Functional changes of the basal ganglia circuitry in Parkinson's disease

Neuronal plasticity and its role in Alzheimer's disease and Parkinson's disease

Neuronal plasticity, the brain's ability to adapt structurally and functionally, is essential for learning, memory, and recovery from injuries. In neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, this plasticity is disrupted, leading to cognitive and motor deficits. This review explores the mechanisms of neuronal plasticity and its effect on Alzheimer's disease and Parkinson's disease. Alzheimer's disease features amyloid-beta plaques and tau tangles that impair synaptic function, while Parkinson's disease involves the loss of dopaminergic neurons affecting motor control. Enhancing neuronal plasticity offers therapeutic potential for these diseases. A systematic literature review was conducted using databases such as PubMed, Scopus, and Google Scholar, focusing on studies of neuronal plasticity in Alzheimer's disease and Parkinson's disease. Data synthesis identified key themes such as synaptic mechanisms, neurogenesis, and therapeutic strategies, linking molecular insights to clinical applications. Results highlight that targeting synaptic plasticity mechanisms, such as long-term potentiation and long-term depression, shows promise. Neurotrophic factors, advanced imaging techniques, and molecular tools (e.g., clustered regularly interspaced short palindromic repeats and optogenetics) are crucial in understanding and enhancing plasticity. Current therapies, including dopamine replacement, deep brain stimulation, and lifestyle interventions, demonstrate the potential to alleviate symptoms and improve outcomes. In conclusion, enhancing neuronal plasticity through targeted therapies holds significant promise for treating neurodegenerative diseases. Future research should integrate multidisciplinary approaches to fully harness the therapeutic potential of neuronal plasticity in Alzheimer's disease and Parkinson's disease.

Lasting Impact: Exploring the Brain Mechanisms that Link Traumatic Brain Injury to Parkinson's Disease

Development of Parkinson's Disease (PD) is linked with a history of traumatic brain injury (TBI), although the mechanisms driving this remain unclear. Of note, many key parallels have been identified between the pathologies of PD and TBI; in particular, PD is characterised by loss of dopaminergic neurons from the substantia nigra (SN), accompanied by broader changes to dopaminergic signalling, disruption of the Locus Coeruleus (LC) and noradrenergic system, and accumulation of aggregated α-synuclein in Lewy Bodies, which spreads in a stereotypical pattern throughout the brain. Widespread disruptions to the dopaminergic and noradrenergic systems, including progressive neuronal loss from the SN and LC, have been observed acutely following injury, some of which have also been identified chronically in TBI patients and preclinical models. Furthermore, changes to α-synuclein expression are also seen both acutely and chronically following injury throughout the brain, although detailed characterisation of these changes and spread of pathology is limited. In this review, we detail the current literature regarding dopaminergic and noradrenergic disruption and α-synuclein pathology following injury, with particular focus on how these changes may predispose individuals to prolonged pathology and progressive neurodegeneration, particularly the development of PD. While it is increasingly clear that TBI is a key risk factor for the development of PD, significant gaps remain in current understanding of neurodegenerative pathology following TBI, particularly chronic manifestations of injury.

Impact of Physical Activity Levels on Parkinson's Disease Motor and Nonmotor Symptoms and Quality of Life in Older Adults With Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) affects motor and nonmotor functions, impacting PD-related quality of life. The role of physical activity (PA) in the management of PD symptoms is increasingly recognized.

PURPOSE

To examine the effects of PA levels on PD motor and nonmotor symptoms, and health-related quality of life, using the Fox Insight study's data set. It also examines PA's moderating effects on the age-PD motor function relationship.

METHODS

In this cross-sectional observational study, 1,288 participants with PD (55.8% men, age: 64.54 ± 9.99) from the Fox Insight study were divided into four groups (N = 322 each) based on their PA level as measured by the Physical Activity Scale for the Elderly (PASE). PD motor and nonmotor symptoms were assessed using the Unified Parkinson's Disease Rating Scale-2 (UPDRS-2), Parkinson's Disease Questionnaire-8 (PDQ-8), Geriatric Depression Scale-Short Form, Penn Parkinson's Daily Activities Questionnaire-15, and EuroQol-Visual Analog Scale. Statistical analyses included Kruskal-Wallis, Pearson's correlation, and multiple linear regression, with alpha set at .05.

RESULTS

Higher PASE correlated with better UPDRS-2, Parkinson's Disease Questionnaire-8, Geriatric Depression Scale-Short Form, Penn Parkinson's Daily Activities Questionnaire-15, and EuroQol-Visual Analog Scale. The study found significant influences of PASE on UPDRS-2, age, Geriatric Depression Scale-Short Form, body mass index, and EQ-VAS (R2adj = .174, F = 53.998, p < .001). Notably, PASE moderated the relationship between age and UPDRS-2, suggesting a pivoting role in slowing PD-related symptom progression with age (R2adj = .145, F = 73.47, p < .001).

CONCLUSION

Increased PA levels are associated with better outcomes in PD motor and nonmotor symptoms, improved PD-related quality of life, and a slowed progression of PD symptoms.

IMPLICATIONS

Promoting higher levels of PA in older adults with PD effectively manages motor and nonmotor symptoms of PD. In addition, early and consistent PA is the key to moderating the progression of PD symptoms.

EAAT2 Activation Regulates Glutamate Excitotoxicity and Reduces Impulsivity in a Rodent Model of Parkinson's Disease

Parkinson's disease (PD) is a systemic disease characterized by motor and nonmotor impairments. Loss of dopaminergic neurons in the substantia nigra pars compacta region in PD disrupts dopamine-glutamate homeostasis in the corticostriatal circuit, contributing to cognitive impairment. In addition, excitatory amino acid transporter-2 (EAAT2), localized predominantly to astrocytes and responsible for > 80% of synaptic glutamate clearance, is downregulated in PD, causing glutamate spillover and excitotoxicity. This altered dopamine-glutamate homeostasis and excitotoxicity may affect reward-mediated decision-making behaviors and promote impulsive behaviors in PD. In this study, we hypothesized that GTS467, a small-molecule activator of EAAT2, could effectively reduce excitotoxicity and treat cognitive impairment without promoting impulsive behavior in PD. Rats that were unilaterally lesioned with the 6-OHDA toxin to produce Parkinsonian symptoms were referred to as lesioned rats. Lesioned rats were trained to meet baseline criteria in a 5-choice serial reaction time task, and the chronic effects of GTS467 were assessed after 3 weeks of treatment. The results showed that chronic treatment with GTS467 significantly improved correct responses and reduced premature impulsive responses and omissions compared with saline treatment. This improvement in performance correlated with a reduction in glutamate levels, an increase in EAAT2 expression, and normalization of NMDA receptor subunit expression and signaling. Furthermore, transcriptomic studies on the prefrontal cortex tissue have shown the differential expression of genes involved in neuroprotection, neuroinflammation, learning, and memory. These results validate the role of glutamate excitotoxicity in promoting impulsive behaviors and suggest that GTS467 can be developed as a therapeutic agent to reduce cognitive impairment and impulsive behaviors in PD.

Neurological Soft Signs at Presentation in Patients With Pediatric Acute-Onset Neuropsychiatric Syndrome

Importance

Studies of brain imaging and movements during rapid eye movement sleep indicate basal ganglia involvement in pediatric acute-onset neuropsychiatric syndrome (PANS). Characterizing neurological findings that commonly present among patients with PANS could improve diagnostic accuracy.

Objectives

To evaluate the prevalence of neurological soft signs (NSSs) that may be associated with basal ganglia dysfunction among youths presenting with PANS and assess whether clinical characteristics of PANS correlate with NSSs that may be associated with basal ganglia dysfunction.

Design, Setting, and Participants

This cohort study included 135 new patients who met strict PANS criteria and were evaluated at the Stanford Children's Immune Behavioral Health Clinic between November 1, 2014, and March 1, 2020. Data on these patients were retrospectively reviewed between December 13, 2020, and September 25, 2023. Sixteen patients were excluded because they had no neurological examination within the first 3 visits and within 3 months of clinical presentation. Statistical analysis was conducted between September 26, 2023, and November 22, 2024.

Main Outcomes and Measures

The following NSSs that may be associated with basal ganglia dysfunction were recorded from medical record review: (1) glabellar tap reflex, (2) tongue movements, (3) milkmaid's grip, (4) choreiform movements, (5) spooning, and (6) overflow movements. Data from prospectively collected symptoms and impairment scales (Global Impairment Score [GIS; score range, 1-100, with higher scores indicating greater impairment] and Caregiver Burden Inventory [score range, 0-96, with higher scores indicating greater caregiver burden]) were included.

Results

The study included 119 patients; the mean (SD) age at PANS onset was 8.2 (3.6) years, the mean (SD) age at initial presentation was 10.4 (3.6) years, and 66 (55.5%) were boys. At least 1 NSS that may be associated with basal ganglia dysfunction was observed in 95 patients (79.8%); the mean (SD) number of NSSs was 2.1 (1.6). Patients with 4 or more NSSs had higher GISs (mean [SD] score, 56.0 [22.6] vs 40.6 [26.7]; P = .05) and more symptoms (mean [SD] number, 15.1 [4.9] vs 11.5 [4.2]; P = .008) than patients with 0 NSSs. There was no significant difference in age at visit or in Caregiver Burden Inventory score. On Poisson and linear regression, the number of NSSs was associated with global impairment, with 1 more sign increasing the GIS by 2.86 (95% CI, 0.09-5.62; P = .04), and with the number of symptoms, with 1 more sign increasing the number of symptoms by 5% (1.05; 95% CI, 1.02-1.08; P = .002), but not with age or duration of PANS at presentation.

Conclusions and Relevance

This cohort study of patients with PANS found a high prevalence of NSSs that may be associated with basal ganglia dysfunction and an association between these NSSs and disease severity that was not associated with younger age. PANS may have a unique profile, suggesting that targeted neurological examinations may support PANS diagnosis.

Variation in brain aging: A review and perspective on the utility of individualized approaches to the study of functional networks in aging

Healthy aging is associated with cognitive decline across multiple domains, including executive function, memory, and attention. These cognitive changes can often influence an individual's ability to function and quality of life. However, the degree to which individuals experience cognitive decline, as well as the trajectory of these changes, exhibits wide variability across people. These cognitive abilities are thought to depend on the coordinated activity of large-scale networks. Like behavioral effects, large variation can be seen in brain structure and function with aging, including in large-scale functional networks. However, tracking this variation requires methods that reliably measure individual brain networks and their changes over time. Here, we review the literature on age-related cognitive decline and on age-related differences in brain structure and function. We focus particularly on functional networks and the individual variation that exists in these measures. We propose that novel individual-centered fMRI approaches can shed new light on patterns of inter- and intra-individual variability in aging. These approaches may be instrumental in understanding the neural bases of cognitive decline.

Review on computational methods for the detection and classification of Parkinson's Disease

BACKGROUND AND OBJECTIVE

The worldwide estimates reveal two-fold increase in incidence of Parkinson's disease (PD) over 25 years. The two-fold increased incidence and lack of proper treatment uplifted a compelling solicitude, nagging towards accurate diagnosis. The present study aims at systematic survey on recent methodologies to light up the panorama of PD through various imaging modalities.

METHODS AND MATERIALS

Centring on imaging modalities of PD detection, this study range over on PD biomarkers such as anatomical and neurotransmitter alterations, serum and genetic delving into features and diagnostic techniques. Reviewed various Machine learning and deep learning models employed for PD detection and their performance offered. Presented a deep focus on existing datasets for PD diagnosis and their limited applicability and the directions needed to extend their applicability. This study also highlights the need of discriminative feature set for proper PD diagnosis and highlights the deep insight into existing machine and deep learning models along with their potential limitations and future directions.

RESULTS

The review highlights that most of the algorithms incorporate some form of machine learning or deep learning to facilitate automated diagnosis of Parkinson's disease (PD). Also highlighted that most methodologies are experimented on T1 weighted MRI data and highlighted they are easily available and less complex in nature.

CONCLUSIONS

In conclusion deep learning models yields promising results on accurate diagnosis of PD and highlights the need of refining the existing methods to handle the challenges in enhancing diagnostic accuracy.

Emergent Aspects of the Integration of Sensory and Motor Functions

This article delves into the intricate mechanisms underlying sensory integration in the executive control of movement, encompassing ideomotor activity, predictive capabilities, and motor control systems. It examines the interplay between motor and sensory functions, highlighting the role of the cortical and subcortical regions of the central nervous system in enhancing environmental interaction. The acquisition of motor skills, procedural memory, and the representation of actions in the brain are discussed emphasizing the significance of mental imagery and training in motor function. The development of this aspect of sensorimotor integration control can help to advance our understanding of the interactions between executive motor control, cortical mechanisms, and consciousness. Bridging theoretical insights with practical applications, it sets the stage for future innovations in clinical rehabilitation, assistive technology, and education. The ongoing exploration of these domains promises to uncover new pathways for enhancing human capability and well-being.

Anti-Tetanus Vaccination Is Associated with Reduced Occurrence and Slower Progression of Parkinson's Disease-A Retrospective Study

Background: Parkinson's disease (PD) is a neurodegenerative disorder that progressively damages the autonomic and central nervous systems, leading to hallmark symptoms such as resting tremor, bradykinesia, and rigidity. Despite extensive research, the underlying cause of PD remains unclear, and current treatments are unable to halt the progression of the disease. In this retrospective study, based on historical electronic health records (EHR) from a national health provider covering the period from 2003 to 2023, we investigated the impact of vaccination and medication purchases on PD occurrence and severity. Methods: Using a case-control design, we compared the vaccination histories of 1446 PD patients with 7230 matched controls to assess the association between vaccination and PD onset. Additionally, we explored statistical associations between vaccination, medication purchases, and PD severity over an average of 9 years of follow-up, utilizing a machine learning algorithm to quantify disease severity based on annual antiparkinsonian medication purchases. Results: Our analysis revealed a significant reduction in PD occurrence following tetanus-diphtheria (Td) vaccination, with an adjusted odds ratio of 0.17 (95% CI [0.04, 0.70]) for PD onset within 5 years post-vaccination. Furthermore, a time-dependent relationship was identified between the duration since vaccination and both the rate of PD onset and disease progression. Notably, we observed that antimicrobial treatments significantly influenced disease severity, consistent with the antibiotic sensitivity profile of Clostridium tetani. Conclusions: These findings support the hypothesis that tetanus vaccination and/or C. tetani eradication may reduce PD occurrence and slow its progression, suggesting promising directions for future research in PD prevention and treatment.

The Interaction Between Nutraceuticals and Gut Microbiota: a Novel Therapeutic Approach to Prevent and Treatment Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons, leading to motor and non-motor symptoms. Emerging research has shed light on the role of gut microbiota in the pathogenesis and progression of PD. Nutraceuticals such as curcumin, berberine, phytoestrogens, polyphenols (e.g., resveratrol, EGCG, and fisetin), dietary fibers have been shown to influence gut microbiota composition and function, restoring microbial balance and enhancing the gut-brain axis. The mechanisms underlying these benefits involve microbial metabolite production, restoration of gut barrier integrity, and modulation of neuroinflammatory pathways. Additionally, probiotics and prebiotics have shown potential in promoting gut health, influencing the gut microbiome, and alleviating PD symptoms. They can enhance the gut's antioxidant capacity of the gut, reduce inflammation, and maintain immune homeostasis, contributing to a neuroprotective environment. This paper provides an overview of the current state of knowledge regarding the potential of nutraceuticals and gut microbiota modulation in the prevention and management of Parkinson's disease, emphasizing the need for further research and clinical trials to validate their effectiveness and safety. The findings suggest that a multifaceted approach involving nutraceuticals and gut microbiota may open new avenues for addressing the challenges of PD and improving the quality of life for affected individuals.

Malignant Catatonia in the Setting of Acute Methamphetamine and Cocaine Intoxication

BACKGROUND

Malignant catatonia is a potentially lethal neuropsychiatric syndrome characterized by psychomotor abnormalities and autonomic instability. Patients with this syndrome require immediate treatment. Various psychiatric conditions and nonpsychiatric medical problems can trigger malignant catatonia. Use of psychostimulant drugs, including methamphetamine and cocaine, has not been previously reported to precipitate malignant catatonia.

CASE SUMMARY

This case concerns a 35-year-old man hospitalized for psychosis due to methamphetamine and cocaine intoxication. He developed malignant catatonia the day after admission. He was treated with lorazepam for malignant catatonia, and his blood pressure was controlled with clonidine. Over 7 days, his condition resolved, and his mental status and vital signs returned to baseline. He was discharged to the community in stable condition and has returned to his baseline functional status. He remains free of catatonia and has maintained abstinence from methamphetamine and cocaine.

CONCLUSIONS

Acute intoxication with psychostimulant drugs is a possible trigger for malignant catatonia, and administration of high potency first-generation antipsychotics in this setting may increase the risk. Patients hospitalized for stimulant intoxication should be monitored for signs and symptoms of catatonia, and D 2 receptor antagonist medications should be used with caution in this population. Our case supports the potential role of altered dopamine and norepinephrine signaling in the pathogenesis of malignant catatonia. The patient provided written and verbal consent to publish the information in this case report.

Utilizing Entropy of Cadence to Optimize Cycling Rehabilitation in Individuals With Parkinson's Disease

BACKGROUND

Previous studies have established that increased Sample Entropy (SampEn) of cadence, a measure of non-linear variability, during dynamic cycling leads to greater improvements in motor function for individuals with Parkinson's disease (PD). However, there is significant variability in responses among individuals with PD due to symptoms and disease progression.

OBJECTIVES

The aim of this study was to develop and test a paradigm for adapting a cycling exercise intervention using SampEn of cadence and rider effort to improve motor function.

METHODS

Twenty-two participants were randomized into either patient-specific adaptive dynamic cycling (PSADC) or non-adaptive (NA) group. SampEn of cadence was calculated after each of the 12 sessions, and motor function was evaluated using the Kinesia test. Pearson's correlation coefficient was used to analyze the relationship between SampEn of cadence and motor function improvement. Multiple linear regression (MLR) was used to identify the strongest predictors of motor function improvement.

RESULTS

Pearson's correlation coefficient revealed a significant correlation between SampEn of cadence and motor function improvements (R2 = -.545, P = .009), suggesting that higher SampEn of cadence led to greater motor function improvement. MLR demonstrated that SampEn of cadence was the strongest predictor of motor function improvement (β = -8.923, t = -2.632, P = .018) over the BMI, Levodopa equivalent daily dose, and effort.

CONCLUSIONS

The findings show that PSADC paradigm promoted a greater improvement in motor function than NA dynamic cycling. These data will be used to develop a predictive model to optimize motor function improvement after cycling in individuals with PD.

When the interoceptive and conceptual clash: The case of oppositional phenomenal self-modelling in Tourette syndrome

Tourette syndrome (TS) has been associated with a rich set of symptoms that are said to be uncomfortable, unwilled, and effortful to manage. Furthermore, tics, the canonical characteristic of TS, are multifaceted, and their onset and maintenance is complex. A formal account that integrates these features of TS symptomatology within a plausible theoretical framework is currently absent from the field. In this paper, we assess the explanatory power of hierarchical generative modelling in accounting for TS symptomatology from the perspective of active inference. We propose a fourfold analysis of sensory, motor, and cognitive phenomena associated with TS. In Section 1, we characterise tics as a form of action aimed at sensory attenuation. In Section 2, we introduce the notion of epistemic ticcing and describe such behaviour as the search for evidence that there is an agent (i.e., self) at the heart of the generative hierarchy. In Section 3, we characterise both epistemic (sensation-free) and nonepistemic (sensational) tics as habitual behaviour. Finally, in Section 4, we propose that ticcing behaviour involves an inevitable conflict between distinguishable aspects of selfhood; namely, between the minimal phenomenal sense of self-which is putatively underwritten by interoceptive inference-and the explicit preferences that constitute the individual's conceptual sense of self. In sum, we aim to provide an empirically informed analysis of TS symptomatology under active inference, revealing a continuity between covert and overt features of the condition.

Overcoming challenges of clinical cell therapies for Parkinson's disease with photobiomodulation

Photobiomodulation (PBM) has emerged as a rapidly growing and innovative therapeutic method for various illnesses in recent years. Due to the irreversible nature of Parkinson's disease (PD), it has proven challenging to impede or postpone the progression of the disease. Despite research on pharmacological approaches to halt neuronal degeneration, the viability of these techniques has been called into doubt due to apprehensions over potential side effects and the ethical implications associated with the utilization of embryonic cell transplantation. Hence, developing an innovative therapeutic approach to halting neuronal degeneration and safeguarding neurons from this neurodegenerative disorder is imperative. This review examines the pathogenesis, challenges, and limitations of conventional PD therapies, allowing a closer examination of PBM's distinctive approach within this medical context. Delving into PBM's therapeutic mechanisms in the cells, the effects of different wavelengths on cell therapies in PD patients, and considerations for patient care administration to overcome traditional challenges, this study offers insights into its potential as a promising avenue for PD management.

Evaluating the Neuroprotective Potential of Novel Benzodioxole Derivatives in Parkinson's Disease via AMPA Receptor Modulation

Parkinson's disease (PD) is a significant health issue because it gradually damages the nervous system. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play a significant role in the development of PD. The current investigation employed hybrid benzodioxole-propanamide (BDZ-P) compounds to get information on AMPA receptors, analyze their biochemical and biophysical properties, and assess their neuroprotective effects. Examining the biophysical characteristics of all the subunits of the AMPA receptor offers insights into the impact of BDZ-P on the desensitization and deactivation rate. It demonstrates a partial improvement in the locomotor capacities in a mouse model of Parkinson's disease. In addition, the in vivo experiment assessed the locomotor activity by utilizing the open-field test. Our findings demonstrated that BDZ-P7 stands out with its remarkable potency, inhibiting the GluA2 subunit nearly 8-fold with an IC50 of 3.03 μM, GluA1/2 by 7.5-fold with an IC50 of 3.14 μM, GluA2/3 by nearly 7-fold with an IC50 of 3.19 μM, and GluA1 by 6.5-fold with an IC50 of 3.2 μM, significantly impacting the desensitization and deactivation rate of the AMPA receptor. BDZ-P7 showed an in vivo impact of partially reinstating locomotor abilities in a mouse model of PD. The results above suggest that the BDZ-P7 compounds show great promise as top contenders for the development of novel neuroprotective therapies.

Prevalence of Neurological Soft Signs at Presentation in Pediatric Acute-Onset Neuropsychiatric Syndrome

Importance

Studies of brain imaging and movements during REM sleep indicate basal ganglia involvement in pediatric acute-onset neuropsychiatric syndrome (PANS). Characterizing neurological findings commonly present in patients with PANS could improve diagnostic accuracy.

Objective

To determine the prevalence of neurological soft signs which may reflect basal ganglia dysfunction (NSS-BG) in youth presenting with PANS and whether clinical characteristics of PANS correlate with NSS-BG. Design, Setting, and Participants: 135 new patients who were evaluated at the Stanford Children's Immune Behavioral Health Clinic between November 1, 2014 and March 1, 2020 and met strict PANS criteria were retrospectively reviewed for study inclusion. 16 patients were excluded because they had no neurological exam within the first three visits and within three months of clinical presentation.

Main Outcomes and Measures

The following NSS-BG were recorded from medical record review: 1) glabellar tap reflex, 2) tongue movements, 3) milkmaid's grip, 4) choreiform movements, 5) spooning, and 6) overflow movements. We included data from prospectively collected symptoms and impairment scales.

Results

The study included 119 patients: mean age at PANS onset was 8.2 years, mean age at initial presentation was 10.4 years, 55.5% were male, and 73.9% were non-Hispanic White. At least one NSS-BG was observed in 95/119 patients (79.8%). Patients had 2.1 NSS-BG on average. Patients with 4 or more NSS-BG had higher scores of global impairment (p=0.052) and more symptoms (p=0.008) than patients with 0 NSS-BG. There was no significant difference in age at visit or reported caregiver burden. On Poisson and linear regression, the number of NSS-BG was associated with global impairment (2.857, 95% CI: 0.092-5.622, p=0.045) and the number of symptoms (1.049, 95% CI: 1.018-1.082, p=0.002), but not age or duration of PANS at presentation.

Conclusions and Relevance

We found a high prevalence of NSS-BG in patients with PANS and an association between NSS-BG and disease severity that is not attributable to younger age. PANS may have a unique NSS-BG profile, suggesting that targeted neurological exams may support PANS diagnosis.

Depressive Symptoms and the Subsequent Risk of Parkinson's Disease: A Nationwide Cohort Study

OBJECTIVE

Only a few studies have focused on depressive symptoms and Parkinson's disease (PD) risk. As a time lag exists from the onset of depressive symptoms to the diagnosis of depression, elucidating the association between depressive symptoms and PD development might be helpful for the early prediction of PD. We investigate the association between depressive symptoms and subsequent PD risk using nationwide population-based cohort database.

DESIGN AND SETTING

Cohort study using the Korean National Health Insurance Service data between 2007 and 2017, with longitudinal follow-up until 2019.

PARTICIPANTS

A total of 98,296 elderly people responded to a self-reported questionnaire from the National Health Screening Program on depressive symptoms.

MEASUREMENTS

The association between depressive symptoms such as 1) decreased activity or motivation, 2) worthlessness, and 3) hopelessness and PD risk was analyzed.

RESULTS

During median 5.06-year follow-up, 839 PD cases occurred: 230 in individuals with depressive symptoms and 609 in those without symptoms. Results showed an increased risk of PD development in those with depressive symptoms (HR = 1.47, 95% CI, 1.26-1.71), with dose-response association between the number of depressive symptoms and PD risk. Even in those already diagnosed with depression, combined depressive symptoms were linked to a higher risk compared to those without symptoms (with symptoms, HR = 2.71, 95% CI, 2.00-3.68; without symptoms, HR = 1.84, 95% CI, 1.43-2.36).

CONCLUSION

Individuals with depressive symptoms were at an increased risk of developing PD, and there was a dose-response association between the number of depressive symptoms and PD risk.

Fractal Analysis in Neurodegenerative Diseases

Neurodegenerative diseases are defined by progressive nervous system dysfunction and death of neurons. The abnormal conformation and assembly of proteins is suggested to be the most probable cause for many of these neurodegenerative disorders, leading to the accumulation of abnormally aggregated proteins, for example, amyloid β (Aβ) (Alzheimer's disease and vascular dementia), tau protein (Alzheimer's disease and frontotemporal lobar degeneration), α-synuclein (Parkinson's disease and Lewy body dementia), polyglutamine expansion diseases (Huntington disease), or prion proteins (Creutzfeldt-Jakob disease). An aberrant gain-of-function mechanism toward excessive intraparenchymal accumulation thus represents a common pathogenic denominator in all these proteinopathies. Moreover, depending upon the predominant brain area involvement, these different neurodegenerative diseases lead to either movement disorders or dementia syndromes, although the underlying mechanism(s) can sometimes be very similar, and on other occasions, clinically similar syndromes can have quite distinct pathologies. Non-Euclidean image analysis approaches such as fractal dimension (FD) analysis have been applied extensively in quantifying highly variable morphopathological patterns, as well as many other connected biological processes; however, their application to understand and link abnormal proteinaceous depositions to other clinical and pathological features composing these syndromes is yet to be clarified. Thus, this short review aims to present the most important applications of FD in investigating the clinical-pathological spectrum of neurodegenerative diseases.

Does Impaired Plantar Cutaneous Vibration Perception Contribute to Axial Motor Symptoms in Parkinson's Disease? Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation

OBJECTIVE

To investigate whether impaired plantar cutaneous vibration perception contributes to axial motor symptoms in Parkinson's disease (PD) and whether anti-parkinsonian medication and subthalamic nucleus deep brain stimulation (STN-DBS) show different effects.

METHODS

Three groups were evaluated: PD patients in the medication "on" state (PD-MED), PD patients in the medication "on" state and additionally "on" STN-DBS (PD-MED-DBS), as well as healthy subjects (HS) as reference. Motor performance was analyzed using a pressure distribution platform. Plantar cutaneous vibration perception thresholds (VPT) were investigated using a customized vibration exciter at 30 Hz.

RESULTS

Motor performance of PD-MED and PD-MED-DBS was characterized by greater postural sway, smaller limits of stability ranges, and slower gait due to shorter strides, fewer steps per minute, and broader stride widths compared to HS. Comparing patient groups, PD-MED-DBS showed better overall motor performance than PD-MED, particularly for the functional limits of stability and gait. VPTs were significantly higher for PD-MED compared to those of HS, which suggests impaired plantar cutaneous vibration perception in PD. However, PD-MED-DBS showed less impaired cutaneous vibration perception than PD-MED.

CONCLUSIONS

PD patients suffer from poor motor performance compared to healthy subjects. Anti-parkinsonian medication in tandem with STN-DBS seems to be superior for normalizing axial motor symptoms compared to medication alone. Plantar cutaneous vibration perception is impaired in PD patients, whereas anti-parkinsonian medication together with STN-DBS is superior for normalizing tactile cutaneous perception compared to medication alone. Consequently, based on our results and the findings of the literature, impaired plantar cutaneous vibration perception might contribute to axial motor symptoms in PD.

An adverse outcome pathway for chemical-induced Parkinson's disease: Calcium is key

Exposure to pesticides is associated with an increased risk of developing Parkinson's disease (PD). Currently, rodent-based risk assessment studies cannot adequately capture neurodegenerative effects of pesticides due to a lack of human-relevant endpoints targeted at neurodegeneration. Thus, there is a need for improvement of the risk assessment guidelines. Specifically, a mechanistic assessment strategy, based on human physiology and (patho)biology is needed, which can be applied in next generation risk assessment. The Adverse Outcome Pathway (AOP) framework is particularly well-suited to provide the mechanistic basis for such a strategy. Here, we conducted a semi-systematic review in Embase and MEDLINE, focused on neurodegeneration and pesticides, to develop an AOP network for parkinsonian motor symptoms. Articles were labelled and included/excluded using the online platform Sysrev. Only primary articles, written in English, focused on effects of pesticides or PD model compounds in models for the brain were included. A total of 66 articles, out of the 1700 screened, was included. PD symptoms are caused by loss of function and ultimately death of dopaminergic neurons in the substantia nigra (SN). Our literature review highlights that a unique feature of these cells that increases their vulnerability is their reliance on continuous low-level influx of calcium. As such, excess intracellular calcium was identified as a central early Key Event (KE). This KE can lead to death of dopaminergic neurons of the SN, and eventually parkinsonian motor symptoms, via four distinct pathways: 1) activation of calpains, 2) endoplasmic reticulum stress, 3) impairment of protein degradation, and 4) oxidative damage. Several receptors have been identified that may serve as molecular initiating events (MIEs) to trigger one or more of these pathways. The proposed AOP network provides the biological basis that can be used to develop a mechanistic testing strategy that captures neurodegenerative effects of pesticides.

Auditory attention measured by EEG in neurological populations: systematic review of literature and meta-analysis

Sensorimotor synchronization strategies have been frequently used for gait rehabilitation in different neurological populations. Despite these positive effects on gait, attentional processes required to dynamically attend to the auditory stimuli needs elaboration. Here, we investigate auditory attention in neurological populations compared to healthy controls quantified by EEG recordings. Literature was systematically searched in databases PubMed and Web of Science. Inclusion criteria were investigation of auditory attention quantified by EEG recordings in neurological populations in cross-sectional studies. In total, 35 studies were included, including participants with Parkinson's disease (PD), stroke, Traumatic Brain Injury (TBI), Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS). A meta-analysis was performed on P3 amplitude and latency separately to look at the differences between neurological populations and healthy controls in terms of P3 amplitude and latency. Overall, neurological populations showed impairments in auditory processing in terms of magnitude and delay compared to healthy controls. Consideration of individual auditory processes and thereafter selecting and/or designing the auditory structure during sensorimotor synchronization paradigms in neurological physical rehabilitation is recommended.

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.

Mechanisms and Functions of Activity-Regulated Cytoskeleton-Associated Protein in Synaptic Plasticity

Activity-regulated cytoskeleton-associated protein (Arc) is one of the most important regulators of cognitive functions in the brain regions. As a hub protein, Arc plays different roles in modulating synaptic plasticity. Arc supports the maintenance of long-term potentiation (LTP) by regulating actin cytoskeletal dynamics, while it guides the endocytosis of AMPAR in long-term depression (LTD). Moreover, Arc can self-assemble into capsids, leading to a new way of communicating among neurons. The transcription and translation of the immediate early gene Arc are rigorous procedures guided by numerous factors, and RNA polymerase II (Pol II) is considered to regulate the precise timing dynamics of gene expression. Since astrocytes can secrete brain-derived neurotrophic factor (BDNF) and L-lactate, their unique roles in Arc expression are emphasized. Here, we review the entire process of Arc expression and summarize the factors that can affect Arc expression and function, including noncoding RNAs, transcription factors, and posttranscriptional regulations. We also attempt to review the functional states and mechanisms of Arc in modulating synaptic plasticity. Furthermore, we discuss the recent progress in understanding the roles of Arc in the occurrence of major neurological disorders and provide new thoughts for future research on Arc.

The Dynamics of Dopamine D2 Receptor-Expressing Striatal Neurons and the Downstream Circuit Underlying L-Dopa-Induced Dyskinesia in Rats

L-dopa (l-3,4-dihydroxyphenylalanine)-induced dyskinesia (LID) is a debilitating complication of dopamine replacement therapy for Parkinson's disease. The potential contribution of striatal D2 receptor (D2R)-positive neurons and downstream circuits in the pathophysiology of LID remains unclear. In this study, we investigated the role of striatal D2R+ neurons and downstream globus pallidus externa (GPe) neurons in a rat model of LID. Intrastriatal administration of raclopride, a D2R antagonist, significantly inhibited dyskinetic behavior, while intrastriatal administration of pramipexole, a D2-like receptor agonist, yielded aggravation of dyskinesia in LID rats. Fiber photometry revealed the overinhibition of striatal D2R+ neurons and hyperactivity of downstream GPe neurons during the dyskinetic phase of LID rats. In contrast, the striatal D2R+ neurons showed intermittent synchronized overactivity in the decay phase of dyskinesia. Consistent with the above findings, optogenetic activation of striatal D2R+ neurons or their projections in the GPe was adequate to suppress most of the dyskinetic behaviors of LID rats. Our data demonstrate that the aberrant activity of striatal D2R+ neurons and downstream GPe neurons is a decisive mechanism mediating dyskinetic symptoms in LID rats.

The Spatiotemporal Dynamics of Facial Movements Reveals the Left Side of a Posed Smile

Humans can recombine thousands of different facial expressions. This variability is due to the ability to voluntarily or involuntarily modulate emotional expressions, which, in turn, depends on the existence of two anatomically separate pathways. The Voluntary (VP) and Involuntary (IP) pathways mediate the production of posed and spontaneous facial expressions, respectively, and might also affect the left and right sides of the face differently. This is a neglected aspect in the literature on emotion, where posed expressions instead of genuine expressions are often used as stimuli. Two experiments with different induction methods were specifically designed to investigate the unfolding of spontaneous and posed facial expressions of happiness along the facial vertical axis (left, right) with a high-definition 3-D optoelectronic system. The results showed that spontaneous expressions were distinguished from posed facial movements as revealed by reliable spatial and speed key kinematic patterns in both experiments. Moreover, VP activation produced a lateralization effect: compared with the felt smile, the posed smile involved an initial acceleration of the left corner of the mouth, while an early deceleration of the right corner occurred in the second phase of the movement, after the velocity peak.

Altered Thalamocortical Signaling in a Mouse Model of Parkinson's Disease

Activation of the primary motor cortex (M1) is important for the execution of skilled movements and motor learning, and its dysfunction contributes to the pathophysiology of Parkinson's disease (PD). A well-accepted idea in PD research, albeit not tested experimentally, is that the loss of midbrain dopamine leads to decreased activation of M1 by the motor thalamus. Here, we report that midbrain dopamine loss altered motor thalamus input in a laminar- and cell type-specific fashion and induced laminar-specific changes in intracortical synaptic transmission. Frequency-dependent changes in synaptic dynamics were also observed. Our results demonstrate that loss of midbrain dopaminergic neurons alters thalamocortical activation of M1 in both male and female mice, and provide novel insights into circuit mechanisms for motor cortex dysfunction in a mouse model of PD.SIGNIFICANCE STATEMENT Loss of midbrain dopamine neurons increases inhibition from the basal ganglia to the motor thalamus, suggesting that it may ultimately lead to reduced activation of primary motor cortex (M1). In contrast with this line of thinking, analysis of M1 activity in patients and animal models of Parkinson's disease report hyperactivation of this region. Our results are the first report that midbrain dopamine loss alters the input-output function of M1 through laminar and cell type specific effects. These findings support and expand on the idea that loss of midbrain dopamine reduces motor cortex activation and provide experimental evidence that reconciles reduced thalamocortical input with reports of altered activation of motor cortex in patients with Parkinson's disease.

The gut microbiota-brain axis in neurological disorder

The gut microbiota (GM) plays an important role in the physiology and pathology of the host. Microbiota communicate with different organs of the organism by synthesizing hormones and regulating body activity. The interaction of the central nervous system (CNS) and gut signaling pathways includes chemical, neural immune and endocrine routes. Alteration or dysbiosis in the gut microbiota leads to different gastrointestinal tract disorders that ultimately impact host physiology because of the abnormal microbial metabolites that stimulate and trigger different physiologic reactions in the host body. Intestinal dysbiosis leads to a change in the bidirectional relationship between the CNS and GM, which is linked to the pathogenesis of neurodevelopmental and neurological disorders. Increasing preclinical and clinical studies/evidence indicate that gut microbes are a possible susceptibility factor for the progression of neurological disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS) and autism spectrum disorder (ASD). In this review, we discuss the crucial connection between the gut microbiota and the central nervous system, the signaling pathways of multiple biological systems and the contribution of gut microbiota-related neurological disorders.

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.

Molecular and Epigenetic Aspects of Opioid Receptors in Drug Addiction and Pain Management in Sport

Opioids are substances derived from opium (natural opioids). In its raw state, opium is a gummy latex extracted from Papaver somniferum. The use of opioids and their negative health consequences among people who use drugs have been studied. Today, opioids are still the most commonly used and effective analgesic treatments for severe pain, but their use and abuse causes detrimental side effects for health, including addiction, thus impacting the user's quality of life and causing overdose. The mesocorticolimbic dopaminergic circuitry represents the brain circuit mediating both natural rewards and the rewarding aspects of nearly all drugs of abuse, including opioids. Hence, understanding how opioids affect the function of dopaminergic circuitry may be useful for better knowledge of the process and to develop effective therapeutic strategies in addiction. The aim of this review was to summarize the main features of opioids and opioid receptors and focus on the molecular and upcoming epigenetic mechanisms leading to opioid addiction. Since synthetic opioids can be effective for pain management, their ability to induce addiction in athletes, with the risk of incurring doping, is also discussed.

Anticipatory Postural Adjustments and Compensatory Postural Responses to Multidirectional Perturbations-Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Postural instability is one of the most restricting motor symptoms for patients with Parkinson's disease (PD). While medication therapy only shows minor effects, it is still unclear whether medication in conjunction with deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves postural stability. Hence, the aim of this study was to investigate whether PD patients treated with medication in conjunction with STN-DBS have superior postural control compared to patients treated with medication alone.

METHODS

Three study groups were tested: PD patients on medication (PD-MED), PD patients on medication and on STN-DBS (PD-MED-DBS), and healthy elderly subjects (HS) as a reference. Postural performance, including anticipatory postural adjustments (APA) prior to perturbation onset and compensatory postural responses (CPR) following multidirectional horizontal perturbations, was analyzed using force plate and electromyography data.

RESULTS

Regardless of the treatment condition, both patient groups showed inadequate APA and CPR with early and pronounced antagonistic muscle co-contractions compared to healthy elderly subjects. Comparing the treatment conditions, study group PD-MED-DBS only showed minor advantages over group PD-MED. In particular, group PD-MED-DBS showed faster postural reflexes and tended to have more physiological co-contraction ratios.

CONCLUSION

medication in conjunction with STN-DBS may have positive effects on the timing and amplitude of postural control.

Crosstalk between Oxidative Stress and Aging in Neurodegeneration Disorders

The world population is aging rapidly, and increasing lifespan exacerbates the burden of age-related health issues. On the other hand, premature aging has begun to be a problem, with increasing numbers of younger people suffering aging-related symptoms. Advanced aging is caused by a combination of factors: lifestyle, diet, external and internal factors, as well as oxidative stress (OS). Although OS is the most researched aging factor, it is also the least understood. OS is important not only in relation to aging but also due to its strong impact on neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Alzheimer's disease (AD), and Parkinson's disease (PD). In this review, we will discuss the aging process in relation to OS, the function of OS in neurodegenerative disorders, and prospective therapeutics capable of relieving neurodegenerative symptoms associated with the pro-oxidative condition.

Directional Deep Brain Stimulation-A Step in the Right Direction? A Systematic Review of the Clinical and Therapeutic Efficacy of Directional Deep Brain Stimulation in Parkinson Disease

BACKGROUND

The use of directional deep brain stimulation (dDBS) electrodes for the treatment of movement disorders such as Parkinson disease (PD) has become relatively widespread. However, the efficacy of dDBS relative to its omnidirectional deep brain stimulation (oDBS) counterpart is not well characterized. This systematic review aims to synthesize the literature comparing clinical and therapeutic outcomes of dDBS relative to oDBS in patients with PD.

METHODS

A systematic literature search for studies with comparative clinical outcome data between dDBS and oDBS was performed across the PubMed, Ovid MEDLINE, and Web of Science databases. Data including therapeutic window (TW) and surrogate measures and the Unified Parkinson's Disease Rating Scale score were collected and summarized across multiple time periods.

RESULTS

Ten studies met the eligibility criteria. Three of these studies evaluated motor performance in the form of Unified Parkinson's Disease Rating Scale III, with none finding differences between dDBS and oDBS. Two studies assessed quality-of-life measures with neither finding differences between dDBS and oDBS. TW or a surrogate measure was assessed in 6 studies; 5 studies found an increase or strong trend toward increase in dDBS relative to oDBS.

CONCLUSIONS

The current evidence, although limited by bias, does suggest that dDBS in the treatment of PD yields improvements in motor symptoms and quality of life that are comparable to oDBS; TW and surrogate measures are consistently improved in patients with PD under a directional configuration relative to omnidirectional.

Efficient suppression of parkinsonian beta oscillations in a closed-loop model of deep brain stimulation with amplitude modulation

Introduction

Parkinson's disease (PD) is a movement disorder characterized by the pathological beta band (15-30 Hz) neural oscillations within the basal ganglia (BG). It is shown that the suppression of abnormal beta oscillations is correlated with the improvement of PD motor symptoms, which is a goal of standard therapies including deep brain stimulation (DBS). To overcome the stimulation-induced side effects and inefficiencies of conventional DBS (cDBS) and to reduce the administered stimulation current, closed-loop adaptive DBS (aDBS) techniques were developed. In this method, the frequency and/or amplitude of stimulation are modulated based on various disease biomarkers.

Methods

Here, by computational modeling of a cortico-BG-thalamic network in normal and PD conditions, we show that closed-loop aDBS of the subthalamic nucleus (STN) with amplitude modulation leads to a more effective suppression of pathological beta oscillations within the parkinsonian BG.

Results

Our results show that beta band neural oscillations are restored to their normal range and the reliability of the response of the thalamic neurons to motor cortex commands is retained due to aDBS with amplitude modulation. Furthermore, notably less stimulation current is administered during aDBS compared with cDBS due to a closed-loop control of stimulation amplitude based on the STN local field potential (LFP) beta activity.

Discussion

Efficient models of closed-loop stimulation may contribute to the clinical development of optimized aDBS techniques designed to reduce potential stimulation-induced side effects of cDBS in PD patients while leading to a better therapeutic outcome.

Respiratory-Swallow Coordination in Individuals with Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Swallowing impairment, including altered physiology and aspiration, occur across the progression of Parkinson's disease (PD). The phase of respiration during which a swallow is initiated has been linked to swallowing impairment and aspiration in cohorts with dysphagia following stroke and head and neck cancer treatment, but has been understudied in PD. If similar findings are shown in individuals with PD, the implications for swallowing assessment and treatment are significant.

OBJECTIVE

The aim of this systematic review and meta-analysis of literature was to examine respiratory-swallow coordination measures and potential implications on swallowing physiology in individuals with PD.

METHODS

An extensive search of 7 databases (PubMed, EMBASE, Central, Web of Science, ProQuest Dissertations & Theses, Scopus, and CINAHL) with predetermined search terms was conducted. Inclusion criteria were individuals with PD and the use of objective evaluations of respiratory-swallow coordination.

RESULTS

Of the 13,760 articles identified, 11 met the inclusion criteria. This review supports the presence of atypical respiratory swallow patterning, respiratory pause duration and lung volume at swallow initiation in individuals with PD. The meta-analysis estimated an occurrence of 60% of non-expiration-expiration and 40% of expiration-expiration respiratory phase patterns surrounding swallowing.

CONCLUSION

Although this systematic review supports the occurrence of atypical respiratory-swallow coordination in individuals with PD, the evidence is limited by the variability in the methods of data acquisition, analysis, and reporting. Future research examining the impact of respiratory swallow coordination on swallowing impairment and airway protection using consistent, comparable, and reproducible methods and metrics in individuals with PD is warranted.

Identification of exosomal biomarkers and its optimal isolation and detection method for the diagnosis of Parkinson's disease: A systematic review and meta-analysis

Recently, there has been growing interest in exosomal biomarkers for their active targeting and specificity for delivering their cargos (proteins, lipids, nucleic acids) from the parent cell to the recipient cell. Currently, the clinical diagnosis of Parkinson's disease (PD) is mainly based on a clinician's neuropsychological examination and motor symptoms (e.g., bradykinesia, rigidity, postural instability, and resting tremor). However, this diagnosis method is not accurate due to overlapping criteria of other neurodegenerative diseases. Exosomes are differentially expressed in PD and a combination of types and contents of exosomes might be used as a biomarker in PD. Here, we systematically reviewed and meta-analyzed exosomal contents, types and sources of exosomes, method of isolation, and protein quantification tools to determine the optimum exosome-related attributes for PD diagnosis. Pubmed, Embase, and ISI Web of Science were searched for relevant studies. 25 studies were included in the meta-analysis. The Ratio of Mean (RoM) with 95% confidence intervals (CI) was calculated to estimate the effect size. Biomarker performances were rated by random-effects meta-analysis with the Restricted Maximum Likelihood (REML) method. The study protocol is available at PROSPERO (CRD42022331885). Exosomal α-synuclein (α-Syn) was significantly altered in PD patients from healthy controls [RoM = 1.67, 95% CI (0.99 to 2.35); p = 0.00] followed by tau [RoM = 1.33, 95% CI (0.79 to 1.87); p = 0.00], PS-129 [RoM = 0.97, 95% CI (0.54 to 1.40); p = 0.00], and DJ-1/PARK7 [RoM = 0.93, 95% CI (0.64 to 1.21); p = 0.00]. Central nervous system derived L1CAM exosome [RoM = 1.24, 95% CI (1.04 to 1.45); p = 0.00] from either plasma [RoM = 1.35, 95% CI (1.09 to 1.61); p = 0.00]; or serum [RoM = 1.47, 95% CI (1.05 to 1.90); p = 0.00] has been found the optimum type of exosome. The exosome isolation by ExoQuick [RoM = 1.16, 95% CI (0.89 to 1.43); p = 0.00] and protein quantification method by ELISA [RoM = 1.28, 95% CI (1.15 to 1.41); p = 0.00] has been found the optimum isolation and quantification method, respectively for PD diagnosis. This meta-analysis suggests that α-Syn in L1CAM exosome derived from blood, isolated by ExoQuick kit, and quantified by ELISA can be used for PD diagnosis.

Regulation of N-type calcium channels by nociceptin receptors and its possible role in neurological disorders

Activation of nociceptin opioid peptide receptors (NOP, a.k.a. opioid-like receptor-1, ORL-1) by the ligand nociceptin/orphanin FQ, leads to G protein-dependent regulation of Cav2.2 (N-type) voltage-gated calcium channels (VGCCs). This typically causes a reduction in calcium currents, triggering changes in presynaptic calcium levels and thus neurotransmission. Because of the widespread expression patterns of NOP and VGCCs across multiple brain regions, the dorsal horn of the spinal cord, and the dorsal root ganglia, this results in the alteration of numerous neurophysiological features. Here we review the regulation of N-type calcium channels by the NOP-nociceptin system in the context of neurological conditions such as anxiety, addiction, and pain.

Dyskinesia and Parkinson's disease: animal model, drug targets, and agents in preclinical testing

INTRODUCTION

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. PD patients exhibit a classic spectrum of motor symptoms, arising when dopamine neurons in the substantia nigra pars compacta are reduced by 60%. The dopamine precursor L-DOPA represents the most effective therapy for improving PD motor dysfunctions, thus far available. Unfortunately, long-term treatment with L-DOPA is associated with the development of severe side effects, resulting in abnormal involuntary movements termed levodopa-induced dyskinesia (LID). Amantadine is the only drug currently approved for the treatment of LID indicating that LID management is still an unmet need in PD and encouraging the search for novel anti-dyskinetic drugs or the assessment of combined therapies with different molecular targets.

AREAS COVERED

This review provides an overview of the main preclinical models used to study LID and of the latest preclinical evidence on experimental and clinically available pharmacological approaches targeting non-dopaminergic systems.

EXPERT OPINION

LIDs are supported by complex molecular and neurobiological mechanisms that are still being studied today. This complexity suggests the need of developing personalized pharmacological approach to obtain an effective amelioration of LID condition and improve the quality of life of PD patients.

Effects of Wu Qin Xi exercise on reactive inhibition in Parkinson’s disease: A randomized controlled clinical trial

Objective

Motor symptom in patients with Parkinson’s disease (PD) are related to reduced motor inhibitory ability (proactive and reactive inhibition). Although exercise has been shown to improve this ability, its effects on different levels of motor inhibition have not been determined.

Materials and methods

Sixty patients with PD aged 55–75 years were allocated randomly to 24-week exercise interventions [Wu Qin Xi exercise (WQX) and stretching exercise (SE)]. The stop signal task and questionnaires were administered pre and post interventions. Twenty-five age-matched healthy controls were recruited to obtain reference values for inhibition.

Results

Compared to healthy controls, patients with PD showed motor inhibition deficits in reactive inhibition, but not in proactive inhibition. Post-intervention, the WQX group showed significant improvement in reactive inhibition compared to the SE group. In both the WQX and SE groups, movement speed was improved post-intervention, accompanied by reduction in negative emotions, stable improvement of sleep quality, and high self-reported satisfaction levels.

Conclusion

This study demonstrated that Wu Qin Xi exercise can improve the reactive inhibition of patients with PD. Our results provide theoretical support for the formulation of reasonable and effective exercise prescriptions for PD rehabilitation.

Clinical trial registration

[http://www.chictr.org.cn], identifier [ChiCTR2000038517].

Postoperative Complication Rates After One-Level Cervical Spine Surgery in Patients with Parkinson Disease: A Database Study

OBJECTIVE

Parkinson disease (PD) is a risk factor for worse surgical outcomes. The degree to which PD affects outcomes in cervical spine surgery is not well understood. Therefore, we characterize rates of postoperative complications among patients with PD who undergo cervical spine surgery.

METHODS

Using the PearlDiver database, we identified patients who underwent 1-level anterior cervical discectomy and fusion (ACDF), posterior cervical fusion (PCF), or discectomy/decompression with concomitant PD between 2011 and 2019. Patients with PD who underwent surgery and had 1 year follow-up were included. Complications 30, 60, and 90 days after surgery were identified and aggregated into body systems (e.g., respiratory and gastrointestinal). Comparison controls without concomitant PD who received cervical spine (C-spine) surgery were matched for age, sex, and comorbidities.

RESULTS

A total of 259,443 ACDFs, 30,929 PCFs, and 29,563 decompressions were identified. Of these procedures, 1117 were performed on patients with PD (0.35%). The highest 90-day complications rates in patients with PD were pulmonary and gastrointestinal related (6.05%) in those who received ACDF, neuro related (8.51%) in those who received PCF, and genitourinary related (8.76%) in those who received a decompression. Compared with patients without PD, postoperative complications rates were similar and not significantly different.

CONCLUSIONS

Patients with PD who receive ACDF have higher rates of pulmonary (6.05%), neurologic (5.24%), and psychiatric (3.23%) complications at 90 days. The differences did not reach statistical significance. This finding suggests that patients with PD do not experience higher rates of acute postoperative complications when undergoing 1-level cervical spine surgery.

The Subthalamic Nucleus Exclusively Evokes Dopamine Release in the Tail of the Striatum

A distinct population of dopamine neurons in the substantia nigra pars lateralis (SNL) has a unique projection to the most caudolateral (tail) region of the striatum. Here, using two electrochemical techniques to measure basal dopamine and electrically evoked dopamine release in anesthetized rats, we characterized this pathway, and compared it with the ‘classic’ nigrostriatal pathway from neighboring substantia nigra pars compacta (SNc) dopamine neurons to the dorsolateral striatum. We found that the tail striatum constitutes a distinct dopamine domain compared with the dorsolateral striatum, with consistently lower basal and evoked dopamine, and diverse dopamine release kinetics. Importantly, electrical stimulation of the SNL and SNc evoked dopamine release in entirely separate striatal regions; the tail and dorsolateral striatum, respectively. Furthermore, we showed that stimulation of the subthalamic nucleus (STN) evoked dopamine release exclusively in the tail striatum, likely via the SNL, consistent with previous anatomical evidence of STN afferents to SNL dopamine neurons. Our work identifies the STN as an important modulator of dopamine release in a novel dopamine pathway to the tail striatum, largely independent of the classic nigrostriatal pathway, which necessitates a revision of the basal ganglia circuitry with the STN positioned as a central integrator of striatal information.

Gut Microbiome and Brain: Scope and Perspectives

Editorial.

Restoration and targeting of aberrant neurotransmitters in Parkinson's disease therapeutics

Neurotransmitters are considered as a fundamental regulator in the process of neuronal growth, differentiation and survival. Parkinson's Disease (PD) occurs due to extensive damage of dopamine-producing neurons; this causes dopamine deficits in the midbrain, followed by the alternation of various other neurotransmitters (glutamate, GABA, serotonin, etc.). It has been observed that fluctuation of neurotransmission in the basal ganglia exhibits a great impact on the pathophysiology of PD. Dopamine replacement therapy, such as the use of L-DOPA, can increase the dopamine level, but it majorly ameliorates the motor symptoms and is also associated with long-term complications (for e.g., LID). While the non-dopaminergic system can efficiently target non-motor symptoms, for instance, the noradrenergic system regulates the synthesis of BDNF via the MAPK pathway, which is important in learning and memory. Herein, we briefly discuss the role of different neurotransmitters, implementation of neurotransmitter receptors in PD. We also illustrate the recent advances of neurotransmitter-based drugs, which are currently under in vivo and clinical studies. Reinstating normal neurotransmitter levels has been believed to be advantageous in the treatment of PD. Thus, there is an increasing demand for drugs that can specifically target the neurotransmission system and reinstate the normal levels of neurotransmitters, which might prevent or delay neurodegeneration in PD.

Striatal D1 Dopamine Neuronal Population Dynamics in a Rat Model of Levodopa-Induced Dyskinesia

Background

The pathophysiology of levodopa-induced dyskinesia (LID) in Parkinson’s disease (PD) is not well understood. Experimental data from numerous investigations support the idea that aberrant activity of D₁ dopamine receptor-positive medium spiny neurons in the striatal direct pathway is associated with LID. However, a direct link between the real-time activity of these striatal neurons and dyskinetic symptoms remains to be established.

Methods

We examined the effect of acute levodopa treatment on striatal c-Fos expression in LID using D₁-Cre PD rats with dyskinetic symptoms induced by chronic levodopa administration. We studied the real-time dynamics of striatal D₁⁺ neurons during dyskinetic behavior using GCaMP₆-based in vivo fiber photometry. We also examined the effects of striatal D₁⁺ neuronal deactivation on dyskinesia in LID rats using optogenetics and chemogenetic methods.

Results

Striatal D₁⁺ neurons in LID rats showed increased expression of c-Fos, a widely used marker for neuronal activation, following levodopa injection. Fiber photometry revealed synchronized overactivity of striatal D₁⁺ neurons during dyskinetic behavior in LID rats following levodopa administration. Consistent with these observations, optogenetic deactivation of striatal D₁⁺ neurons was sufficient to inhibit most of the dyskinetic behaviors of LID animals. Moreover, chemogenetic inhibition of striatal D₁⁺ neurons delayed the onset of dyskinetic behavior after levodopa administration.

Conclusion

Our data demonstrated that aberrant activity of striatal D₁⁺ neuronal population was causally linked with real-time dyskinetic symptoms in LID rats.

Directed Brain Connectivity Identifies Widespread Functional Network Abnormalities in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by topological abnormalities in large-scale functional brain networks, which are commonly analyzed using undirected correlations in the activation signals between brain regions. This approach assumes simultaneous activation of brain regions, despite previous evidence showing that brain activation entails causality, with signals being typically generated in one region and then propagated to other ones. To address this limitation, here, we developed a new method to assess whole-brain directed functional connectivity in participants with PD and healthy controls using antisymmetric delayed correlations, which capture better this underlying causality. Our results show that whole-brain directed connectivity, computed on functional magnetic resonance imaging data, identifies widespread differences in the functional networks of PD participants compared with controls, in contrast to undirected methods. These differences are characterized by increased global efficiency, clustering, and transitivity combined with lower modularity. Moreover, directed connectivity patterns in the precuneus, thalamus, and cerebellum were associated with motor, executive, and memory deficits in PD participants. Altogether, these findings suggest that directional brain connectivity is more sensitive to functional network differences occurring in PD compared with standard methods, opening new opportunities for brain connectivity analysis and development of new markers to track PD progression.

Advances in profiling chromatin architecture shed light on the regulatory dynamics underlying brain disorders

Understanding the exquisitely complex nature of the three-dimensional organization of the genome and how it affects gene regulation remains a central question in biology. Recent advances in sequencing- and imaging-based approaches in decoding the three-dimensional chromatin landscape have enabled a systematic characterization of gene regulatory architecture. In this review, we outline how chromatin architecture provides a reference atlas to predict the functional consequences of non-coding variants associated with human traits and disease. High-throughput perturbation assays such as massively parallel reporter assays (MPRA) and CRISPR-based genome engineering in combination with a reference atlas opened an avenue for going beyond observational studies to experimentally validating the regulatory principles of the genome. We conclude by providing a suggested path forward by calling attention to barriers that can be addressed for a more complete understanding of the regulatory landscape of the human brain.

Microbiota-targeted therapies in inflammation resolution

Gut microbiota has been shown to systemically shape the immunological landscape, modulate homeostasis and play a role in both health and disease. Dysbiosis of gut microbiota promotes inflammation and contributes to the pathogenesis of several major disorders in gastrointestinal tract, metabolic, neurological and respiratory diseases. Much effort is now focused on understanding host-microbes interactions and new microbiota-targeted therapies are deeply investigated as a means to restore health or prevent disease. This review details the immunoregulatory role of the gut microbiota in health and disease and discusses the most recent strategies in manipulating individual patient's microbiota for the management and prevention of inflammatory conditions.

An electrophysiological perspective on Parkinson's disease: symptomatic pathogenesis and therapeutic approaches

Parkinson's disease (PD), or paralysis agitans, is a common neurodegenerative disease characterized by dopaminergic deprivation in the basal ganglia because of neuronal loss in the substantia nigra pars compacta. Clinically, PD apparently involves both hypokinetic (e.g. akinetic rigidity) and hyperkinetic (e.g. tremor/propulsion) symptoms. The symptomatic pathogenesis, however, has remained elusive. The recent success of deep brain stimulation (DBS) therapy applied to the subthalamic nucleus (STN) or the globus pallidus pars internus indicates that there are essential electrophysiological abnormalities in PD. Consistently, dopamine-deprived STN shows excessive burst discharges. This proves to be a central pathophysiological element causally linked to the locomotor deficits in PD, as maneuvers (such as DBS of different polarities) decreasing and increasing STN burst discharges would decrease and increase the locomotor deficits, respectively. STN bursts are not so autonomous but show a "relay" feature, requiring glutamatergic synaptic inputs from the motor cortex (MC) to develop. In PD, there is an increase in overall MC activities and the corticosubthalamic input is enhanced and contributory to excessive burst discharges in STN. The increase in MC activities may be relevant to the enhanced beta power in local field potentials (LFP) as well as the deranged motor programming at the cortical level in PD. Moreover, MC could not only drive erroneous STN bursts, but also be driven by STN discharges at specific LFP frequencies (~ 4 to 6 Hz) to produce coherent tremulous muscle contractions. In essence, PD may be viewed as a disorder with deranged rhythms in the cortico-subcortical re-entrant loops, manifestly including STN, the major component of the oscillating core, and MC, the origin of the final common descending motor pathways. The configurations of the deranged rhythms may play a determinant role in the symptomatic pathogenesis of PD, and provide insight into the mechanism underlying normal motor control. Therapeutic brain stimulation for PD and relevant disorders should be adaptively exercised with in-depth pathophysiological considerations for each individual patient, and aim at a final normalization of cortical discharge patterns for the best ameliorating effect on the locomotor and even non-motor symptoms.

Experimental deep brain stimulation in rodent models of movement disorders

Deep brain stimulation (DBS) is the preferred treatment for therapy-resistant movement disorders such as dystonia and Parkinson's disease (PD), mostly in advanced disease stages. Although DBS is already in clinical use for ~30 years and has improved patients' quality of life dramatically, there is still limited understanding of the underlying mechanisms of action. Rodent models of PD and dystonia are essential tools to elucidate the mode of action of DBS on behavioral and multiscale neurobiological levels. Advances have been made in identifying DBS effects on the central motor network, neuroprotection and neuroinflammation in DBS studies of PD rodent models. The phenotypic dt^sz mutant hamster and the transgenic DYT-TOR1A (ΔETorA) rat proved as valuable models of dystonia for preclinical DBS research. In addition, continuous refinements of rodent DBS technologies are ongoing and have contributed to improvement of experimental quality. We here review the currently existing literature on experimental DBS in PD and dystonia models regarding the choice of models, experimental design, neurobiological readouts, as well as methodological implications. Moreover, we provide an overview of the technical stage of existing DBS devices for use in rodent studies.