Search Results (484)

This study investigates the role of single nucleotide polymorphisms (SNPs) in the SNCA gene, encoding alpha-synuclein, in Alzheimer’s disease (AD). A case–control study was conducted including 95 AD patients and 97 healthy controls. Four SNCA polymorphisms (rs2583988, rs2619363, rs2619364, rs10005233) were analyzed using logistic regression, haplotype estimation, genotype combination analysis, and Random Forest modeling. Significant associations were identified for rs2583988, rs2619364, and rs2619363, while rs10005233 showed no association. The rs2583988 C allele and rs2619364 G allele were more frequent in patients, suggesting increased disease risk. Linkage disequilibrium analysis revealed weak correlations (low r²), indicating largely independent genetic effects. Multivariate logistic regression showed that clinical parameters, rather than genetic variants, were independently associated with AD. Multi-locus genotype analysis demonstrated that specific SNP combinations were linked to increased disease risk. Firth regression confirmed associations in low-frequency genotypes. The outcomes derived from the Random Forest methodology were classified as exploratory and not as proof of clinical predictive utility, attributed to the limited sample size, the absence of external validation, and the educational imbalance. Ordinal logistic regression indicated no association between SNCA variants and cognitive severity, while education had a protective effect. The selected SNCA variants showed exploratory associations with AD in this cohort; however, they failed to maintain their validity as independent predictors in multivariate logistic regression analysis. Before drawing any conclusions regarding screening or risk stratification, these findings require independent replication, correction for multiple testing and functional validation. Full article

Background/Objectives: Parkinson’s disease (PD) is a major neurodegenerative disorder with no cure. The goal is to develop an active immunotherapy targeting aggregated alpha synuclein (aSyn), the root cause of PD. TRB-001 is the lead candidate of a novel class of vaccines. It is a peptide/protein conjugate coupled to sugar residues, which is used to target and activate antigen-presenting cells, and addresses aSyn. Methods: A 33-year-old male, diagnosed with PD seven years previously, with a Hoehn & Yahr stage of 1, taking Levodopa/Benserazide (100/25 mg, 6× per day), Rotigotine (8 mg) and Rasagiline (1 mg), amounting to a Levodopa equivalent daily dose (LEDD) of 940 mg, also complicated by impulse control disorder, requested experimental therapy. He received a total of four TRB-001 administrations (weeks 0, 4, 8 and 34) following informed consent. The workup included safety, immunological and clinical parameters. Results: Vaccinations were well tolerated. They induced a high-titer aSyn-specific antibody (Ab) response. Titer increase was associated with a reduction in aSyn plasma levels, suggesting target engagement. The Ab titer and the reduction in aSyn plasma levels were both long-lived. The boost elicited a recall-type Ab titer increase and triggered avidity maturation (factor 7.8). Abs demonstrated a high degree of selectivity for aggregated aSyn (factor 30). Moreover, they were found to preferentially react with tissue from PD brain lysates. The Movement Disorder Society-Sponsored Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) score for the patient remained essentially stable throughout the observation period of 53 weeks. At the time of the boost, the symptomatic PD therapy was simplified to Levodopa/Carbidopa/Entacapone 100/25/200 mg four times a day, amounting to an LEDD of 532 mg. This put an end to the symptoms of the impulse control disorder. Conclusions: Results obtained suggest that this new class of vaccines may yield Ab responses comparable in magnitude and target avidity to the therapeutic setting of monoclonal Abs. TRB-001 is currently being translated to a randomized, placebo-controlled Phase 1B study. Full article

Background/objectives: Alpha-synuclein (aSyn) is best known for its role in Parkinson’s disease. Increasing evidence suggests a bidirectional relationship between diabetes mellitus and synuclein pathology. Carboxymethyllysine (CML), an advanced glycation end-product, serves as a marker of cumulative glycation stress and tissue damage in diabetes. Our study aimed to evaluate epidermal phosphorylated alpha-synuclein at Ser129 (p-aSyn) immunoreactivity in relation to CML accumulation in epidermis. Methods: Skin punch biopsies were obtained from seven diabetic patients with long-standing type 2 diabetes (T2DM), and from seven healthy volunteers. Tissue samples were processed and analyzed by immunohistochemical DAB-staining for p-aSyn and CML. Quantitative analysis was performed by measuring the percentage area of positive staining using Fiji/ImageJ2. Integrated density was also assessed as a complementary threshold-limited measure of staining signal intensity. Statistical analysis and data visualization were conducted using GraphPad Prism. Comparisons between groups were performed using the exact two-tailed Mann–Whitney U test. Results: Area-fraction analysis showed significantly greater CML-positive staining in diabetic epidermis than in controls (median 10.18 vs. 8.955, p = 0.0262), whereas p-aSyn-positive area fraction did not differ significantly between groups (13.53 vs. 14.64, p = 0.8048). In the complementary integrated density analysis, p-aSyn signal was significantly higher in diabetic epidermis than in controls (21,365 vs. 10,960, p = 0.0023), whereas the increase in CML integrated density did not reach statistical significance (14,165 vs. 6585, p = 0.1282). In diabetic epidermis, both markers showed a more widespread distribution, involving basal keratinocyte cytoplasm and extension into suprabasal layers. Control samples showed staining largely restricted to basal cell contours. In serial sections, p-aSyn and CML showed a similar topographic distribution in diabetic skin. Conclusions: These preliminary observations suggest that chronic diabetic skin changes are associated with increased epidermal CML burden when assessed by area fraction and with higher p-aSyn signal intensity when assessed by integrated density. However, because the study was small and based on semiquantitative DAB immunohistochemistry, the findings should be interpreted cautiously and require validation in larger multimodal studies. Full article

Disease-specific alpha-synuclein (αsyn) strains have been linked to different synucleinopathies. Current αsyn biomarkers are limited to binary detection of pathogenic αsyn in peripheral tissue biopsies or fluids, limiting differential diagnosis. Hence, there is an urgent need for methods that allow strain-specific detection and characterization of αsyn strain architecture. Notably, luminescent conjugated oligothiophenes (LCOs) have been successfully used to detect distinct protein strain conformers in prion diseases and Alzheimer’s disease, highlighting their utility in differentiating disease-specific amyloid structures. Species-dependent differences in αsyn structure are increasingly recognized as one of the critical aspects that shape how fibrils form, propagate and interact with molecular LCO probes. Here, we evaluate the potential of the LCO h-FTAA to differentiate species-specific αsyn strains and conduct a translational investigation using peripheral cardiac tissue of a gut-first synucleinopathy rodent model. Our in vitro data demonstrate strain-specific probe–fibril interactions, reflecting a differential strain architecture and cellular micro-environment. While h-FTAA binds with comparable efficiency to mouse (mo-) and human (hu-) pre-formed fibrils (PFFs), h-FTAA exhibits markedly lower quantum yield when bound to moPFFs versus huPFFs. Spectral imaging revealed h-FTAA-moPFF binding produces blue-shifted maxima (505–550 nm), contrasting with the red-shifted maxima (545–580 nm) of huPFFs. Fluorescence lifetime imaging microscopy confirmed h-FTAA’s intrinsic sensitivity to species-dependent variations through distinct temporal fluorescence signatures (moPFFs: ~0.60–1.5 ns vs. huPFFs: ~0.65–1.0 ns). Our translational investigation showed h-FTAA binding to peripheral cardiac pathology exhibits comparable red-shifted emission, but distinct fluorescence lifetimes of h-FTAA-bound aggregates in moPFF-injected (~1.0–1.4 ns) versus huPFF-injected (~0.69–0.8 ns) rats. Interestingly, we observed distinct blue-shifted emission profiles in a few selected regions of the heart of moPFF-injected rodents, further characterized by extra-long fluorescence decay shifts (~1.5–1.9 ns), reflecting differences in both aggregate conformation and maturity in moPFF-induced compared with huPFF-induced rats. Taken together, our findings underscore the potential of LCO ligands, like h-FTAA, to enable more precise disease staging and diagnosis through peripheral biopsies, complementing existing αsyn biomarker methods. Full article

Introduction: Pathogenic mutations in leucine-rich repeat protein kinase-2 (LRRK2), particularly G2019S, constitute the most common cause of autosomal dominant PD. Methods: Mouse models encoding human mutant alpha-synuclein (SNCA A53T) and LRRK2 G2019S were treated with a brain-penetrant kinase inhibitor (BK40196). Behavior, nigrostriatal and mesolimbic dopamine (DA) pathways were examined. Results: Mice harboring LRRK2 G2019S do not show age-dependent motor symptoms, but mice encoding SNCA A53T display motor deficits, while both strains exhibit anxiety-like behavior and BK40196 improves motor and behavioral defects. BK40196, a multi-kinase inhibitor of Abelson (Abl), Discoidin domain receptor (DDR)-1, c-KIT and FYN, alters microglial morphology and alpha-synuclein levels in SNCA A53T mice and improves DA neurotransmission, primarily via the nigrostriatal system. BK40196 inhibits brain LRRK2 G2019S (IC₅₀ of 89nM) and does not affect phosphorylated or total peripheral LRRK2 levels (lungs, kidneys, liver, etc.). LRRK2 G2019S mice treated with BK40196 exhibit distinct increases in DA in mesolimbic neurons such as the nucleus accumbens (NAcc), suggesting differential mechanisms of DA neurotransmission in mutant alpha-synuclein and LRRK2 models of PD. Conclusions: LRRK2 G2019S may primarily involve mesolimbic pathways leading to nonmotor symptoms independent of the motor and behavioral manifestations associated with alpha-synuclein via the nigrostriatal system. BK40196 may provide a comprehensive and synergistic therapeutic approach that addresses multiple mechanisms to reduce the pathologies related to LRRK2 G2019S and/or SNCA in PD. The multiple pathologies of PD necessitate a holistic approach that simultaneously targets inflammation and autophagy and LRRK2 inhibition. Full article

Since the features of cross-seeding of alpha-synuclein forms may affect the sensitivity and specificity of the test systems, we developed a modified approach to obtain alpha-synuclein amyloid seeds with particle sizes from 20 to 50 nm prepared from either the wild-type protein (α-synWT) or its more fibrillation-prone form A53T (α-synA53T). These seeds had optimal properties for subsequent initiation of fibrillation. Our data showed that the elevated efficiency of alpha-synuclein A53T monomer transformation was hardly affected by the type of used seeds, whereas the addition of the seeds obtained from the alpha-synuclein mutant form to wild-type protein monomers had a significantly smaller effect than α-synWT seeds. Transmission electron microscopy data revealed that in the presence of α-synWT seeds the wild-type alpha-synuclein formed long and wide fibrils, while the addition of α-synA53T seeds led to the formation of long, but thin fibrils. Since the lag period of α-synA53T monomer fibrillation was significantly reduced compared to the wild-type protein, the replacing of α-synWT with α-synA53T in current assay systems designed to detect aberrant forms of α-synuclein in biological fluid samples (e.g., RT-QuIC) could substantially cut the time of analysis. In the future, a set of alpha-synuclein mutant forms could be used for the differential diagnosis of synucleinopathies caused by the different mutations of this protein. Full article

Background: Parkinson’s disease (PD) is clinically heterogeneous, yet the genetic architecture underlying this heterogeneity remains incompletely understood. We examined the genetic correlates of four complementary PD subtyping frameworks: the clinical motor subtype (tremor-dominant [TD] vs. postural instability/gait difficulty [PIGD]), alpha-synuclein seed amplification assay status (SAA+ vs. SAA−), the pathological subtype (brain-first vs. body-first, based on the presence of REM sleep behavior disorder), and the data-driven subtype (diffuse malignant [DM] vs. mild-motor predominant [MMP] vs. intermediate [IM]). Methods: We analyzed 1390 PD patients from the Parkinson’s Progression Markers Initiative (PPMI) with genotypes available for seven PD-associated genes (LRRK2, GBA1, SNCA, PRKN, PINK1, PARK7, VPS35), including specific variant resolutions (LRRK2 G2019S, R1441G/C/H; GBA1 N409S, severe variants; SNCAA53T), and APOE (ε2/ε3/ε4 alleles). Genetic variant frequencies were compared across subtypes using chi-square or Fisher’s exact tests with the Benjamini–Hochberg false discovery rate (FDR) correction. Effect sizes were quantified using Cramér’s V. multivariable logistic regression estimated adjusted odds ratios with Wald-based 95% confidence intervals. Results: Among genotyped PD patients, LRRK2 carriers constituted 13.7% (190/1390; 170 G2019S, 18 R1441G/C/H), GBA1 8.6% (119/1390; 96 N409S, 23 severe), and SNCA 2.0% (28/1390; all A53T). APOE ε4 carriers comprised 23.4% (323/1380). SAA-negative patients were markedly enriched for LRRK2 variants (37.1% vs. 10.2%, p = 3.7 × 10⁻¹⁹, q < 0.001, V = 0.25), specifically G2019S (28.5% vs. 9.6%, p = 4.9 × 10⁻¹¹, q < 0.001) and R1441G/C/H (7.9% vs. 0.5%, p = 2.7 × 10⁻¹², q < 0.001). Body-first PD was enriched for GBA1 carriers (12.3% vs. 6.7%, p = 0.004, q = 0.021) and had less LRRK2 carriers (7.9% vs. 15.0%, p = 0.002, q = 0.013). The DM subtype had the highest GBA1 frequency (14.0% vs. MMP 5.9%, p < 0.001, q = 0.003). After FDR correction, 10 out of 48 univariate tests remained significant. Clinical subtypes (TD vs. PIGD) showed only nominal LRRK2 differences that did not survive FDR correction. The APOE genotype did not differ across any framework. Conclusions: PD subtypes defined by alpha-synuclein pathology (SAA), pathological onset pattern (brain-first/body-first), and data-driven classification (DM/MMP/IM) show distinct genetic profiles that survive multiple comparison correction. LRRK2 variants strongly associate with SAA negativity (V = 0.25); GBA1 variants associate with the severe body-first onset and the diffuse malignant subtype. Full article

Oligomeric species of alpha-synuclein (α-syn) in saliva and phosphorylated α-syn deposits in the skin are established molecular biomarkers for Parkinson’s disease (PD). However, existing research has yet to fully explore the diagnostic potential of non-phosphorylated α-syn and other cutaneous morphometric parameters, such as variations in collagen type IV within the dermis and epidermis or α-syn expression in melanocytes. This study aims to evaluate and compare the diagnostic utility of these skin morphometric parameters in differentiating 32 PD patients from 19 healthy subjects (HSs), while also examining their correlation with salivary α-syn oligomer levels. Skin biopsies were analyzed via immunofluorescence and confocal microscopy, while salivary oligomeric α-syn was quantified through competitive ELISA. Results revealed a significant reduction in α-syn-positive fibres in PD patients compared to HSs (0.91; <0.0001). Conversely, the collagen staining area and the number of α-syn-positive melanocytes were significantly increased in the skin of PD patients. Specifically, the collagen type IV staining area was significantly higher in the dermis and surrounding the sweat glands of PD patients, demonstrating optimal diagnostic power (0.9448; <0.0001). Similarly, the increase in α-syn-positive melanocytes in PD patients showed robust diagnostic potential (0.84; <0.001). Salivary α-syn oligomers accurately discriminated between PD and HS groups. Furthermore, significant correlations were found between collagen type IV and melanocyte morphometric parameters and various clinical scores in PD. Our findings highlight how multimodal morphometric analysis of the skin can enhance diagnostic accuracy in PD, supporting the use of salivary and cutaneous biomarkers as complementary tools that may reflect distinct aspects of PD pathology. Full article

Background and Objectives: Parkinson’s disease (PD) entails the progressive degeneration of dopaminergic neurons in the substantia nigra (SN), accompanied by α-synuclein (α-syn)-enriched Lewy bodies. ITGA7 mediates cell–extracellular matrix adhesion and modulates apoptosis, though its involvement in PD pathogenesis warrants further investigation. Although acupuncture demonstrates neuroprotective effects in PD models, its precise molecular mechanisms remain incompletely understood; therefore, in this study, we explored the relationship between ITGA7 and α-synuclein expression in an MPTP-induced PD mouse model to determine the association between LR3/GB34 acupuncture-induced changes in α-synuclein levels and ITGA7 modulation. Materials and Methods: In the in vivo model, MPTP-induced PD mice underwent immunohistochemistry, immunofluorescence, and Western blotting to assess ITGA7, α-synuclein, and TH levels in the SN and striatal tissues following LR3/GB34 acupuncture. In parallel, for the in vitro mechanistic study, SH-SY5Y neuroblastoma cells treated with MPP⁺ and transfected with ITGA7-siRNA were utilized to examine the involvement of apoptosis-related signaling pathways. Results: In the in vivo model, MPTP administration downregulated ITGA7 and upregulated α-synuclein in SN tissues. Similarly, in vitro exposure of SH-SY5Y cells to MPP⁺ yielded comparable results, revealing an inverse correlation between ITGA7 and α-synuclein. LR3/GB34 acupuncture treatment in the mouse model significantly increased ITGA7 and TH expression while reducing α-synuclein accumulation. To further understand the specific role of ITGA7 observed in these animal findings, we silenced ITGA7 in the MPP⁺-treated cellular model. ITGA7 silencing exacerbated the neurotoxic effects, leading to further TH downregulation, α-synuclein upregulation, Bcl-2 reduction, and Bax/Bcl-2 ratio elevation. Conclusions: Collectively, the histological preservation of dopaminergic neurons following LR3/GB34 acupuncture in the PD mouse model appears to be linked to ITGA7 upregulation. Furthermore, our in vitro findings implicate ITGA7 in the regulation of apoptosis-related signaling cascades, supporting its potential role in mitigating α-synuclein pathology. Full article

Systemic autoimmunity plays an important role in pathogenesis of neurodegenerative diseases. The objective of our study was to explore the seroprevalence of naturally occurring autoantibodies (Aabs) targeting a panel of 14 antigens broadly involved in neurodegenerative diseases such as Alzheimer’s Disease, Parkinson’s Disease, frontotemporal dementia, and vascular dementia. Commonly associated proteins with underlying neuronal pathology of the brain include amyloid-beta (Aβ), tau, alpha-synuclein (α-syn), TDP-43, and FUS. Proteins associated with glial and astrocytic involvement—TREM2 and Chi3Li; proteins related to myelin damage and axonal degeneration—light neurofilaments (NFL), myelin basic protein (MBP); synaptic loss reflected by neurogranin (NRGN), a marker of neuronal injury—neuron specific enolase (NSE); and markers of disturbed calcium homeostasis—VSNL1 and neuroinflammation—MCP-1. Presence and levels of plasma IgG against these antigens were examined using enzyme-linked immunosorbent assay (ELISA) method in patients with dementia, patients with mild cognitive impairment (MCI), and healthy age-matched controls. Aabs against all selected antigens were detected across all groups, including healthy control, with varied seroprevalence levels. For the first time, we report the presence of anti-FUS, anti-TREM2, anti-NRGN, anti-VSNL1, anti-NSE, and anti-MCP1 Aabs. Elevated anti-Chi3Li Aabs in individuals with MCI indicate a disease-associated immune signature linked to early neurodegenerative processes. Overall, these results provide evidence of systemic immune activation accompanying neurodegeneration, underscore the complexity of immune involvement, and highlight the importance of targeting multiple pathological pathways in future immunomodulatory strategies. Full article

Parkinson’s disease (PD) is characterized by the progressive degeneration of dopaminergic neurons and the accumulation of α-synuclein-rich inclusions, largely resulting from impaired protein clearance mechanisms. Copper is an essential redox-active metal in the central nervous system (CNS), but alterations in its homeostasis can promote oxidative stress, mitochondrial dysfunction, and proteostatic failure. In vitro studies indicate that copper can promote α-synuclein misfolding, enhance oxidative stress, and interfere with both the ubiquitin–proteasome system (UPS) and the autophagy–lysosome pathway (ALP). In this review, we critically evaluate mechanistic evidence from cellular models, integrating available animal and clinical data to assess the biological significance of copper-mediated impairment of α-synuclein clearance. We highlight the current research, identify methodological limitations, and discuss whether copper imbalance acts as a primary pathogenic trigger or as a disease-modifying amplifier of proteostatic failure. Furthermore, we consider the translational implications of selectively modulating intracellular copper pools as a therapeutic strategy in PD. Finally, we will highlight unresolved issues, methodological limitations, and emerging targeted therapeutic prospects. Full article

Background: Frontotemporal dementia (FTD) is traditionally classified based on the accumulation of either tau or TDP-43 proteins; however, the presence of alpha-synuclein (α-Syn) in these patients is increasingly recognized as a critical factor driving disease progression. Methods: A comprehensive narrative review of recent clinical, neuropathological, and biochemical studies was conducted, focusing on cases of FTLD-synuclein and the occurrence of alpha-syn as a co-pathology in more common FTD variants. Results: Current evidence indicates that α-syn often co-aggregates with tau and TDP-43 via “cross-seeding” mechanisms, significantly accelerating neuronal loss and contributing to clinical heterogeneity. Although FTLD-synuclein is a rare, distinct subtype that mimics atypical multiple system atrophy, secondary α-syn pathology is common and strongly correlates with rapid cognitive decline. Furthermore, existing diagnostic biomarkers typically fail to detect this pathological overlap, which may explain the limited efficacy in protein-specific clinical trials. Conclusions: α-Syn is a major, yet under-recognized, catalyst of neurodegeneration within the FTD spectrum. The findings emphasize the need for future therapeutic and diagnostic strategies to adopt multi-target approaches, addressing the synergistic toxicity of multiple protein aggregates rather than isolating single protein in isolation. Full article

Alpha-synuclein (αSyn) is one of the most abundant proteins in the nervous system and is currently associated with devastating synucleinopathies, yet its biology extends far beyond this. In this review, we suggest that αSyn-driven disease emerges within specific neural circuits through the combined effects of cell-type-specific roles, subcellular environments, post-translational modifications (PTMs), and co-pathology. These interacting and additive dimensions, rather than αSyn alone, generate the pathological diversity, shaping whether pathology manifests as Parkinson’s disease (PD), Parkinson’s disease dementia (PDD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), or mixed dementia phenotypes. We integrate recent advances on the physiological roles of αSyn in neurons and glia (astrocytes, oligodendrocytes, and microglia), its compartment-dependent (e.g., synaptic and nuclear) functions, and the molecular transitions (e.g., mediated by pS129) that convert functional assemblies into pathogenic conformers. Building on this foundation, we outline mechanisms through which these factors contribute to disease-specific vulnerability, progression, and clinical heterogeneity. Finally, we highlight how this multidimensional perspective on αSyn biology can inform the development of next-generation biomarkers that support precision therapies across distinct disorders. Full article

Transcranial sonography is one of the methods of examination used in atypical parkinsonian syndromes. The assessment is not indicated in the diagnostic criteria of entities in this group e.g., Progressive Supranuclear Palsy, Corticobasal Degeneration, Multiple System Atrophy and Dementia with Lewy Bodies. Atypical parkinsonisms are a group of diseases affected by diverse pathologies including alpha-synuclein or tau among others. Recently broader attention was brought to less common atypical parkinsonisms as Perry syndrome. Atypical parkinsonisms are related to poor response to levodopa treatment, rapid deterioration and unfavorable prognosis. Additionally, the entities often overlap in terms of clinical manifestation, especially in the early stages. Though atypical parkinsonisms are affected by the lack of possibility of obtaining definite in vivo diagnosis, growing interest is associated to supplementary evaluations including neuroimaging. Among these methods could be mentioned magnetic resonance imaging, positron emission tomography, single photon emission computed tomography and transcranial sonography. Transcranial sonography is associated with high accessibility and low cost. The goal of this paper is to highlight the strengths and weaknesses of transcranial sonography in the examination of atypical parkinsonisms. Full article

Parkinson’s disease (PD) is a multifactorial neurodegenerative disorder defined by nigrostriatal dopaminergic neuron loss and the pathological aggregation of alpha synuclein, yet current clinical interventions remain largely symptomatic and fail to alter long-term disease progression. Emerging evidence demonstrates that immune dysregulation and chronic neuroinflammation contribute significantly to PD pathology, supporting the rationale for active immunotherapy as a disease modifying strategy. This review examines contemporary active immunotherapy platforms including peptide vaccines, genetic vaccination strategies, and antigen sensitized dendritic cell (DC) vaccines with emphasis on the dual capacity of DC based approaches to enhance pathological protein clearance and restore immune homeostasis. Technical limitations and translational barriers are evaluated such as immune heterogeneity among patients, the blood–brain barrier, and variability in DC vaccine manufacturing. Finally, future research directions are proposed including individualized immunologic profiling for treatment stratification, long-acting immunomodulatory formulations, and development of isoform specific DC powder vaccines capable of targeted alpha synuclein engagement. Collectively, these advances highlight active immunotherapy as a promising pathway toward disease modification in Parkinson’s disease. Full article