reported that non-motor defects can accompany the motor symptoms; while their severity is not always correlated, it is hypothesized that common pathways may nevertheless be disrupted. In particular, circadian dysfunction and disordered sleep are common non-motor patient complaints in dystonia. Given recent evidence suggesting that the cerebellum contains a circadian oscillator, displays sleep-stage-specific neuronal activity, and sends robust long-range projections to several subcortical regions involved in circadian rhythm regulation, disordered sleep in dystonia may result from cerebellum-mediated dysfunction of the dystonia circuit. Here, we review the evidence linking dystonia, cerebellar network dysfunction, and cerebellar involvement in sleep. Together, these ideas may form the basis for the development of improved pharmacological and surgical interventions that could take advantage of cerebellar circuitry to restore normal motor function as well as non-motor (sleep) behaviors in dystonia.

Recent Investigations on the Functional Role of Cerebellar Neural Networks in Motor Functions & Nonmotor Functions -Neurodegeneration

The cerebellum is a well-established primary brain center in charge of controlling sensorimotor functions and non-motor functions. Recent reports depicted the significance of cerebellum in higher-order cognitive functions, including emotion-processing, language, reward-related behavior, working memory, and social behavior. As it can influence diverse behavioral patterns, any defects in cerebellar functions could invoke neuropsychiatric diseases as indicated by the incidence of alexithymia and induce alterations in emotional and behavioral patterns. Furthermore, its defects can trigger motor diseases, such as ataxia and Parkinson's disease (PD). In this review, we have extensively discussed the role of cerebellum in motor and non-motor functions and how the cerebellum malfunctions in relation to the neural circuit wiring as it could impact brain function and behavioral outcomes in patients with neuropsychiatric diseases. Relevant data regarding cerebellar non-motor functions have been vividly described, along with anatomy and physiology of these functions. In addition to the defects in basal ganglia, the lack of activity in motor related regions of the cerebellum could be associated with the severity of motor symptoms. All together, this review delineates the importance of cerebellar involvement in patients with PD and unravels a crucial link for various clinical aspects of PD with specific cerebellar sub-regions.

Using Real-Time fMRI Neurofeedback to Modulate M1-Cerebellum Connectivity

Objective

The potential of neurofeedback to alter the M1-cerebellum connectivity was explored using motor imagery-based rt-fMRI. These regions were chosen due to their importance in motor performance and motor rehabilitation.

Methods

Four right-handed individuals were recruited to examine the potential to change the M1-cerebellum neurofeedback link. The University of Glasgow Cognitive Neuroimaging Centre used a 3T MRI scanner from January 2019 to January 2020 to conduct this prospective study. Everyone participated in each fMRI session, which included six NF training runs. Participants were instructed to imagine complicated hand motions during the NF training to raise a thermometer bar's height. To contrast the correlation coefficients between the initial and last NF runs, a t-test was performed post hoc.

Results

The neurofeedback connection between M1 and the cerebellum was strengthened in each participant. Motor imagery strategy was a significant task in training M1-cerebellum connectivity as participants used it successfully to enhance the activation level between these regions during M1-cerebellum modulation using real-time fMRI. The t-test and linear regression, on the other hand, showed this increase to be insignificant.

Conclusion

A novel technique to manipulate M1-cerebellum connectivity was discovered using real-time fMRI NF. This study showed that each participant's neurofeedback connectivity between M1 and cerebellum was enhanced. This increase, on the other hand, was insignificant statistically. The results showed that the connectivity between both areas increased positively. Through the integration of fMRI and neurofeedback, M1-cerebellum connectivity can be positively affected.

Identifying the white matter structural network of motor reserve in early Parkinson's disease

INTRODUCTION

Motor reserve refers to the individual capacity to cope with nigrostriatal dopamine depletion in Parkinson's disease (PD). This study aimed to explore the white matter structural network associated with motor reserve in patients with newly diagnosed PD.

METHODS

A total of 238 patients with early-stage drug-naïve PD who underwent ¹⁸F-FP-CIT PET and brain MRI scans at initial assessment were enrolled. We estimated individual motor reserve based on the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) scores and dopamine transporter availability in the posterior putamen using a residual model. Then, we performed threshold-free network-based statistics (TFNBS) analysis to identify the structural brain network associated with the estimated motor reserve. We also assessed the effect of the network connectivity strength on the longitudinal increase in levodopa-equivalent dose (LED).

RESULTS

The mean age at PD symptom onset was 69.10 ± 9.03 years and the mean UPDRS-III score at the time of PD diagnosis was 22.44 ± 9.72. TFNBS analysis identified a motor reserve-associated structural network whose nodes were mainly in the frontal region and cerebellum. Higher network strength (i.e., greater motor reserve) was associated with a slower longitudinal increase in LED during a 3-year follow-up period.

CONCLUSION

The structural brain network is associated with motor reserve in patients with PD. Connectivity strength within the identified network indicates the individual's capacity to tolerate PD-related pathologies, which is maintained with disease progression and affects the long-term motor prognosis of PD.

Action and emotion perception in Parkinson's disease: A neuroimaging meta-analysis

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The neural substrates for action and emotion perception deficits in PD are still unclear.

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We addressed this issue via coordinate-based meta-analyses of previous fMRI data.

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PD patients exhibit decreased response in the basal ganglia.

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PD patients exhibit a trend toward decreased response in the parietal areas.

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PD patients exhibit a trend toward increased activation in the posterior cerebellum.

Patients with Parkinson disease (PD) may show impairments in the social perception. Whether these deficits have been consistently reported, it remains to be clarified which brain alterations subtend them. To this aim, we conducted a neuroimaging meta-analysis to compare the brain activity during social perception in patients with PD versus healthy controls. Our results show that PD patients exhibit a significantly decreased response in the basal ganglia (putamen and pallidum) and a trend toward decreased activity in the mirror system, particularly in the left parietal cortex (inferior parietal lobule and intraparietal sulcus). This reduced activation may be tied to a disruption of cognitive resonance mechanisms and may thus constitute the basis of impaired others’ representations underlying action and emotion perception. We also found increased activation in the posterior cerebellum in PD, although only in a within-group analysis and not in comparison with healthy controls. This cerebellar activation may reflect compensatory mechanisms, an aspect that deserves further investigation. We discuss the clinical implications of our findings for the development of novel social skill training programs for PD patients.

Frontoparietal network resilience is associated with protection against cognitive decline in Parkinson's disease

Though Parkinson's disease is primarily defined as a movement disorder, it is also characterized by a range of non-motor symptoms, including cognitive decline. The onset and progression of cognitive decline in individuals with Parkinson's disease is variable, and the neurobiological mechanisms that contribute to, or protect against, cognitive decline in Parkinson's disease are poorly understood. Using resting-state functional magnetic resonance imaging data collected from individuals with Parkinson's disease with and without cognitive decline, we examined the relationship between topological brain-network resilience and cognition in Parkinson's disease. By leveraging network attack analyses, we demonstrate that relative to individuals with Parkinson's disease experiencing cognitive decline, the frontoparietal network in cognitively stable individuals with Parkinson's disease is significantly more resilient to network perturbation. Our findings suggest that the topological robustness of the frontoparietal network is associated with the absence of cognitive decline in individuals with Parkinson's disease.

Altered Cerebellar Resting-State Functional Connectivity in Early-Stage Parkinson's Disease Patients With Cognitive Impairment

Background: Cognitive impairment is one of the most prominent non-motor symptoms in Parkinson's disease (PD), due in part to known cerebellar dysfunctions. Furthermore, previous studies have reported altered cerebellar functional connectivity (FC) in PD patients. Yet whether these changes are also due to the cognitive deficits in PD remain unclear. Methods: A total of 122 non-dementia participants, including 64 patients with early PD and 58 age- and gender-matched elderly controls were stratified into four groups based on their cognitive status (normal cognition vs. cognitive impairment). Cerebellar volumetry and FC were investigated by analyzing, respectively, structural and resting-state functional MRI data among groups using quality control and quantitative measures. Correlation analysis between MRI metrics and clinical features (motor and cognitive scores) were performed. Results: Compared to healthy control subjects with no cognitive deficits, altered cerebellar FC were observed in early PD participants with both motor and cognitive deficits, but not in PD patients with normal cognition, nor elderly subjects showing signs of a cognitive impairment. Moreover, connectivity between the "motor" cerebellum and SMA was positively correlated with motor scores, while intracerebellar connectivity was positively correlated with cognitive scores in PD patients with cognitive impairment. No cerebellar volumetric difference was observed between groups. Conclusions: These findings show that altered cerebellar FC during resting state in early PD patients may be driven not solely by the motor deficits, but by cognitive deficits as well, hence highlighting the interplay between motor and cognitive functioning, and possibly reflecting compensatory mechanisms, in the early PD.

Altered Cerebellum Spontaneous Activity in Juvenile Autism Spectrum Disorders Associated with Clinical Traits

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. The associations between the cerebellum and clinical traits remain unclear. We performed amplitude of low-frequency fluctuation (ALFF) analysis to explore the associations between spontaneous brain activity and clinical traits. 361 juvenile ASD patients were included from the ABIDEII database. In the ASD group, the mean ALFF values of cerebellum 4 5 were correlated with SRS awareness and communication. The mean ALFF values of cerebellum 6 and vermis 4 5 were both positively correlated with SRS total, awareness, communication, and motivation. In contrast, the mean ALFF values of vermis 1 2 were negatively correlated with SRS total, awareness, and mannerisms. Our study suggests a role of the cerebellum in functional impairments in ASD.

Longitudinal changes in movement-related functional MRI activity in Parkinson's disease patients

INTRODUCTION

Functional brain imaging has shown alterations in the basal ganglia, cortex and cerebellum in Parkinson's disease patients. However, few functional imaging studies have tested how these changes evolve over time. Our study aimed to test the longitudinal progression of movement-related functional activity in Parkinson's disease patients.

METHODS

At baseline, 48 Parkinson's disease patients and 16 healthy controls underwent structural and functional magnetic resonance imaging during a joystick motor task. Patients had repeated imaging after 18-months (n = 42) and 36-months (n = 32). T-tests compared functional responses between Parkinson's disease patients and controls, and linear mixed effects models examined longitudinal differences within Parkinson's disease. Correlations of motor-activity with bradykinesia, rigidity and tremor were undertaken. All contrasts used whole-brain analyses, thresholded at Z > 3.1 with a cluster-wise P < 0.05.

RESULTS

Baseline activation was significantly greater in patients than controls across contralateral parietal and occipital regions, ipsilateral precentral gyrus and thalamus. Longitudinally, patients showed significant increases in cerebellar activity at successive visits following baseline. Task-related activity also increased in the contralateral motor, parietal and temporal areas at 36 months compared to baseline, however this was reduced when controlling for motor task performance.

CONCLUSION

We have shown that there are changes over time in the blood-activation level dependent response of patients with Parkinson's disease undertaking a simple motor task. These changes are observed primarily in the ipsilateral cerebellum and may be compensatory in nature.

Distinct neural circuits are associated with subclinical neuropsychiatric symptoms in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) can present with neuropsychiatric symptoms (here, anxiety, depression, and apathy) at any stage of the disease. We investigated the neural correlates of subclinical neuropsychiatric symptoms in relation to motor and cognitive symptoms in a high-functioning PD cohort.

METHODS

Brain morphometry of the cognitively intact, early-stage (Hoehn & Yahr 2) PD group (n = 48) was compared to matched controls (n = 37). Whole-brain, pairwise, resting-state functional connectivity measures were correlated with neuropsychiatric symptom, motor exam, and global cognitive scores of the PD group.

RESULTS

Factor analysis of highly collinear anxiety, depression, and apathy scores revealed a single principal component (i.e., composite neuropsychiatric symptom score) explaining 71.6% of variance. There was no collinearity between the neuropsychiatric, motor, and cognitive scores. Compared to controls, PD group showed only subcortical changes including amygdala and nucleus accumbens atrophy, and greater pallidal volume. Reduced functional connectivity in the limbic cortical-striatal circuits and increased functional connectivity between the cerebellum and occipito-temporal regions were associated with a more impaired neuropsychiatric profile. This functional connectivity pattern was distinct from those associated with motor deficits and global cognitive functioning. The individual components of the neuropsychiatric symptoms also exhibited unique connectivity patterns.

LIMITATIONS

Patients were scanned in "on-medication" state only and a control group with similar neuropsychiatric symptoms was not included.

CONCLUSION

Abnormal functional connectivity of distinct neural circuits is present even at the subclinical stage of neuropsychiatric symptoms in PD. Neuropsychiatric phenotyping is important and may facilitate early interventions to "reorganize" these circuits and delay/prevent clinical symptom onset.