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Lu J, Zhang X, Shu Z, Han J, Yu N. A dynamic brain network decomposition method discovers effective brain hemodynamic sub-networks for Parkinson's disease. J Neural Eng 2024; 21:026047. [PMID: 38621377 DOI: 10.1088/1741-2552/ad3eb6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 04/15/2024] [Indexed: 04/17/2024]
Abstract
Objective.Dopaminergic treatment is effective for Parkinson's disease (PD). Nevertheless, the conventional treatment assessment mainly focuses on human-administered behavior examination while the underlying functional improvements have not been well explored. This paper aims to investigate brain functional variations of PD patients after dopaminergic therapy.Approach.This paper proposed a dynamic brain network decomposition method and discovered brain hemodynamic sub-networks that well characterized the efficacy of dopaminergic treatment in PD. Firstly, a clinical walking procedure with functional near-infrared spectroscopy was developed, and brain activations during the procedure from fifty PD patients under the OFF and ON states (without and with dopaminergic medication) were captured. Then, dynamic brain networks were constructed with sliding-window analysis of phase lag index and integrated time-varying functional networks across all patients. Afterwards, an aggregated network decomposition algorithm was formulated based on aggregated effectiveness optimization of functional networks in spanning network topology and cross-validation network variations, and utilized to unveil effective brain hemodynamic sub-networks for PD patients. Further, dynamic sub-network features were constructed to characterize the brain flexibility and dynamics according to the temporal switching and activation variations of discovered sub-networks, and their correlations with differential treatment-induced gait alterations were analyzed.Results.The results demonstrated that PD patients exhibited significantly enhanced flexibility after dopaminergic therapy within a sub-network related to the improvement of motor functions. Other sub-networks were significantly correlated with trunk-related axial symptoms and exhibited no significant treatment-induced dynamic interactions.Significance.The proposed method promises a quantified and objective approach for dopaminergic treatment evaluation. Moreover, the findings suggest that the gait of PD patients comprises distinct motor domains, and the corresponding neural controls are selectively responsive to dopaminergic treatment.
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Affiliation(s)
- Jiewei Lu
- College of Artificial Intelligence, Nankai University, Tianjin, People's Republic of China
| | - Xinyuan Zhang
- College of Artificial Intelligence, Nankai University, Tianjin, People's Republic of China
| | - Zhilin Shu
- College of Artificial Intelligence, Nankai University, Tianjin, People's Republic of China
| | - Jianda Han
- College of Artificial Intelligence, Nankai University, Tianjin, People's Republic of China
- Engineering Research Center of Trusted Behavior Intelligence, Ministry of Education, Nankai University, Tianjin, People's Republic of China
- Institute of Intelligence Technology and Robotic Systems, Shenzhen Research Institute of Nankai University, Shenzhen, People's Republic of China
| | - Ningbo Yu
- College of Artificial Intelligence, Nankai University, Tianjin, People's Republic of China
- Engineering Research Center of Trusted Behavior Intelligence, Ministry of Education, Nankai University, Tianjin, People's Republic of China
- Institute of Intelligence Technology and Robotic Systems, Shenzhen Research Institute of Nankai University, Shenzhen, People's Republic of China
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Netukova S, Horakova L, Szabo Z, Krupicka R. Beyond timing and step counting in 360° turning-in-place assessment: a scoping review. Biomed Eng Online 2024; 23:13. [PMID: 38297359 PMCID: PMC10832107 DOI: 10.1186/s12938-024-01208-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 01/22/2024] [Indexed: 02/02/2024] Open
Abstract
BACKGROUND Turning in place is a challenging motor task and is used as a brief assessment test of lower limb function and dynamic balance. This review aims to examine how research of instrumented analysis of turning in place is implemented. In addition to reporting the studied population, we covered acquisition systems, turn detection methods, quantitative parameters, and how these parameters are computed. METHODS Following the development of a rigorous search strategy, the Web of Science and Scopus were systematically searched for studies involving the use of turning-in-place. From the selected articles, the study population, types of instruments used, turn detection method, and how the turning-in-place characteristics were calculated. RESULTS Twenty-one papers met the inclusion criteria. The subject groups involved in the reviewed studies included young, middle-aged, and older adults, stroke, multiple sclerosis and Parkinson's disease patients. Inertial measurement units (16 studies) and motion camera systems (5 studies) were employed for gathering measurement data, force platforms were rarely used (2 studies). Two studies used commercial software for turn detection, six studies referenced previously published algorithms, two studies developed a custom detector, and eight studies did not provide any details about the turn detection method. The most frequently used parameters were mean angular velocity (14 cases, 7 studies), turn duration (13 cases, 13 studies), peak angular velocity (8 cases, 8 studies), jerkiness (6 cases, 5 studies) and freezing-of-gait ratios (5 cases, 5 studies). Angular velocities were derived from sensors placed on the lower back (7 cases, 4 studies), trunk (4 cases, 2 studies), and shank (2 cases, 1 study). The rest (9 cases, 8 studies) did not report sensor placement. Calculation of the freezing-of-gait ratio was based on the acceleration of the lower limbs in all cases. Jerkiness computation employed acceleration in the medio-lateral (4 cases) and antero-posterior (1 case) direction. One study did not reported any details about jerkiness computation. CONCLUSION This review identified the capabilities of turning-in-place assessment in identifying movement differences between the various subject groups. The results, based on data acquired by inertial measurement units across studies, are comparable. A more in-depth analysis of tests developed for gait, which has been adopted in turning-in-place, is needed to examine their validity and accuracy.
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Affiliation(s)
- Slavka Netukova
- Faculty of Biomedical Engineering, Department of Biomedical Informatics, Czech Technical University, Nam Sitna 3105, Prague, Czech Republic.
| | - Lucie Horakova
- Faculty of Biomedical Engineering, Department of Biomedical Informatics, Czech Technical University, Nam Sitna 3105, Prague, Czech Republic
| | - Zoltan Szabo
- Faculty of Biomedical Engineering, Department of Biomedical Informatics, Czech Technical University, Nam Sitna 3105, Prague, Czech Republic
| | - Radim Krupicka
- Faculty of Biomedical Engineering, Department of Biomedical Informatics, Czech Technical University, Nam Sitna 3105, Prague, Czech Republic
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Graham L, Armitage J, Vitorio R, Das J, Barry G, Godfrey A, McDonald C, Walker R, Mancini M, Morris R, Stuart S. Visual Exploration While Walking With and Without Visual Cues in Parkinson's Disease: Freezer Versus Non-Freezer. Neurorehabil Neural Repair 2023; 37:734-743. [PMID: 37772512 PMCID: PMC10666478 DOI: 10.1177/15459683231201149] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
BACKGROUND Visual cues can improve gait in Parkinson's disease (PD), including those experiencing freezing of gait (FOG). However, responses are variable and underpinning mechanisms remain unclear. Visuo-cognitive processing (measured through visual exploration) has been implicated in cue response, but this has not been comprehensively examined. OBJECTIVE To examine visual exploration and gait with and without visual cues in PD who do and do not self-report FOG, and healthy controls (HC). METHODS 17 HC, 21 PD without FOG, and 22 PD with FOG walked with and without visual cues, under single and dual-task conditions. Visual exploration (ie, saccade frequency, duration, peak velocity, amplitude, and fixation duration) was measured via mobile eye-tracking and gait (ie, gait speed, stride length, foot strike angle, stride time, and stride time variability) with inertial sensors. RESULTS PD had impaired gait compared to HC, and dual-tasking made gait variables worse across groups (all P < .01). Visual cues improved stride length, foot strike angle, and stride time in all groups (P < .01). Visual cueing also increased saccade frequency, but reduced saccade peak velocity and amplitude in all groups (P < .01). Gait improvement related to changes in visual exploration with visual cues in PD but not HC, with relationships dependent on group (FOG vs non-FOG) and task (single vs dual). CONCLUSION Visual cues improved visual exploration and gait outcomes in HC and PD, with similar responses in freezers and non-freezers. Freezer and non-freezer specific associations between cue-related changes in visual exploration and gait indicate different underlying visuo-cognitive processing within these subgroups for cue response.
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Affiliation(s)
- Lisa Graham
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
| | - Jordan Armitage
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
| | - Rodrigo Vitorio
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Julia Das
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Gill Barry
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
| | - Alan Godfrey
- Department of Computer and Information Science, Northumbria University, Newcastle, UK
| | | | - Richard Walker
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Martina Mancini
- Department of Neurology, Oregon Health & Science University, Portland, OR, USA
| | - Rosie Morris
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
| | - Samuel Stuart
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UK
- Northumbria Healthcare NHS Foundation Trust, North Shields, UK
- Department of Neurology, Oregon Health & Science University, Portland, OR, USA
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Sousani M, Rojas RF, Preston E, Ghahramani M. Toward a Multi-Modal Brain-Body Assessment in Parkinson's Disease: A Systematic Review in fNIRS. IEEE J Biomed Health Inform 2023; 27:4840-4853. [PMID: 37639416 DOI: 10.1109/jbhi.2023.3308901] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Parkinson's disease (PD) causes impairments in cortical structures leading to motor and cognitive symptoms. While common disease management and treatment strategies mainly depend on the subjective assessment of clinical scales and patients' diaries, research in recent years has focused on advances in automatic and objective tools to help with diagnosing PD and determining its severity. Due to the link between brain structure deficits and physical symptoms in PD, objective brain activity and body motion assessment of patients have been studied in the literature. This study aimed to explore the relationship between brain activity and body motion measures of people with PD to look at the feasibility of diagnosis or assessment of PD using these measures. In this study, we summarised the findings of 24 selected papers from the complete literature review using the Scopus database. Selected studies used both brain activity recording using functional near-infrared spectroscopy (fNIRS) and motion assessment using sensors for people with PD in their experiments. Results include 1) the most common study protocol is a combination of single tasks. 2) Prefrontal cortex is mostly studied region of interest in the literature. 3) Oxygenated haemoglobin (HbO 2) concentration is the predominant metric utilised in fNIRS, compared to deoxygenated haemoglobin (HHb). 4) Motion assessment in people with PD is mostly done with inertial measurement units (IMUs) and electronic walkway. 5) The relationship between brain activity and body motion measures is an important factor that has been neglected in the literature.
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Sparrow D, DeMolles D, Dubaz O, Durso R, Rosner B. Design issues in crossover trials involving patients with Parkinson's disease. Front Neurol 2023; 14:1197281. [PMID: 37670777 PMCID: PMC10476358 DOI: 10.3389/fneur.2023.1197281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/05/2023] [Indexed: 09/07/2023] Open
Abstract
Background and objectives Crossover designs are frequently used to assess treatments for patients with Parkinson's disease. Typically, two-period two-treatment trials include a washout period between the 2 periods and assume that the washout period is sufficiently long to eliminate carryover effects. A complementary strategy might be to jointly model carryover and treatment effects, though this has rarely been done in Parkinson's disease crossover studies. The primary objective of this research is to demonstrate a modeling approach that assesses treatment and carryover effects in one unified mixed model analysis and to examine how it performs in a simulation study and a real data analysis example, as compared to other data analytic approaches used in Parkinson's disease crossover studies. Methods We examined how three different methods of analysis (standard crossover t-test, mixed model with a carryover term included in model statement, and mixed model with no carryover term) performed in a simulation study and illustrated the methods in a real data example in Parkinson's disease. Results The simulation study based on the presence of a carryover effect indicated that mixed models with a carryover term and an unstructured correlation matrix provided unbiased estimates of treatment effect and appropriate type I error. The methods are illustrated in a real data example involving Parkinson's disease. Our literature review revealed that a majority of crossover studies included a washout period but did not assess whether the washout was sufficiently long to eliminate the possibility of carryover. Discussion We recommend using a mixed model with a carryover term and an unstructured correlation matrix to obtain unbiased estimates of treatment effect.
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Affiliation(s)
- David Sparrow
- VA Boston Healthcare System, Boston, MA, United States
- Departments of Medicine and Public Health, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, United States
| | | | - Ornella Dubaz
- VA Boston Healthcare System, Boston, MA, United States
- Department of Neurology, Brigham and Women’s Hospital, Boston, MA, United States
| | - Raymon Durso
- Departments of Medicine and Public Health, Boston University Chobanian and Avedisian School of Medicine, Boston, MA, United States
| | - Bernard Rosner
- Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, MA, United States
- Channing Division for Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
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Vitório R, Morris R, Das J, Walker R, Mancini M, Stuart S. Brain activity response to cues during gait in Parkinson’s disease: A study protocol. PLoS One 2022; 17:e0275894. [PMID: 36395190 PMCID: PMC9671304 DOI: 10.1371/journal.pone.0275894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 09/22/2022] [Indexed: 11/19/2022] Open
Abstract
Various cueing strategies (internal and external) have been used to alleviate gait deficits in Parkinson’s disease (PD). However, it remains unclear which type of cueing strategy is most effective at different disease stages or with more severe walking impairment, such as freezing of gait (FOG). The underlying neural mechanisms of response to cueing are also unknown. This trial aims to: (i) determine brain activity response to cue stimulus (internal, visual, auditory or tactile) when walking in PD and; (ii) examine changes in brain activity to cues at different stages of PD. This ongoing single-site study uses an exploratory observational design, with laboratory application of cues for gait deficit. A total of 80 people with PD who meet the inclusion criteria will be enrolled. Participants are split into groups dependent on their disease stage (classified with the Hoehn and Yahr (H&Y) scale); n = 20 H&YI; n = 30 H&YII; n = 30 H&YIII. Within the H&Y stage II and III groups, we will also ensure recruitment of a sub-group of 15 individuals with FOG within each group. Participants perform walking tasks under several conditions: baseline walking without cues; randomized cued walking conditions [internal and external (visual, auditory and tactile) cues]. A combined functional near-infrared spectroscopy and electroencephalography system quantifies cortical brain activity while walking. Inertial sensors are used to assess gait. Primary outcome measures are cue-related changes in cortical brain activity while walking, including the relative change in cortical HbO2 and the power spectral densities at alpha (8-13Hz), beta (13-30Hz), delta (0.5-4Hz), theta (4-8Hz) and gamma (30-40Hz) frequency bandwidths. Secondary outcome measures are cue-related changes in spatiotemporal gait characteristics. Findings will enhance our understanding about the cortical responses to different cueing strategies and how they are influenced by PD progression and FOG status. This trial is registered at clinicaltrials.gov (NCT04863560; April 28, 2021, https://clinicaltrials.gov/ct2/show/NCT04863560).
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Affiliation(s)
- Rodrigo Vitório
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Rosie Morris
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Julia Das
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Richard Walker
- Northumbria Healthcare NHS Foundation Trust, North Tyneside General Hospital, Newcastle upon Tyne, United Kingdom
| | - Martina Mancini
- Department of Neurology, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Samuel Stuart
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle upon Tyne, United Kingdom
- * E-mail:
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Pasquini J, Brooks DJ, Pavese N. The Cholinergic Brain in Parkinson's Disease. Mov Disord Clin Pract 2021; 8:1012-1026. [PMID: 34631936 DOI: 10.1002/mdc3.13319] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/07/2021] [Accepted: 07/22/2021] [Indexed: 02/06/2023] Open
Abstract
The central cholinergic system includes the basal forebrain nuclei, mainly projecting to the cortex, the mesopontine tegmental nuclei, mainly projecting to the thalamus and subcortical structures, and other groups of projecting neurons and interneurons. This system regulates many functions of human behavior such as cognition, locomotion, and sleep. In Parkinson's disease (PD), disruption of central cholinergic transmission has been associated with cognitive decline, gait problems, freezing of gait (FOG), falls, REM sleep behavior disorder (RBD), neuropsychiatric manifestations, and olfactory dysfunction. Neuropathological and neuroimaging evidence suggests that basal forebrain pathology occurs simultaneously with nigrostriatal denervation, whereas pathology in the pontine nuclei may occur before the onset of motor symptoms. These studies have also detailed the clinical implications of cholinergic dysfunction in PD. Degeneration of basal forebrain nuclei and consequential cortical cholinergic denervation are associated with and may predict the subsequent development of cognitive decline and neuropsychiatric symptoms. Gait problems, FOG, and falls are associated with a complex dysfunction of both pontine and basal forebrain nuclei. Olfactory impairment is associated with cholinergic denervation of the limbic archicortex, specifically hippocampus and amygdala. Available evidence suggests that cholinergic dysfunction, alongside failure of the dopaminergic and other neurotransmitters systems, contributes to the generation of a specific set of clinical manifestations. Therefore, a "cholinergic phenotype" can be identified in people presenting with cognitive decline, falls, and RBD. In this review, we will summarize the organization of the central cholinergic system and the clinical correlates of cholinergic dysfunction in PD.
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Affiliation(s)
- Jacopo Pasquini
- Department of Pathophysiology and Transplantation University of Milan Milan Italy.,Clinical Ageing Research Unit Newcastle University Newcastle upon Tyne United Kingdom
| | - David J Brooks
- Positron Emission Tomography Centre Newcastle University Newcastle upon Tyne United Kingdom.,Department of Nuclear Medicine and PET Centre Aarhus University Hospital Aarhus Denmark
| | - Nicola Pavese
- Clinical Ageing Research Unit Newcastle University Newcastle upon Tyne United Kingdom.,Department of Nuclear Medicine and PET Centre Aarhus University Hospital Aarhus Denmark
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Albin RL, Müller MLTM, Bohnen NI, Spino C, Sarter M, Koeppe RA, Szpara A, Kim K, Lustig C, Dauer WT. α4β2 * Nicotinic Cholinergic Receptor Target Engagement in Parkinson Disease Gait-Balance Disorders. Ann Neurol 2021; 90:130-142. [PMID: 33977560 DOI: 10.1002/ana.26102] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 05/10/2021] [Accepted: 05/10/2021] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Attentional deficits following degeneration of brain cholinergic systems contribute to gait-balance deficits in Parkinson disease (PD). As a step toward assessing whether α4β2* nicotinic acetylcholine receptor (nAChR) stimulation improves gait-balance function, we assessed target engagement of the α4β2* nAChR partial agonist varenicline. METHODS Nondemented PD participants with cholinergic deficits were identified with [18 F]fluoroethoxybenzovesamicol positron emission tomography (PET). α4β2* nAChR occupancy after subacute oral varenicline treatment was measured with [18 F]flubatine PET. With a dose selected from the nAChR occupancy experiment, varenicline effects on gait, balance, and cognition were assessed in a double-masked placebo-controlled crossover study. Primary endpoints were normal pace gait speed and a measure of postural stability. RESULTS Varenicline doses (0.25mg per day, 0.25mg twice daily [b.i.d.], 0.5mg b.i.d., and 1.0mg b.i.d.) produced 60 to 70% receptor occupancy. We selected 0.5mg orally b.i.d for the crossover study. Thirty-three participants completed the crossover study with excellent tolerability. Varenicline had no significant impact on the postural stability measure and caused slower normal pace gait speed. Varenicline narrowed the difference in normal pace gait speed between dual task and no dual task gait conditions, reduced dual task cost, and improved sustained attention test performance. We obtained identical conclusions in 28 participants with treatment compliance confirmed by plasma varenicline measurements. INTERPRETATION Varenicline occupied α4β2* nicotinic acetylcholine receptors, was tolerated well, enhanced attention, and altered gait performance. These results are consistent with target engagement. α4β2* agonists may be worth further evaluation for mitigation of gait and balance disorders in PD. ANN NEUROL 2021;90:130-142.
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Affiliation(s)
- Roger L Albin
- Neurology Service and GRECC, VAAAHS, Ann Arbor, MI.,Department of Neurology, University of Michigan, Ann Arbor, MI.,University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,University of Michigan Parkinson's Foundation Research Center of Excellence, Ann Arbor, MI
| | - Martijn L T M Müller
- University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,University of Michigan Parkinson's Foundation Research Center of Excellence, Ann Arbor, MI.,Department of Radiology, University of Michigan, Ann Arbor, MI
| | - Nicolaas I Bohnen
- Neurology Service and GRECC, VAAAHS, Ann Arbor, MI.,Department of Neurology, University of Michigan, Ann Arbor, MI.,University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,University of Michigan Parkinson's Foundation Research Center of Excellence, Ann Arbor, MI.,Department of Radiology, University of Michigan, Ann Arbor, MI
| | - Cathie Spino
- University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,Department of Biostatistics, University of Michigan, Ann Arbor, MI
| | - Martin Sarter
- University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,Department of Psychology, University of Michigan, Ann Arbor, MI
| | - Robert A Koeppe
- Department of Radiology, University of Michigan, Ann Arbor, MI
| | - Ashley Szpara
- Department of Neurology, University of Michigan, Ann Arbor, MI.,University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI
| | - Kamin Kim
- Department of Psychology, University of Michigan, Ann Arbor, MI
| | - Cindy Lustig
- University of Michigan Parkinson's Foundation Research Center of Excellence, Ann Arbor, MI.,Department of Psychology, University of Michigan, Ann Arbor, MI
| | - William T Dauer
- Neurology Service and GRECC, VAAAHS, Ann Arbor, MI.,Department of Neurology, University of Michigan, Ann Arbor, MI.,University of Michigan Morris K. Udall Parkinson's Disease Research Center of Excellence, Ann Arbor, MI.,Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX.,Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX.,Peter J. O'Donnell Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX
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